Effect of pacing for soft indications on mortality and heart failure in the dual chamber and VVI implantable defibrillator (DAVID) trial

Background: The dual chamber and VVI implantable defibrillator (DAVID) trial demonstrated that dual chamber (DDDR) pacing in defibrillator candidates with impaired ventricular function and no established indication for pacing resulted in worsened congestive heart failure (CHF) or death. Many patients had abnormalities for which pacing is often advocated to improve the management of ventricular dysfunction. Objectives: Evaluate the impact and interaction of nonessential but potentially justifiable reasons to pace ("soft indications"), together with pacing mode, on outcome. Methods: DAVID patients were stratified by those with and without "soft indications" for pacing (rate < 60 beats/min or first-degree atrioventricular block) (n = 169; n = 335, respectively). This analysis also stratified patients by normal and abnormal QRS conduction (QRS >= 110 ms), who were previously found to be affected differently by DDDR pacing. Groups were analyzed according to the combined endpoint of mortality or CHF hospitalization. Results: When assigned to treatment that promoted pacing (DDDR), the incidence of death or CHF tended to be higher in patient subgroups with and without "soft indications," consistent with results from DAVID. Patients with, compared to those without, these abnormalities neither benefited nor were less adversely affected when actively paced. The presence or absence of "soft indications" also provided no additional explanation for the differing outcomes in patient cohorts with and without abnormal QRS conduction. Conclusions: Sinus bradycardia or first-degree atrioventricular block did not ameliorate the poor outcomes associated with dual-chamber compared with VVI pacing, and do not justify conventional dual-chamber pacing in defibrillator recipients with ventricular dysfunction.