ASAIO Journal 2014

Adult Circulatory Support

Modified HeartMate II Driveline Externalization Technique Significantly Decreases Incidence of Infection and Improves Long-Term Survival Ajeet Singh,* Mark J. Russo,* Tracy B. Valeroso,* Allen S. Anderson,† Jonathan D. Rich,† Valluvan Jeevanandam,* and Shahab A. Akhter‡

Driveline (DL) infection has been a major source of morbidity and mortality following HeartMate II left ventricular assist device (LVAD) implant, despite a significantly lower incidence compared with pulsatile flow devices. The purpose of this study was to compare the incidence of DL infection using two different externalization techniques. Between July 1, 2008, and October 15, 2011, 125 consecutive patients underwent HeartMate II LVAD implant at a single institution. Patients that underwent implant in 2008–2009 (n = 45) had the velour portion of the DL externalized (Velour group) and those that were implanted in 2010–2011 (n = 80) had only the silicone portion externalized (Silicone group). Kaplan–Meier analysis with logrank test was used to compare actuarial DL infection-free survival and a composite of death and DL infection-free survival. There were 20/45 (44.4%) DL infections in the Velour group compared with 7/80 (8.8%) in the Silicone group. Driveline infection-free survival was significantly better for the Silicone versus Velour group as was the composite end-point of death and infection-free survival (p < 0.001). Externalization of only the silicone portion of the DL led to a dramatic reduction in infections and significantly improved survival after implant. This represents an opportunity to decrease the incidence of this important cause of morbidity and mortality after LVAD implant. ASAIO Journal 2014; 60:613–616.

a DL infection1 and 35% of patients in the HeartMate II DT trial had a device-related infection.2 Given that DL infections generally cannot be eradicated by antibiotic therapy, surgical debridement, or pump exchange, it is imperative to develop new strategies for minimizing or eliminating this currently frequent complication. The HeartMate II DL is coated with velour for approximately the first half of its length with the remainder being coated with silicone. The most common technique for externalization of the HeartMate II DL has been with exposure of much of its length in the right upper quadrant. A significant length of the velour portion of the DL is exposed as is the entire silicone portion. Different techniques of DL stabilization have been described, including the use of an abdominal binder, a stomal appliance, and a Holister clamp device. It is thought that mobility at the DL exit site leads to poor healing and increased risk of infection. Our program at the University of Chicago Medical Center used this technique for DL placement from 2008 through the end of 2009 in addition to an abdominal binder. In an attempt to decrease the incidence of DL infection, we began to externalize only the silicone portion, leaving the majority of the DL within the preperitoneal pocket. This study compares the relative rates of DL infection by technique and long-term survival between these groups. Methods

Key Words:  LVAD, driveline, infection

The transition from pulsatile to continuous-flow left ven-

Study Design We conducted a retrospective review of all patients undergoing HeartMate II LVAD implantation at the University of Chicago Medical Center from June 1, 2008, through October 15, 2011, after receiving Institutional Review Board approval. The two patient groups analyzed include (1) those with the velour segment of the DL externalized (June 2008–December 2009) and (2) those with only the silicone segment of the DL exposed (January 2010–October 2011). The primary end-points of this study are diagnosis of a DL or pocket infection and long-term survival. The diagnosis of a DL infection was a positive bacterial culture of drainage from the site.

tricular assist devices (LVADs) has been associated with a significant decline in overall complication rates, significantly improved durability, and much better long-term survival for both the bridge to transplant and the destination therapy (DT) indications. Despite these encouraging results, driveline (DL) infection has been a persistent problem. In the HeartMate II bridge to transplant (BTT) trial, 14% of patients developed From the Sections of *Cardiac and Thoracic Surgery and †Cardiology, University of Chicago Medical Center, Chicago, Illinois; and ‡Division of Cardiothoracic Surgery, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin. Submitted for consideration January 2014; accepted for publication in revised form June 2014. Disclosures: Dr. Akhter receives grant support from Thoratec Corporation. Dr. Valluvan Jeevanandam serves as a consultant to Thoratec Corporation and Heartware. Correspondence: Shahab A. Akhter, MD, Division of Cardiothoracic Surgery, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792. Email: [email protected] Copyright © 2014 by the American Society for Artificial Internal Organs

Prophylactic Antibiotic Regimen and DL Care Protocol All patients in both groups received 1–2 g of cefazolin as dosed by weight within 30 minutes before making skin incision. This dose was then administered every 8 hours for three more doses. Driveline site dressing changes were performed daily or more frequently if any drainage was present. The site was cleaned circumferentially with Hibiclens during each dressing change and secured with a gauze dressing and paper tape. The

