Syncope events in bifascicular block patients can be reduced with permanent dual chamber pacing, the PRESS study has shown


Syncope is a common event in bifascicular block patients and its causes are difficult to assess. However, results from the PRESS study have found that by using a dual chamber pacemaker programmed to 60ppm lower rate the number of syncope events can be reduced.

The PRESS (Prevention of syncope through permanent cardiac pacing in patients with bifascicular block) study, recently published in Circulation: Arrhythmia and Electrophysiology, was a multicentre, prospective, randomised, single blinded clinical trial designed to demonstrate a reduction in symptomatic events in patients with bifascicular block and syncope of undetermined origin implanted with a permanent pacemaker.

“Patients with bifascicular block and syncope represent a heterogenous population that is difficult to stratify and where the selection of an appropriate therapy may be challenging,” wrote study investigator Massimo Santini, Cardiovascular Department, San Filipo Neri Hospital, Rome, Italy and others. There are different techniques [ECG, Holter monitoring, Tilt Table Test] used to investigate the cause of underlying syncope; however, these methods “lack in specificity”, they added.

Based on the current evidence, the authors wrote, the American College of Cardiology in conjunction with the American Heart Association and the Heart Rhythm Society recommend “permanent pacemaker implantation as a class IIA indication for bifascicular block patients presenting with syncope of undetermined origin.” However, these guidelines “do not state which pacing modality (single vs. dual chamber) should be chosen for these patients,” Santini et al noted. Therefore, they compared device programming at permanent dual chamber pacing with a 60ppm lower rate and AV interval ≥200msec (DDD60) to backup pacing with a lower rate of 30ppm (DDI30).

In the study, 101 patients were enrolled from March 2005 to February 2009 and implanted with a dual chamber pacemaker (Insignia, Boston Scientific). They were randomised in two parallel arms: the treatment arm consisted of 52 patients with pacemakers programmed to a permanent dual chamber pacing with a 60ppm lower rate and the control arm (49 patients) with devices programmed to backup pacing with a lower rate of 30ppm. The patients were followed for two years after enrolment.

The primary endpoint aimed to demonstrate at two years a reduction in the treatment group of: syncope of any origin, symptomatic pre-syncopal episodes associated with a device intervention (ventricular pacing) and symptomatic episodes associated with intermittent or permanent atrio-ventricular block (any degree).


After the two-year follow-up, 93 patients completed the study. Primary endpoint events were observed in 23 patients, with a significant lower incidence in the study group (HR: 0.32; 95% CI: 0.10 – 0.96; p=0.042). Reduction of any symptoms, associated or not with device intervention, was superior in the treatment arm compared to the control arm (HR: 0.4; 95% CI: 0.25 – 0.78; p=0.0053).

Fourteen patients developed other rhythm diseases (10 symptomatic AV block, two Brady-Tacky, one sinus bradycardia, one permanent atrial fibrillation with slow ventricular response) and met class I indication for pacing. This accounted for an overall 7.4% annual incidence of rhythm disease.

Santini et al concluded that, in patients with bifascicular block, the PRESS study “demonstrated that the use of a pacemaker programmed with a lower rate of 60ppm (DDD60) resulted in a significant reduction of the combination of symptomatic events including syncope, pre-syncope or AV block when compared to a substantially negligible electrical treatment.” Although, they acknowledged that “further randomised studies would be necessary to address some of the remaining questions on the nature of event recurrences in this population, this study suggests that the use of a dual chamber pacemaker might be considered as a means for prevention of symptomatic event recurrences in bifascicular block patients.”

Santini spoke to Cardiac Rhythm News on the main outcome of the study, he said: “The study demonstrates that syncope in patients with bifascicular blocks is very often due to paroxysmal complete AV block and that pacemaker implant may be very useful to prevent it as a first option therapy.”

The PRESS study was sponsored by Boston Scientific.