Progression to chronic atrial fibrillation after pacing: The Canadian Trial Of Physiologic Pacing

Objectives This study examined the effect of physiologic pacing on the deve lopment of chronic atrial fibrillation (CAF) in the Canadian Trial Of Physi ologic Pacing (CTOPP). Background The role of physiologic pacing to prevent CAF remains unclear. S mall randomized studies have suggested a benefit for patients with sick sin us syndrome. No data from a large randomized trial are available. Methods The CTOPP randomized patients undergoing first pacemaker implant to ventricular-based or physiologic pacing (AAI or DDD). Patients who were pr ospectively found to have persistent atrial fibrillation (AF) lasting great er than or equal to one week were defined as having CAF. Kaplan-Meier plots for the development of CAF were compared by log-rank test. The effect of b aseline variables on the benefit of physiologic pacing was evaluated by Cox proportional hazards modeling. Results Physiologic pacing reduced the development of CAF by 27.1%, from 3. 84% per year to 2.8% per year (p = 0.016). Three clinical factors predicted the development of CAF: age greater than or equal to 74 years (p = 0.057), sinoatrial (SA) node disease (p < 0.001) and prior AF (p < 0.001). Subgrou p analysis demonstrated a trend for patients with no history of myocardial infarction or coronary disease (p = 0.09) as well as apparently normal left ventricular function (P = 0.11) to derive greatest benefit. Conclusions Physiologic pacing reduces the annual rate of development of ch ronic AF in patients undergoing first pacemaker implant. Age greater than o r equal to 74 years, SA node disease and prior AF predicted the development of CAF. Patients with structurally normal hearts appear to derive greatest benefits. (J Am Coll Cardiol 2001;38:167-72) (C) 2001 by the American Coll ege of Cardiology.