Ventricular Arrhythmias
During the follow-up, ventricular arrhythmias (consisting of ventricular tachycardia or ventricular fibrillation, which needed anti-tachycardia pacing of defibrillation) after the upgrade to CRT were observed in 4 patients in group 1 (57%), 5 in group 2 (50%) and 12 in group 3 (39%) (p = 0.58).