Increased Variability of the Coupling Interval of Premature Ventricular Contractions as a Predictor of Cardiac Mortality in Patients With Left Ventricular Dysfunction

Background: The characteristics and prognostic value of the variability of premature ventricular contraction (PVC) coupling intervals (CIs) for cardiac mortality are not yet decisive. Methods and Results: In 133 consecutive patients (58 +/- 14 years old, 53 women) who had left ventricular dysfunction (LVD: ejection fraction <50%) and frequent PVCs (>= 10/h) who underwent 24-h ambulatory electrocardiography (AECG) recording and I-123-metaiodobenzylguanidine myocardial single-photon emission computed tomography simultaneously, the heart rate turbulence onset, slope, and T-wave alternans were analyzed from the 24-h AECG. The CI of the PVCs (MEAN(NV)), standard deviation of the CI of the PVCs (SDNV) as an index of the variability of the PVC CI, and their ratio to the preceding N-N intervals (SDNV/SDNN) were calculated from constructed Poincare plots using the annotated 24-h AECG QRS data. The primary endpoint was cardiac mortality. The mean follow-up period was 63 months. Among 133 patients, 114 survived (group 1) and 19 (14%, group 2) died during the follow-up. The MEAN(NV) and SDNV were higher in group 2 (539 +/- 104 vs. 599 +/- 114 ms, P=0.021; 64 +/- 34 vs. 83 +/- 37 ms, P=0.022, respectively). The SDNV, PVC count, and delayed heart/mediastinum ratio remained as significant predictors of cardiac mortality in the binary logistic regression analysis. Conclusions: These results suggest that the SDNV could be another adjunctive parameter for predicting cardiac mortality in LVD.