Image integration into 3-dimensional-electro-anatomical mapping system facilitates safe ablation of ventricular arrhythmias originating from the aortic root and its vicinity

Image integration into 3-dimensional-electro-anatomical mapping system facilitates safe ablation... Abstract Aims During ablation in the vicinity of the coronary arteries establishing a safe distance from the catheter tip to the relevant vessels is mandatory and usually assessed by fluoroscopy alone. The aim of the study was to investigate the feasibility of an image integration module (IIM) for continuous monitoring of the distance of the ablation catheter tip to the main coronary arteries during ablation of ventricular arrhythmias (VA) originating in the sinus of valsalva (SOV) and the left ventricular summit part of which can be reached via the great cardiac vein (GCV). Methods and results Of 129 patients undergoing mapping for outflow tract arrhythmias from June 2014 till October 2015, a total of 39 patients (52.4 ± 18.1 years, 17 female) had a source of origin in the SOV or the left ventricular summit. Radiofrequency (RF) ablation was performed when a distance of at least 5 mm could be demonstrated with IIM. A safe distance in at least one angiographic plane could be demonstrated in all patients with a source of origin in the SOV, whereas this was not possible in 50% of patients with earliest activation in the summit area. However, using the IIM a safe position at an adjacent site within the GCV could be obtained in three of these cases and successful RF ablation performed safely without any complications. Ablation was successful in 100% of patients with an origin in the SOV, whereas VAs originating from the left ventricular summit could be abolished completely in only 60% of cases. Conclusion Image integration combining electroanatomical mapping and fluoroscopy allows assessment of the safety of a potential ablation site by continuous real-time monitoring of the spatial relations of the catheter tip to the coronary vessels prior to RF application. It aids ablation in anatomically complex regions like the SOV or the ventricular summit providing biplane angiograms merged into the three-dimensional electroanatomical map. Idiopathic ventricular arrhythmia , Catheter ablation , Fluoroscopy , Image integration , 3D mapping system Introduction What’s new? Ablation of ventricular arrhythmias with a site of origin in the aortic root and its proximity using image integration of coronary angiograms is feasible and safe. Image integration can aid in finding safe ablation sites in anatomically complex regions like the left ventricular summit by simulating a biplane angiography. Image integration makes a second arterial puncture unnecessary and may avoid vascular complications while still offering real-time monitoring of distances from catheter tip to nearest coronary artery.The sinus of valsalva (SOV)1,2 as well as the left ventricular summit3–5 which can be reached via the great cardiac vein (GCV) are recognized as common sites of ventricular arrhythmias (VA) and can be successfully treated with radiofrequency (RF) ablation (RFA). Because of the close proximity of major coronary arteries performing coronary angiography to ensure adequate distance to the ablation catheter tip is mandatory. Usually a distance of at least 5 mm to the adjacent coronary vessels is regarded as safe6 and has to be demonstrated during coronary angiography. However, a second arterial puncture is necessary to evaluate the ablation catheter tip with relation to the coronary ostia in a single image in case of SOV Vas,2,7 which might increase the frequency of complications at the access site. Considering the ablation of VAs from the GCV evaluation of the relation of the catheter tip to the coronary arteries in the area of the left ventricular summit can be very challenging and often multiple planes are needed to ascertain sufficient distance at the earliest site.5,8 The goal of our study was to determine the feasibility of the image integration module (IIM) for RFA of VAs in these anatomically complex regions of the heart with regard to visualization of safe catheter positions. Methods Study protocol and patient population In a consecutive group of 129 patients with focal VAs referred for ablation to our institution from June 2014 until October 2015 the site of origin (SOO) was determined by activation and pace mapping. In case of localization to the SOV or the left ventricular summit, patients were included in this study and image integration of coronary angiograms used to guide ablation. The study was approved by the Institutional Ethics Committee of the University Heart Center Hamburg. Technology description The CartoUnivu™ Module has been described by our group and elsewhere.9,10 In brief, a registration plate is needed to align the Carto® 3 System to the co-ordinates of the conventional fluoroscopy system (Allura Xper FD10, Koninklijke Philips N.V., Eindhoven, The Netherlands). Furthermore, a software upgrade consists of a registration window, a connectivity icon, CartoUnivu™ Module Tool Bar, and a new Map/Image selection. The only additional step in a typical CartoUnivu™ procedure is the registration after initialization which is done by capturing a fluoroscopy image of the disc marker over the registration plate. Electrophysiological study Electrophysiological study was performed in a fasting state after informed consent was obtained. Anti-arrhythmic (AA) drugs were discontinued for at least five half-lives. The procedure was performed under conscious sedation using propofol, fentanyl, and midazolam with continuous monitoring of blood pressure and oxygen saturation during spontaneous ventilation unless the VAs were completely suppressed by these measures. In case of non-inducibility, an orciprenaline infusion (5 mg/500 mL NaCl saline 0.9%) was started to induce a 20% increment of heart rate. Surface electrocardiograms and bipolar endocardial electrograms were continuously monitored and stored on a computer-based digital amplifier/recorder system (LabSystem PRO®, Bard Electrophysiology Inc., Lowell, MA, USA). Access to the mapping region with a 3.5 mm externally irrigated-tip ablation catheter (NaviStar ThermoCool®, Biosense Webster) was achieved retrogradely after puncture of the right femoral artery in case of left-sided procedures and via the right femoral vein in case of epicardial mapping via the GCV. Heparin was administered to maintain an activated clotting time >300 s when arterial access was obtained. Activation mapping was performed in all cases in order to identify the site of earliest ventricular activation during the ventricular tachycardia (VT) or the ventricular premature depolarizations (VPDs). The local activation time was measured from onset of the electrogram (earliest positive or negative defection) of the distal bipole of the mapping catheter to the earliest onset of the QRS complex in any ECG lead. Additionally, pace mapping was performed using the distal bipolar electrodes of the mapping catheter at a pacing cycle length of 500 ms with the lowest stimulus amplitude (varying from 3 to 10 mA) and pulse width (1.0–2.0 ms) producing stable ventricular capture. The correlation index (CI) for the pace map was determined using the Carto 3.2 CorrelationTM Module (Biosense Webster Johnson and Johnson, Diamond Bar, CA, USA), which is calculated as the average correlation of the 12 surface electrocardiographic leads. A perfect pace map was defined as a 99% CI, whereas a CI of at least 95% was considered an excellent and a CI of ≥ 90% a good pace map. The site with earliest local ventricular activation and/or at least excellent pace map was considered the SOO. The position of the catheter tip was determined using electroanatomic mapping data in combination with the fluoroscopical image. Integration of coronary angiography images into the Carto® 3 System and distance measurement When a site within the SOV with potentially close anatomic proximity to the coronary vasculature was identified as a potential ablation target, selective angiography of the coronary arteries was performed. For the angiograms, non-ionic-iodinated contrast medium (Imeron® 350, 350 mg Iod/mL, Iomeprol, Bracco Imaging, Konstanz, Germany) was injected into the left main coronary artery via a Judkins left 4 or the right coronary artery via a Judkins right 4. Angiography cine loops were recorded in a standard plane (AP), acquisition of further projections was left to the operators’ preference. Care was taken to record a whole cardiac cycle to account for movement of the coronary vessels during systole. The angiograms were provided as background movies to continuously assess the anatomic relationship and distance between the coronary arteries and the ablation catheter tip (Figure 1) during the RFA. Distance measurements prior to ablation were performed using the integrated measurement tool connecting the electroanatomical point with earliest activation to the point at which the coronary artery was projected to the shell of the three-dimensional (3D) model. However, this was not possible in case of mapping of the GCV because naturally the distal coronary arteries could not be accessed with the mapping catheter. Therefore, the distance was assessed fluoroscopically using the width of the catheter tip (3.5 mm) as an orientation to estimate the distance to the relevant coronary artery. Figure 1 View largeDownload slide Two screenshots from IIM are given. Both panels (A and B) represent the 3D geometry of the aortic root. Coronary angiograms of the