Animal study on surface-modified defibrillator systems: Indications for enhanced infection resistance

One of the most important problems with ICD systems is infection. The aim o f this study was an in vivo evaluation of the efficacy of defibrillator sys tems in terms of infection resistance. The polyurethane leads were coupled with heparin and loaded with the antibiotic gentamicin, while the PGs were modified to release gentamicin, Group I was comprised of 10 pigs implanted with either a standard or a modified system for 2 weeks; group 11 was impla nted during 4 weeks. The lead was inserted into the heart wall via the jugu lar vein. The other end was subcutaneously tunneled to the armpit where the PG was positioned. A cocktail of Staphylococcus aureus and epidermidis was injected at the site of the PG. Evaluation was performed macroscopically, by taking bacterial swabs during explantation and by microscopic processing . The results showed that 3 out of 5 modified defibrillator-systems in grou p I and 1-2 out of 5 in group II were judged as noninfected, whereas all st andard systems were infected. Infection rates of the remaining modified def ibrillators showed variances, as found with the standards, from slight to m oderate to high, to even high/severe in group 11 (Ix standard and Ix modifi ed), With the modified systems, this may he related to production of humora l factors by an intensified early tissue reaction, as indicated by a swelli ng at day 6 at the site of the PG, When infected, whether or not modified, usually only Staphylococcus aureus was present. Spreading of infection seem ed to occur by inoculation via blood, for example, based on the observation that group II in general showed an increase in infected fibrotic overgrowt h in the heart, while infectious problems were low in the jugular vein. It is concluded that the modification at short term shows enhanced infection r esistance. An increased infection rate already at 4 weeks, however, indicat es that the modification may not hold in the long run. Special attention is needed concerning the more intense early tissue reaction, (C) 2001 John Wi ley & Sons. Inc.