Late outcomes of subcostal exchange of the HeartMate II left ventricular assist device: a word of caution

Late outcomes of subcostal exchange of the HeartMate II left ventricular assist device: a word of... Abstract OBJECTIVES Previous studies have shown the usefulness of the subcostal exchange of the HeartMate II left ventricular assist device for device malfunction. However, long-term data are still limited. METHODS Between March 2004 and July 2017, 41 of 568 (7.2%) patients who had received a HeartMate II implant at our institution had a device exchange via a subcostal incision. We summarized early and late outcomes. RESULTS Forty-one patients had a total of 48 subcostal pump exchanges. Indications for device exchange included device thrombosis (n = 31, 76%), driveline infection (n = 2, 5%) and driveline injury (n = 8, 19%). All of the procedures were successful, and there were no in-hospital deaths. A Kaplan–Meier survival curve showed 30-day and 1-year survival rates after subcostal exchange of 100% and 94.6%, respectively. However, 10 (25%) patients had left ventricular assist device-related infections following subcostal exchange that included 7 pump pocket infections and 3 driveline infections. Freedom from left ventricular assist device-related infection at 1 year after subcostal exchange was 79.3%. Thirteen (32%) patients had device malfunction due to pump thrombosis that required a 2nd device exchange. Seven patients had recurrent thrombosis. Three (7%) patients had a stroke. Freedom from device thrombosis and from a stroke event at 1 year was 74.4%. CONCLUSIONS Subcostal pump exchange can be safely performed. However, there is a substantial risk of infection and recurrent thrombosis. Careful follow-up for late complications is mandatory. Ventricular assist device , Subcostal exchange , Device thrombosis , Device infection INTRODUCTION Device malfunction including device thrombosis is a not uncommon and potentially fatal complication during continuous-flow left ventricular assist device (LVAD) support. Since the initial reports of the abrupt increase in the incidence of device thrombosis with the HeartMate II (HM II, Abbott, Abbott Park, IL, USA) [1, 2], a yearly thrombosis rate of about 10% has been noted by the Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) reports [3]. The most recent report showed a higher incidence of device malfunctions involving the controller, battery and cable in addition to failure of the pump itself [4]. Once device malfunction is confirmed, early device exchange rather than watchful waiting is recommended to minimize the risk of adverse events [5]. The subcostal approach has been reported to be the preferred method for device exchange for patients who do not have inflow and outflow issues, because it is a less invasive procedure associated with shorter intensive care unit times and fewer postoperative complications than resternotomy [6–8]. However, data on the long-term clinical outcomes of this procedure are limited. In this study, our aim was to assess for late outcomes of patients who had subcostal HM II exchange. MATERIALS AND METHODS Patient selection This study was approved by the institutional review board of the Columbia University Medical Center. Between March 2004 and July 2017, 60 of 568 (10.6%) patients who had received a HM II implant at Columbia University Medical Center received a device exchange. Among them, the 41 (7.2%) patients who underwent subcostal exchange comprise our cohort of interest. Indication and surgical technique for subcostal exchange Once device malfunction is suspected, analysis of the log file is routinely performed. Radiographs are taken to detect driveline injury. Computed tomography angiography is used preoperatively to assess for kinking, malposition and thrombus in the inflow and outflow cannulas [9, 10]. For patients who have suspected device thrombosis, we routinely perform an echocardiographic ramp study [11] in addition to measuring serial serum lactate dehydrogenase and plasma-free haemoglobin levels. Our treatment algorithm for device thrombosis was reported previously [5]. Since June 2011, we have elected to perform a subcostal incision over a resternotomy for device exchange, unless there is a need to access the outflow or inflow cannulas (due to thrombus, infection or kinking of the graft) or to perform a concomitant cardiac procedure requiring sternotomy. Our surgical technique for subcostal HM II exchange was reported previously [6]. Briefly, a reverse J-shaped incision is made from the xiphoid process to the left mid-clavicular line to expose the pump from the bend relief site to the inflow arm. Cardiopulmonary bypass is initiated via femoral vessel cannulation. Most recently, a more limited incision (2 separate incisions) has been applied in order to minimize delayed wound healing (Fig. 1). Figure 1: View largeDownload slide A limited incision consisting of 2 separate incisions is now applied in order to minimize wound healing delay after subcostal exchange. Figure 1: View largeDownload slide A limited incision consisting of 2 separate incisions is now applied in order to minimize wound healing delay after subcostal exchange. Data collection and follow-up Medical records were reviewed for collection of baseline characteristics, postoperative complications and outcomes. Median support duration from initial subcostal exchange to time of analysis was 1876 days (1309–2292). Follow-up information was available and collected until 31 July 2017 for all patients. Postoperative complications included right ventricular failure, acute kidney injury, ventricular arrhythmia, gastrointestinal bleeding, LVAD-related infection, stroke and device thrombosis according to INTERMACS definitions. Driveline and pump pocket infections were confirmed by wound culture and radiological