DOI: 10.1097/MAT.0000000000000121

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614 SINGH et al. dressing changes were performed using sterile technique, and this was performed by the patients upon discharge home. Every patient was also counseled on wearing an abdominal binder. Driveline Externalization Technique In the velour externalization group (velour group), the DL was brought out directly from the preperitoneal pocket through the abdominal wall in the right upper quadrant with the majority of the velour portion of the DL exposed. A subcuticular stitch is placed at the exit site to obliterate the space between the DL and the skin edge and an anchoring stitch is placed to secure the DL to the skin to minimize movement of the DL. This is done at approximately 6 cm from the exit site. The modified technique involved externalization of only the silicone portion of the DL (silicone group), leaving the velour portion buried in the preperitoneal pocket. The tunneling device was passed inferiorly through the exit site and then curved upward before traversing the abdominal wall into the pocket. The velour–silicone interface was placed 2 cm from the exit site within the subcutaneous layer and the DL was tunneled subcutaneously for a length of approximately 10–12 cm. The DL is placed posterior to the LVAD. The skin exit site is again secured with a dissolvable subcuticular stitch and the DL is anchored to the skin approximately 6 cm from the exit site (Figure 1). The externalization techniques are also shown comparatively in Figure 2. Data Analysis The primary outcomes of the study were DL infection and survival on LVAD support in patients with or without postimplantation DL infection. Kaplan–Meier analysis was used to estimate cumulative survival rates, and groups were compared using the log rank test. Patients who were transplanted at the time of analysis were censored from the survival analysis. Variables are presented as mean ± SD and percentages were appropriate. Comparison of continuous variables was performed using Student’s t-test, whereas discrete variables were compared using χ2 or Fisher’s exact tests were indicated. For all analyses, a p value of 0.05 or less was considered statistically significant. All data were analyzed using SPSS version 17.0 (SPSS, Chicago, IL).

Figure 1. Radiographic image of driveline course and externalization site. The circle denotes the driveline exit site and the solid line denotes the silicone–velour interface of the driveline coating. The driveline is placed posterior to the LVAD in the preperitoneal pocket.

Results One hundred twenty-five patients underwent HeartMate II LVAD implantation at the University of Chicago Medical Center between July 1, 2008, and October 15, 2011. There were 45 patients in the velour group (2008–2009) and 80 in the silicone group (2010–2011). There were 20 (44.4%) DL infections in the velour group compared with 7 (8.8%) in the silicone group. There were no pump pocket infections in either group by imaging studies. The mean time for the diagnosis of DL infection in the velour group was 6.1 ± 0.8 months (range

Figure 2. A: Patient image with velour portion of the driveline externalized in the right upper quadrant. B: Patient image with only the silicone portion of the driveline externalized with velour–silicone interface 2–3 cm below the skin.



DRIVELINE TECHNIQUE DECREASES INFECTION

Figure 3. Kaplan–Meier analysis of freedom from driveline infection while on support. n = 45 in the velour group (solid line) and n = 80 in the silicone group (dashed line). p < 0.001 between groups.

1–11 months). Between the two groups, neither was there any significant difference in INTERMACS score nor was there any significant difference in experience between the BTT and DT groups. The most common organisms isolated were methicillin-sensitive Staphylococcus aureus and pseudomonas. Mean follow-up duration was 628.2 ± 231.1 days, and time at risk for DL infection was 76,525 days. In the velour group, freedom from DL infection was 80% at 1 year and 63% at 2 years by Kaplan–Meier analysis, whereas it was maintained at 91% at both time points in the silicone group (p < 0.001) (Figure 3). For the composite end-point of freedom from DL infection and death, there was an even more marked and sustained difference between groups: 25% in the velour group versus 69% in the silicone group at both 1 year and out to 500 days (p < 0.001) (Figure 4). Discussion Left ventricular assist device-related infections pose a significant risk to patients receiving mechanical circulatory support

Figure 4. Kaplan–Meier analysis of freedom from driveline infection and death while on support. n = 45 in the velour group (solid line) and n = 80 in the silicone group (dashed line). p < 0.001 between groups.

