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Health See other Health Articles Title: AF and HF Together: A Vicious Electromechanical Cycle Medscape... Atrial Fibrillation and Heart Failure: What's the Connection? LaPrincess Brewer, MD: I am Dr LaPrincess Brewer, an advanced cardiology fellow here at Mayo Clinic. During today's Mayo Clinic Talk, we will be discussing atrial fibrillation and heart failure, both of which have emerged as cardiovascular epidemics over the past decade. I am joined by Dr Bernard Gersh, professor of medicine, who specializes in clinical electrophysiology. Atrial fibrillation and heart failure share common risk factors and frequently coexist. What is the pathophysiology behind atrial fibrillation and heart failure? Bernard J Gersh, MD: It is a question of cause, consequence, or both. There is no doubt that atrial fibrillation can precipitate heart failure. You lose atrial transport and have rapid ventricular rates. Atrial fibrillation can increase mitral regurgitation, and there is the entity of tachycardia-induced left ventricular dysfunction. Studies in animals have shown that not just a rapid rate but an irregular rate can stimulate the neurohormonal system and cause heart failure. The reverse also applies, and heart failure results in atrial stretch, atrial fibrosis, diastolic dysfunction (which can also increase atrial dysfunction and atrial volume), and atrial volume overload, although a large left atrium leads to electrical inhomogeneity. I can understand why heart failure also causes atrial fibrillation. The other point is that heart failure activates the neurohormonal system and that, in turn, can cause atrial fibrillation. It's both a cause and a consequence, but I think of it as a vicious electromechanical cycle. They both feed upon each other. Dr Brewer: What is the frequency of atrial fibrillation in patients with heart failure? Dr Gersh: It depends on the New York Heart Association class. If you look at the trials of people with class 3 and 4 heart failure, the frequency is approximately 40%; and with class 2 to 3 heart failure, it is approximately 15%.[1] In one of our studies, and in a Framingham study over about 5 years, 20% of people with atrial fibrillation had heart failure, and the reverse was true as well.[2] Dr Brewer: The prognostic significance of atrial fibrillation in patients with heart failure remains controversial. Can you talk about the impact on prognosis for these patients? Dr Gersh: It is less controversial now. It's not good from either a symptomatic or a prognostic standpoint. In some of the trials and in such trials as the Framingham study,[2] the development of atrial fibrillation independently was associated with a significant increase in subsequent mortality. They may have developed atrial fibrillation because they were deteriorating. Rather than blaming it all on the atrial fibrillation; it's bad news. In someone with compensated left ventricular dysfunction, the development of atrial fibrillation is an adverse prognostic finding. There also is a very interesting group of people with "tachycardia-induced cardiomyopathy" who have no underlying structural heart disease that we know of but who develop atrial fibrillation and heart failure, and they seem to respond (at least from the symptomatic and ejection-fraction standpoint) to correction of the atrial fibrillation. I don't know whether their heart function returns to normal, but that is a group in whom atrial fibrillation is the cause. Rhythm vs Rate Control Dr Brewer: Atrial fibrillation and heart failure share common mechanisms. What are the benefits of medical vs interventional treatment? Dr Gersh: The AF-CHF trial done in Canada[3] that compared rhythm control with rate control did not come up with the answers that I expected. There was no difference in outcomes between rhythm control vs rate control. It raises several questions. One of the issues in that trial was that a surprising number of people in the rate-control arm actually maintained sinus rhythm. However, this contradicts some of the previous registry studies (which were not necessarily in heart-failure patients) that showed that patients in sinus rhythm did better.[4,5] We don't know whether that is because they were in sinus rhythm. Was the fact that they were in sinus rhythm a favorable prognostic sign? It doesn't mean that trying to maintain sinus rhythm is beneficial. Post Comment Private Reply Ignore Thread
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