The DAVID (Dual Chamber and VVI Implantable Defibrillator) II trial.

OBJECTIVES: The purpose of this study was to determine whether atrial pacing is a safe alternative to minimal (backup-only) ventricular pacing in defibrillator recipients with impaired ventricular function. BACKGROUND: The DAVID (Dual Chamber and VVI Implantable Defibrillator) trial demonstrated that dual chamber rate responsive pacing as compared with ventricular backup-only pacing worsens the combined end point of mortality and heart failure hospitalization. Although altered ventricular activation from right ventricular pacing was presumed to be the likely cause for these maladaptive effects, this supposition is unproven. METHODS: In all, 600 patients with impaired ventricular function from 29 North American sites, who required an implanted defibrillator for primary or secondary prevention, with no clinical indication for pacing, were randomly assigned to atrial pacing (at 70 beats/min) versus minimal ventricular pacing (at 40 beats/min) and followed up for a mean of 2.7 years. RESULTS: There were no significant differences between pacing arms in patients' baseline characteristics, use of heart failure medications, and combined primary end point of time to death or heart failure hospitalization during follow-up, with an overall incidence of 11.1%, 16.9%, and 24.6% at 1, 2, and 3 years, respectively. Similarly, the incidence of atrial fibrillation, syncope, appropriate or inappropriate shocks, and quality of life measures did not significantly differ between treatment groups. CONCLUSIONS: The effect of atrial pacing on event-free survival and quality of life was not substantially worse than, and was likely equivalent to, backup-only ventricular pacing. Atrial pacing may be considered a "safe alternative" when pacing is desired in defibrillator recipients, but affords no clear advantage or disadvantage over a ventricular pacing mode that minimizes pacing altogether. (Dual Chamber and VVI Implantable Defibrillator [DAVID] Trial II; NCT00187187).

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 >or= 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.

Abnormal conduction increases risk of adverse outcomes from right ventricular pacing.

OBJECTIVES: The purpose of this study was to determine whether QRS duration or morphology increased the risk of adverse outcome in the DAVID (Dual Chamber and VVI Implantable Defibrillator) trial. BACKGROUND: The DAVID trial found an increased risk of the combined end point of death and new or worsening congestive heart failure (CHF) in defibrillator recipients who were paced DDDR-70 versus VVI-40. METHODS: We analyzed the combined end point in patients with abnormal QRS duration (AbQRS) (> or =110 ms) compared with those with normal QRS duration (NQRS) (<110 ms). RESULTS: The QRS data were available for 496 of the 506 patients enrolled in the trial, including 223 patients with NQRS (45%) and 273 patients with AbQRS (55%). In patients in whom defibrillators were programmed to pace infrequently (VVI-40), having an NQRS or AbQRS was not an indicator of increased risk of adverse outcome. However, among patients in whom defibrillators were programmed in a manner that promoted more frequent ventricular pacing (DDDR-70), there was a significant adverse interaction with AbQRS; this combination was independently associated with a higher risk for developing CHF or death (p = 0.017). CONCLUSIONS: Although patients with AbQRS tended to have other risk factors associated with poor outcome, the interaction of QRS duration with ventricular pacing (DDDR-70) independently contributed to a worse outcome and therefore, was a marker of patients in whom such treatment may be harmful. This should not imply that right ventricular pacing in NQRS patients is safe but rather that pacing in the context of an AbQRS is probably best avoided.

Factors determining ICD implantation in drug therapy patients after termination of antiarrythmics versus implantable defibrillators trial.

Because of a significant survival benefit in the defibrillator arm of the Antiarrhythmics versus Implantable Defibrillator (AVID) Trial, patients in the antiarrhythmic drug (AAD) arm were advised to undergo ICD implantation. Despite this recommendation, ICD implantation in AAD patients was variable, with a large number of patients not undergoing ICD implantation. Patients were grouped by those who had been on AAD < 1 year (n = 111) and those on AAD > 1 year (n = 223). Multiple clinical and socioeconomic factors were evaluated to identify those who might be associated with a decision to implant an ICD. The primary reason for patients not undergoing ICD implantation was collected, as well as reasons for a delayed implantation, occurring later than 3 months from study termination. Of 111 patients on AAD for less than 1 year, 53 received an ICD within 3 months compared to 40/223 patients on AAD for more than 1 year (P < 0.001). Patient refusal was the most common reason to not implant an ICD in patients on drug < 1 year; physician recommendation against implantation was the most common in patients on drug > 1 year. Multivariate analysis showed ICD recipients on AAD < 1 year were more likely to be working and have a history of myocardial infarction (MI), while those on AAD > 1 year were more likely to be working, have a history of MI and ventricular fibrillation, and less likely to have experienced syncope, as compared to those who did not get an ICD. Having private insurance may have played a role in younger patients receiving an ICD.