Two-thirds of all late percutaneous DLI occurred in patients who had the pump implanted as destination therapy, and on multivariate analysis, duration of support was independently associated with increased risk of developing late percutaneous DLI; this risk rose 4% for each month on support. When analyzed as a time-dependent covariate, development of a late percutaneous DLI did not significantly affect late survival in either the No Abx group (HR: 0.164, [0.022, 1.21], p = 0.076) or the Abx group (HR: 0.21, [0.03, 1.6], p = 0.131).
This study demonstrates that raw incidence of and time-related freedom from late percutaneous DLI was similar in patients who received chronic prophylactic antibiotics after VAD implantation compared with those who did not receive chronic prophylactic antibiotics. Similar to a new report,11 we found that length of support after VAD implant was most predictive of development of late percutaneous DLI, and not surprisingly, the majority of percutaneous DLI occurred in destination therapy patients. In contrast to other studies,5 we did not observe a negative impact on survival in patients who developed a late percutaneous DLI.
Although this is the first study to specifically compare patients receiving antibiotics for DLI prevention with those who did not, it outlines that the likelihood that other factors play a more influential role for the development of DLI. For instance, trauma has consistently been identified as an important causative factor for the development of DLI.12,13 An adherent interface between the velour of the driveline and the patient’s tissues is critical for the protection against entry of microorganisms and subsequent infection. As patients become increasingly mobile after LVAD implantation, shearing and torsion of this site can disrupt this intact surface and continued sliding of the driveline prevents future readherence. This promotes a new tract adjacent to the driveline, which can then hypothetically serve as a portal for deeper infection.4 All patients in this series were educated not only in sterile driveline site care but also of the importance of driveline immobilization. Although not uniform between the two institutions participating in this study or all the operating surgeons, the following are some maneuvers we employ to prevent mechanical stress on the driveline exit site. Early postoperatively, an anchoring stitch is placed on the skin and the driveline is secured to this area approximately 6 inches from the exit site. This point of fixation serves to protect against tugging in the early postoperative period as tension will be exerted at this point and not the exit site while it is healing and becoming incorporated. In addition, a pursestring suture is also fashioned in the subdermal layer immediately at the exit site to encourage sealing of the skin to the driveline itself. In addition, we avoid allowing this site to become wet until well after it has become healed and the skin incorporated onto the driveline. We believe that these maneuvers are likely far more critical than antibiotic prophylaxis in the prevention of late percutaneous DLI. Certainly, patient compliance with daily site care and “buy-in” to the importance of avoidance of trauma will play a crucial role in reducing the incidence of these events in the future.
When a patient has a suspected percutaneous DLI, we favor readmission to the hospital and instituting intravenous antibiotic therapy as soon as possible. We obtain blood cultures as well as a driveline site swab for culture. Consistent with others,4,7 staphylococci were present in the majority of cultures we obtain from driveline swab site swab. It is well documented that organisms found in the bloodstream can match those found at the driveline exit site and vice versa.14–16 Computerized tomography can be obtained to evaluate for deeper fluid collections; however, in our experience, interference from the device makes definitive evaluation challenging. Ultrasonography can also be used to evaluate the patient for abscesses or deeper fluid collections.
Progression of a superficial percutaneous DLI to a deeper pump pocket infection is a significant concern and may result in the need for device exchange or urgent transplantation.17–19 Furthermore, device exchange or transplantation for significant driveline infection is much less morbid than for a pump pocket infection. Device exchange for infection can be performed with low morbidity and low rate in reinfection if performed before development of a frank pump pocket infection.19 As a result, one institution (University of Michigan Health System) in this study is aggressive at device exchange, whereas the other (MC) has been successful in local treatment of these infections, including vacuum-assisted therapy20,21 and even local surgical debridement.22 Although the approaches to treatment of percutaneous DLI differed between institutions, the prevention strategies employed before developing the infection was the focus of this study.
Although percutaneous DLI is recognized as the “Achilles’ Heel” of LVAD therapy, prevention is the best intervention for addressing this complication rather than treating the complication itself once it develops. In our practice, thorough patient education includes respecting the importance of driveline immobilization, daily driveline site care, and early recognition of possible percutaneous DLI. Routine follow-up evaluation after LVAD implantation with inspection of the driveline exit site is also critical. If an infection develops, the aforementioned interventions are employed for early diagnosis and treatment. A multidisciplinary approach with involvement of surgeons, nursing staff, VAD coordinators, cardiologists, and infectious disease specialists optimizes effective management of these patients.
As mentioned earlier, this was a comparison of two different institutions and thus reflects two different practices. This was responsible for some of the disparate findings between cohorts and between outcomes. The majority of patients at University of Michigan Health System were implanted as bridge to transplant, whereas most at MC were destination therapy, and this also reflects why the cohort from MC was older. Other preoperative clinical characteristics were generally equivalent. There were more redo sternotomies, concomitant valve procedures, and longer operative times at MC, and despite these differences, late DLI was still similar compared with the University of Michigan Health System cohort. This emphasizes the point that while these factors have been identified as risk factors for increased risk of percutaneous DLI, the most important factor is likely maintenance of the site and avoidance of trauma. Chronic prophylactic antibiotics did not seem to play a significant role in preventing percutaneous DLI in this study.
This study has several important limitations that need acknowledged. Although this data was prospectively collected, it was retrospectively analyzed. In comparing the practices of two different institutions, differences in patient populations were also encountered. These differences existed in preoperative characteristics, operative data, and early postoperative outcomes. Despite this, interestingly, outcomes of primary interest, specifically percutaneous DLI was similar between the groups. We were not able to confirm a history of trauma as a cause of DLI in the majority of patients. Also, importantly, while all patients received perioperative prophylactic antibiotics, there was a wide variation in practices in this regard as to the types of antibiotics and duration postoperatively.
In summary, we demonstrate similar incidence of percutaneous DLI in patients receiving chronic antibiotic prophylaxis in addition to daily site care compared with those who only performed daily site care without antibiotics. The development of DLI did not negatively impact late survival in these patients. Duration of support was identified as the highest risk factor for development of percutaneous DLI after LVAD implant.
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Keywords:Copyright © 2013 by the American Society for Artificial Internal Organs
infection; driveline; mechanical circulatory support