Right ventricular outflow tract reconstruction using a polytetrafluoroethylene conduit in Ross patients

Right ventricular outflow tract reconstruction using a polytetrafluoroethylene conduit in Ross... Abstract OBJECTIVES The type of conduit used for right ventricular outflow tract (RVOT) reconstruction during the Ross procedure remains problematic because of the limited availability of pulmonary allografts and the unsatisfactory long-term results associated with the use of xenografts. Polytetrafluoroethylene (PTFE) conduits have been proposed as an alternative. This study evaluated the results of RVOT reconstruction using a PTFE conduit during the Ross procedure. METHODS Between 2007 and 2015, 28 patients underwent RVOT reconstruction using PTFE conduits. The mean age of the patients was 35.9 ± 18.1 (range 4–58) years. The total root replacement technique was used in all patients. The mean PTFE conduit size was 25.3 ± 2.3 mm. RESULTS The early mortality rate was 3.6% (1 patient). The mean follow-up duration was 48.5 ± 31.2 months; there were no late deaths. The transprosthetic gradients increased significantly over time. The conduit size was the only independent predictor of peak RVOT gradient progression (P = 0.02). None of the patients demonstrated significant RVOT regurgitation. One patient required an RVOT reoperation. CONCLUSIONS The PTFE conduit demonstrates acceptable haemodynamic results at the mid-term follow-up and could be considered as an alternative substitute for RVOT reconstruction during the Ross procedure. Ross operation, Right ventricular outflow tract reconstruction, Polytetrafluoroethylene conduits INTRODUCTION The Ross procedure is an alternative to mechanical prosthesis implantation that provides physiological haemodynamics and excellent long-term survival, while avoiding the need for anticoagulation and resulting in a minimal risk of thromboembolism [1–3]. Despite these advantages, the Ross procedure has a serious limitation in that it requires a double-valve intervention. Pulmonary allografts are the gold standard for right ventricular outflow tract (RVOT) reconstruction during the Ross procedure. However, the availability of allografts is limited. The use of xenografts for RVOT reconstruction remains controversial, especially in young patients [4, 5]. In some series, xenografts have demonstrated unsatisfactory long-term results [5, 6]. Therefore, polytetrafluoroethylene (PTFE) conduits have been proposed as an option for use during RVOT reconstruction [7, 8]. In this observational study, we evaluated the results of RVOT reconstruction using PTFE valved conduits during the Ross procedure. MATERIALS AND METHODS Patients Between January 2007 and December 2015, 28 consecutive patients underwent RVOT reconstruction using a PTFE valved conduit at our institute. Our institutional review board approved this study, and this report describes the retrospective analysis of the results. The mean age of the patients was 35.9 ± 18.1 (range 4–58) years, including 5 paediatric patients [median age 8.0 years, interquartile range (IQR) 6.0–8.5 years] and 23 adult patients (mean age 40.5 ± 11.1 years). RVOT reconstruction using a PTFE valved conduit was performed during the Ross procedure in 27 patients; 1 patient underwent PTFE conduit implantation during a reoperation (due to xenograft stenosis) 8 years after the initial Ross procedure. All operations were performed by the same surgeon. The presence of a primary aortic valve lesion was the main indication for surgery, in accordance with the European Society of Cardiology and the European Association for Cardio-Thoracic Surgery guidelines for the management of patients with valvular heart disease [9]. The contraindications for autograft implantation included connective tissue diseases, pulmonary valve anomalies, coronary artery disease, other valve pathologies requiring valve replacement and severe concomitant diseases. Aortic stenosis was found in 13 (46%), aortic insufficiency in 10 (36%) and 4 (14%) patients had mixed lesions. The preoperative patient characteristics are listed in Table 1. Table 1: Preoperative patient characteristics Number of patients 28 Age (years), mean ± SD 35.9 ± 18.1 Body surface area (m2), mean ± SD 1.68 ± 0.39 Sex, n (%)  Male 19 (68)  Female 9 (32) Aortic valve disease aetiology, n (%)  Bicuspid 19 (68)  Rheumatic 3 (11)  Endocarditis 5 (18) Aortic valve haemodynamic lesions, n (%)  Stenosis 13 (46)  Insufficiency 10 (36)  Mixed lesion 4 (14) Previous interventions, n (%)  Aortic valve repair 1 (4)  Ross procedure 1 (4) NYHA functional class, n (%)  II 16 (57)  III 12 (43) Left ventricular ejection fraction (%), mean ± SD 63.2 ± 11.6 Number of patients 28 Age (years), mean ± SD 35.9 ± 18.1 Body surface area (m2), mean ± SD 1.68 ± 0.39 Sex, n (%)  Male 19 (68)  Female 9 (32) Aortic valve disease aetiology, n (%)  Bicuspid 19 (68)  Rheumatic 3 (11)  Endocarditis 5 (18) Aortic valve haemodynamic lesions, n (%)  Stenosis 13 (46)  Insufficiency 10 (36)  Mixed lesion 4 (14) Previous interventions, n (%)  Aortic valve repair 1 (4)  Ross procedure 1 (4) NYHA functional class, n (%)  II 16 (57)  III 12 (43) Left ventricular ejection fraction (%), mean ± SD 63.2 ± 11.6 NYHA: New York Heart Association; SD: standard deviation. Table 1: Preoperative patient characteristics Number of patients 28 Age (years), mean ± SD 35.9 ± 18.1 Body surface area (m2), mean ± SD 1.68 ± 0.39 Sex, n (%)  Male 19 (68)  Female 9 (32) Aortic valve disease aetiology, n (%)  Bicuspid 19 (68)  Rheumatic 3 (11)  Endocarditis 5 (18) Aortic valve haemodynamic lesions, n (%)  Stenosis 13 (46)  Insufficiency 10 (36)  Mixed lesion 4 (14) Previous interventions, n (%)  Aortic valve repair 1 (4)  Ross procedure 1 (4) NYHA functional class, n (%)  II 16 (57)  III 12 (43) Left ventricular ejection fraction (%), mean ± SD 63.2 ± 11.6 Number of patients 28 Age (years), mean ± SD 35.9 ± 18.1 Body surface area (m2), mean ± SD 1.68 ± 0.39 Sex, n (%)  Male 19 (68)  Female 9 (32) Aortic valve disease aetiology, n (%)  Bicuspid 19 (68)  Rheumatic 3 (11)  Endocarditis 5 (18) Aortic valve haemodynamic lesions, n (%)  Stenosis 13 (46)  Insufficiency 10 (36)  Mixed lesion 4 (14) Previous interventions, n (%)  Aortic valve repair 1 (4)  Ross procedure 1 (4) NYHA functional class, n (%)  II 16 (57)  III 12 (43) Left ventricular ejection fraction (%), mean ± SD 63.2 ± 11.6 NYHA: New York Heart Association; SD: standard deviation. Conduit features RVOT was reconstructed using a commercial PTFE valved conduit (CardiaMed, Penza, Russia; Fig. 1) in all cases. The inflow and outflow components of the conduit were manufactured from PTFE vascular grafts (Ecoflone, St. Petersburg, Russia). The middle component containing 3 leaflets and sinuses was made from a 0.1-mm-thick PTFE membrane (Preclude; W. L. Gore & Associates, Newark, DE, USA). The different conduit components were assembled manually using PTFE sutures (Gore-Tex Sutures; W. L. Gore & Associates). The conduit sutures were sealed using silicone glue (Med-1511 Adhesive Silicone; Nusil Technology, Carpinteria, CA, USA). Figure 1: View largeDownload slide A polytetrafluoroethylene valved conduit. (A) External view. (B) A pattern of the conduit. Figure 1: View largeDownload slide A polytetrafluoroethylene valved conduit. (A) External view. (B) A pattern of the conduit. Operative technique Cardiopulmonary bypass followed a standard procedure involving aortic and bicaval cannulation combined with moderate hypothermia (33–34°C). Myocardial protection was achieved using antegrade cardioplegia (Custodiol, Dr Kohler Pharma, Alsbach-Hahnlein, Germany). The pulmonary autograft was implanted using the total root replacement technique in all patients as previously described [10]. In 2 patients with aortic root dilatation, external reinforcement of the pulmonary autograft was performed using a vascular graft. The mean PTFE conduit size was 25.3 ± 2.3 (range 20–27) mm. The choice of conduit size for adults was based on the distal portion of the pulmonary artery diameter and was as large as possible (25 or 27 mm). The choice of conduit size for paediatric patients was based on Z-value (median 1.12, IQR 0.75–1.37). The proximal tubular portion of the PTFE conduit was obliquely cut to adjust its size to match the RVOT diameter. Both the proximal and distal anastomoses were performed using continuous 5/0 PTFE sutures (Gore-Tex Sutures; Fig. 2). In most patients (n = 20; 71%), RVOT reconstruction was performed after cross-clamp removal to reduce the myocardial ischemia time. The operative characteristics are provided in Table 2. Table 2: Operative data Cardiopulmonary bypass time (min), mean ± SD 148.3 ± 29.1 Cross-clamp time (min), mean ± SD 122.3 ± 21.4 Concomitant procedures, n (%)  Mitral valve repair 2 (7)  Tricuspid valve repair 1 (4) RVOT reconstruction  Mean graft size (mm), mean ± SD 25.3 ± 2.3   20, n (%) 3 (11)   22, n (%) 1 (4)   23, n (%) 2 (7)   25, n (%) 8 (29)   27, n (%) 14 (50) Cardiopulmonary bypass time (min), mean ± SD 148.3 ± 29.1 Cross-clamp time (min), mean ± SD 122.3 ± 21.4 Concomitant procedures, n (%)  Mitral valve repair 2 (7)  Tricuspid valve repair 1 (4) RVOT reconstruction  Mean graft size (mm), mean ± SD 25.3 ± 2.3   20, n (%) 3 (11)   22, n (%) 1 (4)   23, n (%) 2 (7)   25, n (%) 8 (29)   27, n (%) 14 (50) RVOT: right ventricular outflow tract; SD: standard deviation. Table 2: Operative data Cardiopulmonary bypass time (min), mean ± SD 148.3 ± 29.1 Cross-clamp time (min), mean ± SD 122.3 ± 21.4 Concomitant procedures, n (%)  Mitral valve repair 2 (7)  Tricuspid valve repair 1 (4) RVOT reconstruction  Mean graft size (mm), mean ± SD 25.3 ± 2.3   20, n (%) 3 (11)   22, n (%) 1 (4)   23, n (%) 2 (7)   25, n (%) 8 (29)   27, n (%) 14 (50) Cardiopulmonary bypass time (min), mean ± SD 148.3 ± 29.1 Cross-clamp time (min), mean ± SD 122.3 ± 21.4 Concomitant procedures, n (%)  Mitral valve repair 2 (7)  Tricuspid valve repair 1 (4) RVOT reconstruction  Mean graft size (mm), mean ± SD 25.3 ± 2.3   20, n (%) 3 (11)   22, n (%) 1 (4)   23, n (%) 2 (7)   25, n (%) 8 (29)   27, n (%) 14 (50) RVOT: right ventricular outflow tract; SD: standard deviation. Figure 2: View largeDownload slide Right ventricular outflow tract reconstruction using a polytetrafluoroethylene valved conduit during the Ross procedure. The pulmonary autograft and ascending aorta are wrapped using a Dacron vascular prosthesis. Figure 2: View largeDownload slide Right ventricular outflow tract reconstruction using a polytetrafluoroethylene valved conduit during the Ross procedure. The pulmonary autograft and ascending aorta are wrapped using a Dacron vascular prosthesis. Postoperative management Oral anticoagulants were prescribed for 3 months postoperatively and were replaced with low-dose aspirin in patients with sinus rhythm documented by 24-h Holter monitoring. Postoperative evaluation Each patient underwent transoesophageal echocardiography (Philips ie33, Philips Healthcare, Cleveland, OH, USA or Vivid 7, General Electric Healthcare, Little Chalfont, UK) to evaluate the autograft and the right-sided graft function, after being weaned off cardiopulmonary bypass. Transthoracic echocardiography was performed before discharge from the hospital. The transvalvular pulmonary gradients were measured using continuous-wave Doppler ultrasound that employed the simplified Bernoulli equation. PTFE conduit regurgitation severity was evaluated using the colour flow Doppler, according to the guidelines of the European Association of Echocardiography [11]; the regurgitation was graded as none/trivial, mild, moderate or severe. The right ventricle systolic function was estimated by measuring the fractional area change from the apical 4-chamber view. After discharge, follow-up examinations were scheduled annually. If a patient was unable to attend an annual clinic visit, a telephone survey was performed. Echocardiograms obtained from external physicians were reanalysed at our institute by an experienced sonographer. Magnetic resonance imaging (MRI) was performed (Philips Achieva 1.5 T, Philips Healthcare) in 5 (18%) patients to estimate conduit leaflets mobility and haemodynamic characteristics. Eight (29%) patients underwent computed tomography (CT) scanning (Toshiba Aquilion One 320 slice CT, Toshiba, Tokyo, Japan) to assess conduit calcification, deformation and stenosis. The period between the time of surgery and each event or the end of the follow-up period constituted a separate observation. The follow-up period ended in April 2017. Postoperative events were classified according to the 2008 Society of Thoracic Surgeons/American Association for Thoracic Surgery/European Association for Cardio-Thoracic Surgery guidelines [12]. Early mortality was defined as death due to any cause occurring in the hospital or within 30 days of the surgery; late mortality was defined as death occurring after that period. RVOT conduit dysfunction was defined as a peak systolic gradient of >40 mmHg or the presence of moderate to severe conduit valve insufficiency. Statistical analysis Statistical analysis was performed using Stata, version 13.0 (StataCorp, College Station, TX, USA). Continuous data are presented as mean ± standard deviation or as median and IQR (25th–75th percentile). Categorical data are described as absolute numbers and relative frequencies. The 2 groups were compared using the Wilcoxon matched-pairs signed-rank test. McNemar’s test was used to compare 2 groups of categorical data. The Kaplan–Meier method was used to evaluate survival, which is presented as 95% confidence intervals. A longitudinal mixed-effects linear regression was used to validate RVOT gradient predictors over time. The analysis included factors such as age, sex, body surface area, aortic valve morphology (bicuspid or tricuspid), aortic valve lesion (stenosis or insufficiency), prior operations and RVOT conduit size as fixed effects; the unique patient identification number was used as a random effect. Two-sided P-values <0.05 were considered statistically significant. RESULTS Among the study patients, the early mortality rate was 3.6% (1 patient). The early mortality was caused by heart failure due to myocardial infarction and was not associated with the use of the PTFE conduit. There were no cases of reoperation due to bleeding. The mean follow-up duration was 48.5 ± 31.2 months (range 6–120 months) and was 100% complete (27 patients). There were no late deaths. The survival rate at 5 years was 96.3% (95% confidence interval 76.5–99.5%). At the final follow-up, 15 (56%) patients were classified as the New York Heart Association (NYHA) functional Class I and 12 (44%) as Class II. One (4%) patient had paroxysmal atrial fibrillation at the final follow-up and continued warfarin treatment. There were no cases of infective endocarditis of the autograft or PTFE conduit nor were there cases of thromboembolisms or major haemorrhagic events during the follow-up period. At discharge, the peak and mean pressure gradients across the conduit were 11.6 ± 4.9 and 6.5 ± 3.1 mmHg, respectively. Twenty-six (96%) patients had trace or no RVOT regurgitation; 1 (4%) patient had mild regurgitation. Over time, a gradual increase in the transprosthetic gradient was observed (Fig. 3). At the last follow-up, the peak and mean pressure gradients were significantly higher than those at discharge, whereas the RVOT regurgitation grades were similar (Table 3). Longitudinal mixed-effects linear modelling revealed that conduit size diameter (P = 0.02) was the only predictor of peak RVOT gradient progression (Table 4). None of the patients had right ventricular dysfunction or severe tricuspid regurgitation according to transthoracic echocardiography at follow-up. Table 3: Echocardiography results Variables At discharge (n = 27) At last follow-up (n = 27) P-value Left ventricular ejection fraction (%), mean ± SD 58.2 ± 7.6 61.9 ± 6.2 0.32 RV FAC (%), mean ± SD 42.1 ± 7.1 40.3 ± 6.8 0.23 RVOT regurgitation, n (%)  None/trivial 26 (96) 24 (89) 0.89  Mild 1 (4) 3 (11) 0.62  Moderate/severe 0 0 RVOT gradient (mmHg), mean ± SD  Mean 6.5 ± 3.1 11.9 ± 6.7 <0.001  Peak 11.6 ± 4.9 21.1 ± 9.6 <0.001 Tricuspid regurgitation, n (%)  None/trivial 21 (78) 17 (63) 0.63  Mild 6 (22) 9 (33) 0.61  Moderate 0 1 (4) 1.0 Variables At discharge (n = 27) At last follow-up (n = 27) P-value Left ventricular ejection fraction (%), mean ± SD 58.2 ± 7.6 61.9 ± 6.2 0.32 RV FAC (%), mean ± SD 42.1 ± 7.1 40.3 ± 6.8 0.23 RVOT regurgitation, n (%)  None/trivial 26 (96) 24 (89) 0.89  Mild 1 (4) 3 (11) 0.62  Moderate/severe 0 0 RVOT gradient (mmHg), mean ± SD  Mean 6.5 ± 3.1 11.9 ± 6.7 <0.001  Peak 11.6 ± 4.9 21.1 ± 9.6 <0.001 Tricuspid regurgitation, n (%)  None/trivial 21 (78) 17 (63) 0.63  Mild 6 (22) 9 (33) 0.61  Moderate 0 1 (4) 1.0 FAC: fractional area change; RV: right ventricle; RVOT: right ventricular outflow tract; SD: standard deviation. Table 3: Echocardiography results Variables At discharge (n = 27) At last follow-up (n = 27) P-value Left ventricular ejection fraction (%), mean ± SD 58.2 ± 7.6 61.9 ± 6.2 0.32 RV FAC (%), mean ± SD 42.1 ± 7.1 40.3 ± 6.8 0.23 RVOT regurgitation, n (%)  None/trivial 26 (96) 24 (89) 0.89  Mild 1 (4) 3 (11) 0.62  Moderate/severe 0 0 RVOT gradient (mmHg), mean ± SD  Mean 6.5 ± 3.1 11.9 ± 6.7 <0.001  Peak 11.6 ± 4.9 21.1 ± 9.6 <0.001 Tricuspid regurgitation, n (%)  None/trivial 21 (78) 17 (63) 0.63  Mild 6 (22) 9 (33) 0.61  Moderate 0 1 (4) 1.0 Variables At discharge (n = 27) At last follow-up (n = 27) P-value Left ventricular ejection fraction (%), mean ± SD 58.2 ± 7.6 61.9 ± 6.2 0.32 RV FAC (%), mean ± SD 42.1 ± 7.1 40.3 ± 6.8 0.23 RVOT regurgitation, n (%)  None/trivial 26 (96) 24 (89) 0.89  Mild 1 (4) 3 (11) 0.62  Moderate/severe 0 0 RVOT gradient (mmHg), mean ± SD  Mean 6.5 ± 3.1 11.9 ± 6.7 <0.001  Peak 11.6 ± 4.9 21.1 ± 9.6 <0.001 Tricuspid regurgitation, n (%)  None/trivial 21 (78) 17 (63) 0.63  Mild 6 (22) 9 (33) 0.61  Moderate 0 1 (4) 1.0 FAC: fractional area change; RV: right ventricle; RVOT: right ventricular outflow tract; SD: standard deviation. Table 4: The change in the peak pressure gradient across the polytetrafluoroethylene conduit (longitudinal mixed-effects linear model) Risk factor Coefficient SE P-value Sex (men) 3.95 2.20 0.07 Age −0.06 0.09 0.48 RVOT conduit size −1.51 0.65 0.02 Previous operation 1.02 4.14 0.81 Aortic valve lesion (AS) −1.16 2.20 0.60 Bicuspid aortic valve 1.69 2.70 0.53 Risk factor Coefficient SE P-value Sex (men) 3.95 2.20 0.07 Age −0.06 0.09 0.48 RVOT conduit size −1.51 0.65 0.02 Previous operation 1.02 4.14 0.81 Aortic valve lesion (AS) −1.16 2.20 0.60 Bicuspid aortic valve 1.69 2.70 0.53 AS: aortic stenosis; RVOT: right ventricular outflow tract; SE: standard error. Table 4: The change in the peak pressure gradient across the polytetrafluoroethylene conduit (longitudinal mixed-effects linear model) Risk factor Coefficient SE P-value Sex (men) 3.95 2.20 0.07 Age −0.06 0.09 0.48 RVOT conduit size −1.51 0.65 0.02 Previous operation 1.02 4.14 0.81 Aortic valve lesion (AS) −1.16 2.20 0.60 Bicuspid aortic valve 1.69 2.70 0.53 Risk factor Coefficient SE P-value Sex (men) 3.95 2.20 0.07 Age −0.06 0.09 0.48 RVOT conduit size −1.51 0.65 0.02 Previous operation 1.02 4.14 0.81 Aortic valve lesion (AS) −1.16 2.20 0.60 Bicuspid aortic valve 1.69 2.70 0.53 AS: aortic stenosis; RVOT: right ventricular outflow tract; SE: standard error. Video 1 Early postoperative magnetic resonance imaging of the polytetrafluoroethylene valved conduit in the pulmonary artery position. Video 1 Early postoperative magnetic resonance imaging of the polytetrafluoroethylene valved conduit in the pulmonary artery position. Close Video 2 Computed tomography angiography 5 years after surgery. Three-dimensional reconstruction of the polytetrafluoroethylene valved conduit in the pulmonary artery position. Video 2 Computed tomography angiography 5 years after surgery. Three-dimensional reconstruction of the polytetrafluoroethylene valved conduit in the pulmonary artery position. Close Figure 3: View largeDownload slide The peak pressure gradient across the polytetrafluoroethylene valved conduit over time. Box plots depict medians, interquartile ranges and non-outlier ranges. N: number of patients. Figure 3: View largeDownload slide The peak pressure gradient across the polytetrafluoroethylene valved conduit over time. Box plots depict medians, interquartile ranges and non-outlier ranges. N: number of patients. In 1 case, an RVOT reoperation was required 7 years after the initial Ross procedure due to a patient–prosthesis mismatch (the transvalvular gradient increased to 70 mmHg). The patient underwent the original operation at 4 years of age when a 20-mm PTFE conduit was implanted. There was no conduit calcification, thrombosis or intimal hyperplasia noted when the conduit was revised. A 26-mm cryopreserved pulmonary allograft was implanted during the redo procedure. This patient also had severe aortic regurgitation, due to autograft dilatation, necessitating autograft valve replacement with a mechanical prosthesis. The procedure and postoperative period were uncomplicated. Follow-up MRI at 58.0 (IQR 36.0–100.0) months revealed mobile conduit leaflets that completely opened during systole and closed during diastole. There was no evidence of anything more significant than mild regurgitation (see Video 1). The median CT follow-up period was 50.0 (IQR 30.0–100.0) months. CT showed no calcification of the leaflets or vascular grafts and no conduit deformations or stenosis (see Video 2). DISCUSSION The Ross procedure is an attractive alternative to prosthetic aortic valve replacement with advantages that include a minimal thromboembolism risk and anticoagulation avoidance. Studies have shown that the incidence of valve-related complications after the Ross procedure is lower than that after mechanical prosthesis implantation [1, 13]. Excellent long-term survival after the Ross procedure has also been demonstrated, exceeding that of patients with mechanical prostheses [1]. Nevertheless, the Ross procedure is not widely used. One reason for this is the need for a double-valve intervention and an increased risk of repeat operations due to RVOT graft degeneration. At our institute, the Ross procedure is offered as an alternative surgical treatment for aortic valve disease to all children and other patients with an active lifestyle who desire to avoid a lifelong anticoagulation therapy. The cryopreserved pulmonary allograft is the most widely used graft for RVOT reconstruction and several studies have demonstrated good late results. In the German Ross Registry (comprising 1779 adult patients), freedom from reoperations involving pulmonary allografts was 92.3% at 15 years [14]. David et al. [3] also reported a freedom from allograft reoperation of 93.6% at 20 years. In paediatric patients, freedom from allograft reoperation after the Ross procedure is less and varies between studies, depending on the age of the patient population. According to the Italian Paediatric Ross Registry (305 patients), freedom from allograft reintervention at 15 years is 82% [15]. In the German Ross Registry (263 paediatric patients), the rate was 79% at 12 years [16]. The main mechanism of bioprosthesis degeneration involves an immune response to donor cell antigens. To reduce immunogenicity and improve durability, decellularized pulmonary allografts were proposed. In a study by Costa et al. [17], decellularized fresh allografts demonstrated lower rates of structural valve degeneration and greater freedom from reoperations than did cryopreserved allografts in patients undergoing the Ross procedure. Several other studies have also demonstrated that freedom from RVOT conduit dysfunction in the paediatric population (Ross and non-Ross patients) was significantly worse when conventional cryopreserved pulmonary allografts were used in comparison with decellularized allografts [18, 19]. The main disadvantage of allografts is their limited availability. Thus, alternative grafts for RVOT reconstruction have been proposed such as porcine root grafts, pericardial xenografts, bovine jugular venous conduits and PTFE conduits. Several studies reported promising results using different xenografts during the Ross procedure. Hechadi et al. [4] did not find differences between porcine root grafts (17 patients) and pulmonary allografts (37 patients) in terms of haemodynamic performance at a mean follow-up of 8.2 years; however, the calcific degeneration progressed more rapidly in the xenografts. Juthier et al. [20] also reported good early and mid-term results using different stent-less porcine root models in 61 patients. They concluded that porcine aortic root grafts are an acceptable alternative for RVOT reconstruction when pulmonary homografts are unavailable. In a meta-analysis that included 137 patients (7 studies) undergoing RVOT reconstruction with porcine root grafts during the Ross procedure, the rate of structural valve deterioration was 7.1% at 45 months of follow-up, and the rate of reintervention was 2.1% [21]. However, different xenograft results have also been reported [5, 6]. Miskovic et al. [5] and Weimar et al. [6] reported that the durability of porcine aortic root grafts in the RVOT position was unacceptably low. In the German Ross Registry, patients with bioprostheses (149 patients) implanted in RVOT had significantly higher risk of reintervention due to pulmonary conduit dysfunction than did those receiving allografts [14]. Bovine jugular venous conduits have also been proposed for paediatric RVOT reconstruction, showing 10-year freedom from reintervention of 60–70% depending on the conduit size and patient age [22]. Previously, we presented the results of using different xenografts for RVOT reconstruction during the Ross procedure [10]. The haemodynamic performance and failure rates of all types of xenografts were worse than those for allografts. In contrast, pericardial xenografts showed acceptable results in older patients [23]. Thus, we believe that the use of xenografts during the Ross procedure should be restricted, especially in younger patients. All biological grafts (pulmonary allografts and xenografts) are susceptible to deterioration caused by immunological factors. Therefore, the use of synthetic grafts for RVOT reconstruction looks attractive. Different types of handmade PTFE conduits have been proposed [8, 24, 25]. Microporous structure of PTFE impedes cellular penetration, inflammation and calcification; therefore, these conduits have good biocompatibility and