left coronary artery were provided as background movies to monitor the distance from the ablation catheter tip to the nearest coronary vessel. The distance is measured using the integrated distance measurement tool. Figure 1 View largeDownload slide Two screenshots from IIM are given. Both panels (A and B) represent the 3D geometry of the aortic root. Coronary angiograms of the left coronary artery were provided as background movies to monitor the distance from the ablation catheter tip to the nearest coronary vessel. The distance is measured using the integrated distance measurement tool. Radiofrequency catheter ablation After identifying a potentially successful ablation site (earliest activation and at least −20 ms before QRS onset and/or perfect pace map) the distance of the catheter tip to the nearest coronary artery was accessed in all available projections and ablation was performed if the distance was ≥5 mm in at least one projection. When this safe distance could not be demonstrated despite the use of multiple angulations the ablation catheter was carefully repositioned to the closest safe site und RFA was delivered if activation and pace mapping were acceptable (i.e. local activation at least −15 ms and CI ≥ 90%). If VAs could not be abolished adjacent anatomical structures were mapped. Radiofrequency applications were performed in a power-controlled mode with a maximum temperature of 48 °C. The maximum output chosen was 30 W in the aortic cusps, whereas 20 W was chosen during ablation within the GCV. When an acceleration or reduction in the frequency of VT or PVCs was observed during the first 20 seconds of the application, the RF delivery was continued for a maximum of 180 s. Otherwise the RF delivery was terminated and the catheter was repositioned. During catheter ablation the 12-lead electrocardiogram was monitored for ST-segment changes indicating coronary artery injury. Repeat angiography was performed if the catheter tip was within 5–10 mm of one of the main epicardial coronary vessels. Procedural endpoint and follow-up The procedural endpoint was the complete abolition of VT and VPDs and non-inducibility with the same stimulation protocol used at the beginning of the procedure. A waiting period of 30 min after the last RF application was always applied in order to exclude early recurrences. A 24 h monitoring period followed the ablation procedure in all patients. Successful catheter ablation was defined as no recurrence of the treated VA during 6 months of follow-up. Electrocardiographical characteristics Sinus rhythm and VA ECG morphologies were examined on a 12-lead ECG with electronic callipers on the digital amplifier/recorder system. Care was taken to use correct 12-lead electrode placement. Lead gain was uniform with a paper speed of 100 mm/s. The following assessments, formerly described as discriminating between left and right sided SOO, were made on the surface ECG: (i) precordial transition, (ii) the transitional zone index,11 (iii) the V2S/V3R index,12 (iv) the V2 transition ratio,13 (v) the R-wave duration index,2 and the (vi) R/S amplitude index2 to assess the sensitivity of these parameters to correctly predict the left-sided localization in our cohort. Statistical analysis Continuous variables are expressed as mean standard deviation or as median with range or interquartile range as specified. Comparisons between groups were performed by using non-parametric statistics, specifically the Fisher’s exact test as well as one-way analysis of variance (ANOVA) to test for significant differences between means. A two-tailed P-value of <0.05 was considered statistically significant. A statistical software package (SPSS 23.0, IBM Corporation, New York, NY, USA) was used for analysis. Results Patients’ characteristics From the 129 patients referred to our institution, a total of 39 consecutive patients [22 (56%) men, mean age 52.4 ± 18.1 years] were included in this study. The SOO was the left ventricular summit in eight patients and the SOV in 31 patients. Within the latter group the arrhythmia could be confined to the left coronary cusp (LCC) in 15 patients, to the right coronary cusp (RCC) in nine, and to the junction of the LCC and RCC (LCC–RCC) in seven. All patients had frequent symptomatic VAs as assessed during 24 h Holter monitoring with an average arrhythmia burden of 19.1 ± 11.3% VPDs/24 h. The predominating arrhythmia was VPDs in 28 patients (72%), non-sustained VT (nsVT) in 7 patients (18%), and sustained VT in four patients (10%). The patients had received at least one AA drug (AAD) prior to ablation (median 2 AADs, range 1–3). Structural cardiomyopathy was present in nine patients (23%), echocardiographic evaluation revealed an average ejection fraction of 57 ± 9.7%. Further patients' characteristics are given in Table 1. Table 1 Baseline characteristics   Site of origin     P-value    LCC (n = 15)  LCC–RCC (n = 7)  RCC (n = 9)  GCV (n = 8)  Total (n = 39)  Gender (male)  9 (60%)  4 (57.1%)  4 (44.4%)  5 (62.5%)  22 (56.4%)  0.868  Age (years)  56.9 ± 13.9  60.3 ± 11.9  37.9 ± 24.9  53.51 ± 13.9  52.4 ± 18.1  0.05  Height (cm)  177 ± 9  176 ± 4  174 ± 10  175 ± 10  176 ± 9  0.74  Weight (kg)  86.0 ± 18.6  83.6 ± 11.4  73.6 ± 19.7  85.6 ± 17.3  82.6 ± 17.6  0.34  BMI (kg/m2)  27.0 ± 4.2  26.7 ± 2.7  23.9 ± 4.4  28.2 ± 5.6  26.5 ± 4.4  0.22  Structural heart disease   Ischaemic cardiomyopathy  2 (13%)  3 (43%)  1 (11%)  2 (25%)  8 (20%)  0.314   Dilated cardiomyopathy  0 (0%)  0 (0%)  0 (0%)  1 (13%)  1 (3%)  0.253   EF  58.7 ± 7.2  58.5 ± 9.9  57.4 ± 11.3  53.4 ± 7.0  57.3 ± 9.7  0.59   ICD implanted  0 (0%)  2 (28.6%)  1 (11.1%)  1 (12.5%)  4 (10.3%)  0.132   Hypertension  8 (53.3%)  6 (85.7%)  2 (22.2%)  6 (75%)  22 (56.4%)  0.056   Diabetes  1 (6.7%)  0 (0%)  0 (0%)  1 (12.5%)  2 (5.1%)  0.818   Anti-arrhythmic drug  1.5 ± 0.6  1.6 ± 0.5  1.7 ± 0.5  1.6 ± 0.5  1.6 ± 0.5  0.896  Clinical arrhythmia   VPD  14 (93%)  4 (57%)  5 (56%)  5 (63%)  28 (72%)  0.255   nsVT  1 (14%)  3 (43%)  3 (33%)  0 (0%)  7 (18%)  0.012   VT  0 (0%)  0 (0%)  1 (11%)  3 (37%)  4 (10%)  0.04   VPD-burden (%)  16.6 ± 9.1  20.4 ± 10.2  22.6 ± 17.5  19.0 ± 7.2  19.1 ± 11.3  0.67  Clinical symptoms   Syncope  0 (0%)  0 (0%)  1 (11.1%)  0 (0%)  1 (2.6%)  0.615   Dyspnoea  12 (80%)  7 (100%)  6 (66.7%)  5 (62.5%)  30 (76.9%)  0.327   Palpitations  14 (93.3%)  6 (85.7%)  9 (100%)  8 (100%)  37 (94.9%)  0.656    Site of origin     P-value    LCC (n = 15)  LCC–RCC (n = 7)  RCC (n = 9)  GCV (n = 8)  Total (n = 39)  Gender (male)  9 (60%)  4 (57.1%)  4 (44.4%)  5 (62.5%)  22 (56.4%)  0.868  Age (years)  56.9 ± 13.9  60.3 ± 11.9  37.9 ± 24.9  53.51 ± 13.9  52.4 ± 18.1  0.05  Height (cm)  177 ± 9  176 ± 4  174 ± 10  175 ± 10  176 ± 9  0.74  Weight (kg)  86.0 ± 18.6  83.6 ± 11.4  73.6 ± 19.7  85.6 ± 17.3  82.6 ± 17.6  0.34  BMI (kg/m2)  27.0 ± 4.2  26.7 ± 2.7  23.9 ± 4.4  28.2 ± 5.6  26.5 ± 4.4  0.22  Structural heart disease   Ischaemic cardiomyopathy  2 (13%)  3 (43%)  1 (11%)  2 (25%)  8 (20%)  0.314   Dilated cardiomyopathy  0 (0%)  0 (0%)  0 (0%)  1 (13%)  1 (3%)  0.253   EF  58.7 ± 7.2  58.5 ± 9.9  57.4 ± 11.3  53.4 ± 7.0  57.3 ± 9.7  0.59   ICD implanted  0 (0%)  2 (28.6%)  1 (11.1%)  1 (12.5%)  4 (10.3%)  0.132   Hypertension  8 (53.3%)  6 (85.7%)  2 (22.2%)  6 (75%)  22 (56.4%)  0.056   Diabetes  1 (6.7%)  0 (0%)  0 (0%)  1 (12.5%)  2 (5.1%)  0.818   Anti-arrhythmic drug  1.5 ± 0.6  1.6 ± 0.5  1.7 ± 0.5  1.6 ± 0.5  1.6 ± 0.5  0.896  Clinical arrhythmia   VPD  14 (93%)  4 (57%)  5 (56%)  5 (63%)  28 (72%)  0.255   nsVT  1 (14%)  3 (43%)  3 (33%)  0 (0%)  7 (18%)  0.012   VT  0 (0%)  0 (0%)  1 (11%)  3 (37%)  4 (10%)  0.04   VPD-burden (%)  16.6 ± 9.1  20.4 ± 10.2  22.6 ± 17.5  19.0 ± 7.2  19.1 ± 11.3  0.67  Clinical symptoms   Syncope  0 (0%)  0 (0%)  1 (11.1%)  0 (0%)  1 (2.6%)  0.615   Dyspnoea  12 (80%)  7 (100%)  6 (66.7%)  5 (62.5%)  30 (76.9%)  0.327   Palpitations  14 (93.3%)  6 (85.7%)  9 (100%)  8 (100%)  37 (94.9%)  0.656  Numbers are given in mean  ±  standard deviation where appropriate. Results from Fisher’s exact test (categorical data) and one-way ANOVA (continuous variables). LCC, left coronary cusp; RCC, right coronary cusp; GCV, great cardiac vein, BMI, body mass index; EF, ejection fraction; VPD, ventricular premature depolarization; nsVT, non-sustained ventricular tachycardia; VT, sustained ventricular tachycardia. Distance from the successful ablation site to the nearest coronary artery A safe distance of ≥ 5 mm from the catheter tip to the coronary artery system could be demonstrated in all of the patients with a source of origin within the SOV. The average distance to the nearest coronary artery ostium was 19.6 ± 4.6 mm for the LCC group, 23.9 ± 2.0 mm for the LCC–RCC group, and 21.2 ± 5.2 mm for the RCC group as determined using the integrated measurement tool. This was not possible in case of VAs originating from the left ventricular summit, and distances were assessed using the 3.5 mm catheter tip as a reference. The distance to the closest coronary artery was <5 mm in four cases (50%) at the site of earliest ventricular activation despite the use of multiple angulations. In three of these occasions, repositioning of the catheter tip resulted in a safe position within the coronary sinus maintaining promising activation times and pace maps (Figure 2) and RFA was attempted. In the remaining case, the left ventricular summit area was relatively small (Figure 3) and safe positions were associated with poor pace maps and activation times. After repositioning the catheter tip the average distance in the GCV group was still significantly