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Ann Thorac Surg 1999;68:1875-1877
© 1999 The Society of Thoracic Surgeons

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How to Do It

A novel method to reduce device-related infections in patients supported with the HeartMate device

^a Department of Thoracic and Cardiovascular Surgery, Heart Center North Rhine-Westphalia, Ruhr University of Bochum, Bad Oeynhausen, Germany
^b Thermo Cardiosystems, Inc, Woburn, Massachusetts, USA

Address reprint requests to Dr El-Banayosy, Herzzentrum NRW, Klinik für Thorax und Kardiovaskularchirurgie, Georgstr 11, D-32545 Bad Oeynhausen, Germany

	Abstract

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Improved implantable left ventricular assist device technology has made survival to heart transplantation a near certainty. Nevertheless, infection remains a major risk to recipients of current percutaneous systems. We developed a modified implantation technique applied to the last 9 of 30 patients who received the HeartMate vented electric left ventricular assist system (LVAS). Covering the upper surface of the pump with a patch of knitted graft material was followed by a decline in the incidence of pocket infections from 33.3% to 11.1%. This modification compares favorably to that of a lengthened percutaneous driveline tunnel in reducing device-related infection.

	Introduction

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The development of implantable left ventricular assist devices has inaugurated a new era of mechanical circulatory support and made sustained, effective therapy for end-stage congestive heart failure a reality. Current systems offer patients resolution of their heart failure symptoms, improved mobility, and the ability to await transplantation at home. Until recently, infection, thrombembolic complications, design durability and energy transfer [1–6] have limited wider application and acceptance of this mechanical circulatory assist therapy. In all such devices, infection has been shown to negatively affect quality of life and patient mobility. The TCI HeartMate left ventricular assist system (LVAS) (Thermo Cardiosystems, Inc, Woburn, MA), available in Germany in both electric and pneumatically driven versions, has been successfully used in heart failure centers worldwide as a bridge to transplantation. In our out-of-hospital (OOH) experience with patients receiving HeartMate LVAS support, infection was the most frequent cause of hospital readmission. Multiple risk factors for infection are present in such patients. A reduced general and nutritional condition, long-term hospitalization, colonization with nosocomial pathogens, pulmonary congestion, extensive transfusion, chronic central venous access, and drive-line tunnel length have all been implicated (Frazier OH, personal communication, September 1998).

After observing several patients develop infections that were accompanied by profuse serosanguineous secretions from the percutaneous drive-line exit site, we hypothesized that susceptibility to infection was increased by an inadequate drive-line tunnel length. These patients shared a similar implantation method: preperitoneal pocket placement and a left lower quadrant percutaneous exit site. In each, an impediment to the development of a firm fibrous capsule appeared to be present. Despite scrupulous exit site care, delayed wound healing suggested that enhanced attachment of the pump body to the pump rocket would effectively mimic a longer drive-line tunnel and reduce fluid development in the pump rocket.

We describe a modified implantation technique (intended to reduce device infection) performed in the last 9 of a series of 30 patients supported with the HeartMate vented electric (VE) LVAS.

	Technique

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After median sternotomy and pericardiotomy, transesophageal echocardiography was performed to exclude a patent foramen ovale and to evaluate right heart function. The midline incision was then extended to the umbilicus. After preparing a pocket in the rectus sheath, extracorporeal circulation with a standard cardiopulmonary bypass circuit was initiated. Through a left ventricular apical cardiotomy, the left ventricular assist device inflow cannula was secured by means of a felt strip and pledgetted sutures. Inflow grafts and outflow grafts were sealed with fibrin glue and connected.

The inflow tract was wrapped with a 38-mm knitted Dacron (Hemashield; Boston Scientific, Meadox, Meadox Medicals, Inc, Oakland, NJ) graft, the outflow tract with a 32-mm Hemashield graft, and the aortic graft with a 22-mm Hemashield graft. The graft sections were secured with a nonabsorbable purse-string suture. A patch of the remaining Hemashield material was secured with sterile silicone adhesive to the upper surface of the ventricle and fixed by 4-0 silk threads (Fig 1). After patch application, the HeartMate VE LVAS was placed into the pocket. Intended to enhance fibrous adhesion and pump fixation, the graft may also serve to reduce transmitted rotary motion. The reduced mechanical effects probably enhance fibrosis, thus reducing serosanguineous fluid elaboration.

View larger version (127K): [in this window] [in a new window]   Fig 1. Hemashield patch applied to the upper surface of the pump.

