The Role of Atrial Fibrillation in CRT-D Patients: The ALTITUDE Study Group

Atrial fibrillation and flutter (AF) are common and can have adverse effects in patients with left ventricular dysfunction. The present study assessed the long-term implications of AF on shock incidence and survival in patients with implantable cardiac resynchronization devices followed on a remote monitoring network. Patients implanted with cardiac resynchronization therapy defibrillators (CRT-D) manufactured by Boston Scientific, who regularly communicated information over a secure network, were eligible for enrollment in this study. Atrial fibrillation burden was calculated using atrial sense histograms. Shock episode electrograms were adjudicated by a panel of electrophysiologists. Both univariate and multivariate logistic regression models adjusting for age, gender, and device type were used to analyze the effects of AF on overall survival and the incidence of ICD therapies. A total of 63,866 patients were included in this analysis and 2,173 first shock episodes were adjudicated. Three hundred and eighty-eight first shock episodes (18%) were classed as due to AF with a rapid ventricular response. The overall incidence of AF was 47.1%. Regardless of shock occurrence, any AF burden was associated with decreased survival compared with no AF (AF burden .0.01%, p,0.001). Conclusions: In an unselected population of patients with implantable resynchronization cardiac devices, remotely followed via a secure network, atrial fibrillation is extremely prevalent, and even low burdens of AF are associated with worsened outcome.