In real world practice, DT is not performed in a substantial number of patients, most of these in the absence of legitimate reasons. The clinical impact of DT vs. no DT remains unclear until the not negligible complication rate is compared against the long-term potential benefit.

Background— Syncope in patients with bifascicular block (BFB) is a common event whose causes might be difficult to assess. Methods and Results— Prevention of syncope through permanent cardiac pacing in patients with bifascicular block (PRESS) is a multicenter, prospective, randomized, single-blinded study designed to demonstrate a reduction in symptomatic events in patients with bifascicular block and syncope of undetermined origin implanted with permanent pacemaker. Device programming mode (NASPE/BPEG code) at DDD with a lower rate of 60 ppm is compared with backup pacing at DDI with a lower rate of 30 ppm. The end point consisted of (1) syncope, (2) symptomatic presyncopal episodes associated with a device intervention (ventricular pacing), and (3) symptomatic episodes associated with intermittent or permanent atrioventricular block (any degree). One hundred one patients were enrolled and randomized. Primary end point events at 2 years were observed in 23 patients, with a significant lower incidence in the study group (hazard ratio, 0.32; 95% confidence interval [CI], 0.10–0.96; P =0.042). Reduction of any symptoms, associated or not with device intervention, was superior in DDD60 compared with DDI30 (hazard ratio, 0.4; 95% confidence interval, 0.25–0.78; P =0.0053). Fourteen patients developed other rhythm diseases and met class I indication for pacing. The annual incidence of rhythm disease development was 7.4%. Conclusions— In patients with bifascicular block and syncope of undetermined origin, the use of a dual chamber pacemaker programmed to DDD60 led to a significant reduction of syncope or symptomatic events associated with a cardioinhibitory origin, compared with DDI30 programming. Symptoms associated with a new onset of rhythm disease were found in 15% of the population at 2 years.

In most patients with rate-responsive devices, a single sensor is sufficient to achieve a satisfactory rate response. A dual sensor combination and optimization provides an additional benefit only in a selected population with an advanced atrial chronotropic disease.