We followed an antibiotic and infection management protocol, which begins with the short-term prophylactic administration of cefazolin (3 x 2 g daily) until all drains were removed. Average time to drain removal was 4 days (range 3 to 7 days). Patients with local exit site infections did not receive specific systemic treatment. In the presence of systemic signs of infection, antibiotics are prescribed according to antimicrobial sensitivity. Commonly, cultures of Staphylococcus prompted to the initiation of flucloxacillin 6 to 8 g daily. Methicillin-resistant S aureus was treated with vancomycin to blood levels of 20 to 40 mg/L. In uncontrolled cases, rifampicin (10 g/kg daily) was added according to liver and renal function. The antibiotic regime was applied for at least 28 days (range 18 to 90 days).

Since the TCI HeartMate became available in our institution in 1993, 14 patients received the pneumatically driven (IP) and 30 the VE device. The pneumatic HeartMate was implanted intraperitoneally, while the HeartMate VE systems have been implanted extraperitoneally into a pocket created anterior to the posterior wall of the rectus sheath. Seven of 21 patients (33.3%) without patch application to the ventricle had a pocket infection occurring on postoperative day (POD) 30 to 111 (mean POD 58).

Our most recent series of 9 patients were supported for a period between 29 and 337 days (mean 113.8 ± 91.2 days), while duration of support in the previous 21 HeartMate patients (without patch) was 18 to 535 days (mean 148 ± 135.5 days) (p = 0.273). Three have since received a transplant, 4 patients are still awaiting transplantation at home, while 2 patients died under support. One of them had multiple organ failure after 56 days of support. In the other patient, a pump failure occurred after 140 days of support, resulting from a disconnected infusion with blood leaking into the pump filter causing the failure. The patient was immediately switched to the pneumatic system. He died later from multiple organ failure and sepsis. The relatives of both patients refused their consent to an autopsy.

Only 2 patients had signs of systemic infection (positive blood cultures, body temperature > 38.5°C, white blood cells >12,000 mL). One of them had a pocket infected with Enterococcus faecalis and Pseudomonas species on POD 42. He was treated successfully with long-term antibiotics and was discharged home free from infection. In all 9 patients, wound dressing changes were reduced from one to two times daily to two to three times weekly.

Pump explantation after heart transplantation (n = 3) was not associated with major difficulties resulting from tissue ingrowth, but was comparable with Novacor pump explantation. Postoperative total blood loss after the transplant procedure was 1,400, 1,800, and 800 mL.

	Comment

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Infection in patients with implantable left ventricular assist devices is a common problem and considerably affects the long-term application of these devices. Device-related infection increases hospital stay, hospital readmission rates, and costs. Furthermore, infections negatively influence quality of life, a factor that may limit broad acceptance of the technology.

Our institution has experience with two implantable mechanical circulatory support systems: the Novacor LVAS and the TCI HeartMate LVAS. Preoperative risk factors in patients receiving either device were comparable, while the same surgeons and the same ventricular assist device team applied the identical postoperative care protocols. Differences in drive-line tunnel length alone may account for pocket infection being more common in HeartMate recipients than in Novacor recipients. The longer drive-line tunnel inherent to a right upper quadrant exit site may provide greater protection from ascending infection than the shorter tunnel obtained with the left lower quadrant exit site used in our early HeartMate VE LVAS series. Patch application is supposed to lead to an increase in tissue ingrowth, producing the protective equivalent of a lengthened drive-line tunnel. This was evident in the decline of pocket infections from 33.3% to 11.1% and a corresponding decrease in the incidence of other infectious complications (Table 1). Pocket infection occurring after patch application did not negatively affect the outcome of patients, and has been described by other authors [2–4].

	Acknowledgments

 
We thank the German Association of Organ Recipients (Reg. Ass.) for grant support.

	References

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1. McCarthy P.M., Schmitt S.K., Vargo R.L., Gordon S., Keys T.F., Hobbs R.E. Implantable LVAD infections. Ann Thorac Surg 1996;61:359-365.[Abstract/Free Full Text]
2. Argenziano M., Catanese K.A., Moazami N., et al. The influence of infection on survival and successful transplantation in patients with left ventricular assist devices. J Heart Lung Transplant 1997;16:822-831.[Medline]
3. Springer W.E., Wasler A., Radovancevic B., et al. Retrospective analysis of infection in patients undergoing support with left ventricular assist systems. ASAIO J 1996;42:M763-M765.[Medline]
4. McCarthy P.M., Smedira N.O., Vargo R.L., et al. One hundred patients with the HeartMate left ventricular assist device. J Thorac Cardiovasc Surg 1998;115:904-912.[Abstract/Free Full Text]
5. DeRose J.J., Umana J.P., Argenziano M., et al. Implantable left ventricular assist devices provide an excellent outpatient bridge to transplantation and recovery. J Am Coll Cardiol 1997;30:1773-1777.[Abstract]
6. Koul B., Solem J.O., Steen S., Casimir-Ahn H., Granfeldt H., Lönn U.J. HeartMate left ventricular assist device as bridge to heart transplantation. Ann Thorac Surg 1998;65:1625-1630.[Abstract/Free Full Text]

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