observation of fluid collections [12]. Stroke was confirmed by a brain imaging study. Duration to heart transplant was calculated as time from initial subcostal exchange. Statistical analysis Continuous variables are reported as mean ± standard deviation. The 95% confidence intervals (CIs) are additionally represented. Kaplan–Meier analysis was used to calculate survival rates and freedom from device complications with plots truncated after 3 years due to limited observations at later time points. Statistical significance was defined as a 2-sided α ≤ 0.05. Statistical analysis was performed using Stata 14 software (Stata Corp, College Station, TX, USA). RESULTS Patient baseline characteristics Baseline characteristics are summarized in Table 1. The mean age was 54.6 ± 13.5 years; 80% were men; 32% had ischaemic and 61% had dilated aetiologies; 63% were designated for bridge to transplant. Table 1: Baseline characteristics at the time of the primary subcostal device exchange   n = 41  Age (years)  54.6 ± 13.5  Male (%)  33 (80)  BMI (kg/m2)  27.3 ± 5.4  BSA (m2)  2.0 ± 0.2  Intention to treat     BTT  26 (63)   DT  15 (37)  Aetiology of cardiomyopathy     Dilated  25 (61)   Ischaemic  13 (32)   Other  3 (7)  Hypertension  21 (51)  Diabetes mellitus  12 (29)  Hyperlipidaemia  15 (37)  Indication for exchange     Device thrombosis  31 (76)   Driveline infection  2 (5)   Driveline injury  8 (19)  Incisional approach     Extended J-shaped incision  35 (85)   Modified 2-incision approach  6 (15)  Support duration to subcostal exchange (days)  462 (178–778)  Preoperative laboratory values     WBC (×1000/ml)  7.3 ± 2.0   Haemoglobin (g/dl)  10.6 ± 2.0   Haematocrit (%)  32.5 ± 5.5   Platelets (×1000/ml)  178.2 ± 68.0   LDH (U/l)  1080 (420–1753)   INR  1.6 (1.2–1.9)   BUN (mg/dl)  22.0 (15.0–31.0)   Creatinine (mg/dl)  1.3 (1.0–1.6)  Pump parameters     Pump flow (l/min)  5.3 ± 0.9   Pump speed (rpm)  9150 ± 500   Pulsatility index  4.9 ± 1.8   Power (W)  5.8 ± 1.5  CPB time (min)  22 (12–27)  Length of ICU stay (days)  5 (4–8)    n = 41  Age (years)  54.6 ± 13.5  Male (%)  33 (80)  BMI (kg/m2)  27.3 ± 5.4  BSA (m2)  2.0 ± 0.2  Intention to treat     BTT  26 (63)   DT  15 (37)  Aetiology of cardiomyopathy     Dilated  25 (61)   Ischaemic  13 (32)   Other  3 (7)  Hypertension  21 (51)  Diabetes mellitus  12 (29)  Hyperlipidaemia  15 (37)  Indication for exchange     Device thrombosis  31 (76)   Driveline infection  2 (5)   Driveline injury  8 (19)  Incisional approach     Extended J-shaped incision  35 (85)   Modified 2-incision approach  6 (15)  Support duration to subcostal exchange (days)  462 (178–778)  Preoperative laboratory values     WBC (×1000/ml)  7.3 ± 2.0   Haemoglobin (g/dl)  10.6 ± 2.0   Haematocrit (%)  32.5 ± 5.5   Platelets (×1000/ml)  178.2 ± 68.0   LDH (U/l)  1080 (420–1753)   INR  1.6 (1.2–1.9)   BUN (mg/dl)  22.0 (15.0–31.0)   Creatinine (mg/dl)  1.3 (1.0–1.6)  Pump parameters     Pump flow (l/min)  5.3 ± 0.9   Pump speed (rpm)  9150 ± 500   Pulsatility index  4.9 ± 1.8   Power (W)  5.8 ± 1.5  CPB time (min)  22 (12–27)  Length of ICU stay (days)  5 (4–8)  Values are represented as mean ± SD, median (Q1–Q3) or n (%). BMI: body mass index; BSA: body surface area; BTT: bridge to transplant; BUN: blood urea nitrogen; CPB: cardiopulmonary bypass; DT: destination therapy; ICU: intensive care unit; INR: international normalized ratio; LDH: lactate dehydrogenase; WBC: white blood cells. Table 1: Baseline characteristics at the time of the primary subcostal device exchange   n = 41  Age (years)  54.6 ± 13.5  Male (%)  33 (80)  BMI (kg/m2)  27.3 ± 5.4  BSA (m2)  2.0 ± 0.2  Intention to treat     BTT  26 (63)   DT  15 (37)  Aetiology of cardiomyopathy     Dilated  25 (61)   Ischaemic  13 (32)   Other  3 (7)  Hypertension  21 (51)  Diabetes mellitus  12 (29)  Hyperlipidaemia  15 (37)  Indication for exchange     Device thrombosis  31 (76)   Driveline infection  2 (5)   Driveline injury  8 (19)  Incisional approach     Extended J-shaped incision  35 (85)   Modified 2-incision approach  6 (15)  Support duration to subcostal exchange (days)  462 (178–778)  Preoperative laboratory values     WBC (×1000/ml)  7.3 ± 2.0   Haemoglobin (g/dl)  10.6 ± 2.0   Haematocrit (%)  32.5 ± 5.5   Platelets (×1000/ml)  178.2 ± 68.0   LDH (U/l)  1080 (420–1753)   INR  1.6 (1.2–1.9)   BUN (mg/dl)  22.0 (15.0–31.0)   Creatinine (mg/dl)  1.3 (1.0–1.6)  Pump parameters     Pump flow (l/min)  5.3 ± 0.9   Pump speed (rpm)  9150 ± 500   Pulsatility index  4.9 ± 1.8   Power (W)  5.8 ± 1.5  CPB time (min)  22 (12–27)  Length of ICU stay (days)  5 (4–8)    n = 41  Age (years)  54.6 ± 13.5  Male (%)  33 (80)  BMI (kg/m2)  27.3 ± 5.4  BSA (m2)  2.0 ± 0.2  Intention to treat     BTT  26 (63)   DT  15 (37)  Aetiology of cardiomyopathy     Dilated  25 (61)   Ischaemic  13 (32)   Other  3 (7)  Hypertension  21 (51)  Diabetes mellitus  12 (29)  Hyperlipidaemia  15 (37)  Indication for exchange     Device thrombosis  31 (76)   Driveline infection  2 (5)   Driveline injury  8 (19)  Incisional approach     Extended J-shaped incision  35 (85)   Modified 2-incision approach  6 (15)  Support duration to subcostal exchange (days)  462 (178–778)  Preoperative laboratory values     WBC (×1000/ml)  7.3 ± 2.0   Haemoglobin (g/dl)  10.6 ± 2.0   Haematocrit (%)  32.5 ± 5.5   Platelets (×1000/ml)  178.2 ± 68.0   LDH (U/l)  1080 (420–1753)   INR  1.6 (1.2–1.9)   BUN (mg/dl)  22.0 (15.0–31.0)   Creatinine (mg/dl)  1.3 (1.0–1.6)  Pump parameters     Pump flow (l/min)  5.3 ± 0.9   Pump speed (rpm)  9150 ± 500   Pulsatility index  4.9 ± 1.8   Power (W)  5.8 ± 1.5  CPB time (min)  22 (12–27)  Length of ICU stay (days)  5 (4–8)  Values are represented as mean ± SD, median (Q1–Q3) or n (%). BMI: body mass index; BSA: body surface area; BTT: bridge to transplant; BUN: blood urea nitrogen; CPB: cardiopulmonary