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with mortality ranging between 10% and 44%.3 Even though the number of annual LVAD implants has increased fivefold from 2006 to 2011, the incidence of infection still ranges from 30% to 50%.4 Preventing infection is thus a priority in advancing methods to reduce mortality and improve long-term outcomes. The approach we took was to revisit the structure and placement of the DL at its point of entry through the skin. Exit-site porosity in a DL component correlates with tissue ingrowth, which holds a number of secondary consequences. With the velour group, the implant demonstrated excellent tissue adhesions. However, as a result, without total stabilization, even minor trauma could cause irreversible disruption to the skin, adding to the risk for infection. On the contrary, with only the silicone externalized, a sinus is formed and the DL demonstrated a low porosity, potentially preventing a degree of bacterial seeding. As a result, the DL placement showed little to no skin adhesion at all. Minor trauma to the DL by this modified technique did not disrupt the skin–DL interface and thus may be responsible for decreasing the risk of infection. Furthermore, the internalized velour portion acts as an additional anchor within the preperitoneal pocket and the subcutaneous plane to bolster DL stability. Historically, in the dialysis catheter model, clinical observations suggested that limited internal cuff tissue ingrowth significantly contributed to a high incidence of exit-site infection.5 Situated further up the catheter, past dermal barriers, the dialysis catheter cuff experiences soft tissue interaction that has long been known to reduce the risk of infection by enhancing vascular tissue ingrowth.6 The field has since experimented with alternative components, such as collagen fibers and titanium meshes, to find more porous cuff materials that will continue to reinforce the position of the catheter within the body and reduce the incidence of infection.7,8 Curbing this incidence would not only reduce the risk of infections but also infection-related complications. Infection, potentially devastating on its own, also contributes to bleeding and thromboembolic events including cerebrovascular accidents.9 In conclusion, externalization of only the silicone portion of the DL has decreased the incidence of DL infection from 40% to approximately 9% in these two cohorts of continuousflow LVAD patients. There was no significant difference in the incidence of DL infection during the first 30 days post-implant between groups. LVAD-related infections during this early time period likely reflect intraoperative issues and are probably not associated with DL externalization technique. This has led to an increase in long-term survival and a dramatic reduction in readmission rates and resource utilization at our institution. Our study has several important limitations. This is a single institution retrospective analysis, and we are currently involved in a multi-institutional prospective study to investigate the potential reduction of DL infection using this specific DL externalization technique. In addition, the follow-up period in the silicone group was shorter than in the velour group and these patients will continue to be followed to determine if late DL infection is significantly more prevalent than within the first 2 years. This will provide a definitive answer to whether the timeline to initial event leading to DL infection is just delayed in the silicone group or if, in fact, the lower incidence is maintained in the longer term. Based on the current study, we believe that modification of the externalization technique to expose only the

616 SINGH et al. silicone portion of the DL represents an important advance in prevention of LVAD-related infection and subsequent morbidity and mortality. This is even more important in the DT population where significant growth in this therapy is anticipated. References 1. Miller LW, Pagani FD, Russell SD, et al; HeartMate II Clinical Investigators: Use of a continuous-flow device in patients awaiting heart transplantation. N Engl J Med 357: 885–896, 2007. 2. Slaughter MS, Rogers JG, Milano CA, et al; HeartMate II Investigators: Advanced heart failure treated with continuous-flow left ventricular assist device. N Engl J Med 361: 2241–2251, 2009. 3. Herrmann M, Weyand M, Greshake B, et al: Left ventricular assist device infection is associated with increased mortality but is not a contraindication to transplantation. Circulation 95: 814– 817, 1997.

4. Nienaber J, Wilhelm MP, Sohail MR: Current concepts in the diagnosis and management of left ventricular assist device infections. Expert Rev Anti Infect Ther 11: 201–210, 2013. 5. Schreuders PD, Salthouse TN, von Recum AF: Normal wound healing compared to healing within porous Dacron implants. J Biomed Mater Res 22: 121–135, 1988. 6. Oreopoulos DG: Peritoneal dialysis–year 2010. Perit Dial Int 16: 109–112, 1996. 7. Walboomers F, Paquay YC, Jansen JA: A new titanium fiber meshcuffed peritoneal dialysis catheter: Evaluation and comparison with a Dacron-cuffed tenckhoff catheter in goats. Perit Dial Int 21: 254–262, 2001. 8. Arita T, Asoda S, Koshitomae H, Katakura H, Takakuda K: Collagen fiber anchoring platforms for percutaneous devices. ASAIO J 56: 235–240, 2010. 9. McCarthy PM, Schmitt SK, Vargo RL, Gordon S, Keys TF, Hobbs RE: Implantable LVAD infections: implications for permanent use of the device. Ann Thorac Surg 61: 359–365, 1996.

Modified HeartMate II driveline externalization technique significantly decreases incidence of infection and improves long-term survival.

Driveline (DL) infection has been a major source of morbidity and mortality following HeartMate II left ventricular assist device (LVAD) implant, desp...
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