So when should sinus rhythm be restored?

Cardiology Review® Online, November 2007, Volume 24, Issue 11

This review summarizes an important substudy of the Rate Control Versus Electrical Cardioversion (RACE) trial, which randomized 522 patients with atrial fibrillation (AF) to rate versus rhythm control treatment strategies and followed them for up to 2.3 years with a primary composite endpoint that included cardiovascular mortality, heart failure, thromboembolic complications, bleeding, severe adverse effects of anti-arrhythmic agents, and pacemaker implantation.

This review summarizes an important substudy of the Rate Control Versus Electrical Cardioversion (RACE) trial, which randomized 522 patients with atrial fibrillation (AF) to rate versus rhythm control treatment strategies and followed them for up to 2.3 years with a primary composite endpoint that included cardiovascular mortality, heart failure, thromboembolic complications, bleeding, severe adverse effects of anti-arrhythmic agents, and pacemaker implantation. This substudy examined the effect of hypertension on outcomes in 256 patients. The primary endpoint occurred more frequently in hypertensive patients than in normotensive patients. In addition, amongst patients with hypertension, those randomized to a rhythm control strategy had a higher incidence of experiencing an endpoint compared to those hypertensive patients randomized to rate control. This is in contrast to the overall results of RACE, which concur with the results of the larger Atrial Fibrillation Following Investigation of Rhythm Management (AFFIRM) Trial—namely that rate and rhythm control arms are not significantly different.1

How do we apply the results of RACE and AFFIRM to individual patients in clinical practice? Are there patients who should be offered one strategy over the other despite the findings of RACE and AFFIRM? There are data to suggest that maintaining sinus rhyhm in patients with congestive heart failure (CHF) may be advantageous.2 In a substudy of AFFIRM, 245 patients underwent 6-minute walks at initial, 2-month, and yearly visits. This study showed that the presence of AF was associated with worsening New York Heart Association functional class and that there was a modest improvement in 6-minute walk time with restoration and maintenance of sinus rhythm. The advantage of maintaining sinus rhythm in the heart failure population has also been shown in studies of catheter ablation. One study examined 58 consecutive patients with CHF and left ventricular ejection fraction (LVEF) <45% and found that when compared to matched controls, the patients with CHF had significant improvement in LVEF, exercise capacity, symptoms, and quality of life after successful ablation for AF.3 More recently, the Pulmonary Vein Antrum Isolation versus AV Node Ablation with Biventricular Pacing for the Treatment of Atrial Fibrillation in Patients with Congestive Heart Failure (PABA-CHF) study demonstrated that pulmonary vein isolation with restoration of sinus rhythm was superior to AV junction ablation with biventricular pacing.4

This substudy shows that in patients with hypertension, heart rate control may be safer than treatment with antiarrhythmic agents. However, as the clinical vignette highlights, there are patients who may continue to have symptoms of AF despite adequate heart rate control. In some clinical situations (such as CHF) sinus rhythm may have advantages over heart rate control. In these cases, restoration of sinus rhythm may be the best option. Perhaps we need to consider different and hopefully safer means of restoring and maintaining sinus rhythm. Newer antiarrhythmic agents currently in development and catheter-based treatments such as pulmonary vein isolation may offer this advantage.