bypass; DT: destination therapy; ICU: intensive care unit; INR: international normalized ratio; LDH: lactate dehydrogenase; WBC: white blood cells. Indications for subcostal exchange included device thrombosis (n = 31, 76%), driveline infection (n = 2, 5%) and driveline injury (n = 8, 19%). The extended J incision was used in 35 (85%) patients, whereas 6 underwent a modified 2-incision approach. Median duration on LVAD support until subcostal exchange was 462 (178–778) days. Early outcomes There were no in-hospital deaths after subcostal exchange. Early postoperative complications included right ventricular failure (n = 2), acute kidney injury (n = 4), ventricular tachycardia (n = 5), gastrointestinal bleeding (n = 2) and amiodarone-induced thyrotoxicosis (n = 1). Follow-up complications Freedom from LVAD-related infection 30 days and 1 year after subcostal exchange was 95.1% and 79.3%, respectively (Fig. 2A). Ten (25%) patients had pump pocket or driveline infection following subcostal exchange (Table 2). Two patients had early pump pocket infection during the indexed hospitalization and underwent surgical incision and drainage. The remaining 8 LVAD-related infections occurred a mean of 462 (95% CI 22–903) days after subcostal exchange, with 3 patients who developed infection after 1 year. Four required incision and drainage with vacuum-assisted closure therapy, all of whom had chronic infection and required later surgical debridement. One patient had an LVAD explant and subsequent reinsertion 2 weeks after the infection resolved. The other 3 patients who had isolated driveline infection were managed with long-term antibiotic therapy and did not have recurrent infection. Staphylococcus genus and Pseudomonas aeruginosa were the most commonly detected pathogens on wound culture (Table 2). Table 2: Left ventricular assist device-related infection after subcostal exchange   n = 10  LVAD-related infection     Driveline infection  3   Pump pocket infection  7  Pathogens     Staphylococcus      Methicillin-sensitive  1    Methicillin-resistant  1    Staphylococcus lugdunensis  1   Pseudomonas aeruginosa  3   Serratia marcescens  2   Enterococcus faecalis (formerly Enterobacter faecalis)  1   Culture negative  1    n = 10  LVAD-related infection     Driveline infection  3   Pump pocket infection  7  Pathogens     Staphylococcus      Methicillin-sensitive  1    Methicillin-resistant  1    Staphylococcus lugdunensis  1   Pseudomonas aeruginosa  3   Serratia marcescens  2   Enterococcus faecalis (formerly Enterobacter faecalis)  1   Culture negative  1  LVAD: left ventricular assist device. Table 2: Left ventricular assist device-related infection after subcostal exchange   n = 10  LVAD-related infection     Driveline infection  3   Pump pocket infection  7  Pathogens     Staphylococcus      Methicillin-sensitive  1    Methicillin-resistant  1    Staphylococcus lugdunensis  1   Pseudomonas aeruginosa  3   Serratia marcescens  2   Enterococcus faecalis (formerly Enterobacter faecalis)  1   Culture negative  1    n = 10  LVAD-related infection     Driveline infection  3   Pump pocket infection  7  Pathogens     Staphylococcus      Methicillin-sensitive  1    Methicillin-resistant  1    Staphylococcus lugdunensis  1   Pseudomonas aeruginosa  3   Serratia marcescens  2   Enterococcus faecalis (formerly Enterobacter faecalis)  1   Culture negative  1  LVAD: left ventricular assist device. Figure 2: View largeDownload slide Freedom from adverse events: (A) left ventricular assist device-related infection; (B) device thrombosis and stroke. CI: confidence interval. Figure 2: View largeDownload slide Freedom from adverse events: (A) left ventricular assist device-related infection; (B) device thrombosis and stroke. CI: confidence interval. Freedom from device thrombosis and a stroke event 30 days and 1 year after subcostal exchange was 100% and 74.4%, respectively (Fig. 2B). Three (7%) patients suffered a stroke at 17, 28 and 86 days after the exchange. Thirteen (32%) patients had recurrent device malfunction requiring surgical interventions at a mean of 454 (95% CI 118–789) days after the initial subcostal exchange. Twelve had device thrombosis, 7 of whom had recurrent thrombosis (the indication for the initial and 2nd device exchanges was device thrombosis). These patients required a 2nd device exchange via a subcostal exchange (n = 6), a device exchange via resternotomy (n = 4) or a heart transplant (n = 2). One patient had driveline injury after the exchange and required a resubcostal exchange. Freedom from recurrent device malfunction at 1 year was 88%. Late outcomes Of 41 patients, 21 (51%) had a heart transplant a mean of 268 (95% CI 175–361) days after the initial subcostal exchange. The Kaplan–Meier survival curve showed 30-day and 1-year survival rates after subcostal exchange of 100% and 94.6%, respectively (Fig. 3). Figure 3: View largeDownload slide Survival after subcostal exchange. CI: confidence interval. Figure 3: View largeDownload slide Survival after subcostal exchange. CI: confidence interval. DISCUSSION We examined early and late outcomes after subcostal device exchange for HM II device malfunction. Many studies have reported the subcostal technique to be a procedure with a low early mortality rate [13, 14]. Likewise, there were no in-hospital deaths with the subcostal exchange in our study, further supporting the safeness of this surgical technique when device exchange is warranted. However, LVAD-related infections and recurrent device malfunction are major causes of morbidity during the late follow-up period. With the rising frequency and duration of support on LVAD therapy, preventive measures and appropriate management of these device complications are necessary. Device-related infection is one of the most common causes for readmission for patients on