By Cara Pellegrini, MD
Assistant Professor of Medicine, University of California, San Francisco, Cardiology Division; Electrophysiology Section, San Francisco VA Medical Center
Dr. Pellegrini reports no financial relationships relevant to this field of study.
SYNOPSIS: Rate control and rhythm control strategies for cardiac surgery patients with postoperative atrial fibrillation lead to similar hospital durations, similar complication rates, and similar very low rates of atrial fibrillation at 60-day follow-up.
SOURCE: Gillinov AM, Bagiella E, Moskowitz AJ, et al. Rate control versus rhythm control for atrial fibrillation after cardiac surgery. N Eng J Med 2016 [Epub ahead of print].
Atrial fibrillation (AF) is the most common complication after cardiac surgery, with an incidence of 20-50%. It is associated with prolonged hospitalizations, increased complications, and inflated costs. Evidence about how it should best be managed is inconclusive, and this has translated into major variations in practice patterns. Thus, the Cardiothoracic Surgical Trials Network, with funding from the NIH and Canadian Institutes of Health, conducted a randomized, controlled trial across 23 sites in the United States and Canada to examine the best initial treatment strategy.
Of the 2,109 patients who underwent cardiac surgery and had no previous history of AF, 695 developed AF and 523 were randomized to rate control, with a goal heart rate < 100 bpm vs. rhythm control with amiodarone, with or without a rate-slowing agent. If AF persisted for > 24-48 hours after randomization, electrical cardioversion was recommended. Anti-coagulation was also recommended if AF persisted or was recurrent 48 hours after randomization. The primary outcome was total number of days in the hospital (ED visits included) in the first 60 days following randomization. Secondary outcomes included length of index hospitalization, readmissions, heart rhythm, time to conversion, and adverse events, with need for pacemaker and death noted specifically.
The study population was mostly white men in the their late 60s. One-third of subjects had a history of diabetes and only 13% had a history of heart failure. About 40% underwent isolated coronary artery bypass grafting (CABG), another 40% underwent isolated valve surgery (repair or replacement), with 20% enduring both procedures. The median number of hospital days was 5.1 in the rate-control group and five in the rhythm control group. There were no significant differences between groups in any hospitalization parameters or overall serious adverse events, including thromboembolic and bleeding events and death. Freedom from AF was similarly high in both groups: 84.2% (rate control) and 86.9% (rhythm control) of patients were free from AF from discharge to 60 days. Those in the rate-control arm had a slightly slower resolution of AF, and were significantly less likely to have been in a stable heart rhythm without AF from day 30 to day 60 than those in the rhythm-control arm (93.8% vs. 97.9%; P = 0.02). The authors concluded that there was no net clinical advantage to either approach; both strategies resulted in similar hospitalization durations, similar complication rates, and similar low rates of persistent AF at 60 days.
AF is quite common following cardiac surgery, with an incidence approaching 50% in those who underwent combined CABG and valve surgery (28% valve surgery alone and 34% CABG only). Happily, it is also generally transient and self-limited in those without a previous atrial arrhythmia history; regardless of treatment assignment, the vast majority of patients were no longer in AF at the end of the study. Even among those with AF at the time of hospital discharge (~8%), if AF had resolved by 30 days (as it did in about half of them), none were found to be in AF at 60-day follow-up. This is a different beast than generic new-onset AF.
The high crossover rate of about 25% in both directions is notable. Most patients in the rate-control arm switched to a rhythm-control strategy due to failure of rate control, and most patients in the rhythm-control arm discontinued amiodarone early due to adverse effects. This high rate of crossover, together with similar cardioversion rates (9.2% in the rate-control group and 13.8% in the rhythm-control group), as well as nearly identical rates of anticoagulation use at time of hospital discharge (42.7% in the rate-control arm and 43.3% in the rhythm control arm) and duration (44.8 and 44.9 days, respectively), may help explain the convergence of outcomes. The reason for similar anticoagulation rates despite a between-group difference in protocol-specified indication for anticoagulation initiation (46.2% in the rate-control group and 31.8% in the rhythm-control group met criteria) is not clear.
When this trial was far along in its enrollment, the American College of Cardiology, the American Heart Association, and the Heart Rhythm Society published joint guidelines for AF management. These guidelines recommended rate control with beta-blockers as the first-line therapy for patients with stable hemodynamics. This recommendation was based in part on extrapolation of the Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) trial, which found no benefit (and some harm) to rhythm control in elderly, non-surgical AF patients. The Gillinov et al study certainly doesn’t refute that recommendation; there is no clear, marked advantage to the rhythm-control strategy. However, this study would suggest that there are tradeoffs to the different strategies — toxic effects and intolerances if given amiodarone and a slower resolution of AF and slightly higher AF prevalence during follow-up if not. The authors stated that the management decision ultimately should belong to the individual patient and provider.