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BOSTON -- More aggressive, intermittent antibiotics around intervention on implanted cardiac devices had no substantial impact on clinically meaningful infections, a cluster randomized trial determined, although the researchers said the results did not rule out a modest impact.

The primary outcome of hospitalization attributed to device infection -- whether from pocket infection, sepsis, or endocarditis, as documented in the clinical record -- occurred at a similarly low rate as with the conventional single preoperative dose of cefazolin (0.78% versus 1.03%, OR 0.77, P=0.10), Andrew Krahn, MD, of the University of British Columbia in Vancouver, reported here at the Heart Rhythm Society meeting.

The results of the Prevention of Arrhythmia Device Infection Trial (PADIT) showed that the incremental strategy of adding a single dose of vancomycin preoperatively along with intraoperative bacitracin pocket wash and 2 days of oral cephalosporin postoperatively also did not have a significant impact on infections requiring surgical intervention or mortality. Nor were there any subgroups of high-risk patients who had significant or outsized benefit from the more aggressive approach.

Still, adverse events related to the antibiotics in the study were "quite rare" and were similar between the incremental and conventional antibiotic groups (0.3% and 0.2%), with the exception of more allergic reactions in the group receiving vancomycin.

With 19,603 patients in the center-randomized design, which Krahn called the largest device trial to date, it had 86% power to detect the prespecified 35% difference in infection rates.

A smaller advantage to the more aggressive regimen, perhaps on the order of 20%, would be consistent with the results, Krahn noted at a press conference at the meeting, pointing out that the infection rate was half what was expected when the trial was designed: "One might interpret that as there is a small effect, but it was too small for this kind of study to detect and find it significant."

"We obviously were seeking a definitive result, which would have established this as mandatory for all patients. That did not take place," he told MedPage Today. "I think the clinical interpretation of this is going to be that providers are going to look for patients they think are at the highest risk and consider the incremental investment ... The adverse effects or the downsides to doing this were pretty trivial."

The discussant for the study, Bruce Wilkoff, MD, of the Cleveland Clinic and chair of the Data Safety Monitoring Board for the trial, called the question clinically important, noting that "therapy has been all over the place for antibiotic prophylaxis -- most of it borrowed from other disciplines."

However, the low rates seen in both groups might not hold up in the rest of the world, he cautioned.

Indeed, rates tend to be higher than 1% in the United States and have been as high as 6% in certain types of procedures like generator replacement, Jagmeet Singh, MD, PhD, of Massachusetts General Hospital in Boston, who was not involved in the study, told MedPage Today.

Wilkoff said the low rates in the trial were "a testament to the care system in Canada, and they are to be congratulated. It's also a testament to what happens to if you have uniformity across a system." In addition, monitoring of rates in the trial might have made it a quality-of-care issue at participating centers that drove rates lower.

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