LVAD support, with a reported incidence in up to 59% of patients [15–20]. Driveline infection is the most common LVAD-related infection [17] because it is often the site of entry for pathogens. Staphylococci are the most common pathogens reported, followed by pseudomonads [17, 21, 22]. If it is not properly treated, infection of the driveline can subsequently invade the pump pocket and cause systemic bloodstream complications, which can result in death. Although device-related infections are well-described in the literature, our study is the first to assess the incidence of infection as a consequence of device exchange. In our cohort, 25% of patients had an LVAD-related infection after subcostal exchange. Notably, 70% of these patients suffered from pump pocket infection that was not related to driveline infection, including 2 patients who had early pocket infection. Furthermore, it is important to note that the majority of device-related infections occurred after the patients were discharged following subcostal exchange. Prior studies have mentioned that most LVAD infections occur out of the hospital as a result of trauma at the driveline site [21, 22]. This result speaks to the fact that, whereas device exchange is an invasive procedure that can increase the susceptibility of patients to infection, the high rate of infection is inevitable largely due to the percutaneous nature of the HM II devices. Techniques to stabilize the driveline and minimize trauma are currently in development [23, 24]. Moreover, we thought that some of the late pocket infections were related to delayed wound healing resulting from the extended J incision with transection of the rectus muscles, fascia and ribs. These patients returned with probable pump pocket contamination from the incision. Based on our observations, we now perform a more limited 2-incision approach, as was done for 6 patients in this study, to minimize the opportunity and entry site for infection. Since we implemented this technique, we have not seen any type of pump pocket infection. The best treatment for LVAD-associated infections is device explant and/or heart transplant [25], but this option is often not available. Overall, patients in our study with driveline and pump pocket infections were managed successfully with antibiotic therapy and surgical debridement with or without vacuum-assisted closure. Device thrombosis is another detrimental complication of LVAD therapy that has become of particular concern in recent years. Since 2011, the incidence of HM II device thrombosis has increased [1, 2]. Adherence to a standardized practice for clinical management was shown to reduce the risk of early device thrombosis in the PREVENT clinical trial [26]; however, many thromboembolic events also occur as late complications in patients on LVAD support. Once device thrombosis occurs, early device exchange should be considered rather than a watch and wait approach [5]. Although subcostal exchange is our preferred technique for device exchange, this approach carries the risk of missing a thrombus outside the pump. Furthermore, when pump thrombosis is precipitated by anatomical abnormalities of the device (such as inflow malpositioning or outflow kinking), a resternotomy can help to correct the anomaly and minimize the risk of recurrence. We previously reported a high rate of recurrent thrombosis (31%) in patients who had a prior device exchange (subcostal or sternotomy) for thrombosis [27]. Similarly, in this study, 7 of 29 (24%) patients had a recurrent thrombotic event and underwent 2nd device exchange or explant. Recent studies suggest that device positioning, particularly inflow graft angulation and pump pocket depth, influence the risk of device thrombosis; hence a careful surgical technique should be used to ensure proper positioning of the LVAD at time of implant [28]. Moreover, there is an association between these 2 major complications of device exchange. Heightened inflammation as a result of infection can predispose a patient to a procoagulant status and increase the risk of having a thromboembolic event [29, 30]. Among the 12 patients who had device thrombosis requiring recurrent device exchange, 3 (25%) had a device-related infection within 2 months prior to the thrombotic event. Limitations Our study has several limitations. First, it is a single-centre retrospective study. Second, there are currently no standard criteria for infection in patients on LVAD support; hence the criteria for infection remains largely variable among studies. A consistent definition is needed in order to develop a better method for prevention and management of LVAD-associated infections. Furthermore, although we have focused only on device-specific complications, several other factors including gastrointestinal bleeding and systemic infection are large contributors to the morbidity and mortality of patients on LVAD support. CONCLUSION In conclusion, subcostal exchange is a safe procedure that can be performed with no in-hospital deaths and good long-term outcomes. However, a high prevalence of device-associated infections and thromboembolism persist following device exchange. Careful management of these complications is mandatory. 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Google Scholar CrossRef Search ADS PubMed  28 Taghavi S, Ward C, Jayarajan SN, Gaughan J, Wilson LM, Mangi AA. Surgical technique influences HeartMate II left ventricular assist device thrombosis. Ann Thorac Surg  2013; 96: 1259– 65. Google Scholar CrossRef Search ADS PubMed  29 Shah P, Mehta VM, Cowger JA, Aaronson KD, Pagani FD. Diagnosis of hemolysis and device thrombosis with lactate dehydrogenase during left ventricular assist device support. J Hear Lung Transplant  2014; 33: 102– 4. Google Scholar CrossRef Search ADS   30 Uriel N, Han J, Morrison KA, Nahumi N, Yuzefpolskaya M, Garan AR et al.   Device thrombosis in HeartMate II continuous-flow left ventricular assist devices: a multifactorial phenomenon. J Hear Lung Transplant  2014; 33: 51– 9. Google Scholar CrossRef Search ADS   © 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