lower with an average of 6.9 ± 2.2 mm (Table 2). Table 2 Procedural parameters   Site of origin     P-value    LCC (n = 15)  LCC–RCC (n = 7)  RCC (n = 9)  GCV (n = 8)  Total (n = 39)  Acute success  15 (100%)  7 (100%)  9 (100%)  5 (62.5%)  36 (92.3%)  0.014  Recurrence  1 (7%)  0 (0%)  1 (14.3%)  1 (20%)  3 (8.4%)  0.346  Procedure time (min)  106.3 ± 42.7  140.7 ± 62.9  147.8 ± 64.3  134.4 ± 70.0  127.8 ± 58.4  0.327  Distance to coronary artery (mm)  19.6 ± 4.6  23.9 ± 2.0  21.2 ± 5.2  6.9 ± 2.2  18.1 ± 7.1  <0.001  Fluoroscopy time (min)  12.5 ± 9.2  13.6 ± 12.6  16.2 ± 16.2  19.4 ± 5.2  14.9 ± 11.1  0.548  DAP (cGycm2)  987 ± 765  1246 ± 837  932 ± 1373  2777 ± 2321  1388 ± 1469  0.024  RF duration (sec)  400 ± 249  660 ± 677  408 ± 277  415 ± 195  452 ± 361  0.432  Maximal power (W)  25.9 ± 3.0  28.5 ± 1.6  27.8 ± 2.4  15.0 ± 1.7  25.0 ± 5.5  <0.001  Total energy (J)  9607 ± 5353  18709 ± 18756  8620 ± 6231  6126 ± 3815  10410 ± 9799  0.207  Activation time (ms)  −34.6 ± 7.6  −31.4 ± 7.4  −33.1 ± 7.7  −27.6 ± 3.5  −32.3 ± 7.2  0.159  CI  97.0 ± 1.9  97.4 ± 2.2  97.6 ± 1.7  97.8 ± 1.75  97.3 ± 1.9  0.784    Site of origin     P-value    LCC (n = 15)  LCC–RCC (n = 7)  RCC (n = 9)  GCV (n = 8)  Total (n = 39)  Acute success  15 (100%)  7 (100%)  9 (100%)  5 (62.5%)  36 (92.3%)  0.014  Recurrence  1 (7%)  0 (0%)  1 (14.3%)  1 (20%)  3 (8.4%)  0.346  Procedure time (min)  106.3 ± 42.7  140.7 ± 62.9  147.8 ± 64.3  134.4 ± 70.0  127.8 ± 58.4  0.327  Distance to coronary artery (mm)  19.6 ± 4.6  23.9 ± 2.0  21.2 ± 5.2  6.9 ± 2.2  18.1 ± 7.1  <0.001  Fluoroscopy time (min)  12.5 ± 9.2  13.6 ± 12.6  16.2 ± 16.2  19.4 ± 5.2  14.9 ± 11.1  0.548  DAP (cGycm2)  987 ± 765  1246 ± 837  932 ± 1373  2777 ± 2321  1388 ± 1469  0.024  RF duration (sec)  400 ± 249  660 ± 677  408 ± 277  415 ± 195  452 ± 361  0.432  Maximal power (W)  25.9 ± 3.0  28.5 ± 1.6  27.8 ± 2.4  15.0 ± 1.7  25.0 ± 5.5  <0.001  Total energy (J)  9607 ± 5353  18709 ± 18756  8620 ± 6231  6126 ± 3815  10410 ± 9799  0.207  Activation time (ms)  −34.6 ± 7.6  −31.4 ± 7.4  −33.1 ± 7.7  −27.6 ± 3.5  −32.3 ± 7.2  0.159  CI  97.0 ± 1.9  97.4 ± 2.2  97.6 ± 1.7  97.8 ± 1.75  97.3 ± 1.9  0.784  Numbers are given in mean ± standard deviation where appropriate. Results from Fisher’s exact test (categorical data) and one-way ANOVA (continuous variables). LCC, left coronary cusp; RCC, right coronary cusp; GCV, great cardiac vein, DAP, dose area product; RF, radiofrequency; CI, correlation index. Table 3 Procedural parameters   No repositioning within GCV (n = 4)  Repositioning within GCV (n = 4)  P-value  Acute success from GCV  2 (50%)  2 (50%)  1.0  Acute success from adjacent anatomical site  0 (0%)  1 (25%) LCC  1.0  Recurrence  0 (0%)  1 (33%)  0.599  Activation time at SOO (ms)  −27.0 ± 3.5  −26.3 ± 2.7  0.753  Activation time ablation site within GCV  −21.0 ± 1.0  0.04  CI at SOO  97.3 ± 1.0  97.3 ± 2.8  0.830  CI at ablation site  93.6 ± 3.2  0.152  RF duration (s)  454 ± 229  363 ± 171  0.575  Maximal power (W)  16.0 ± 1.6  13.7 ± 0.6  0.06  Total energy (J)  7331 ± 4393  4520 ± 2818  0.351    No repositioning within GCV (n = 4)  Repositioning within GCV (n = 4)  P-value  Acute success from GCV  2 (50%)  2 (50%)  1.0  Acute success from adjacent anatomical site  0 (0%)  1 (25%) LCC  1.0  Recurrence  0 (0%)  1 (33%)  0.599  Activation time at SOO (ms)  −27.0 ± 3.5  −26.3 ± 2.7  0.753  Activation time ablation site within GCV  −21.0 ± 1.0  0.04  CI at SOO  97.3 ± 1.0  97.3 ± 2.8  0.830  CI at ablation site  93.6 ± 3.2  0.152  RF duration (s)  454 ± 229  363 ± 171  0.575  Maximal power (W)  16.0 ± 1.6  13.7 ± 0.6  0.06  Total energy (J)  7331 ± 4393  4520 ± 2818  0.351  Numbers are given in mean ± standard deviation where appropriate. Results from Fisher’s exact test (categorical data) and one-way ANOVA (continuous variables). GCV, great cardiac vein, SOO, site of origin, CI, correlation index; RF, radiofrequency. Figure 2 View largeDownload slide Coronary angiograms of the left coronary artery were provided during mapping of the GCV. Notably, the SOO is marked by the catheter tip that is shown fluoroscopically directly adjacent to the circumflex artery. With careful repositioning in this simulated biplane view a safe site could be found more medially. Figure 2 View largeDownload slide Coronary angiograms of the left coronary artery were provided during mapping of the GCV. Notably, the SOO is marked by the catheter tip that is shown fluoroscopically directly adjacent to the circumflex artery. With careful repositioning in this simulated biplane view a safe site could be found more medially. Figure 3 View largeDownload slide Two screenshots from IIM are given. Even after careful mapping no reasonable safe site within the GCV could be found due to a narrow bifurcation angle. Figure 3 View largeDownload slide Two screenshots from IIM are given. Even after careful mapping no reasonable safe site within the GCV could be found due to a narrow bifurcation angle. Endocardial mapping and catheter ablation A complete elimination of the clinical arrhythmia at the end of the procedure was achieved in all patients with VAs originating in the SOV with an average of 3.2 ± 2.2 RFA, whereas complete abolishment could only be achieved in five of eight (60%) patients in the GCV patients (Table 2). The local activation time did not significantly differ between the four groups at the site of ablation attempt. Likewise, the mean CI was not statistically different between groups. However, the maximum power delivered was significantly lower in the GCV group as compared with the other three locations (15.0 ± 1.7 W, LCC 25.9 ± 3.0 W, LCC–RCC 29.5 ± 1.6 W, RCC 27.7 ± 2.4 W, P < 0.001) which was in concordance with a lower total energy applied in the GCV group compared with the other locations as a total (6126 ± 3815 J vs. 11378 ± 10501 J; P = 0.035) despite a slightly higher number of RF applications (5.0 ± 4.0 vs. 3.2 ± 2.2; P = 0.205). Another major difference was the need to ablate slightly remote from the site of earliest activation in case of VAs originating from the left ventricular summit. In 50% of cases, a safe distance could not be demonstrated at the initially mapped site despite the use of multiple fluoroscopic angulations. However, this could be achieved with careful catheter repositioning in three patients while maintaining promising activation times (Figure 1). In two of these cases ablation was successful with immediate cessation of VAs despite later local activation (5 ms in each case), whereas in the other case VAs were only suppressed (activation time 8 ms later). Despite significantly later local activation (−21.0 ± 1.0 vs. −27.0 ± 3.5 ms; P = 0.039) time and insignificantly lower CI (93.6 ± 3.2% vs. 97.3 ± 1.0%; P = 0.152) after repositioning the catheter within the GCV there was no significant difference with regard to acute ablation success (50% vs. 50%; P = 1.0) or recurrence rates (0% vs. 33%; P = 0.59) (Table 3). Electrocardiographic and characteristics There were significant differences in the precordial transition between groups with earliest transition in the GCV group and latest in the RCC group as shown in Table 4. Despite obvious overlap all GCV patients had a transition at V1 whereas this was never the case for an SOO in the RCC or LCC–RCC. Table 4 Electrocardiographic parameters   Site of origin     P-value    LCC (n = 15)  LCC–RCC (n = 7)  RCC (n = 9)  GCV (n = 8)  Total (n = 39)  Precordial transition   V1  9 (60%)  0 (0%)  0 (0%)  8 (100%)  17 (43.6%)  <0.001   V2  2 (13.3%)  3 (42.9%)  3 (33.3%)  0 (0%)  8 (20.5%)  0.016   ≥V3  4 (26.7%)  4 (57.1%)  6 (66.7)  0 (0%)  14 (35.9%)  0.013  TZ score index  −1.8 ± 1.1  −1.1 ± 1.0  −0.75 ± 1.0  −2.7 ± 0.6  −1.6 ± 1.2  0.003  TZ score index < 0  13 (93%)  4 (67%)  4 (50%)  7 (100%)  28 (80%)  0.035  V2S/V3R index  0.9 ± 1.0  0.49 ± 0.43  1.6 ± 1.0  0.22 ± 0.06  0.97 ± 0.98  0.039  V2S/V3R index ≤ 1.5  8 (89%)  7 (100%)  5 (56%)  3 (100%)  23 (82%)  0.134  V2 transition ratio ≥ 0.6  8 (89%)  7 (100%)  8 (89%)  3 (100%)  26 (93%)  1.0  R-wave duration index ≥ 50%  12 (80%)  1 (14%)  2 (22%)  8 (100%)  23 (59%)  <0.001  R/S-amplitude index ≥ 30%  11 (73%)  7 (100%)  6 (67%)  3 (100%)  27 (79%)  0.388    Site of origin     P-value    LCC (n = 15)  LCC–RCC (n = 7)  RCC (n = 9)  GCV (n = 8)  Total (n = 39)  Precordial transition   V1  9 (60%)  0 (0%)  0 (0%)  8 (100%)  17 (43.6%)  <0.001   V2  2 (13.3%)  3 (42.9%)  3 (33.3%)  0 (0%)  8 (20.5%)  0.016   ≥V3  4 (26.7%)  4 (57.1%)  6 (66.7)  0 (0%)  14 (35.9%)  0.013  TZ score index  −1.8 ± 1.1  −1.1 ± 1.0  −0.75 ± 1.0  −2.7 ± 0.6  −1.6 ± 1.2  0.003  TZ score index < 0  13 (93%)  4 (67%)  4 (50%)  7 (100%)  28 (80%)  0.035  V2S/V3R index  0.9 ± 1.0  0.49 ± 0.43  1.6 ± 1.0  0.22 ± 0.06  0.97 ± 0.98  0.039  V2S/V3R index ≤ 1.5  8 (89%)  7 (100%)  5 (56%)  3 (100%)  23 (82%)  0.134  V2 transition ratio ≥ 0.6  8 (89%)  7 (100%)  8 (89%)  3 (100%)  26 (93%)  1.0  R-wave duration index ≥ 50%  12 (80%)  1 (14%)  2 (22%)  8 (100%)  23 (59%)  <0.001  R/S-amplitude index ≥ 30%  11 (73%)  7 (100%)  6 (67%)  3 (100%)  27 (79%)  0.388  Numbers are given in mean ± standard deviation where appropriate. Results from Fisher’s exact test (categorical data) and one-way ANOVA (continuous variables). LCC, left coronary cusp; RCC, right coronary cusp; GCV, great cardiac vein, TZ, transitional zone. Considering our group of patients the sensitivity of the above-mentioned indices and scores to correctly determine a left-sided SOO was highest for the V2 transition ratio (using the cutoff ≥ 0.6) with a 93% sensitivity (95% CI 75–98%) whereas the R-wave