low antigenicity and demonstrate resistance to degeneration and calcification [22]. Histological examinations of explanted PTFE grafts have shown that over time, their surfaces are covered by thin collagenous tissue with partial endothelialization, whereas the leaflets, which have smaller micropores, remained intact without cellular penetration or evidence of calcification [22]. The first application of PTFE for RVOT reconstruction was performed by Yamagishi et al. [26] in patients with tetralogy of Fallot. A transannular pericardial patch with a bicuspid or unicuspid PTFE valve was used. The same authors proposed a combined autologous conduit consisting of a posterior aortic wall, with non-coronary cusp, and a patch with a bicuspid PTFE valve for RVOT reconstruction during the Ross procedure in paediatric patients. This technique allowed the conduit to grow as the patients aged [27]. A serious disadvantage of this technique was the high rate of transvalvular regurgitation caused by the cusps getting stuck in the open position. Expanded PTFE conduits and patches with bulging sinuses created by heating were proposed to generate a vortex flow between the leaflets and the graft, leading to physiological valve closing [7]. Nevertheless, there are contradictory data on the thermal treatment effect on the mechanical properties and morphological characteristics of PTFE material [28, 29]. A multicentre study in Japan, including 725 patients with congenital heart defects (right ventricular outflow hypoplasia or atresia) and 69 Ross patients, revealed 10-year freedom from reoperation of 95.4% and 92.3% for the expanded PTFE conduits and patches, respectively; however, the mean follow-up was only 3.6 years [30]. Takabayashi et al. [8] reported other types of handmade trileaflet PTFE conduits created intraoperatively using PTFE sheets and vascular grafts. Acceptable haemodynamic results were observed at the mid-term follow-up in 11 patients undergoing RVOT reconstruction with this type of conduit during the Ross procedure. Moreover, other types of handmade PTFE conduits were investigated with encouraging early and mid-term results [25]. Thus, the follow-up periods for all PTFE conduits described in the literature are relatively short. Moreover, the disadvantages of a handmade prosthesis include additional intraoperative time and precise technical requirement needed to fabricate them and the absence of haemodynamic testing before implantation, possibly leading to bleeding or early conduit failure. In this study, we presented our experience with the commercial PTFE conduits for RVOT reconstruction. Thus, all conduits were tested by a manufacturer using a pulse duplicator and included assessment of transprosthetic gradient, effective orifice area and absence of leakage. Our study revealed that the PTFE valved conduit demonstrates acceptable haemodynamic parameters at mid-term follow-up. Echocardiography, CT and MRI examinations did not identify calcification, deformation or stenosis of the conduits nor was significant postoperative regurgitation identified. Moreover, we found that conduit size affects mid-term haemodynamic results. Smaller-sized conduits were related to higher transprosthetic gradients at follow-up. Therefore, the largest possible conduit should be used to prevent conduit stenosis. The choice of the optimal PTFE conduit size for RVOT reconstruction differs between studies. Miyazaki et al. [30] were guided by Rowlatt’s formula; the Z-score calculation was used in other studies [24]. However, most authors are in complete agreement with conduit oversizing to achieve better results. We also used some oversizing during RVOT reconstruction; however, we did not perform special calculations. Most of our adult patients received 27–29-mm conduit sizes when allografts or xenografts are used. We believe that the rule is also feasible for PTFE conduits. However, the 27-mm diameter is the largest available size for this graft type, which is restricted by the maximum available PTFE vascular graft size. Nevertheless, the mean body surface area of the study group was relatively small, which is why we did not have any cases of patient–prosthesis mismatch and obtained acceptable haemodynamic results at follow-up. Limitations This study also has some limitations. It was a retrospective single-centre study involving relatively few patients. The mean follow-up period was also relatively short, and long-term follow-up results are needed. In addition, postoperative CT and MRI were not performed on the whole study population due to distant location of some patients from the clinic. Moreover, this study did not compare the use of PTFE valved conduit with other graft types for RVOT reconstruction. CONCLUSION The results of this study show that the PTFE conduit could be considered as an alternative substitute for RVOT reconstruction during the Ross procedure. Conflict of interest: none declared. REFERENCES 1 Andreas M , Wiedemann D , Seebacher G , Rath C , Aref T , Rosenhek R et al. The Ross procedure offers excellent survival compared with mechanical aortic valve replacement in a real-world setting . Eur J Cardiothorac Surg 2014 ; 46 : 409 – 13 . Google Scholar CrossRef Search ADS PubMed 2 Weimar T , Charitos EI , Liebrich M , Roser D , Tzanavaros I , Doll N et al. Quo vadis pulmonary autograft—the ross procedure in its second decade: a single-center experience in 645 patients . Ann Thorac Surg 2014 ; 97 : 167 – 74 . Google Scholar CrossRef Search ADS PubMed 3 David TE , David C , Woo A , Manlhiot C. The Ross procedure: outcomes at 20 years . J Thorac Cardiovasc Surg 2014 ; 147 : 85 – 93 . Google Scholar CrossRef Search ADS PubMed 4 Hechadi J , Gerber BL , Coche E , Melchior J , Jashari R , Glineur D et al. Stentless xenografts as an alternative to pulmonary homografts in the Ross operation . Eur J Cardiothorac Surg 2013 ; 44 : e32 – 9 . Google Scholar CrossRef Search ADS PubMed 5 Miskovic A , Monsefi N , Doss M , Özaslan F , Karimian A , Moritz A. Comparison between homografts and Freestyle® bioprosthesis for right ventricular outflow tract replacement in Ross procedures . Eur J Cardiothorac Surg 2012 ; 42 : 927 – 33 . Google Scholar CrossRef Search ADS PubMed 6 Weimar T , Roser D , Liebrich M , Horke A , Doll N , Hemmer WB. Strategies for biological heart valve replacement: stentless xenografts fail to evolve into an alternative pulmonary valve substitute in a Ross procedure . Biotechnol J 2013 ; 8 : 345 – 51 . Google Scholar CrossRef Search ADS PubMed 7 Miyazaki T , Yamagishi M , Nakashima A , Fukae K , Nakano T , Yaku H et al. Expanded polytetrafluoroethylene valved conduit and patch with bulging sinuses in right ventricular outflow tract reconstruction . J Thorac Cardiovasc Surg 2007 ; 134 : 327 – 32 . Google Scholar CrossRef Search ADS PubMed 8 Takabayashi S , Kado H , Shiokawa Y , Fukae K , Nakano T. Modified Ross procedure using a conduit with a synthetic valve . Eur J Cardiothorac Surg 2004 ; 26 : 1087 – 91 . Google Scholar CrossRef Search ADS PubMed 9 Falk V , Baumgartner H , Bax JJ , De Bonis M , Hamm C , Holm PJ et al. 2017 ESC/EACTS Guidelines for the management of valvular heart disease: the Task Force for the Management of Valvular Heart Disease of the European Society of Cardiology (ESC) and the European Association for Cardio-Thoracic Surgery (EACTS) . Eur J Cardiothorac Surg 2017 ; 52 : 616 – 64 . Google Scholar CrossRef Search ADS PubMed 10 Karaskov A , Sharifulin R , Zheleznev S , Demin I , Lenko E , Bogachev-Prokophiev A. Results of the Ross procedure in adults: a single-centre experience of 741 operations . Eur J Cardiothorac Surg 2016 ; 49 : e97 – 104 . Google Scholar CrossRef Search ADS PubMed 11 Lancellott P , Tribouilloy C , Hagendorff A , Moura L , Popescu BA , Agricola E et al. European Association of Echocardiography recommendations for the assessment of valvular regurgitation. Part 1: aortic and pulmonary regurgitation (native valve disease) . Eur J Echocardiogr 2010 ; 11 : 223 – 44 . Google Scholar CrossRef Search ADS PubMed 12 Akins CW , Miller DC , Turina MI , Kouchoukos NT , Blackstone EH , Grunkemeier GL et al. Guidelines for reporting mortality and morbidity after cardiac valve interventions . J Thorac Cardiovasc Surg 2008 ; 135 : 732 – 8 . Google Scholar CrossRef Search ADS PubMed 13 Miskovic A , Monsefi N , Karimian-Tabrizi A , Zierer A , Moritz A. A 17-year, single-centre experience with the Ross procedure: fulfilling the promise of a durable option without anticoagulation? Eur J Cardiothorac Surg 2016 ; 49 : 514 – 19 . Google Scholar CrossRef Search ADS PubMed 14 Sievers HH , Stierle U , Charitos EI , Takkenberg JJ , Hörer J , Lange R et al. A multicentre evaluation of the autograft procedure for young patients undergoing aortic valve replacement: update on the German Ross Registry . Eur J Cardiothorac Surg 2016 ; 49 : 212 – 18 . 