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Ann Thorac Surg 1999;67:554-555
© 1999 The Society of Thoracic Surgeons

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Case Reports

Treatment of infected left ventricular assist device using antibiotic-impregnated beads

^a Department of Cardiothoracic, LDS Hospital, Salt Lake City, Utah, USA
^b Department of Orthopedic Surgery, LDH Hospital, Salt Lake City, Utah, USA
^c Department of Anesthesia, LDS Hospital, Salt Lake City, Utah, USA
^d Department of Medicine, LDS Hospital, Salt Lake City, Utah, USA

Accepted for publication July 31, 1998.

Address reprint requests to Dr Long, Mechanical Circulatory Support, LDS Hospital, 324 Tenth Avenue, Suite 160, Salt Lake City, UT 84103
e-mail: jimlong{at}ihc.com

	Abstract

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There is no well-established therapy for treating infections of heart-assist or artificial heart devices, a serious problem with life-threatening consequences. We used a promising new approach in which antibiotic-impregnated polymethylmethacrylate beads were placed around an implanted left ventricular assist device to control an external blood pump infection in a bridge-to-transplant patient. In this case report, we describe the potential of antimicrobial-impregnated polymethylmethacrylate beads for in situ control of infections involving external surfaces of cardiovascular devices.

	Introduction

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Infections of heart-assist devices and artificial hearts are serious problems with no well-established method of treatment. Infections can occur within these pumps, on outer surfaces, or along percutaneous drivelines. The following methods of treatment have been tried for external surface infections: systemic antibiotic therapy, surgical revision of percutaneous drivelines, debridement, and device exchange [1]. Limitations associated with these treatments include recurrent infections and high risks associated with device replacement or removal.

A 49-year-old male heart transplant candidate facing life-threatening cardiac decompensation underwent implantation of a TCI HeartMate (Thermo Cardiosystems Inc, Woburn, MA) left ventricular assist device (LVAD). The procedure and the postoperative course were routine except for delays in transplantation caused by preexisting human leukocyte antigen alloimmunization.

At 6 months after LVAD implantation, a vigorous immunosuppression regimen was initiated to reduce human leukocyte antigen alloimmunization. Ten weeks into this therapy, the patient began having subxyphoid pain adjacent to the LVAD, and then he developed localized tenderness and erythema suggestive of infection although he did not have fever or leukocytosis. Ultrasound imaging revealed a localized collection of fluid near the outflow conduit of the LVAD.

The preperitoneal LVAD pocket was surgically explored after 8 months of LVAD support. A 20-mL collection of purulent fluid was discovered at the junction of the outflow conduit and the LVAD body that communicated with the entire LVAD surface. Multiple samples had Gram-positive cocci and cultures later identified as Staphylococcus epidermidis. The cause of this late-appearing infection is unknown. With a well-incorporated percutaneous driveline, the likelihood of bacterial migration along the driveline was low. The most plausible source of infection was intraoperative seeding with a low virulence organism that remained dormant until a period of rigorous immunosuppression. The LVAD pocket was irrigated and debrided, and a percutaneous irrigation-drainage system was established for initial control.

To move beyond the limitations of percutaneous irrigation and drainage, we then designed a completely closed antibiotic delivery system. The LVAD pocket was reexplored and the irrigation-drainage system was removed. Results of gram stains for bacteria were still positive. To reduce residual bacterial contamination, the wound was aggressively irrigated using a Pulsavac (Zimmer Inc, Warsaw, IN). Antimicrobial cleanser (4% chlorhexadine gluconate, Purdue Frederick, Norwalk, CT) was used to scrub residual film, possibly entrapping bacteria, from the surface of the LVAD.

