Table 1.

Study population characteristics

	All patients (n=454)
Age(mean±SD), yrs	67.6±12.3
Female, %	23.8
White, %	81.1
Nonischemic cardiomyopathy, %	42.4
Hypertension, %	73.1
Diabetes, %	33.4
Use class I or III antiarrhythmic drugs, %	16.7
Use beta-blockers, %	84.5
Left ventricular ejection fraction(mean±SD), %	29.3±12.2
New York Heart Association heart failure class I-II, %	49.3
New York Heart Association heart failure class III-IV, %	50.7
Single-chamber implantable cardioverter-defibrillator, %	7.5
Dual-chamber implantable cardioverter-defibrillator, %	22.8
Cardiac resynchronization therapy defibrillator, %	69.7
Device manufacturer Medtronic, %	67.7
Device manufacturer Guidant/Boston Scientific, %	17.5
Device manufacturer St. Jude/Abbott, %	13.5
Device manufacturer Biotronic, %	1.3
Atrial-paced rhythm, n(%)	62(13.7)
Ventricular-paced rhythm, n(%)	282(62.1)
Atrio-ventricular paced rhythm, n(%)	110(24.2)
Heart rate (mean±SD), beats per minute	70.1±12.3
QRS duration (mean±SD), ms	130.7±35.3
Bazett-corrected QT interval (mean±SD), ms	484.0±51.3