duration index (cutoff ≥ 0.5) had the lowest sensitivity with 59% (95% CI 42–74%). Procedural complications At the end of the procedure no clinical or electrocardiographical signs of myocardial ischaemia were noted. Repeat coronary angiography which was performed in 4 of 39 patients (distance of <10 mm to the left coronary artery during ablation in the GCV, respectively) showed no signs of acute coronary artery injury. Echocardiography immediately after the procedure and the day after revealed no evidence of structural damage to the aortic root or significant valvular insufficiency. One patient developed a pseudoaneurysm of the common femoral artery post-procedurally which could successfully treated with ultrasound-guided thrombin injection. No other acute complications were noted. Follow-up A complete follow-up of 6 months was completed for all of the 36 patients with acutely successful ablation, from which 33 (91.6%) remained free from VAs. Of the three patients with recurrence the SOO was the RCC in one case and the GCV in the other whereas the third occurred in the LCC group. These patients were receiving beta-blocking agents as were all patients with structural heart disease. There was no statistically significant association between localization of the VAs and recurrence rate (Table 2). Discussion Catheter ablation of VAs in the SOV and the region of the left ventricular summit remains a challenging procedure due to the potentially close anatomical relationship between the SOO and major coronary vessels. We conducted a feasibility study using an IIM to guide ablation in these anatomically complex locations. A distance of >5 mm to the coronary ostia was demonstrated in all 30 patients with an SOO in the SOV and RFA could safely be performed in 100% of cases with acute abolishment of VPD. In the patients with an SOO in the GCV, the distance to the closest coronary artery was <5 mm in 50% (4/8) of cases and RFA could not be delivered at the site of earliest activation. Guided by the IIM a safe position could be found by slight catheter movements within the coronary sinus in 75% of these patients. Use of image integration module during ablation within the sinus of valsalva Without the use of image integration coronary angiograms have to be shown on the offline angiography monitor and compared with the live monitor showing the real-time position of the catheter tip. Estimating the distance between the catheter tip and the coronary vessels in this way with sufficient accuracy requires much experience and may not be possible in certain cases. Therefore, in some centres the intracardiac echocardiography has been used in case of ablation within the aortic root to visualize the catheter tip in relation to the coronary artery ostia.14 However, this adds cost as well as complexity to the procedure and the ability to display the spatial relationship between catheter tip and coronary artery is limited in case of more distal segments, e.g. in case of ablation in the distal GCV. Another possibility to continuously monitor the distances is to repeatedly inject contrast media into the coronary arteries during RF application and perform ablation under fluoroscopic observation or at least mark the coronary ostia with the angiographic catheter.2,7 However, this requires an additional arterial puncture and can potentially result in vascular complications, use of significant amounts of contrast media as well as prolonged fluoroscopy time. Finally, performing angiography and displaying the coronary arteries in the same location with image overlay has been another feasible approach. However, the determined distance to the coronary artery ostia is dependent on the angiography plane used in relation to the exact position of the catheter tip and coronary ostium within the cusp region resulting in varying degrees of foreshortening. The fact that the integrated measurement tool used in this work does not assess distances only in one plane but within the 3D map can avoid this issue to a degree. In our experience, the disadvantages of the formerly mentioned approaches can be circumvented by the use of the IIM while still providing a real-time image of the ablation catheter in relation to the coronary vasculature. Use of the image integration module during ablation within the great cardiac vein Ablation of VAs in the region of the left ventricular summit can successfully performed at the site of earliest activation from the GCV (Figure 4).3–5 Figure 4 View largeDownload slide Using this emulated biplane view (AP and LAO 30°) a safe distance to the diagonal branch can be demonstrated in the AP view while a safe distance to the left anterior descending artery is displayed in the LAO 30° view. Figure 4 View largeDownload slide Using this emulated biplane view (AP and LAO 30°) a safe distance to the diagonal branch can be demonstrated in the AP view while a safe distance to the left anterior descending artery is displayed in the LAO 30° view. However, in a significant proportion of patients this site is localized too close to the coronary vasculature and slight catheter movements within the coronary sinus are needed to find a safe catheter position.5,8 In this context, another advantage of the IIM is the possibility to simulate biplane angiography simply by providing two different planes in the main map viewer and the additional map viewer including the according angiograms. Using appropriate planes in the two Carto® viewers it is possible to quickly identify acceptable ablation sites (≥5 mm to the coronary arteries in at least one plane) and perform successful RF application even in sites slightly remote from the initial position (Figure 2). As already shown by our group and others another major limiting factor concerning procedural success remains inadequate power energy delivery.4,5 This is reflected well in the results of this study with maximal power applied as well as total power delivered being significantly lower in the GCV group. As the local activation times and CIs are comparable, this seems to be one plausible explanation for the lower acute success rates compared with the SOV. Technical limitations In this study as well in a previously published work from our and other groups,9,10 this technology has been proved to be robust with regard to map-shift or other technical disturbances which have not occurred during our procedures so far. Conclusion This feasibility study shows that IIM which has previously been shown to be easily integrated in the workflow of the Carto® 3 mapping system can be useful for ablation of focal VAs originating in the SOV and the distal GCV. In the setting of arrhythmias arising from these areas, the ability to directly merge the angiographic cine loop into the 3D-electro-anatomical map allows for real-time monitoring of the spatial relationship between the ablation catheter tip and the relevant coronary arteries. Conflict of interest: none declared. References 1 Yamada T, McElderry HT, Doppalapudi H, Murakami Y, Yoshida Y, Yoshida N et al.   Idiopathic ventricular arrhythmias originating from the aortic root prevalence, electrocardiographic and electrophysiologic characteristics, and results of radiofrequency catheter ablation. J Am Coll Cardiol  2008; 52: 139– 47. Google Scholar CrossRef Search ADS PubMed  2 Ouyang F, Fotuhi P, Ho SY, Hebe J, Volkmer M, Goya M et al.   Repetitive monomorphic ventricular tachycardia originating from the aortic sinus cusp: electrocardiographic characterization for guiding catheter ablation. J Am Coll Cardiol  2002; 39: 500– 8. Google Scholar CrossRef Search ADS PubMed  3 Yamada T, McElderry HT, Doppalapudi H, Okada T, Murakami Y, Yoshida Y et al.   Idiopathic ventricular arrhythmias originating from the left ventricular summit: anatomic concepts relevant to ablation. Circ Arrhythm Electrophysiol  2010; 3: 616– 23. Google Scholar CrossRef Search ADS PubMed  4 Baman TS, Ilg KJ, Gupta SK, Good E, Chugh A, Jongnarangsin K et al.   Mapping and ablation of epicardial idiopathic ventricular arrhythmias from within the coronary venous system. Circ Arrhythm Electrophysiol  2010; 3: 274– 9. Google Scholar CrossRef Search ADS PubMed  5 Steven D, Pott C, Bittner A, Sultan A, Wasmer K, Hoffmann BA et al.   Idiopathic ventricular outflow tract arrhythmias from the great cardiac vein: challenges and risks of catheter ablation. Int J Cardiol  2013; 169: 366– 70. Google Scholar CrossRef Search ADS PubMed  6 D'Avila A, Gutierrez P, Scanavacca M, Reddy V, Lustgarten DL, Sosa E et al.   Effects of radiofrequency pulses delivered in the vicinity of the coronary arteries: implications for nonsurgical transthoracic epicardial catheter ablation to treat ventricular tachycardia. Pacing Clin Electrophysiol  2002; 25: 1488– 95. Google Scholar CrossRef Search ADS PubMed  7 Yamada T, Murakami Y, Yoshida N, Okada T, Shimizu T, Toyama J et al.   Preferential conduction across the ventricular outflow septum in ventricular arrhythmias originating from the aortic sinus cusp. J Am Coll Cardiol  2007; 50: 884– 91. Google Scholar CrossRef Search ADS PubMed  8 Yokokawa M, Latchamsetty R, Good E, Chugh A, Pelosi FJr, Crawford T et al.   Ablation of epicardial ventricular arrhythmias from nonepicardial sites. Heart Rhythm  2011; 8: 1525– 9. Google Scholar CrossRef Search ADS PubMed  9 Akbulak RO, Schaffer B, Jularic M, Moser J, Schreiber D, Salzbrunn T et al.   Reduction of radiation exposure in atrial fibrillation ablation using a new image integration module: a prospective randomized trial in patients undergoing pulmonary vein isolation. J Cardiovasc Electrophysiol  2015; 26: 747– 53. Google Scholar CrossRef Search ADS PubMed  10 Christoph M, Wunderlich C, Moebius S, Forkmann M, Sitzy J, Salmas J et al.   