An in situ, slow release antibiotic delivery system was then implanted. Tobramycin (4.8 g), vancomycin (2.0 g), and polymethylmethacrylate (PMMA) (60.0 g) (Howmedica Inc., Rutherford, NJ) powders were combined and mixed into cement [3–6]. The antibiotic-impregnated PMMA was shaped into 0.5- to 1.0-cm diameter beads, which were threaded onto strands of stainless steel wire to facilitate removal later. The sharp ends of the wire were pigtailed to reduce the risk of inducing injury. About 200 beads were packed around the device. The wound was then closed leaving two small, temporary drains attached to a closed, low suction drainage system.

The patient remained afebrile with normal leukocyte count and negative blood cultures until transplantation 9 days later. Systemic levels of vancomycin and tobramycin were measured, confirming negligible systemic absorption of local antibiotics. Antibiotic concentrations around the LVAD, however, were high (140 µg/mL for vancomycin and 1,880 µg/mL for tobramycin, measured from drainage fluid).

At transplantation, the beads and the device were removed. Results of multiple Gram stains and cultures were negative. The patient convalesced satisfactorily with no evidence of infection, and as of 6 months after discharge was doing well.

	Comment

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We used antibiotic-impregnated PMMA beads to control an infection on the external surface of the LVAD. Although negative cultures and Gram stains at device explant are not absolute proof that infection was eradicated, not just suppressed, such evidence is highly compelling.

Compared with systemic antibiotics, PMMA bead therapy clearly provided high local levels of antibiotics without significant systemic absorption. In this case, local antibiotic concentrations were approximately 3.5 and 150 times therapeutic systemic levels for vancomycin and tobramycin, respectively.

Further research is indicated with in situ antimicrobial delivery using PMMA beads for cardiovascular devices. Issues to be explored to assure safe and effective delivery include selection, amount and elution characteristics of antibiotic and antifungal agents to maximize local effect while avoiding systemic toxicity; optimum bead material, size, shape, and positioning; the need for and duration of concurrent systemic antimicrobial therapy; resistance issues; and whether this concept could be adapted for infection prophylaxis. Experience using PMMA beads for chronic osteomyelitis and infected orthopedic hardware should serve as a foundation for further adapting this experience to cardiovascular device infections [3–6].

In treating infections involving external surfaces of cardiovascular devices we recommend aggressive surgical wound debridement and cleansing coupled with in situ placement of antimicrobial-impregnated polymethylmethacrylate beads to achieve high local drug concentrations. Innovative approaches such as this are needed to prevent and control cardiovascular device infections, especially with mechanical circulatory support systems advancing toward permanent therapy [2].

	References

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1. Holman W.L., Murrah C.P., Ferguson E.R., Bourge R.C., McGiffin D.C., Kirklin J.K. Infections during extended circulatory support: University of Alabama at Birmingham experience 1989 to 1994. Ann Thorac Surg 1996;61:366-371.[Abstract/Free Full Text]
2. McCarthy P.M., Schmitt S.K., Vargo R.L., Gordon S., Keyes T.F., Hobbs R.E. Implantable LVAD infections: implications for permanent use of the device. Ann Thorac Surg 1996;61:359-365.[Abstract/Free Full Text]
3. Wininger D.A., Fass R.J. Antibiotic-impregnated cement and beads for orthopedic infections. Antimicrob Agents Chemother 1996;12:2675-2679.
4. Popham G.J., Mangino P., Seligson D., Henry S.L. Antibiotic-impregnated beads. : Part I: bead implantation versus systemic therapy. Orthop Rev 1991;3:242-247.
5. Popham G.J., Mangino P., Seligson D., Henry S.L. Antibiotic-impregnated beads. : Part II: factors in antibiotic selection. Orthop Rev 1991;4:331-337.
6. Wilson K.J., Cierny G., Adams K.R., Mader J.T. Comparative evaluation of the diffusion of tobramycin and cefotaxime out of antibiotic-impregnated polymethylmethacrylate beads. J Orthop Res 1988;2:279-286.

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by McKellar, S. H. Articles by Long, J. W. Search for Related Content PubMed PubMed Citation Articles by McKellar, S. H. Articles by Long, J. W.