Late outcomes of subcostal exchange of the HeartMate II left ventricular assist device: a word of caution

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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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10.1093/ejcts/ezy159
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Abstract

Abstract OBJECTIVES Previous studies have shown the usefulness of the subcostal exchange of the HeartMate II left ventricular assist device for device malfunction. However, long-term data are still limited. METHODS Between March 2004 and July 2017, 41 of 568 (7.2%) patients who had received a HeartMate II implant at our institution had a device exchange via a subcostal incision. We summarized early and late outcomes. RESULTS Forty-one patients had a total of 48 subcostal pump exchanges. Indications for device exchange included device thrombosis (n = 31, 76%), driveline infection (n = 2, 5%) and driveline injury (n = 8, 19%). All of the procedures were successful, and there were no in-hospital deaths. A Kaplan–Meier survival curve showed 30-day and 1-year survival rates after subcostal exchange of 100% and 94.6%, respectively. However, 10 (25%) patients had left ventricular assist device-related infections following subcostal exchange that included 7 pump pocket infections and 3 driveline infections. Freedom from left ventricular assist device-related infection at 1 year after subcostal exchange was 79.3%. Thirteen (32%) patients had device malfunction due to pump thrombosis that required a 2nd device exchange. Seven patients had recurrent thrombosis. Three (7%) patients had a stroke. Freedom from device thrombosis and from a stroke event at 1 year was 74.4%. CONCLUSIONS Subcostal pump exchange can be safely performed. However, there is a substantial risk of infection and recurrent thrombosis. Careful follow-up for late complications is mandatory. Ventricular assist device , Subcostal exchange , Device thrombosis , Device infection INTRODUCTION Device malfunction including device thrombosis is a not uncommon and potentially fatal complication during continuous-flow left ventricular assist device (LVAD) support. Since the initial reports of the abrupt increase in the incidence of device thrombosis with the HeartMate II (HM II, Abbott, Abbott Park, IL, USA) [1, 2], a yearly thrombosis rate of about 10% has been noted by the Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) reports [3]. The most recent report showed a higher incidence of device malfunctions involving the controller, battery and cable in addition to failure of the pump itself [4]. Once device malfunction is confirmed, early device exchange rather than watchful waiting is recommended to minimize the risk of adverse events [5]. The subcostal approach has been reported to be the preferred method for device exchange for patients who do not have inflow and outflow issues, because it is a less invasive procedure associated with shorter intensive care unit times and fewer postoperative complications than resternotomy [6–8]. However, data on the long-term clinical outcomes of this procedure are limited. In this study, our aim was to assess for late outcomes of patients who had subcostal HM II exchange. MATERIALS AND METHODS Patient selection This study was approved by the institutional review board of the Columbia University Medical Center. Between March 2004 and July 2017, 60 of 568 (10.6%) patients who had received a HM II implant at Columbia University Medical Center received a device exchange. Among them, the 41 (7.2%) patients who underwent subcostal exchange comprise our cohort of interest. Indication and surgical technique for subcostal exchange Once device malfunction is suspected, analysis of the log file is routinely performed. Radiographs are taken to detect driveline injury. Computed tomography angiography is used preoperatively to assess for kinking, malposition and thrombus in the inflow and outflow cannulas [9, 10]. For patients who have suspected device thrombosis, we routinely perform an echocardiographic ramp study [11] in addition to measuring serial serum lactate dehydrogenase and plasma-free haemoglobin levels. Our treatment algorithm for device thrombosis was reported previously [5]. Since June 2011, we have elected to perform a subcostal incision over a resternotomy for device exchange, unless there is a need to access the outflow or inflow cannulas (due to thrombus, infection or kinking of the graft) or to perform a concomitant cardiac procedure requiring sternotomy. Our surgical technique for subcostal HM II exchange was reported previously [6]. Briefly, a reverse J-shaped incision is made from the xiphoid process to the left mid-clavicular line to expose the pump from the bend relief site to the inflow arm. Cardiopulmonary bypass is initiated via femoral vessel cannulation. Most recently, a more limited incision (2 separate incisions) has been applied in order to minimize delayed wound healing (Fig. 1). Figure 1: View largeDownload slide A limited incision consisting of 2 separate incisions is now applied in order to minimize wound healing delay after subcostal exchange. Figure 1: View largeDownload slide A limited incision consisting of 2 separate incisions is now applied in order to minimize wound healing delay after subcostal exchange. Data collection and follow-up Medical records were reviewed for collection of baseline characteristics, postoperative complications and outcomes. Median support duration from initial subcostal exchange