This study was aimed at the evaluation of a new protocol of antibiotic prophylaxis, stratified according to individual infective risk calculated with the Shariff score at the moment of cardiac implantable electronic device (CIED) implantation.

Prospective, single centre, cohort study. Patients undergoing CIED surgery in a 3-years period were considered for participation. In particular, patients were eligible if undergoing first implantation or replacement or upgrade of pacemaker or implantable cardioverter-defibrillator (ICD), including cardiac resynchronization therapy (CRT).

At the time of enrolment, before index procedure, the Shariff score was calculated for every patient. According to the score, patients were stratified in two groups: low infective risk (score <3) and high infective risk (score ≥3). Two different protocols of antibiotic prophylaxis were administered according to risk stratification. Patients in the "low risk" group were treated with only two doses of antibiotics, both intravenous, of whom the first one hour before skin incision and the second after eight hours. Patients in the "high risk" group were treated with intravenous prophylaxis for two full days (of whom the first administration one hour before skin incision and the others every eight hours), followed by other seven days of oral prophylaxis, for a total of nine days. Thereby, every patient received one administration of intravenous antibiotic one hour before skin incision and a second administration after eight hours, while patients in the low risk group did not receive other antibiotics and patients in the high risk group continued intravenous antibiotics every eight hours for two days, followed by oral antibiotics for other seven days.

The intended drug for antibiotic prophylaxis was amoxicillin + clavulanic acid unless the patient had a history of allergic reactions to penicillin. The dosage was dependent on renal function: for intravenous amoxicillin + clavulanic acid 2.2 g in patients with creatinine clearance (CrCl) <30 ml/min and 1.2 g in patients with CrCl >30ml/min, for oral amoxicillin + clavulanic acid 1 g every 8 hours in patients with <30 ml/min and 1 g every 12 hours in patients with CrCl >30ml/min. In case of penicillin allergy, clindamycin was chosen. The intravenous dosage was 600 mg every 8 hours for CrCl <30 ml/min and 600 mg every 12 hours for CrCl >30 ml/min, while the oral dosage was 450 mg every 8 hours for CrCl <30 ml/min and 450 mg every 12 hours for CrCl >30 ml/min.

Patients who were already in antibiotic therapy at the time of index procedure (for reasons other than CIED implantation) were not stratified in one of the two groups: post-operative antibiotics were continued according to clinical indications and not to the study protocol. This group included patients with a documented or suspected infection before surgery in whom the CIED procedure was judged not deferrable.

Inclusion Criteria:

• first implantation or replacement or upgrade of pacemaker or ICD

Exclusion Criteria:

• age 18 years
• ongoing pregnancy
• inability to express informed consent

patients undergoing CIED-related intervention