Fluoroscopy integrated 3D mapping significantly reduces radiation exposure during ablation for a wide spectrum of cardiac arrhythmias. Europace  2015; 17: 928– 37. Google Scholar CrossRef Search ADS PubMed  11 Yoshida N, Inden Y, Uchikawa T, Kamiya H, Kitamura K, Shimano M et al.   Novel transitional zone index allows more accurate differentiation between idiopathic right ventricular outflow tract and aortic sinus cusp ventricular arrhythmias. Heart Rhythm  2011; 8: 349– 56. Google Scholar CrossRef Search ADS PubMed  12 Yoshida N, Yamada T, McElderry HT, Inden Y, Shimano M, Murohara T et al.   A novel electrocardiographic criterion for differentiating a left from right ventricular outflow tract tachycardia origin: the V2S/V3R index. J Cardiovasc Electrophysiol  2014; 25: 747– 53. Google Scholar CrossRef Search ADS PubMed  13 Betensky BP, Park RE, Marchlinski FE, Hutchinson MD, Garcia FC, Dixit S et al.   The V(2) transition ratio: a new electrocardiographic criterion for distinguishing left from right ventricular outflow tract tachycardia origin. J Am Coll Cardiol  2011; 57: 2255– 62. Google Scholar CrossRef Search ADS PubMed  14 Hoffmayer KS, Dewland TA, Hsia HH, Badhwar N, Hsu JC, Tseng ZH et al.   Safety of radiofrequency catheter ablation without coronary angiography in aortic cusp ventricular arrhythmias. Heart Rhythm  2014; 11: 1117– 21. Google Scholar CrossRef Search ADS PubMed  Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2017. For permissions, please email: journals.permissions@oup.com. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Europace Oxford University Press

Image integration into 3-dimensional-electro-anatomical mapping system facilitates safe ablation of ventricular arrhythmias originating from the aortic root and its vicinity

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Abstract

Abstract Aims During ablation in the vicinity of the coronary arteries establishing a safe distance from the catheter tip to the relevant vessels is mandatory and usually assessed by fluoroscopy alone. The aim of the study was to investigate the feasibility of an image integration module (IIM) for continuous monitoring of the distance of the ablation catheter tip to the main coronary arteries during ablation of ventricular arrhythmias (VA) originating in the sinus of valsalva (SOV) and the left ventricular summit part of which can be reached via the great cardiac vein (GCV). Methods and results Of 129 patients undergoing mapping for outflow tract arrhythmias from June 2014 till October 2015, a total of 39 patients (52.4 ± 18.1 years, 17 female) had a source of origin in the SOV or the left ventricular summit. Radiofrequency (RF) ablation was performed when a distance of at least 5 mm could be demonstrated with IIM. A safe distance in at least one angiographic plane could be demonstrated in all patients with a source of origin in the SOV, whereas this was not possible in 50% of patients with earliest activation in the summit area. However, using the IIM a safe position at an adjacent site within the GCV could be obtained in three of these cases and successful RF ablation performed safely without any complications. Ablation was successful in 100% of patients with an origin in the SOV, whereas VAs originating from the left ventricular summit could be abolished completely in only 60% of cases. Conclusion Image integration combining electroanatomical mapping and fluoroscopy allows assessment of the safety of a potential ablation site by continuous real-time monitoring of the spatial relations of the catheter tip to the coronary vessels prior to RF application. It aids ablation in anatomically complex regions like the SOV or the ventricular summit providing biplane angiograms merged into the three-dimensional electroanatomical map. Idiopathic ventricular arrhythmia , Catheter ablation , Fluoroscopy , Image integration , 3D mapping system Introduction What’s new? Ablation of ventricular arrhythmias with a site of origin in the aortic root and its proximity using image integration of coronary angiograms is feasible and safe. Image integration can aid in finding safe ablation sites in anatomically complex regions like the left ventricular summit by simulating a biplane angiography. Image integration makes a second arterial puncture unnecessary and may avoid vascular complications while still offering real-time monitoring of distances from catheter tip to nearest coronary artery.The sinus of valsalva (SOV)1,2 as well as the left ventricular summit3–5 which can be reached via the great cardiac vein (GCV) are recognized as common sites of ventricular arrhythmias (VA) and can be successfully treated with radiofrequency (RF) ablation (RFA). Because of the close proximity of major coronary arteries performing coronary angiography to ensure adequate distance to the ablation catheter tip is mandatory. Usually a distance of at least 5 mm to the adjacent coronary vessels is regarded as safe6 and has to be demonstrated during coronary angiography. However, a second arterial puncture is necessary to evaluate the ablation catheter tip with relation to the coronary ostia in a single image in case of SOV Vas,2,7 which might increase the frequency of complications at the access site. Considering the ablation of VAs from the GCV evaluation of the relation of the catheter tip to the coronary arteries in the area of the left ventricular summit can be very challenging and often multiple planes are needed to ascertain sufficient distance at the earliest site.5,8 The goal of our study was to determine the feasibility of the image integration module (IIM) for RFA of VAs in these anatomically complex regions of the heart with regard to visualization of safe catheter positions. Methods Study protocol and patient population In a consecutive group of 129 patients with focal VAs referred for ablation to our institution from June 2014 until October 2015 the site of origin (SOO) was determined by activation and pace mapping. In case of localization to the SOV or the left ventricular summit, patients were included in this study and image integration of coronary angiograms used to guide ablation. The study was approved by the Institutional Ethics Committee of the University Heart Center Hamburg. Technology description The CartoUnivu™ Module has been described by our group and elsewhere.9,10 In brief, a registration plate is needed to align the Carto® 3 System to the co-ordinates of the conventional fluoroscopy system (Allura Xper FD10, Koninklijke Philips N.V., Eindhoven, The Netherlands). Furthermore, a software upgrade consists of a registration window, a connectivity icon, CartoUnivu™ Module Tool Bar, and a new Map/Image selection. The only additional step in a typical CartoUnivu™ procedure is the registration after initialization which is done by capturing a fluoroscopy image of the disc marker over the registration plate. Electrophysiological study Electrophysiological study was performed in a fasting state after informed consent was obtained. Anti-arrhythmic (AA) drugs were discontinued for at least five half-lives. The procedure was performed under conscious sedation using propofol, fentanyl, and midazolam with continuous monitoring of blood pressure and oxygen saturation during spontaneous ventilation unless the VAs were completely suppressed by these measures. In case of non-inducibility, an orciprenaline infusion (5 mg/500 mL NaCl saline 0.9%) was started to induce a 20% increment of heart rate. Surface electrocardiograms and bipolar endocardial electrograms were continuously monitored and stored on a computer-based digital amplifier/recorder system (LabSystem PRO®, Bard Electrophysiology Inc., Lowell, MA, USA). Access to the mapping region with a 3.5 mm externally irrigated-tip ablation catheter (NaviStar ThermoCool®, Biosense Webster) was achieved retrogradely after puncture of the right femoral artery in case of left-sided procedures and via the right femoral vein in case of epicardial mapping via the GCV. Heparin was administered to maintain an activated clotting time >300 s when arterial access was obtained. Activation mapping was performed in all cases in order to identify the site of earliest ventricular activation during the ventricular tachycardia (VT) or the ventricular premature depolarizations (VPDs). The local activation time was measured from onset of the electrogram (earliest positive or negative defection) of the distal bipole of the mapping catheter to the earliest onset of the QRS complex in any ECG lead. Additionally, pace mapping was performed using the distal bipolar electrodes of the mapping catheter at a pacing cycle length of 500 ms with the lowest stimulus amplitude (varying from 3 to 10 mA) and pulse width (1.0–2.0 ms) producing stable ventricular capture. The correlation index (CI) for the pace map was determined using the Carto 3.2 CorrelationTM Module (Biosense Webster Johnson and Johnson, Diamond Bar, CA, USA), which is calculated as the average correlation of the 12 surface electrocardiographic leads. A perfect pace map was defined as a 99% CI, whereas a CI of at least 95% was considered an excellent and a CI of ≥ 90% a good pace map. The site with earliest local ventricular activation and/or at least excellent pace map was considered the SOO. The position of the catheter tip was determined using electroanatomic mapping data in combination with the fluoroscopical image. Integration of coronary angiography