Prediction of Pacemaker Requirement in Patients With Unexplained Syncope: The DROP Score

Background: Implantable loop recorders (ILR) are increasingly utilised in the evaluation of unexplained syncope. However, they are expensive and do not protect against future syncope. Objectives: To compare patients requiring permanent pacemaker (PPM) implantation during ILR follow-up with those without abnormalities detected on ILR in order to identify potential predictors of benefit from upfront pacing. Methods: We analysed 100 consecutive patients receiving ILR: Group 1 (n=50) underwent PPM insertion due to bradyarrhythmias detected on ILR; Group 2 (n=50) had no arrhythmias detected on ILR over >3 years follow-up. Baseline clinical characteristics, syncope history, electrocardiographic and echocardiographic parameters were assessed to identify predictors of ultimate requirement for pacing. Results: Group 1 (64% male, median age 70.8 years; IQR 65.5–78.8) were older than Group 2 (58% male, median 60.2 years; IQR 44.0–73.0 p=0.001) and were less likely to have related historical factors such as overheating, posture and exercise (98% vs 70% p<0.001). PR interval was also longer in Group 1 (192±51 vs 169±23 p=0.006) with greater prevalence of distal conduction system disease (30% vs 4.3% p=0.002). Significant univariate predictors for PPM insertion were distal conduction disease (p=0.007), first degree atrioventricular (AV) block (p=0.003), absence of precipitating factors (p=0.004), and age >65 years (p=0.001). Injury sustained, recurrent syncope, history of atrial fibrillation (AF) or heart failure, left atrial (LA) size and left ventricular ejection fraction (LVEF) were not predictive. These significant predictors were incorporated into the DROP score¹ (0–4). Using time-to-event analysis, no patients with a score of 0 progressed to pacing, while higher scores (3–4) strongly predicted pacing requirement (log-rank p<0.001). Conclusion: The DROP score may be helpful in identifying patients likely to benefit from upfront permanent pacemaker (PPM) insertion following unexplained syncope. Larger prospective studies are required to validate this tool.