Atrial fibrillation is associated with increased morbidity and mortality, in part because AF is a marker for other cardiovascular risk factors such as hypertension, valvular disease and left ventricular dysfunction. AF is also deleterious in its own right, due to the rapid, irregular heart rate, loss of atrial systole and atrial thromboembolism. Thus, there is a long history of attempting to restore and maintain normal sinus rhythm through cardioversion and anti-arrhythmic drug therapy.
More recently, several large trials have found no mortality benefit to the rhythm approach over the rate approach (anticoagulating and controlling ventricular rate), and the pendulum has started to swing towards rate control. However, an analysis of one of these trials suggested that there was, in fact, a benefit to sinus rhythm which may have been offset by mortality associated with anti-arrhythmic drug therapy. It is speculated that if sinus rhythm could be maintained without resorting to antiarrhythmics, the rhythm control approach might be beneficial after all. Thus the potential appeal of catheter-based ablation of atrial fibrillation which does not rely so much on anti-arrhythmic drugs.
In today’s NEJM, Hsu et al from Bordeaux, France investigate catheter ablation of atrial fibrillation in congestive heart failure. They studied 58 consecutive patients with at least class II CHF and echocardiographically documented ejection fractions less than 45%, who were undergoing catheter-based ablation of AF. Ejection fraction, symptoms and exercise capacity before and up to one year after the procedure were studied. These patients were also compared to 58 matched controls with normal ejection fractions undergoing the same procedure.
The authors observed substantial improvement in ejection fraction after ablation, from a mean of 36% before the procedure to 57% at one year post-procedure. NYHA class improved from 2.3 to about 1.5. Bicycle ergometer exercise time increased from 11 minutes to 14 minutes (in the control group without CHF, it increased from 14 to 16 minutes).
The authors also looked at their results among patients with adequate vs inadequate rate control before the procedure (average HR 72 vs 103). The ejection fraction improved by 23% in patients with poor rate control and by 17% in those with good rate control. In the absence of structural heart disease, EF increased by 24%; in patients with structural heart disease it increased by 16%.
The authors conclude:
Restoration and maintenance of sinus rhythm by catheter ablation without the use of drugs in patients with congestive heart failure and atrial fibrillation significantly improve cardiac function, symptoms, exercise capacity and quality of life.
I have some reservations about this study. First of all, it is not clear to me how exactly to evaluate a comparison of an ejection fraction in atrial fibrillation (the baseline) with one obtained in normal sinus rhythm. The EF is difficult to measure accurately in fibrillation; furthermore, the decrease in EF in atrial fibrillation which is due in part to tachycardia, in part to the absence of atrial contraction may not exactly reflect the actual decrease in LV contractility. Thus, I am not as impressed by the large increase in ejection fraction as I would have been if the before and after measurements had been taken in sinus rhythm.
Second, the rise in ejection fraction was less among patients with inadequate rate control before the procedure, but the authors do not state how the functional improvements (exercise time and functional status) fared in these two groups. Were they substantially less in those patients with adequate rate control?
Finally, as the authors themselves note, this was not a trial designed to evaluate mortality. But they go on to state that
Since a reduced left ventricular ejection fraction is an important predictor of mortality, the significant improvement in left ventricular function after ablation could be important in improving survival.
I would emphasize the word could here.
Note: there are three other atrial fibrillation articles in this issue. In an editorial, Stevenson and Stevenson summarize nicely the status of catheter ablation for atrial fibrillation and the potential problems and future approaches. Page reviews the approach to newly diagnosed atrial fibrillation. And there is an article on outpatient treatment of recent-onset AF with the “pill-in-the-pocket” approach.
This article points to an interesting future for arrhythmia cardiologists. The new bill approving ICD’s for all patients with EF<35% is about to come into effect this January. As if they won’t be busy enough. This study points to a superiority of ablation over rate control for atrial fibrillation. Get to know your favorite arrhythmia specialist, you’ll be calling them, often.
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Comment by Mad House Madman — December 3, 2004 @ 1:03 pm
The corresponding author of this article, Dr. Pierre Jais, has emailed me this reply:
I went back to the article, to see if I had misunderstood or misstated the methods. The description of the echocardiographic determination of ejection fraction at baseline is as follows:
From the above description, I don’t think it was unreasonable to assume that the initial EF was determined while the patients were still in atrial fibrillation.
Thus, the author’s reply represents a significant clarification.
Comment by mjmd — December 14, 2004 @ 2:41 pm
We discussed the “pill-in-the-pocket” article during cardio journal club this week. Consensus was that it was not that impressive. It was a very limited group of patients that were eligible for inclusion – approached that of including only those with lone afib. There was no placebo arm – they state that other studies had shown the effectiveness of propafenone or flecainide, so placebo comparison was not needed. This I think reduces the rigor of the study.
Also, there was no objective data to show that the patient was truly in afib when they had “palpitations”. No use of event recorders or implantable loop recorders to show that the perceived palpitations were in fact afib. In patients with new onset afib, it may self terminate, so it is quite possible the “palpitations” would have stopped without popping the pill in the pocket. I believe that a placebo arm would have been useful despite their claims of efficacy for propafenone and flecainide.
Most patients with afib do not meet their inclusion criteria, so I hope that practitioners do not implement this approach in patients dissimilar to those in the study. Additionally, many episodes of afib are asymptomatic, so the patients could have been having many more events than realized.
Comment by CardioNP — December 16, 2004 @ 12:24 am