images into the Carto® 3 System and distance measurement When a site within the SOV with potentially close anatomic proximity to the coronary vasculature was identified as a potential ablation target, selective angiography of the coronary arteries was performed. For the angiograms, non-ionic-iodinated contrast medium (Imeron® 350, 350 mg Iod/mL, Iomeprol, Bracco Imaging, Konstanz, Germany) was injected into the left main coronary artery via a Judkins left 4 or the right coronary artery via a Judkins right 4. Angiography cine loops were recorded in a standard plane (AP), acquisition of further projections was left to the operators’ preference. Care was taken to record a whole cardiac cycle to account for movement of the coronary vessels during systole. The angiograms were provided as background movies to continuously assess the anatomic relationship and distance between the coronary arteries and the ablation catheter tip (Figure 1) during the RFA. Distance measurements prior to ablation were performed using the integrated measurement tool connecting the electroanatomical point with earliest activation to the point at which the coronary artery was projected to the shell of the three-dimensional (3D) model. However, this was not possible in case of mapping of the GCV because naturally the distal coronary arteries could not be accessed with the mapping catheter. Therefore, the distance was assessed fluoroscopically using the width of the catheter tip (3.5 mm) as an orientation to estimate the distance to the relevant coronary artery. Figure 1 View largeDownload slide Two screenshots from IIM are given. Both panels (A and B) represent the 3D geometry of the aortic root. Coronary angiograms of the left coronary artery were provided as background movies to monitor the distance from the ablation catheter tip to the nearest coronary vessel. The distance is measured using the integrated distance measurement tool. Figure 1 View largeDownload slide Two screenshots from IIM are given. Both panels (A and B) represent the 3D geometry of the aortic root. Coronary angiograms of the left coronary artery were provided as background movies to monitor the distance from the ablation catheter tip to the nearest coronary vessel. The distance is measured using the integrated distance measurement tool. Radiofrequency catheter ablation After identifying a potentially successful ablation site (earliest activation and at least −20 ms before QRS onset and/or perfect pace map) the distance of the catheter tip to the nearest coronary artery was accessed in all available projections and ablation was performed if the distance was ≥5 mm in at least one projection. When this safe distance could not be demonstrated despite the use of multiple angulations the ablation catheter was carefully repositioned to the closest safe site und RFA was delivered if activation and pace mapping were acceptable (i.e. local activation at least −15 ms and CI ≥ 90%). If VAs could not be abolished adjacent anatomical structures were mapped. Radiofrequency applications were performed in a power-controlled mode with a maximum temperature of 48 °C. The maximum output chosen was 30 W in the aortic cusps, whereas 20 W was chosen during ablation within the GCV. When an acceleration or reduction in the frequency of VT or PVCs was observed during the first 20 seconds of the application, the RF delivery was continued for a maximum of 180 s. Otherwise the RF delivery was terminated and the catheter was repositioned. During catheter ablation the 12-lead electrocardiogram was monitored for ST-segment changes indicating coronary artery injury. Repeat angiography was performed if the catheter tip was within 5–10 mm of one of the main epicardial coronary vessels. Procedural endpoint and follow-up The procedural endpoint was the complete abolition of VT and VPDs and non-inducibility with the same stimulation protocol used at the beginning of the procedure. A waiting period of 30 min after the last RF application was always applied in order to exclude early recurrences. A 24 h monitoring period followed the ablation procedure in all patients. Successful catheter ablation was defined as no recurrence of the treated VA during 6 months of follow-up. Electrocardiographical characteristics Sinus rhythm and VA ECG morphologies were examined on a 12-lead ECG with electronic callipers on the digital amplifier/recorder system. Care was taken to use correct 12-lead electrode placement. Lead gain was uniform with a paper speed of 100 mm/s. The following assessments, formerly described as discriminating between left and right sided SOO, were made on the surface ECG: (i) precordial transition, (ii) the transitional zone index,11 (iii) the V2S/V3R index,12 (iv) the V2 transition ratio,13 (v) the R-wave duration index,2 and the (vi) R/S amplitude index2 to assess the sensitivity of these parameters to correctly predict the left-sided localization in our cohort. Statistical analysis Continuous variables are expressed as mean standard deviation or as median with range or interquartile range as specified. Comparisons between groups were performed by using non-parametric statistics, specifically the Fisher’s exact test as well as one-way analysis of variance (ANOVA) to test for significant differences between means. A two-tailed P-value of <0.05 was considered statistically significant. A statistical software package (SPSS 23.0, IBM Corporation, New York, NY, USA) was used for analysis. Results Patients’ characteristics From the 129 patients referred to our institution, a total of 39 consecutive patients [22 (56%) men, mean age 52.4 ± 18.1 years] were included in this study. The SOO was the left ventricular summit in eight patients and the SOV in 31 patients. Within the latter group the arrhythmia could be confined to the left coronary cusp (LCC) in 15 patients, to the right coronary cusp (RCC) in nine, and to the junction of the LCC and RCC (LCC–RCC) in seven. All patients had frequent symptomatic VAs as assessed during 24 h Holter monitoring with an average arrhythmia burden of 19.1 ± 11.3% VPDs/24 h. The predominating arrhythmia was VPDs in 28 patients (72%), non-sustained VT (nsVT) in 7 patients (18%), and sustained VT in four patients (10%). The patients had received at least one AA drug (AAD) prior to ablation (median 2 AADs, range 1–3). Structural cardiomyopathy was present in nine patients (23%), echocardiographic evaluation revealed an average ejection fraction of 57 ± 9.7%. Further patients' characteristics are given in Table 1. Table 1 Baseline characteristics   Site of origin     P-value    LCC (n = 15)  LCC–RCC (n = 7)  RCC (n = 9)  GCV (n = 8)  Total (n = 39)  Gender (male)  9 (60%)  4 (57.1%)  4 (44.4%)  5 (62.5%)  22 (56.4%)  0.868  Age (years)  56.9 ± 13.9  60.3 ± 11.9  37.9 ± 24.9  53.51 ± 13.9  52.4 ± 18.1  0.05  Height (cm)  177 ± 9  176 ± 4  174 ± 10  175 ± 10  176 ± 9  0.74  Weight (kg)  86.0 ± 18.6  83.6 ± 11.4  73.6 ± 19.7  85.6 ± 17.3  82.6 ± 17.6  0.34  BMI (kg/m2)  27.0 ± 4.2  26.7 ± 2.7  23.9 ± 4.4  28.2 ± 5.6  26.5 ± 4.4  0.22  Structural heart disease   Ischaemic cardiomyopathy  2 (13%)  3 (43%)  1 (11%)  2 (25%)  8 (20%)  0.314   Dilated cardiomyopathy  0 (0%)  0 (0%)  0 (0%)  1 (13%)  1 (3%)  0.253   EF  58.7 ± 7.2  58.5 ± 9.9  57.4 ± 11.3  53.4 ± 7.0  57.3 ± 9.7  0.59   ICD implanted  0 (0%)  2 (28.6%)  1 (11.1%)  1 (12.5%)  4 (10.3%)  0.132   Hypertension  8 (53.3%)  6 (85.7%)  2 (22.2%)  6 (75%)  22 (56.4%)  0.056   Diabetes  1 (6.7%)  0 (0%)  0 (0%)  1 (12.5%)  2 (5.1%)  0.818   Anti-arrhythmic drug  1.5 ± 0.6  1.6 ± 0.5  1.7 ± 0.5  1.6 ± 0.5  1.6 ± 0.5  0.896  Clinical arrhythmia   VPD  14 (93%)  4 (57%)  5 (56%)  5 (63%)  28 (72%)  0.255   nsVT  1 (14%)  3 (43%)  3 (33%)  0 (0%)  7 (18%)  0.012   VT  0 (0%)  0 (0%)  1 (11%)  3 (37%)  4 (10%)  0.04   VPD-burden (%)  16.6 ± 9.1  20.4 ± 10.2  22.6 ± 17.5  19.0 ± 7.2  19.1 ± 11.3  0.67  Clinical symptoms   Syncope  0 (0%)  0 (0%)  1 (11.1%)  0 (0%)  1 (2.6%)  0.615   Dyspnoea  12 (80%)  7 (100%)  6 (66.7%)  5 (62.5%)  30 (76.9%)  0.327   Palpitations  14 (93.3%)  6 (85.7%)  9 (100%)  8 (100%)  37 (94.9%)  0.656    Site of origin     P-value    LCC (n = 15)  LCC–RCC (n = 7)  RCC (n = 9)  GCV (n = 8)  Total (n = 39)  Gender (male)  9 (60%)  4 (57.1%)  4 (44.4%)  5 (62.5%)  22 (56.4%)  0.868  Age (years)  56.9 ± 13.9  60.3 ± 11.9  37.9 ± 24.9  53.51 ± 13.9  52.4 ± 18.1  0.05  Height (cm)  177 ± 9  176 ± 4  174 ± 10  175 ± 10  176 ± 9  0.74  Weight (kg)  86.0 ± 18.6  83.6 ± 11.4  73.6 ± 19.7  85.6 ± 17.3  82.6 ± 17.6  0.34  BMI (kg/m2)  27.0 ± 4.2  26.7 ± 2.7  23.9 ± 4.4  28.2 ± 5.6  26.5 ± 4.4  0.22  Structural heart disease   Ischaemic cardiomyopathy  2 (13%)  3 (43%)  1 (11%)  2 (25%)  8 (20%)  0.314   Dilated cardiomyopathy  0 (0%)  0 (0%)  0 (0%)  1 (13%)  1 (3%)  0.253   EF  58.7 ± 7.2  58.5 ± 9.9  57.4 ± 11.3  53.4 ± 7.0  57.3 ± 9.7  0.59   ICD implanted  0 (0%)  2 (28.6%)  1 (11.1%)  1 (12.5%)  4 (10.3%)  0.132   Hypertension  8 (53.3%)  6 (85.7%)  2 (22.2%)  6 (75%)  22 (56.4%)  0.056   Diabetes  1 (6.7%)  0 (0%)  0 (0%)  1 (12.5%)  2 (5.1%)  0.818   Anti-arrhythmic drug  1.5 ± 0.6  1.6 ± 0.5  1.7 ± 0.5  1.6 ± 0.5  1.6 ± 0.5  0.896  Clinical arrhythmia   VPD  14 (93%)  4 (57%)  5 (56%)  5 (63%)  28 (72%)  0.255   nsVT  1 (14%)  3 (43%)  3 (33%)  0 (0%)  7 (18%)  0.012   VT  0 (0%)  0 (0%)  1 (11%)  3 (37%)  4 (10%)  0.04   VPD-burden (%)  16.6 ± 9.1  20.4 ± 10.2  22.6 ± 17.5  19.0 ± 7.2  19.1 ± 11.3  0.67  Clinical symptoms   Syncope  0 (0%)  0 (0%)  1 (11.1%)  0 (0%)  1 (2.6%)  0.615   Dyspnoea  12 (80%)  7 (100%)  6 (66.7%)  5 (62.5%)  30 (76.9%)  0.327   Palpitations  