PADIT score predicts CIED infection risk

David Birnie

Five independent predictors of cardiac implantable electronic device (CIED) infection have been identified which could be used to aid physicians and patients in decision-making about device therapy through the use of an infection risk scoring system. The predictors and scoring system are the outcome of the Prevention of Arrhythmia Device Infection Trial (PADIT), a cluster randomised trial which sought to assess the efficacy of additional antibiotic measures compared with a conventional single dose of pre-operative antibiotics among CIED patients.

CIED infection is a major complication that usually requires device removal, can be costly, leads to prolonged hospitalisation and is associated with a short-term mortality rate of up to 18%, David Birnie (University of Ottawa Heart Institute; Canada) the study’s lead author, wrote in the Journal of the American College of Cardiology (JACC) in December 2019. Given these risks, developing strategies to reduce infection and defining predictors of increased infection risk are important goals, Birnie noted.

Birnie and the PADIT study team predicted that incremental antimicrobial prophylaxis would reduce the risk of hospitalisation for device infection compared with a conventional strategy of a single dose of a pre-procedural antibiotic. The primary outcome of the trial was admission to hospital for proven CIED or pocket infection within one year of device implantation. Patients having CIEDs implanted—including a new or replacement pacemaker, implantable cardioverter defibrillator (ICD) or cardiac resynchronisation therapy (CRT), as well as a pocket or lead revision—at 28 sites in Canada and the Netherlands were included in the trial, which took place over four six-month periods between December 2012 and September 2016. In total, 19,603 patients underwent device procedures, with 19,559 having then completed a follow-up visit. Patients were randomised in clusters to conventional treatment (n=9,627) or incremental antibiotics (n=9,976). In the conventional arm, a single dose of cefazolin 1–2g was administered intravenously (IV) 60 minutes before skin incision or vancomycin 1–1.5g IV in penicillin-allergic patients. In the incremental antibiotic strategy, patients received IV cefazolin as well as pre-operative vancomycin.

Of the patients taking part in the trial, the study team found that hospitalisation for infection occurred in 177 (0.9%) within one year of follow-up. The main study results have previously been reported and found that hospitalisation for infection was reduced by incremental therapy (23% reduction, nonsignificant); and the nonsignificance was in part attributable to the unexpectedly low infection rate.

In the current analysis, the study team examined predictors of infection and developed a final prediction model using five independent predictors. These included: prior procedures (P), age (A), depressed estimated glomerular filtration rate (D), immunocompromised (I) and type of procedure (T). The risk score was then calculated for each patient by summing the points assigned to each predictor, with a risk score ranging from 0 to 15 points classifying patients into low, intermediate and high risk groups. Based on this classification, 13,828 patients were at low risk (score: 0 to four), 4,151 patients were at intermediate risk (score five or six) and 1,406 were at high risk, (score equal to or above seven). Hospitalisation rates for the groups stood at 0.51%, 1.42% and 3.41% respectively.

Birnie and colleagues note that the PADIT infection risk score is likely to be helpful to physicians and patients in shared decision making about device therapy, adding that many patients and families are not aware of the risks and benefits of ICD generator replacement, for example, and that patients often overestimate the benefits and underestimate the risks of ICD generator change These observations are largely consistent with a meta-analysis of findings from many smaller studies. Birnie believes the score will be helpful for shared decision making around CIED therapy and for clinical researchers. Further validation and modification with future high-quality datasets are warranted. An online version of the PADIT score is available here.

Commenting on the study in an accompanying editorial comment, which was also published in JACC Suneet Mittal and Simon Tsiouris (Valley Hospital Health System, Ridgewood, USA) wrote that the identification of patients at low risk, may be the “most valuable lesson of PADIT”. Mittal and Tsiouris added: “Patients with pacemakers accounted for nearly half of the total cohort but had a major infection rate of only 0.4%. For the remaining patients, the good news is that the perception of infection risk has not matched the observed reality; the bad news is that it then becomes that much harder to budge the needle to a more favourable status for our patients with CIEDs.”


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