to time of analysis was 1876 days (1309–2292). Follow-up information was available and collected until 31 July 2017 for all patients. Postoperative complications included right ventricular failure, acute kidney injury, ventricular arrhythmia, gastrointestinal bleeding, LVAD-related infection, stroke and device thrombosis according to INTERMACS definitions. Driveline and pump pocket infections were confirmed by wound culture and radiological observation of fluid collections [12]. Stroke was confirmed by a brain imaging study. Duration to heart transplant was calculated as time from initial subcostal exchange. Statistical analysis Continuous variables are reported as mean ± standard deviation. The 95% confidence intervals (CIs) are additionally represented. Kaplan–Meier analysis was used to calculate survival rates and freedom from device complications with plots truncated after 3 years due to limited observations at later time points. Statistical significance was defined as a 2-sided α ≤ 0.05. Statistical analysis was performed using Stata 14 software (Stata Corp, College Station, TX, USA). RESULTS Patient baseline characteristics Baseline characteristics are summarized in Table 1. The mean age was 54.6 ± 13.5 years; 80% were men; 32% had ischaemic and 61% had dilated aetiologies; 63% were designated for bridge to transplant. Table 1: Baseline characteristics at the time of the primary subcostal device exchange   n = 41  Age (years)  54.6 ± 13.5  Male (%)  33 (80)  BMI (kg/m2)  27.3 ± 5.4  BSA (m2)  2.0 ± 0.2  Intention to treat     BTT  26 (63)   DT  15 (37)  Aetiology of cardiomyopathy     Dilated  25 (61)   Ischaemic  13 (32)   Other  3 (7)  Hypertension  21 (51)  Diabetes mellitus  12 (29)  Hyperlipidaemia  15 (37)  Indication for exchange     Device thrombosis  31 (76)   Driveline infection  2 (5)   Driveline injury  8 (19)  Incisional approach     Extended J-shaped incision  35 (85)   Modified 2-incision approach  6 (15)  Support duration to subcostal exchange (days)  462 (178–778)  Preoperative laboratory values     WBC (×1000/ml)  7.3 ± 2.0   Haemoglobin (g/dl)  10.6 ± 2.0   Haematocrit (%)  32.5 ± 5.5   Platelets (×1000/ml)  178.2 ± 68.0   LDH (U/l)  1080 (420–1753)   INR  1.6 (1.2–1.9)   BUN (mg/dl)  22.0 (15.0–31.0)   Creatinine (mg/dl)  1.3 (1.0–1.6)  Pump parameters     Pump flow (l/min)  5.3 ± 0.9   Pump speed (rpm)  9150 ± 500   Pulsatility index  4.9 ± 1.8   Power (W)  5.8 ± 1.5  CPB time (min)  22 (12–27)  Length of ICU stay (days)  5 (4–8)    n = 41  Age (years)  54.6 ± 13.5  Male (%)  33 (80)  BMI (kg/m2)  27.3 ± 5.4  BSA (m2)  2.0 ± 0.2  Intention to treat     BTT  26 (63)   DT  15 (37)  Aetiology of cardiomyopathy     Dilated  25 (61)   Ischaemic  13 (32)   Other  3 (7)  Hypertension  21 (51)  Diabetes mellitus  12 (29)  Hyperlipidaemia  15 (37)  Indication for exchange     Device thrombosis  31 (76)   Driveline infection  2 (5)   Driveline injury  8 (19)  Incisional approach     Extended J-shaped incision  35 (85)   Modified 2-incision approach  6 (15)  Support duration to subcostal exchange (days)  462 (178–778)  Preoperative laboratory values     WBC (×1000/ml)  7.3 ± 2.0   Haemoglobin (g/dl)  10.6 ± 2.0   Haematocrit (%)  32.5 ± 5.5   Platelets (×1000/ml)  178.2 ± 68.0   LDH (U/l)  1080 (420–1753)   INR  1.6 (1.2–1.9)   BUN (mg/dl)  22.0 (15.0–31.0)   Creatinine (mg/dl)  1.3 (1.0–1.6)  Pump parameters     Pump flow (l/min)  5.3 ± 0.9   Pump speed (rpm)  9150 ± 500   Pulsatility index  4.9 ± 1.8   Power (W)  5.8 ± 1.5  CPB time (min)  22 (12–27)  Length of ICU stay (days)  5 (4–8)  Values are represented as mean ± SD, median (Q1–Q3) or n (%). BMI: body mass index; BSA: body surface area; BTT: bridge to transplant; BUN: blood urea nitrogen; CPB: cardiopulmonary bypass; DT: destination therapy; ICU: intensive care unit; INR: international normalized ratio; LDH: lactate dehydrogenase; WBC: white blood cells. Table 1: Baseline characteristics at the time of the primary subcostal device exchange   n = 41  Age (years)  54.6 ± 13.5  Male (%)  33 (80)  BMI (kg/m2)  27.3 ± 5.4  BSA (m2)  2.0 ± 0.2  Intention to treat     BTT  26 (63)   DT  15 (37)  Aetiology of cardiomyopathy     Dilated  25 (61)   Ischaemic  13 (32)   Other  3 (7)  Hypertension  21 (51)  Diabetes mellitus  12 (29)  Hyperlipidaemia  15 (37)  Indication for exchange     Device thrombosis  31 (76)   Driveline infection  2 (5)   Driveline injury  8 (19)  Incisional approach     Extended J-shaped incision  35 (85)   Modified 2-incision approach  6 (15)  Support duration to subcostal exchange (days)  462 (178–778)  Preoperative laboratory values     WBC (×1000/ml)  7.3 ± 2.0   Haemoglobin (g/dl)  10.6 ± 2.0   Haematocrit (%)  32.5 ± 5.5   Platelets (×1000/ml)  178.2 ± 68.0   LDH (U/l)  1080 (420–1753)   INR  1.6 (1.2–1.9)   BUN (mg/dl)  22.0 (15.0–31.0)   Creatinine (mg/dl)  1.3 (1.0–1.6)  Pump parameters     Pump flow (l/min)  5.3 ± 0.9   Pump speed (rpm)  9150 ± 500   Pulsatility index  4.9 ± 1.8   Power (W)  5.8 ± 1.5  CPB time (min)  22 (12–27)  Length of ICU stay (days)  5 (4–8)    n = 41  Age (years)  54.6 ± 13.5  Male (%)  33 (80)  BMI (kg/m2)  27.3 ± 5.4  BSA (m2)  2.0 ± 0.2  Intention to treat     BTT  26 (63)   DT  15 (37)  Aetiology of cardiomyopathy     Dilated  25 (61)   Ischaemic  13 (32)   Other  3 (7)  Hypertension  21 (51)  Diabetes mellitus  12 (29)  Hyperlipidaemia  15 (37)  Indication for exchange     Device thrombosis  31 (76)   Driveline infection  2 (5)   Driveline injury  8 (19)  Incisional approach     Extended J-shaped incision  35 (85)   Modified 2-incision approach  6 (15)  Support duration to subcostal exchange (days)  462 (178–778)  Preoperative laboratory values     WBC (×1000/ml)  7.3 ± 2.0   Haemoglobin (g/dl)  10.6 ± 2.0   Haematocrit (%)  32.5 ± 5.5   Platelets (×1000/ml)  178.2 ± 68.0   LDH (U/l)  1080 (420–1753)   INR  1.6 (1.2–1.9)   BUN (mg/dl)  