14 (93.3%)  6 (85.7%)  9 (100%)  8 (100%)  37 (94.9%)  0.656  Numbers are given in mean  ±  standard deviation where appropriate. Results from Fisher’s exact test (categorical data) and one-way ANOVA (continuous variables). LCC, left coronary cusp; RCC, right coronary cusp; GCV, great cardiac vein, BMI, body mass index; EF, ejection fraction; VPD, ventricular premature depolarization; nsVT, non-sustained ventricular tachycardia; VT, sustained ventricular tachycardia. Distance from the successful ablation site to the nearest coronary artery A safe distance of ≥ 5 mm from the catheter tip to the coronary artery system could be demonstrated in all of the patients with a source of origin within the SOV. The average distance to the nearest coronary artery ostium was 19.6 ± 4.6 mm for the LCC group, 23.9 ± 2.0 mm for the LCC–RCC group, and 21.2 ± 5.2 mm for the RCC group as determined using the integrated measurement tool. This was not possible in case of VAs originating from the left ventricular summit, and distances were assessed using the 3.5 mm catheter tip as a reference. The distance to the closest coronary artery was <5 mm in four cases (50%) at the site of earliest ventricular activation despite the use of multiple angulations. In three of these occasions, repositioning of the catheter tip resulted in a safe position within the coronary sinus maintaining promising activation times and pace maps (Figure 2) and RFA was attempted. In the remaining case, the left ventricular summit area was relatively small (Figure 3) and safe positions were associated with poor pace maps and activation times. After repositioning the catheter tip the average distance in the GCV group was still significantly lower with an average of 6.9 ± 2.2 mm (Table 2). Table 2 Procedural parameters   Site of origin     P-value    LCC (n = 15)  LCC–RCC (n = 7)  RCC (n = 9)  GCV (n = 8)  Total (n = 39)  Acute success  15 (100%)  7 (100%)  9 (100%)  5 (62.5%)  36 (92.3%)  0.014  Recurrence  1 (7%)  0 (0%)  1 (14.3%)  1 (20%)  3 (8.4%)  0.346  Procedure time (min)  106.3 ± 42.7  140.7 ± 62.9  147.8 ± 64.3  134.4 ± 70.0  127.8 ± 58.4  0.327  Distance to coronary artery (mm)  19.6 ± 4.6  23.9 ± 2.0  21.2 ± 5.2  6.9 ± 2.2  18.1 ± 7.1  <0.001  Fluoroscopy time (min)  12.5 ± 9.2  13.6 ± 12.6  16.2 ± 16.2  19.4 ± 5.2  14.9 ± 11.1  0.548  DAP (cGycm2)  987 ± 765  1246 ± 837  932 ± 1373  2777 ± 2321  1388 ± 1469  0.024  RF duration (sec)  400 ± 249  660 ± 677  408 ± 277  415 ± 195  452 ± 361  0.432  Maximal power (W)  25.9 ± 3.0  28.5 ± 1.6  27.8 ± 2.4  15.0 ± 1.7  25.0 ± 5.5  <0.001  Total energy (J)  9607 ± 5353  18709 ± 18756  8620 ± 6231  6126 ± 3815  10410 ± 9799  0.207  Activation time (ms)  −34.6 ± 7.6  −31.4 ± 7.4  −33.1 ± 7.7  −27.6 ± 3.5  −32.3 ± 7.2  0.159  CI  97.0 ± 1.9  97.4 ± 2.2  97.6 ± 1.7  97.8 ± 1.75  97.3 ± 1.9  0.784    Site of origin     P-value    LCC (n = 15)  LCC–RCC (n = 7)  RCC (n = 9)  GCV (n = 8)  Total (n = 39)  Acute success  15 (100%)  7 (100%)  9 (100%)  5 (62.5%)  36 (92.3%)  0.014  Recurrence  1 (7%)  0 (0%)  1 (14.3%)  1 (20%)  3 (8.4%)  0.346  Procedure time (min)  106.3 ± 42.7  140.7 ± 62.9  147.8 ± 64.3  134.4 ± 70.0  127.8 ± 58.4  0.327  Distance to coronary artery (mm)  19.6 ± 4.6  23.9 ± 2.0  21.2 ± 5.2  6.9 ± 2.2  18.1 ± 7.1  <0.001  Fluoroscopy time (min)  12.5 ± 9.2  13.6 ± 12.6  16.2 ± 16.2  19.4 ± 5.2  14.9 ± 11.1  0.548  DAP (cGycm2)  987 ± 765  1246 ± 837  932 ± 1373  2777 ± 2321  1388 ± 1469  0.024  RF duration (sec)  400 ± 249  660 ± 677  408 ± 277  415 ± 195  452 ± 361  0.432  Maximal power (W)  25.9 ± 3.0  28.5 ± 1.6  27.8 ± 2.4  15.0 ± 1.7  25.0 ± 5.5  <0.001  Total energy (J)  9607 ± 5353  18709 ± 18756  8620 ± 6231  6126 ± 3815  10410 ± 9799  0.207  Activation time (ms)  −34.6 ± 7.6  −31.4 ± 7.4  −33.1 ± 7.7  −27.6 ± 3.5  −32.3 ± 7.2  0.159  CI  97.0 ± 1.9  97.4 ± 2.2  97.6 ± 1.7  97.8 ± 1.75  97.3 ± 1.9  0.784  Numbers are given in mean ± standard deviation where appropriate. Results from Fisher’s exact test (categorical data) and one-way ANOVA (continuous variables). LCC, left coronary cusp; RCC, right coronary cusp; GCV, great cardiac vein, DAP, dose area product; RF, radiofrequency; CI, correlation index. Table 3 Procedural parameters   No repositioning within GCV (n = 4)  Repositioning within GCV (n = 4)  P-value  Acute success from GCV  2 (50%)  2 (50%)  1.0  Acute success from adjacent anatomical site  0 (0%)  1 (25%) LCC  1.0  Recurrence  0 (0%)  1 (33%)  0.599  Activation time at SOO (ms)  −27.0 ± 3.5  −26.3 ± 2.7  0.753  Activation time ablation site within GCV  −21.0 ± 1.0  0.04  CI at SOO  97.3 ± 1.0  97.3 ± 2.8  0.830  CI at ablation site  93.6 ± 3.2  0.152  RF duration (s)  454 ± 229  363 ± 171  0.575  Maximal power (W)  16.0 ± 1.6  13.7 ± 0.6  0.06  Total energy (J)  7331 ± 4393  4520 ± 2818  0.351    No repositioning within GCV (n = 4)  Repositioning within GCV (n = 4)  P-value  Acute success from GCV  2 (50%)  2 (50%)  1.0  Acute success from adjacent anatomical site  0 (0%)  1 (25%) LCC  1.0  Recurrence  0 (0%)  1 (33%)  0.599  Activation time at SOO (ms)  −27.0 ± 3.5  −26.3 ± 2.7  0.753  Activation time ablation site within GCV  −21.0 ± 1.0  0.04  CI at SOO  97.3 ± 1.0  97.3 ± 2.8  0.830  CI at ablation site  93.6 ± 3.2  0.152  RF duration (s)  454 ± 229  363 ± 171  0.575  Maximal power (W)  16.0 ± 1.6  13.7 ± 0.6  0.06  Total energy (J)  7331 ± 4393  4520 ± 2818  0.351  Numbers are given in mean ± standard deviation where appropriate. Results from Fisher’s exact test (categorical data) and one-way ANOVA (continuous variables). GCV, great cardiac vein, SOO, site of origin, CI, correlation index; RF, radiofrequency. Figure 2 View largeDownload slide Coronary angiograms of the left coronary artery were provided during mapping of the GCV. Notably, the SOO is marked by the catheter tip that is shown fluoroscopically directly adjacent to the circumflex artery. With careful repositioning in this simulated biplane view a safe site could be found more medially. Figure 2 View largeDownload slide Coronary angiograms of the left coronary artery were provided during mapping of the GCV. Notably, the SOO is marked by the catheter tip that is shown fluoroscopically directly adjacent to the circumflex artery. With careful repositioning in this simulated biplane view a safe site could be found more medially. Figure 3 View largeDownload slide Two screenshots from IIM are given. Even after careful mapping no reasonable safe site within the GCV could be found due to a narrow bifurcation angle. Figure 3 View largeDownload slide Two screenshots from IIM are given. Even after careful mapping no reasonable safe site within the GCV could be found due to a narrow bifurcation angle. Endocardial mapping and catheter ablation A complete elimination of the clinical arrhythmia at the end of the procedure was achieved in all patients with VAs originating in the SOV with an average of 3.2 ± 2.2 RFA, whereas complete abolishment could only be achieved in five of eight (60%) patients in the GCV patients (Table 2). The local activation time did not significantly differ between the four groups at the site of ablation attempt. Likewise, the mean CI was not statistically different between groups. However, the maximum power delivered was significantly lower in the GCV group as compared with the other three locations (15.0 ± 1.7 W, LCC 25.9 ± 3.0 W, LCC–RCC 29.5 ± 1.6 W, RCC 27.7 ± 2.4 W, P < 0.001) which was in concordance with a lower total energy applied in the GCV group compared with the other locations as a total (6126 ± 3815 J vs. 11378 ± 10501 J; P = 0.035) despite a slightly higher number of RF applications (5.0 ± 4.0 vs. 3.2 ± 2.2; P = 0.205). Another major difference was the need to ablate slightly remote from the site of earliest activation in case of VAs originating from the left ventricular summit. In 50% of cases, a safe distance could not be demonstrated at the initially mapped site despite the use of multiple fluoroscopic angulations. However, this could be achieved with careful catheter repositioning in three patients while maintaining promising activation times (Figure 1). In two of these cases ablation was successful with immediate cessation of VAs despite later local activation (5 ms in each case), whereas in the other case VAs were only suppressed (activation time 8 ms later). Despite significantly later local activation (−21.0 ± 1.0 vs. −27.0 ± 3.5 ms; P = 0.039) time and insignificantly lower CI (93.6 ± 3.2% vs. 97.3 ± 1.0%; P = 0.152) after repositioning the catheter within the GCV there was no significant difference with regard to acute ablation success (50% vs. 50%; P = 1.0) or recurrence rates (0% vs. 33%; P = 0.59) (Table 3). Electrocardiographic and characteristics There were significant differences in the precordial transition between groups with earliest transition in the GCV group and latest in the RCC group as shown in Table 4. Despite obvious overlap all GCV patients had a transition at V1 whereas this was never the case for an SOO in the RCC or LCC–RCC. Table 4 Electrocardiographic parameters   Site of origin     P-value    LCC (n = 15)  LCC–RCC (n = 7)  RCC (n = 9)  GCV (n = 8)  Total (n = 39)  Precordial transition   V1  9 (60%)  0 (0%)  0 (0%)  8 (100%)  17 (43.6%)  <0.001   V2  2 (13.3%)  3 (42.9%)  3 (33.3%)  0 (0%)  8 (20.5%)  0.016   ≥V3  4 (26.7%)  4 (57.1%)  6 (66.7)  0 (0%)  14 (35.9%)  0.013  TZ score index  −1.8 ± 1.1  −1.1 ± 1.0  −0.75 ± 1.0  −2.7 ± 0.6  −1.6 ± 1.2  0.003  TZ score index < 0  13 (93%)  4 (67%)  4 (50%)  7 (100%)  28 (80%)  0.035  V2S/V3R index  0.9 ± 1.0  0.49 ± 0.43  1.6 ± 1.0  0.22 ± 0.06  0.97 ± 0.98  0.039  