Lower than Expected Burden of Premature Ventricular Contractions Impairs Myocardial Function

AIMS: We aimed to explore the burden of frequent premature ventricular contractions (PVCs) associated with myocardial dysfunction in patients with outflow tract arrhythmia (OTA). We hypothesized that this threshold is lower than the previously suggested threshold of 24 000 PVCs/24 h (24%PVC) when systolic function is assessed by strain echocardiography. Furthermore, we aimed to characterize OTA patients with malignant arrhythmic events. METHODS AND RESULTS: We included 52 patients referred for OTA ablation (46 ± 12 years, 58% female). Left ventricular global longitudinal strain (GLS) and mechanical dispersion were assessed by speckle tracking echocardiography. A subset underwent cardiac magnetic resonance imaging. PVC burden (%PVC) was assessed by Holter recording. Sinus rhythm QRS duration and PVC QRS duration were recorded from electrocardiogram, and the ratio was calculated (PVC QRS duration / sinus rhythm QRS duration). Median %PVC was 7.2 (0.2-60.0%). %PVC correlated with GLS (R = 0.44, P = 0.002) and with mechanical dispersion (R = 0.48, P < 0.001), but not with ejection fraction (R = 0.22, P = 0.12). %PVC was higher in patients with impaired systolic function by GLS (worse than -18%) compared with patients with normal function (22% vs. 5%, P = 0.001). Greater than 8%PVC optimally identified patients with abnormal GLS (area under the curve 0.79). Serious arrhythmic events occurred in 11/52 (21%) patients characterized by high QRS ratios (1.56 vs. 1.91, P < 0.001). CONCLUSIONS: More than 8%PVC was associated with impaired systolic function by GLS, which is a lower threshold than previously reported. Patients with serious arrhythmic events had higher QRS ratios, which may represent a more malignant phenotype of OTA.