22.0 (15.0–31.0)   Creatinine (mg/dl)  1.3 (1.0–1.6)  Pump parameters     Pump flow (l/min)  5.3 ± 0.9   Pump speed (rpm)  9150 ± 500   Pulsatility index  4.9 ± 1.8   Power (W)  5.8 ± 1.5  CPB time (min)  22 (12–27)  Length of ICU stay (days)  5 (4–8)  Values are represented as mean ± SD, median (Q1–Q3) or n (%). BMI: body mass index; BSA: body surface area; BTT: bridge to transplant; BUN: blood urea nitrogen; CPB: cardiopulmonary bypass; DT: destination therapy; ICU: intensive care unit; INR: international normalized ratio; LDH: lactate dehydrogenase; WBC: white blood cells. Indications for subcostal exchange included device thrombosis (n = 31, 76%), driveline infection (n = 2, 5%) and driveline injury (n = 8, 19%). The extended J incision was used in 35 (85%) patients, whereas 6 underwent a modified 2-incision approach. Median duration on LVAD support until subcostal exchange was 462 (178–778) days. Early outcomes There were no in-hospital deaths after subcostal exchange. Early postoperative complications included right ventricular failure (n = 2), acute kidney injury (n = 4), ventricular tachycardia (n = 5), gastrointestinal bleeding (n = 2) and amiodarone-induced thyrotoxicosis (n = 1). Follow-up complications Freedom from LVAD-related infection 30 days and 1 year after subcostal exchange was 95.1% and 79.3%, respectively (Fig. 2A). Ten (25%) patients had pump pocket or driveline infection following subcostal exchange (Table 2). Two patients had early pump pocket infection during the indexed hospitalization and underwent surgical incision and drainage. The remaining 8 LVAD-related infections occurred a mean of 462 (95% CI 22–903) days after subcostal exchange, with 3 patients who developed infection after 1 year. Four required incision and drainage with vacuum-assisted closure therapy, all of whom had chronic infection and required later surgical debridement. One patient had an LVAD explant and subsequent reinsertion 2 weeks after the infection resolved. The other 3 patients who had isolated driveline infection were managed with long-term antibiotic therapy and did not have recurrent infection. Staphylococcus genus and Pseudomonas aeruginosa were the most commonly detected pathogens on wound culture (Table 2). Table 2: Left ventricular assist device-related infection after subcostal exchange   n = 10  LVAD-related infection     Driveline infection  3   Pump pocket infection  7  Pathogens     Staphylococcus      Methicillin-sensitive  1    Methicillin-resistant  1    Staphylococcus lugdunensis  1   Pseudomonas aeruginosa  3   Serratia marcescens  2   Enterococcus faecalis (formerly Enterobacter faecalis)  1   Culture negative  1    n = 10  LVAD-related infection     Driveline infection  3   Pump pocket infection  7  Pathogens     Staphylococcus      Methicillin-sensitive  1    Methicillin-resistant  1    Staphylococcus lugdunensis  1   Pseudomonas aeruginosa  3   Serratia marcescens  2   Enterococcus faecalis (formerly Enterobacter faecalis)  1   Culture negative  1  LVAD: left ventricular assist device. Table 2: Left ventricular assist device-related infection after subcostal exchange   n = 10  LVAD-related infection     Driveline infection  3   Pump pocket infection  7  Pathogens     Staphylococcus      Methicillin-sensitive  1    Methicillin-resistant  1    Staphylococcus lugdunensis  1   Pseudomonas aeruginosa  3   Serratia marcescens  2   Enterococcus faecalis (formerly Enterobacter faecalis)  1   Culture negative  1    n = 10  LVAD-related infection     Driveline infection  3   Pump pocket infection  7  Pathogens     Staphylococcus      Methicillin-sensitive  1    Methicillin-resistant  1    Staphylococcus lugdunensis  1   Pseudomonas aeruginosa  3   Serratia marcescens  2   Enterococcus faecalis (formerly Enterobacter faecalis)  1   Culture negative  1  LVAD: left ventricular assist device. Figure 2: View largeDownload slide Freedom from adverse events: (A) left ventricular assist device-related infection; (B) device thrombosis and stroke. CI: confidence interval. Figure 2: View largeDownload slide Freedom from adverse events: (A) left ventricular assist device-related infection; (B) device thrombosis and stroke. CI: confidence interval. Freedom from device thrombosis and a stroke event 30 days and 1 year after subcostal exchange was 100% and 74.4%, respectively (Fig. 2B). Three (7%) patients suffered a stroke at 17, 28 and 86 days after the exchange. Thirteen (32%) patients had recurrent device malfunction requiring surgical interventions at a mean of 454 (95% CI 118–789) days after the initial subcostal exchange. Twelve had device thrombosis, 7 of whom had recurrent thrombosis (the indication for the initial and 2nd device exchanges was device thrombosis). These patients required a 2nd device exchange via a subcostal exchange (n = 6), a device exchange via resternotomy (n = 4) or a heart transplant (n = 2). One patient had driveline injury after the exchange and required a resubcostal exchange. Freedom from recurrent device malfunction at 1 year was 88%. Late outcomes Of 41 patients, 21 (51%) had a heart transplant a mean of 268 (95% CI 175–361) days after the initial subcostal exchange. The Kaplan–Meier survival curve showed 30-day and 1-year survival rates after subcostal exchange of 100% and 94.6%, respectively (Fig. 3). Figure 3: View largeDownload slide Survival after subcostal exchange. CI: confidence interval. Figure 3: View largeDownload slide Survival after subcostal exchange. CI: confidence interval. DISCUSSION We examined early and late outcomes after subcostal device exchange for HM II device malfunction. Many studies have reported the subcostal technique to be a procedure with a low early mortality rate [13, 14]. Likewise, there were no in-hospital deaths with the subcostal exchange in our study, further supporting the safeness