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Google Scholar PubMed 22 Yamamoto Y , Yamagishi M , Miyazaki T. Current status of right ventricular outflow tract reconstruction: complete translation of a review article originally published in Kyobu Geka 2014;67:65–77 . Gen Thorac Cardiovasc Surg 2015 ; 63 : 131 – 41 . Google Scholar CrossRef Search ADS PubMed 23 Karaskov A , Bogachev-Prokophiev A , Sharifulin R , Zheleznev S , Demin I , Pivkin A et al. Right ventricular outflow tract replacement with xenografts in Ross patients older than 60 years . Ann Thorac Surg 2016 ; 101 : 2252 – 9 . Google Scholar CrossRef Search ADS PubMed 24 Yamashita E , Yamagishi M , Miyazaki T , Maeda Y , Yamamoto Y , Kato N et al. Smaller-sized expanded polytetrafluoroethylene conduits with a fan-shaped valve and bulging sinuses for right ventricular outflow tract reconstruction . Ann Thorac Surg 2016 ; 102 : 1336 – 44 . Google Scholar CrossRef Search ADS PubMed 25 Kim H , Sung SC , Chang YH , Lee HD , Park JA. A new simplified technique for making tricuspid expanded polytetrafluoroethylene valved conduit for right ventricular outflow reconstruction . Ann Thorac Surg 2013 ; 95 : e131 – 3 . Google Scholar CrossRef Search ADS PubMed 26 Yamagishi M , Kurosawa H. Outflow reconstruction of tetralogy of Fallot using a Gore-Tex valve . Ann Thorac Surg 1993 ; 56 : 1414. Google Scholar CrossRef Search ADS PubMed 27 Yamagishi M , Emmoto T , Wada Y , Oka T. Pulmonary reconstruction in the Ross procedure: combined autologous aortic and polytetrafluoroethylene valve . J Thorac Cardiovasc Surg 1998 ; 116 : 1076 – 7 . Google Scholar CrossRef Search ADS PubMed 28 Shinkawa T , Tang X , Gossett JM , Mustafa T , Hategekimana F , Watanabe F et al. Valved polytetrafluoroethylene conduits for right ventricular outflow tract reconstruction . Ann Thorac Surg 2015 ; 100 : 129 – 37 . Google Scholar CrossRef Search ADS PubMed 29 Zhu G , Yuan Q , Hock Yeo J , Nakao M. Thermal treatment of expanded polytetrafluoroethylene (ePTFE) membranes for reconstruction of a valved conduit . BME 2015 ; 26 : S55 – 62 . Google Scholar CrossRef Search ADS 30 Miyazaki T , Yamagishi M , Maeda Y , Yamamoto Y , Taniguchi S , Sasaki Y et al. Expanded polytetrafluoroethylene conduits and patches with bulging sinuses and fan-shaped valves in right ventricular outflow tract reconstruction: multicentre study in Japan . J Thorac Cardiovasc Surg 2011 ; 142 : 1122 – 9 . Google Scholar CrossRef Search ADS PubMed © The Author(s) 2018. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png European Journal of Cardio-Thoracic Surgery Oxford University Press

Right ventricular outflow tract reconstruction using a polytetrafluoroethylene conduit in Ross patients

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Oxford University Press
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© The Author(s) 2018. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.
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1010-7940
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1873-734X
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10.1093/ejcts/ezy128
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Abstract

Abstract OBJECTIVES The type of conduit used for right ventricular outflow tract (RVOT) reconstruction during the Ross procedure remains problematic because of the limited availability of pulmonary allografts and the unsatisfactory long-term results associated with the use of xenografts. Polytetrafluoroethylene (PTFE) conduits have been proposed as an alternative. This study evaluated the results of RVOT reconstruction using a PTFE conduit during the Ross procedure. METHODS Between 2007 and 2015, 28 patients underwent RVOT reconstruction using PTFE conduits. The mean age of the patients was 35.9 ± 18.1 (range 4–58) years. The total root replacement technique was used in all patients. The mean PTFE conduit size was 25.3 ± 2.3 mm. RESULTS The early mortality rate was 3.6% (1 patient). The mean follow-up duration was 48.5 ± 31.2 months; there were no late deaths. The transprosthetic gradients increased significantly over time. The conduit size was the only independent predictor of peak RVOT gradient progression (P = 0.02). None of the patients demonstrated significant RVOT regurgitation. One patient required an RVOT reoperation. CONCLUSIONS The PTFE conduit demonstrates acceptable haemodynamic results at the mid-term follow-up and could be considered as an alternative substitute for RVOT reconstruction during the Ross procedure. Ross operation, Right ventricular outflow tract reconstruction, Polytetrafluoroethylene conduits INTRODUCTION The Ross procedure is an alternative to mechanical prosthesis implantation that provides physiological haemodynamics and excellent long-term survival, while avoiding the need for anticoagulation and resulting in a minimal risk of thromboembolism [1–3]. Despite these advantages, the Ross procedure has a serious limitation in that it requires a double-valve intervention. Pulmonary allografts are the gold standard for right ventricular outflow tract (RVOT) reconstruction during the Ross procedure. However, the availability of allografts is limited. The use of xenografts for RVOT reconstruction remains controversial, especially in young patients [4, 5]. In some series, xenografts have demonstrated unsatisfactory long-term results [5, 6]. Therefore, polytetrafluoroethylene (PTFE) conduits have been proposed as an option for use during RVOT reconstruction [7, 8]. In this observational study, we evaluated the results of RVOT reconstruction using PTFE valved conduits during the Ross procedure. MATERIALS AND METHODS Patients Between January 2007 and December 2015, 28 consecutive patients underwent RVOT reconstruction using a PTFE valved conduit at our institute. Our institutional review board approved this study, and this report describes the retrospective analysis of the results. The mean age of the patients was 35.9 ± 18.1 (range 4–58) years, including 5 paediatric patients [median age 8.0 years, interquartile range (IQR) 6.0–8.5 years] and 23 adult patients (mean age 40.5 ± 11.1 years). RVOT reconstruction using a PTFE valved conduit was performed during the Ross procedure in 27 patients; 1 patient underwent PTFE conduit implantation during a reoperation (due to xenograft stenosis) 8 years after the initial Ross procedure. All operations were performed by the same surgeon. The presence of a primary aortic valve lesion was the main indication for surgery, in accordance with the European Society of Cardiology and the European Association for Cardio-Thoracic Surgery guidelines for the management of patients with valvular heart disease [9]. The contraindications for autograft implantation included connective tissue diseases, pulmonary valve anomalies, coronary artery disease, other valve pathologies requiring valve replacement and severe concomitant diseases. Aortic stenosis was found in 13 (46%), aortic insufficiency in 10 (36%) and 4 (14%) patients had mixed lesions. The preoperative patient characteristics are listed in Table 1. Table 1: Preoperative patient characteristics Number of patients 28 Age (years), mean ± SD 35.9 ± 18.1 Body surface area (m2), mean ± SD 1.68 ± 0.39 Sex, n (%)  Male 19 (68)  Female 9 (32) Aortic valve disease aetiology, n (%)  Bicuspid 19 (68)  Rheumatic 3 (11)  Endocarditis 5 (18) Aortic valve haemodynamic lesions, n (%)  Stenosis 13 (46)  Insufficiency 10 (36)  Mixed lesion 4 (14) Previous interventions, n (%)  Aortic valve repair 1 (4)  Ross procedure 1 (4) NYHA functional class, n (%)  II 16 (57)  III 12 (43) Left ventricular ejection fraction (%), mean ± SD 63.2 ± 11.6 Number of patients 28 Age (years), mean ± SD 35.9 ± 18.1 Body surface area (m2), mean ± SD 1.68 ± 0.39 Sex, n (%)  Male 19 (68)  Female 9 (32) Aortic valve disease aetiology, n (%)  Bicuspid 19 (68)  Rheumatic 3 (11)  Endocarditis 5 (18) Aortic valve haemodynamic lesions, n (%)  Stenosis 13 (46)  Insufficiency 10 (36)  Mixed lesion 4 (14) Previous interventions, n (%)  Aortic valve repair 1 (4)  Ross procedure 1 (4) NYHA functional class, n (%)  II 16 (57)  III 12 (43) Left ventricular ejection fraction (%), mean ± SD 63.2 ± 11.6 NYHA: New York Heart Association; SD: standard deviation. Table 1: Preoperative patient characteristics Number of patients 28 Age (years), mean ± SD 35.9 ± 18.1 Body surface area (m2), mean ± SD 1.68 ± 0.39 Sex, n (%)  Male 19 (68)  Female 9 (32) Aortic valve disease aetiology, n (%)  Bicuspid 19 (68)  Rheumatic 3 (11)  Endocarditis 5 (18) Aortic valve haemodynamic lesions, n (%)  Stenosis 13 (46)  Insufficiency 10 (36)  Mixed lesion 4 (14) Previous interventions, n (%)  Aortic valve repair 1 (4)  Ross procedure 1 (4) NYHA functional class, n (%)  II 16 (57)  III 12 (43) Left ventricular ejection fraction (%), mean ± SD 63.2 ± 11.6 Number of patients 28 Age (years), mean ± SD 35.9 ± 18.1 Body surface area (m2), mean ± SD 1.68 ± 0.39 Sex, n (%)  Male 19 (68)  Female 9 (32) Aortic valve disease aetiology, n (%)  Bicuspid 19 (68)  Rheumatic 3 (11)  Endocarditis 5 (18) Aortic valve haemodynamic lesions, n (%)  Stenosis 13 (46)  Insufficiency 10 (36)  Mixed lesion 4 (14) Previous interventions, n (%)  Aortic valve repair 1 (4)  Ross procedure 1 (4) NYHA functional class, n (%)  II 16 (57)  III 12 (43) Left ventricular ejection fraction (%), mean ± SD 63.2 ± 11.6 NYHA: New York Heart Association; SD: standard deviation. Conduit features RVOT was reconstructed using a commercial PTFE valved conduit (CardiaMed, Penza, Russia; Fig. 1) in all cases. The inflow and outflow components of the conduit were manufactured from PTFE vascular grafts (Ecoflone, St. Petersburg, Russia). The middle component containing 3 leaflets and sinuses was made from a 0.1-mm-thick PTFE membrane (Preclude; W. L. Gore & Associates, Newark, DE, USA). The different conduit components were assembled manually using PTFE sutures (Gore-Tex Sutures; W. L. Gore & Associates). The conduit sutures were sealed using silicone glue (Med-1511 Adhesive Silicone; Nusil Technology, Carpinteria, CA, USA). Figure 1: View largeDownload slide A polytetrafluoroethylene valved conduit. (A) External view. (B) A pattern of the conduit. Figure 1: View largeDownload slide A polytetrafluoroethylene valved conduit. (A) External view. (B) A pattern of the conduit. Operative technique Cardiopulmonary bypass followed a standard procedure involving aortic and bicaval cannulation combined with moderate hypothermia (33–34°C). Myocardial protection was achieved using antegrade cardioplegia (Custodiol, Dr Kohler Pharma, Alsbach-Hahnlein, Germany). The pulmonary autograft was implanted using the total root replacement technique in all patients as previously described [10]. In 2 patients with aortic root dilatation, external reinforcement of the pulmonary autograft was performed using a vascular graft. The mean PTFE conduit size was 25.3 ± 2.3 (range 20–27) mm. The choice of conduit size for adults was based on the distal portion of the pulmonary artery diameter and was as large as possible (25 or 27 mm). The choice of conduit size for paediatric patients was based on Z-value (median 1.12, IQR 0.75–1.37). The proximal tubular portion of the PTFE conduit was obliquely cut to adjust its size to match the RVOT diameter. Both the proximal and distal anastomoses were performed using continuous 5/0 PTFE sutures (Gore-Tex Sutures; Fig. 2). In most patients (n = 20; 71%), RVOT reconstruction was performed after cross-clamp removal to reduce the myocardial ischemia time. The operative characteristics are provided in Table 2. Table 2: Operative data Cardiopulmonary bypass time (min), mean ± SD 148.3 ± 29.1 Cross-clamp time (min), mean ± SD 122.3 ± 21.4 Concomitant procedures, n (%)  Mitral valve repair 2 (7)  Tricuspid valve repair 1 (4) RVOT reconstruction  Mean graft size (mm), mean ± SD 25.3 ± 2.3   20, n (%) 3 (11)   22, n (%) 1 (4)   23, n (%) 2 (7)   25, n (%) 8 (29)   27, n (%) 14 (50) Cardiopulmonary bypass time (min), mean ± SD 148.3 ± 29.1 Cross-clamp time (min), mean ± SD 122.3 ± 21.4 Concomitant procedures, n (%)  Mitral valve repair 2 (7)  Tricuspid valve repair 1 (4) RVOT reconstruction  Mean graft size (mm), mean ± SD 25.3 ± 2.3   20, n (%) 3 (11)   22, n (%) 1 (4)   23, n (%) 2 (7)   25, n (%) 8 (29)   27, n (%) 14 (50) RVOT: right ventricular outflow tract; SD: standard deviation. Table 2: Operative data Cardiopulmonary bypass time (min), mean ± SD 148.3 ± 29.1 Cross-clamp time (min), mean ± SD 122.3 ± 21.4 Concomitant procedures, n (%)  Mitral valve repair 2 (7)  Tricuspid valve repair 1 (4) RVOT reconstruction  Mean graft size (mm), mean ± SD 25.3 ± 2.3   20, n (%) 3 (11)   22, n (%) 1 (4)   23, n (%) 2 (7)   25, n (%) 8 (29)   27, n (%) 14 (50) Cardiopulmonary bypass time (min), mean ± SD 148.3 ± 29.1 Cross-clamp time (min), mean ± SD 122.3 ± 21.4 Concomitant procedures, n (%)  Mitral valve repair 2 (7)  Tricuspid valve repair 1 (4) RVOT reconstruction  Mean graft size (mm), mean ± SD 25.3 ± 2.3   20, n (%) 3 (11)   22, n (%) 1 (4)   23, n (%) 2 (7)   25, n (%) 8 (29)   27, n (%) 14 (50) RVOT: right ventricular outflow tract; SD: standard deviation. Figure 2: View largeDownload slide Right ventricular outflow tract reconstruction using a polytetrafluoroethylene valved conduit during the Ross procedure. The pulmonary autograft and ascending aorta are wrapped using a Dacron vascular prosthesis. Figure 2: View largeDownload slide Right ventricular outflow tract reconstruction using a polytetrafluoroethylene valved conduit during the Ross procedure. The pulmonary autograft and ascending aorta are wrapped using a Dacron vascular prosthesis. Postoperative management Oral anticoagulants were prescribed for 3 months postoperatively and were replaced with low-dose aspirin in patients with sinus rhythm documented by 24-h Holter monitoring. Postoperative evaluation Each patient underwent transoesophageal echocardiography (Philips ie33, Philips Healthcare, Cleveland, OH, USA or Vivid 7, General Electric Healthcare, Little Chalfont, UK) to evaluate the autograft and the right-sided graft function, after being weaned off cardiopulmonary bypass. Transthoracic echocardiography was performed before discharge from the hospital. The transvalvular pulmonary gradients were measured using continuous-wave Doppler ultrasound that employed the simplified Bernoulli equation. PTFE conduit regurgitation severity was evaluated using the colour flow Doppler, according to the guidelines of the European Association of Echocardiography [11]; the regurgitation was graded as none/trivial, mild, moderate or severe. The right ventricle systolic function was estimated by measuring the fractional area change from the apical 4-chamber view. After discharge, follow-up examinations were scheduled annually. If a patient was unable to attend an annual clinic visit, a telephone survey was performed. Echocardiograms obtained from external physicians were reanalysed at our institute by an experienced sonographer. Magnetic resonance imaging (MRI) was performed (Philips Achieva 1.5 T, Philips Healthcare) in 5 (18%) patients to estimate conduit leaflets mobility and haemodynamic characteristics. Eight (29%) patients underwent computed tomography (CT) scanning (Toshiba Aquilion One 320 slice CT, Toshiba, Tokyo, Japan) to assess conduit calcification, deformation and stenosis. The period between the time of surgery and each event or the end of the follow-up period constituted a separate observation. The follow-up period ended in April 2017. Postoperative events were classified according to the 2008 Society of Thoracic Surgeons/American Association for Thoracic Surgery/European Association for Cardio-Thoracic Surgery guidelines [12]. Early mortality was defined as death due to any cause occurring in the hospital or within 30 days of the surgery; late mortality was defined as death occurring after that period. RVOT conduit dysfunction was defined as a peak systolic gradient of >40 mmHg or the presence of moderate to severe conduit valve insufficiency. Statistical analysis Statistical analysis was performed using Stata, version 13.0 (StataCorp, College Station, TX, USA). Continuous data are presented as mean ± standard deviation or as median and IQR (25th–75th percentile). Categorical data are described as absolute numbers and relative frequencies. The 2 groups were compared using the Wilcoxon matched-pairs signed-rank test. McNemar’s test was used to compare 2 groups of categorical data. The Kaplan–Meier method was used to evaluate survival, which is presented as 95% confidence intervals. A longitudinal mixed-effects linear regression was used to validate RVOT gradient predictors over time. The analysis included factors such as age, sex, body surface area, aortic valve morphology (bicuspid or tricuspid), aortic valve lesion (stenosis or insufficiency), prior operations and RVOT conduit size as fixed effects; the unique patient identification number was used as a random effect. Two-sided P-values <0.05 were considered statistically significant. RESULTS Among the study patients, the early mortality rate was 3.6% (1 patient). The early mortality was caused by heart failure due to myocardial infarction and was not associated with the use of the PTFE conduit. There were no cases of reoperation due to bleeding. The mean follow-up duration was 48.5 ± 31.2 months (range 6–120 months) and was 100% complete (27 patients). There were no late deaths. The survival rate at 5 years was 96.3% (95% confidence interval 76.5–99.5%). At the final follow-up, 15 (56%) patients were classified as the New York Heart Association (NYHA) functional Class I and 12 (44%) as Class II. One (4%) patient had paroxysmal atrial fibrillation at the