Hourly premature atrial contractions in 24-h holter ECG monitoring of acute ischemic stroke patients: insights from the FIND-AF 2 trial

Abstract

An increased number of premature atrial contractions (PACs) has been associated with an increased risk of atrial fibrillation (AF) and ischemic stroke. Prior studies used 24-hours or 48-hours of ECG monitoring and thresholds of ≥720 PACs/24 hours to define excessive supraventricular ectopy (ESVEA). To determine whether shorter durations of ECG monitoring (e.g. one hour) would suffice to identify most patients who have ≥720 PACs/24 hours. FIND-AF 2 is a multicenter trial including patients ≥60 years with recent ischemic stroke and no prior AF. Patients are randomized to enhanced, prolonged and intensified ECG monitoring or usual care. All patients received a 24-hours Holter-ECG prior to randomization to exclude AF and to quantify the number of PACs. In this analysis, 5,231 patients with complete 24-hours Holter-ECGs and without AF were evaluated. Holter-ECGs were divided into hourly intervals. PAC positivity was defined as ≥30 PACs in at least one hour. The ≥720 PAC/24 hours criterion served as reference standard. Sensitivity, specificity, and the Youden index were calculated across cumulative monitoring durations. Distributional analyses were performed among PAC-positive recordings. A total of 1,054 recordings met the ≥720 PAC/24 hours criterion. Overall, 2,147 Holter-ECGs were classified as PAC-positive. Among PAC-positive recordings, patients with ≥720 PAC/24 hours exhibited a substantially higher number of hours with ≥30 PACs compared with <720 PAC/24 hours (median 17 vs 2 hours, p<0.001), demonstrating near-complete separation of distributions (Figure 1). After 1 hour, the ≥30 PAC threshold showed high specificity (96%) and moderate sensitivity (70%) for identifying ≥720 PAC/24 hours. Sensitivity increased while specificity declined with longer monitoring, with optimal discrimination after 7 hours (Youden index 0.801; sensitivity 94%, specificity 86%) (Figure 2). High daily PAC burden reflects sustained hourly PAC activity rather than isolated peaks. A single-hour threshold provides a highly specific early rule-in approach, while 7-hour monitoring achieves optimal balance. Short ECG monitoring for a few hours may be used to risk-stratify ischemic stroke patients for prolonged ECG monitoring.Figure 1Figure 2.