of this surgical technique when device exchange is warranted. However, LVAD-related infections and recurrent device malfunction are major causes of morbidity during the late follow-up period. With the rising frequency and duration of support on LVAD therapy, preventive measures and appropriate management of these device complications are necessary. Device-related infection is one of the most common causes for readmission for patients on LVAD support, with a reported incidence in up to 59% of patients [15–20]. Driveline infection is the most common LVAD-related infection [17] because it is often the site of entry for pathogens. Staphylococci are the most common pathogens reported, followed by pseudomonads [17, 21, 22]. If it is not properly treated, infection of the driveline can subsequently invade the pump pocket and cause systemic bloodstream complications, which can result in death. Although device-related infections are well-described in the literature, our study is the first to assess the incidence of infection as a consequence of device exchange. In our cohort, 25% of patients had an LVAD-related infection after subcostal exchange. Notably, 70% of these patients suffered from pump pocket infection that was not related to driveline infection, including 2 patients who had early pocket infection. Furthermore, it is important to note that the majority of device-related infections occurred after the patients were discharged following subcostal exchange. Prior studies have mentioned that most LVAD infections occur out of the hospital as a result of trauma at the driveline site [21, 22]. This result speaks to the fact that, whereas device exchange is an invasive procedure that can increase the susceptibility of patients to infection, the high rate of infection is inevitable largely due to the percutaneous nature of the HM II devices. Techniques to stabilize the driveline and minimize trauma are currently in development [23, 24]. Moreover, we thought that some of the late pocket infections were related to delayed wound healing resulting from the extended J incision with transection of the rectus muscles, fascia and ribs. These patients returned with probable pump pocket contamination from the incision. Based on our observations, we now perform a more limited 2-incision approach, as was done for 6 patients in this study, to minimize the opportunity and entry site for infection. Since we implemented this technique, we have not seen any type of pump pocket infection. The best treatment for LVAD-associated infections is device explant and/or heart transplant [25], but this option is often not available. Overall, patients in our study with driveline and pump pocket infections were managed successfully with antibiotic therapy and surgical debridement with or without vacuum-assisted closure. Device thrombosis is another detrimental complication of LVAD therapy that has become of particular concern in recent years. Since 2011, the incidence of HM II device thrombosis has increased [1, 2]. Adherence to a standardized practice for clinical management was shown to reduce the risk of early device thrombosis in the PREVENT clinical trial [26]; however, many thromboembolic events also occur as late complications in patients on LVAD support. Once device thrombosis occurs, early device exchange should be considered rather than a watch and wait approach [5]. Although subcostal exchange is our preferred technique for device exchange, this approach carries the risk of missing a thrombus outside the pump. Furthermore, when pump thrombosis is precipitated by anatomical abnormalities of the device (such as inflow malpositioning or outflow kinking), a resternotomy can help to correct the anomaly and minimize the risk of recurrence. We previously reported a high rate of recurrent thrombosis (31%) in patients who had a prior device exchange (subcostal or sternotomy) for thrombosis [27]. Similarly, in this study, 7 of 29 (24%) patients had a recurrent thrombotic event and underwent 2nd device exchange or explant. Recent studies suggest that device positioning, particularly inflow graft angulation and pump pocket depth, influence the risk of device thrombosis; hence a careful surgical technique should be used to ensure proper positioning of the LVAD at time of implant [28]. Moreover, there is an association between these 2 major complications of device exchange. Heightened inflammation as a result of infection can predispose a patient to a procoagulant status and increase the risk of having a thromboembolic event [29, 30]. Among the 12 patients who had device thrombosis requiring recurrent device exchange, 3 (25%) had a device-related infection within 2 months prior to the thrombotic event. Limitations Our study has several limitations. First, it is a single-centre retrospective study. Second, there are currently no standard criteria for infection in patients on LVAD support; hence the criteria for infection remains largely variable among studies. A consistent definition is needed in order to develop a better method for prevention and management of LVAD-associated infections. Furthermore, although we have focused only on device-specific complications, several other factors including gastrointestinal bleeding and systemic infection are large contributors to the morbidity and mortality of patients on LVAD support. CONCLUSION In conclusion, subcostal exchange is a safe procedure that can be performed with no in-hospital deaths and good long-term outcomes. However, a high prevalence of device-associated infections and thromboembolism persist following device exchange. Careful management of these complications is mandatory. 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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 10, 2018

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