final follow-up and continued warfarin treatment. There were no cases of infective endocarditis of the autograft or PTFE conduit nor were there cases of thromboembolisms or major haemorrhagic events during the follow-up period. At discharge, the peak and mean pressure gradients across the conduit were 11.6 ± 4.9 and 6.5 ± 3.1 mmHg, respectively. Twenty-six (96%) patients had trace or no RVOT regurgitation; 1 (4%) patient had mild regurgitation. Over time, a gradual increase in the transprosthetic gradient was observed (Fig. 3). At the last follow-up, the peak and mean pressure gradients were significantly higher than those at discharge, whereas the RVOT regurgitation grades were similar (Table 3). Longitudinal mixed-effects linear modelling revealed that conduit size diameter (P = 0.02) was the only predictor of peak RVOT gradient progression (Table 4). None of the patients had right ventricular dysfunction or severe tricuspid regurgitation according to transthoracic echocardiography at follow-up. Table 3: Echocardiography results Variables At discharge (n = 27) At last follow-up (n = 27) P-value Left ventricular ejection fraction (%), mean ± SD 58.2 ± 7.6 61.9 ± 6.2 0.32 RV FAC (%), mean ± SD 42.1 ± 7.1 40.3 ± 6.8 0.23 RVOT regurgitation, n (%)  None/trivial 26 (96) 24 (89) 0.89  Mild 1 (4) 3 (11) 0.62  Moderate/severe 0 0 RVOT gradient (mmHg), mean ± SD  Mean 6.5 ± 3.1 11.9 ± 6.7 <0.001  Peak 11.6 ± 4.9 21.1 ± 9.6 <0.001 Tricuspid regurgitation, n (%)  None/trivial 21 (78) 17 (63) 0.63  Mild 6 (22) 9 (33) 0.61  Moderate 0 1 (4) 1.0 Variables At discharge (n = 27) At last follow-up (n = 27) P-value Left ventricular ejection fraction (%), mean ± SD 58.2 ± 7.6 61.9 ± 6.2 0.32 RV FAC (%), mean ± SD 42.1 ± 7.1 40.3 ± 6.8 0.23 RVOT regurgitation, n (%)  None/trivial 26 (96) 24 (89) 0.89  Mild 1 (4) 3 (11) 0.62  Moderate/severe 0 0 RVOT gradient (mmHg), mean ± SD  Mean 6.5 ± 3.1 11.9 ± 6.7 <0.001  Peak 11.6 ± 4.9 21.1 ± 9.6 <0.001 Tricuspid regurgitation, n (%)  None/trivial 21 (78) 17 (63) 0.63  Mild 6 (22) 9 (33) 0.61  Moderate 0 1 (4) 1.0 FAC: fractional area change; RV: right ventricle; RVOT: right ventricular outflow tract; SD: standard deviation. Table 3: Echocardiography results Variables At discharge (n = 27) At last follow-up (n = 27) P-value Left ventricular ejection fraction (%), mean ± SD 58.2 ± 7.6 61.9 ± 6.2 0.32 RV FAC (%), mean ± SD 42.1 ± 7.1 40.3 ± 6.8 0.23 RVOT regurgitation, n (%)  None/trivial 26 (96) 24 (89) 0.89  Mild 1 (4) 3 (11) 0.62  Moderate/severe 0 0 RVOT gradient (mmHg), mean ± SD  Mean 6.5 ± 3.1 11.9 ± 6.7 <0.001  Peak 11.6 ± 4.9 21.1 ± 9.6 <0.001 Tricuspid regurgitation, n (%)  None/trivial 21 (78) 17 (63) 0.63  Mild 6 (22) 9 (33) 0.61  Moderate 0 1 (4) 1.0 Variables At discharge (n = 27) At last follow-up (n = 27) P-value Left ventricular ejection fraction (%), mean ± SD 58.2 ± 7.6 61.9 ± 6.2 0.32 RV FAC (%), mean ± SD 42.1 ± 7.1 40.3 ± 6.8 0.23 RVOT regurgitation, n (%)  None/trivial 26 (96) 24 (89) 0.89  Mild 1 (4) 3 (11) 0.62  Moderate/severe 0 0 RVOT gradient (mmHg), mean ± SD  Mean 6.5 ± 3.1 11.9 ± 6.7 <0.001  Peak 11.6 ± 4.9 21.1 ± 9.6 <0.001 Tricuspid regurgitation, n (%)  None/trivial 21 (78) 17 (63) 0.63  Mild 6 (22) 9 (33) 0.61  Moderate 0 1 (4) 1.0 FAC: fractional area change; RV: right ventricle; RVOT: right ventricular outflow tract; SD: standard deviation. Table 4: The change in the peak pressure gradient across the polytetrafluoroethylene conduit (longitudinal mixed-effects linear model) Risk factor Coefficient SE P-value Sex (men) 3.95 2.20 0.07 Age −0.06 0.09 0.48 RVOT conduit size −1.51 0.65 0.02 Previous operation 1.02 4.14 0.81 Aortic valve lesion (AS) −1.16 2.20 0.60 Bicuspid aortic valve 1.69 2.70 0.53 Risk factor Coefficient SE P-value Sex (men) 3.95 2.20 0.07 Age −0.06 0.09 0.48 RVOT conduit size −1.51 0.65 0.02 Previous operation 1.02 4.14 0.81 Aortic valve lesion (AS) −1.16 2.20 0.60 Bicuspid aortic valve 1.69 2.70 0.53 AS: aortic stenosis; RVOT: right ventricular outflow tract; SE: standard error. Table 4: The change in the peak pressure gradient across the polytetrafluoroethylene conduit (longitudinal mixed-effects linear model) Risk factor Coefficient SE P-value Sex (men) 3.95 2.20 0.07 Age −0.06 0.09 0.48 RVOT conduit size −1.51 0.65 0.02 Previous operation 1.02 4.14 0.81 Aortic valve lesion (AS) −1.16 2.20 0.60 Bicuspid aortic valve 1.69 2.70 0.53 Risk factor Coefficient SE P-value Sex (men) 3.95 2.20 0.07 Age −0.06 0.09 0.48 RVOT conduit size −1.51 0.65 0.02 Previous operation 1.02 4.14 0.81 Aortic valve lesion (AS) −1.16 2.20 0.60 Bicuspid aortic valve 1.69 2.70 0.53 AS: aortic stenosis; RVOT: right ventricular outflow tract; SE: standard error. Video 1 Early postoperative magnetic resonance imaging of the polytetrafluoroethylene valved conduit in the pulmonary artery position. Video 1 Early postoperative magnetic resonance imaging of the polytetrafluoroethylene valved conduit in the pulmonary artery position. Close Video 2 Computed tomography angiography 5 years after surgery. Three-dimensional reconstruction of the polytetrafluoroethylene valved conduit in the pulmonary artery position. Video 2 Computed tomography angiography 5 years after surgery. Three-dimensional reconstruction of the polytetrafluoroethylene valved conduit in the pulmonary artery position. Close Figure 3: View largeDownload slide The peak pressure gradient across the polytetrafluoroethylene valved conduit over time. Box plots depict medians, interquartile ranges and non-outlier ranges. N: number of patients. Figure 3: View largeDownload slide The peak pressure gradient across the polytetrafluoroethylene valved conduit over time. Box plots depict medians, interquartile ranges and non-outlier ranges. N: number of patients. In 1 case, an RVOT reoperation was required 7 years after the initial Ross procedure due to a patient–prosthesis mismatch (the transvalvular gradient increased to 70 mmHg). The patient underwent the original operation at 4 years of age when a 20-mm PTFE conduit was implanted. There was no conduit calcification, thrombosis or intimal hyperplasia noted when the conduit was revised. A 26-mm cryopreserved pulmonary allograft was implanted during the redo procedure. This patient also had severe aortic regurgitation, due to autograft dilatation, necessitating autograft valve replacement with a mechanical prosthesis. The procedure and postoperative period were uncomplicated. Follow-up MRI at 58.0 (IQR 36.0–100.0) months revealed mobile conduit leaflets that completely opened during systole and closed during diastole. There was no evidence of anything more significant than mild regurgitation (see Video 1). The median CT follow-up period was 50.0 (IQR 30.0–100.0) months. CT showed no calcification of the leaflets or vascular grafts and no conduit deformations or stenosis (see Video 2). DISCUSSION The Ross procedure is an attractive alternative to prosthetic aortic valve replacement with advantages that include a minimal thromboembolism risk and anticoagulation avoidance. Studies have shown that the incidence of valve-related complications after the Ross procedure is lower than that after mechanical prosthesis implantation [1, 13]. Excellent long-term survival after the Ross procedure has also been demonstrated, exceeding that of patients with mechanical prostheses [1]. Nevertheless, the Ross procedure is not widely used. One reason for this is the need for a double-valve intervention and an increased risk of repeat operations due to RVOT graft degeneration. At our institute, the Ross procedure is offered as an alternative surgical treatment for aortic valve disease to all children and other patients with an active lifestyle who desire to avoid a lifelong anticoagulation therapy. The cryopreserved pulmonary allograft is the most widely used graft for RVOT reconstruction and several studies have demonstrated good late results. In the German Ross Registry (comprising 1779 adult patients), freedom from reoperations involving pulmonary allografts was 92.3% at 15 years [14]. David et al. [3] also reported a freedom from allograft reoperation of 93.6% at 20 years. In paediatric patients, freedom from allograft reoperation after the Ross procedure is less and varies between studies, depending on the age of the patient population. According to the Italian Paediatric Ross Registry (305 patients), freedom from allograft reintervention at 15 years is 82% [15]. In the German Ross Registry (263 paediatric patients), the rate was 79% at 12 years [16]. The main mechanism of bioprosthesis degeneration involves an immune response to donor cell antigens. To reduce immunogenicity and improve durability, decellularized pulmonary allografts were proposed. In a study by Costa et al. [17], decellularized fresh allografts demonstrated lower rates of structural valve degeneration and greater freedom from reoperations than did