V2S/V3R index ≤ 1.5  8 (89%)  7 (100%)  5 (56%)  3 (100%)  23 (82%)  0.134  V2 transition ratio ≥ 0.6  8 (89%)  7 (100%)  8 (89%)  3 (100%)  26 (93%)  1.0  R-wave duration index ≥ 50%  12 (80%)  1 (14%)  2 (22%)  8 (100%)  23 (59%)  <0.001  R/S-amplitude index ≥ 30%  11 (73%)  7 (100%)  6 (67%)  3 (100%)  27 (79%)  0.388    Site of origin     P-value    LCC (n = 15)  LCC–RCC (n = 7)  RCC (n = 9)  GCV (n = 8)  Total (n = 39)  Precordial transition   V1  9 (60%)  0 (0%)  0 (0%)  8 (100%)  17 (43.6%)  <0.001   V2  2 (13.3%)  3 (42.9%)  3 (33.3%)  0 (0%)  8 (20.5%)  0.016   ≥V3  4 (26.7%)  4 (57.1%)  6 (66.7)  0 (0%)  14 (35.9%)  0.013  TZ score index  −1.8 ± 1.1  −1.1 ± 1.0  −0.75 ± 1.0  −2.7 ± 0.6  −1.6 ± 1.2  0.003  TZ score index < 0  13 (93%)  4 (67%)  4 (50%)  7 (100%)  28 (80%)  0.035  V2S/V3R index  0.9 ± 1.0  0.49 ± 0.43  1.6 ± 1.0  0.22 ± 0.06  0.97 ± 0.98  0.039  V2S/V3R index ≤ 1.5  8 (89%)  7 (100%)  5 (56%)  3 (100%)  23 (82%)  0.134  V2 transition ratio ≥ 0.6  8 (89%)  7 (100%)  8 (89%)  3 (100%)  26 (93%)  1.0  R-wave duration index ≥ 50%  12 (80%)  1 (14%)  2 (22%)  8 (100%)  23 (59%)  <0.001  R/S-amplitude index ≥ 30%  11 (73%)  7 (100%)  6 (67%)  3 (100%)  27 (79%)  0.388  Numbers are given in mean ± standard deviation where appropriate. Results from Fisher’s exact test (categorical data) and one-way ANOVA (continuous variables). LCC, left coronary cusp; RCC, right coronary cusp; GCV, great cardiac vein, TZ, transitional zone. Considering our group of patients the sensitivity of the above-mentioned indices and scores to correctly determine a left-sided SOO was highest for the V2 transition ratio (using the cutoff ≥ 0.6) with a 93% sensitivity (95% CI 75–98%) whereas the R-wave duration index (cutoff ≥ 0.5) had the lowest sensitivity with 59% (95% CI 42–74%). Procedural complications At the end of the procedure no clinical or electrocardiographical signs of myocardial ischaemia were noted. Repeat coronary angiography which was performed in 4 of 39 patients (distance of <10 mm to the left coronary artery during ablation in the GCV, respectively) showed no signs of acute coronary artery injury. Echocardiography immediately after the procedure and the day after revealed no evidence of structural damage to the aortic root or significant valvular insufficiency. One patient developed a pseudoaneurysm of the common femoral artery post-procedurally which could successfully treated with ultrasound-guided thrombin injection. No other acute complications were noted. Follow-up A complete follow-up of 6 months was completed for all of the 36 patients with acutely successful ablation, from which 33 (91.6%) remained free from VAs. Of the three patients with recurrence the SOO was the RCC in one case and the GCV in the other whereas the third occurred in the LCC group. These patients were receiving beta-blocking agents as were all patients with structural heart disease. There was no statistically significant association between localization of the VAs and recurrence rate (Table 2). Discussion Catheter ablation of VAs in the SOV and the region of the left ventricular summit remains a challenging procedure due to the potentially close anatomical relationship between the SOO and major coronary vessels. We conducted a feasibility study using an IIM to guide ablation in these anatomically complex locations. A distance of >5 mm to the coronary ostia was demonstrated in all 30 patients with an SOO in the SOV and RFA could safely be performed in 100% of cases with acute abolishment of VPD. In the patients with an SOO in the GCV, the distance to the closest coronary artery was <5 mm in 50% (4/8) of cases and RFA could not be delivered at the site of earliest activation. Guided by the IIM a safe position could be found by slight catheter movements within the coronary sinus in 75% of these patients. Use of image integration module during ablation within the sinus of valsalva Without the use of image integration coronary angiograms have to be shown on the offline angiography monitor and compared with the live monitor showing the real-time position of the catheter tip. Estimating the distance between the catheter tip and the coronary vessels in this way with sufficient accuracy requires much experience and may not be possible in certain cases. Therefore, in some centres the intracardiac echocardiography has been used in case of ablation within the aortic root to visualize the catheter tip in relation to the coronary artery ostia.14 However, this adds cost as well as complexity to the procedure and the ability to display the spatial relationship between catheter tip and coronary artery is limited in case of more distal segments, e.g. in case of ablation in the distal GCV. Another possibility to continuously monitor the distances is to repeatedly inject contrast media into the coronary arteries during RF application and perform ablation under fluoroscopic observation or at least mark the coronary ostia with the angiographic catheter.2,7 However, this requires an additional arterial puncture and can potentially result in vascular complications, use of significant amounts of contrast media as well as prolonged fluoroscopy time. Finally, performing angiography and displaying the coronary arteries in the same location with image overlay has been another feasible approach. However, the determined distance to the coronary artery ostia is dependent on the angiography plane used in relation to the exact position of the catheter tip and coronary ostium within the cusp region resulting in varying degrees of foreshortening. The fact that the integrated measurement tool used in this work does not assess distances only in one plane but within the 3D map can avoid this issue to a degree. In our experience, the disadvantages of the formerly mentioned approaches can be circumvented by the use of the IIM while still providing a real-time image of the ablation catheter in relation to the coronary vasculature. Use of the image integration module during ablation within the great cardiac vein Ablation of VAs in the region of the left ventricular summit can successfully performed at the site of earliest activation from the GCV (Figure 4).3–5 Figure 4 View largeDownload slide Using this emulated biplane view (AP and LAO 30°) a safe distance to the diagonal branch can be demonstrated in the AP view while a safe distance to the left anterior descending artery is displayed in the LAO 30° view. Figure 4 View largeDownload slide Using this emulated biplane view (AP and LAO 30°) a safe distance to the diagonal branch can be demonstrated in the AP view while a safe distance to the left anterior descending artery is displayed in the LAO 30° view. However, in a significant proportion of patients this site is localized too close to the coronary vasculature and slight catheter movements within the coronary sinus are needed to find a safe catheter position.5,8 In this context, another advantage of the IIM is the possibility to simulate biplane angiography simply by providing two different planes in the main map viewer and the additional map viewer including the according angiograms. Using appropriate planes in the two Carto® viewers it is possible to quickly identify acceptable ablation sites (≥5 mm to the coronary arteries in at least one plane) and perform successful RF application even in sites slightly remote from the initial position (Figure 2). As already shown by our group and others another major limiting factor concerning procedural success remains inadequate power energy delivery.4,5 This is reflected well in the results of this study with maximal power applied as well as total power delivered being significantly lower in the GCV group. As the local activation times and CIs are comparable, this seems to be one plausible explanation for the lower acute success rates compared with the SOV. Technical limitations In this study as well in a previously published work from our and other groups,9,10 this technology has been proved to be robust with regard to map-shift or other technical disturbances which have not occurred during our procedures so far. Conclusion This feasibility study shows that IIM which has previously been shown to be easily integrated in the workflow of the Carto® 3 mapping system can be useful for ablation of focal VAs originating in the SOV and the distal GCV. In the setting of arrhythmias arising from these areas, the ability to directly merge the angiographic cine loop into the 3D-electro-anatomical map allows for real-time monitoring of the spatial relationship between the ablation catheter tip and the relevant coronary arteries. Conflict of interest: none declared. References 1 Yamada T, McElderry HT, Doppalapudi H, Murakami Y, Yoshida Y, Yoshida N et al.   Idiopathic ventricular arrhythmias originating from the aortic root prevalence, electrocardiographic and electrophysiologic characteristics, and results of radiofrequency catheter ablation. J Am Coll Cardiol  2008; 52: 139– 47. Google Scholar CrossRef Search ADS PubMed  2 Ouyang F, Fotuhi P, Ho SY, Hebe J, Volkmer M, Goya M et al.   Repetitive monomorphic ventricular tachycardia originating from the aortic sinus cusp: electrocardiographic characterization for guiding catheter ablation. J Am Coll Cardiol  2002; 39: 500– 8. 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All rights reserved. © The Author 2017. For permissions, please email: journals.permissions@oup.com.

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EuropaceOxford University Press

Published: Mar 1, 2018

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