The 1+1 trial : A prospective trial of a dual- versus a single-chamber implantable defibrillator in patients with slow ventricular tachycardias

The tachycardia detection interval (TDI) in implantable cardioverter/defibrillators (ICDs) is conventionally programmed according to the slowest documented ventricular tachycardia (VT), with a safety margin of 30 to 60 ms. With this margin, VTs above the TDI may occur. However, longer TDIs are associated with an increased risk of inappropriate therapy. We hypothesized that patients with slow VTs (2 minutes). After 6 months, a crossover analysis was performed. Total follow-up was 1 year. One hundred two patients were included in the study. The programmed TDI was 500+/-36 ms during the dual-chamber phase and 424+/-63 ms during the single-chamber phase. For the primary end point (inappropriate therapies, VTs above the TDI, or VTs with detection delay), a moderate superiority of the dual-chamber mode was found: Mann-Whitney estimator=0.6661; 95% CI, 0.5565 to 0.7758; P=0.0040. Dual-chamber detection with a longer TDI improves VT detection and does not increase the rate of inappropriate therapies despite a considerable increase in tachycardia burden.