Echocardiography
Echocardiography was performed within one month before ICD/CRT-D implantation and during the follow-up period in all the study patients. Echocardiographic parameters, including LVEF, LA dimension, LV volume, and estimated pulmonary artery systolic pressure (PASP), were measured using GE Vivid 9 or Philips IE33. LVEF and LV volume (end-diastolic phase and end-systolic phase) were quantified by the two-dimensional guided biplane Simpson’s method of disc measurements by echocardiography. PASP was estimated from the tricuspid regurgitant jet velocity using the modified Bernoulli equation and adding the estimated right atrial pressure based on the diameter and collapsibility of the inferior vena cava.