cryopreserved allografts in patients undergoing the Ross procedure. Several other studies have also demonstrated that freedom from RVOT conduit dysfunction in the paediatric population (Ross and non-Ross patients) was significantly worse when conventional cryopreserved pulmonary allografts were used in comparison with decellularized allografts [18, 19]. The main disadvantage of allografts is their limited availability. Thus, alternative grafts for RVOT reconstruction have been proposed such as porcine root grafts, pericardial xenografts, bovine jugular venous conduits and PTFE conduits. Several studies reported promising results using different xenografts during the Ross procedure. Hechadi et al. [4] did not find differences between porcine root grafts (17 patients) and pulmonary allografts (37 patients) in terms of haemodynamic performance at a mean follow-up of 8.2 years; however, the calcific degeneration progressed more rapidly in the xenografts. Juthier et al. [20] also reported good early and mid-term results using different stent-less porcine root models in 61 patients. They concluded that porcine aortic root grafts are an acceptable alternative for RVOT reconstruction when pulmonary homografts are unavailable. In a meta-analysis that included 137 patients (7 studies) undergoing RVOT reconstruction with porcine root grafts during the Ross procedure, the rate of structural valve deterioration was 7.1% at 45 months of follow-up, and the rate of reintervention was 2.1% [21]. However, different xenograft results have also been reported [5, 6]. Miskovic et al. [5] and Weimar et al. [6] reported that the durability of porcine aortic root grafts in the RVOT position was unacceptably low. In the German Ross Registry, patients with bioprostheses (149 patients) implanted in RVOT had significantly higher risk of reintervention due to pulmonary conduit dysfunction than did those receiving allografts [14]. Bovine jugular venous conduits have also been proposed for paediatric RVOT reconstruction, showing 10-year freedom from reintervention of 60–70% depending on the conduit size and patient age [22]. Previously, we presented the results of using different xenografts for RVOT reconstruction during the Ross procedure [10]. The haemodynamic performance and failure rates of all types of xenografts were worse than those for allografts. In contrast, pericardial xenografts showed acceptable results in older patients [23]. Thus, we believe that the use of xenografts during the Ross procedure should be restricted, especially in younger patients. All biological grafts (pulmonary allografts and xenografts) are susceptible to deterioration caused by immunological factors. Therefore, the use of synthetic grafts for RVOT reconstruction looks attractive. Different types of handmade PTFE conduits have been proposed [8, 24, 25]. Microporous structure of PTFE impedes cellular penetration, inflammation and calcification; therefore, these conduits have good biocompatibility and low antigenicity and demonstrate resistance to degeneration and calcification [22]. Histological examinations of explanted PTFE grafts have shown that over time, their surfaces are covered by thin collagenous tissue with partial endothelialization, whereas the leaflets, which have smaller micropores, remained intact without cellular penetration or evidence of calcification [22]. The first application of PTFE for RVOT reconstruction was performed by Yamagishi et al. [26] in patients with tetralogy of Fallot. A transannular pericardial patch with a bicuspid or unicuspid PTFE valve was used. The same authors proposed a combined autologous conduit consisting of a posterior aortic wall, with non-coronary cusp, and a patch with a bicuspid PTFE valve for RVOT reconstruction during the Ross procedure in paediatric patients. This technique allowed the conduit to grow as the patients aged [27]. A serious disadvantage of this technique was the high rate of transvalvular regurgitation caused by the cusps getting stuck in the open position. Expanded PTFE conduits and patches with bulging sinuses created by heating were proposed to generate a vortex flow between the leaflets and the graft, leading to physiological valve closing [7]. Nevertheless, there are contradictory data on the thermal treatment effect on the mechanical properties and morphological characteristics of PTFE material [28, 29]. A multicentre study in Japan, including 725 patients with congenital heart defects (right ventricular outflow hypoplasia or atresia) and 69 Ross patients, revealed 10-year freedom from reoperation of 95.4% and 92.3% for the expanded PTFE conduits and patches, respectively; however, the mean follow-up was only 3.6 years [30]. Takabayashi et al. [8] reported other types of handmade trileaflet PTFE conduits created intraoperatively using PTFE sheets and vascular grafts. Acceptable haemodynamic results were observed at the mid-term follow-up in 11 patients undergoing RVOT reconstruction with this type of conduit during the Ross procedure. Moreover, other types of handmade PTFE conduits were investigated with encouraging early and mid-term results [25]. Thus, the follow-up periods for all PTFE conduits described in the literature are relatively short. Moreover, the disadvantages of a handmade prosthesis include additional intraoperative time and precise technical requirement needed to fabricate them and the absence of haemodynamic testing before implantation, possibly leading to bleeding or early conduit failure. In this study, we presented our experience with the commercial PTFE conduits for RVOT reconstruction. Thus, all conduits were tested by a manufacturer using a pulse duplicator and included assessment of transprosthetic gradient, effective orifice area and absence of leakage. Our study revealed that the PTFE valved conduit demonstrates acceptable haemodynamic parameters at mid-term follow-up. Echocardiography, CT and MRI examinations did not identify calcification, deformation or stenosis of the conduits nor was significant postoperative regurgitation identified. Moreover, we found that conduit size affects mid-term haemodynamic results. Smaller-sized conduits were related to higher transprosthetic gradients at follow-up. Therefore, the largest possible conduit should be used to prevent conduit stenosis. The choice of the optimal PTFE conduit size for RVOT reconstruction differs between studies. Miyazaki et al. [30] were guided by Rowlatt’s formula; the Z-score calculation was used in other studies [24]. However, most authors are in complete agreement with conduit oversizing to achieve better results. We also used some oversizing during RVOT reconstruction; however, we did not perform special calculations. Most of our adult patients received 27–29-mm conduit sizes when allografts or xenografts are used. We believe that the rule is also feasible for PTFE conduits. However, the 27-mm diameter is the largest available size for this graft type, which is restricted by the maximum available PTFE vascular graft size. Nevertheless, the mean body surface area of the study group was relatively small, which is why we did not have any cases of patient–prosthesis mismatch and obtained acceptable haemodynamic results at follow-up. Limitations This study also has some limitations. It was a retrospective single-centre study involving relatively few patients. The mean follow-up period was also relatively short, and long-term follow-up results are needed. In addition, postoperative CT and MRI were not performed on the whole study population due to distant location of some patients from the clinic. Moreover, this study did not compare the use of PTFE valved conduit with other graft types for RVOT reconstruction. CONCLUSION The results of this study show that the PTFE conduit could be considered as an alternative substitute for RVOT reconstruction during the Ross procedure. Conflict of interest: none declared. REFERENCES 1 Andreas M , Wiedemann D , Seebacher G , Rath C , Aref T , Rosenhek R et al. 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Thermal treatment of expanded polytetrafluoroethylene (ePTFE) membranes for reconstruction of a valved conduit . BME 2015 ; 26 : S55 – 62 . Google Scholar CrossRef Search ADS 30 Miyazaki T , Yamagishi M , Maeda Y , Yamamoto Y , Taniguchi S , Sasaki Y et al. Expanded polytetrafluoroethylene conduits and patches with bulging sinuses and fan-shaped valves in right ventricular outflow tract reconstruction: multicentre study in Japan . J Thorac Cardiovasc Surg 2011 ; 142 : 1122 – 9 . Google Scholar CrossRef Search ADS PubMed © The Author(s) 2018. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices)

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European Journal of Cardio-Thoracic SurgeryOxford University Press

Published: Apr 5, 2018

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