Right Ventricular Pacing Increases Risk of Appropriate Implantable Cardioverter–Defibrillator Shocks Asymmetrically

Background: Right ventricular pacing (RVP) increases risk of atrial fibrillation in patients with implantable cardioverter–defibrillators (ICDs), but ventricular proarrhythmia is less clear. We analyzed a large remote monitoring database to assess this question. Methods and Results: Patients with single- or dual-chamber ICDs, engaged in remote monitoring for at least 6 months and with unchanged tachycardia programming, were included. %RVP was derived for each weekly transmission. ICD electrograms preceding the first shock were adjudicated. Among 425 625 transmissions received from 8435 patients, 389 appropriate shocks occurred over a mean follow-up of 15.0±8.8 months. In a time-dependent Cox proportional hazards model, transmissions with 80% to 98% RVP were associated with a hazard ratio of 1.56 for an appropriate shock in the subsequent week compared with <1% RVP (95% CI, 1.01–2.41; P =0.04). By contrast, ≥98% RVP trended toward a lower risk of an appropriate shock (hazard ratio, 0.61; 95% CI, 0.33–1.12; P =0.108). Lifetime cumulative %RVP was closely correlated with weekly %RVP ( R 2 =0.907) and was similarly associated with increased risk of appropriate shocks at 80% to 98% RVP (hazard ratio, 1.57; 95% CI, 1.01–2.44; P =0.046) but not at ≥98% RVP (hazard ratio, 0.49; 95% CI, 0.24–1.01; P =0.052). These results were driven by dual-chamber devices, but unaffected by PVC counts or programming. Male sex and age were also associated with appropriate ICD shocks. Conclusions: Increasing frequency of RVP is associated with a progressively increased risk of appropriate ICD shocks until ≥98% RVP. RVP may have ventricular proarrhythmia because of competition of paced and intrinsic rhythm in ICD patients.