Definition
VTA was defined as a sustained ventricular tachycardia and fibrillation which was treated by ICD and/or lasted >30 seconds. RR-NSVT was defined as an episode of VT that met the ICD therapy detection criteria which terminated before defibrillator intervention. A frequent RR-NSVT was defined as ≥3 runs for one day observed before or without following VTAs. A cluster RR-NSVT was defined as ≥3 episodes for 6 months observed before or without following VTAs (Supplemental Figure 1). An electrical storm was defined as ≥3 episodes of VTAs within 24 hours. A CRT responder was defined as a decrease in LV end-systolic volume of ≥15% and/or an absolute increase of >5% in LVEF at the 6-month or 1-year visit compared to the baseline echocardiography12.
Cardiovascular mortality was defined as death due to HF, sudden cardiac death, or VTAs. All-cause mortality was defined as death due to cardiovascular mortality, sepsis, or malignancy.
Study endpoints
The primary endpoint was defined as the occurrence of VTAs. The secondary endpoints were defined as the occurrence of an electrical storm, admission for HF, cardiovascular mortality, and all-cause mortality.