Atrial fibrillation (AF), the most common cardiac arrhythmia, affects 2.2 million Americans and is reaching epidemic proportions since its prevalence grows as the older population continues to increase. AF is a major risk factor for stroke if it is not appropriately diagnosed and managed. Updated guidelines on the management of patients with AF were jointly released by the American College of Cardiology, the American Heart Association, and the Heart Rhythm Society in the December 2010 Journal of the American College of Cardiology. “The guidelines reflect a consensus of expert opinion and a thorough review of clinical research,” explains L. Samuel Wann, MD, MACC, FAHA, who chaired the expert group writing committee. “The new recommendations update guidelines that were previously released in 2006. They are based on evidence from clinical trials, as well as expert opinion. The update was precipitated by several new areas of research that have recently become available.”
Major Modifications to Atrial Fibrillation Recommendations
Several major modifications were offered in the updated guidelines for AF, one of which focuses on heart rate control (Table 1). The RACE II study was one of the primary reasons for revising the guidelines on heart rate control. It found that a strict heart rate control regimen with exercise testing provided no benefit over a more lenient heart rate control regimen. “This is an important modification because it means that physicians won’t need such rigid heart rate reevaluations, which often require exercise tests and the use of multiple drugs,” says Dr. Wann. “Symptomatic patients, however, do require treatment, and the long-term adverse effects of persistent tachycardia on ventricular function are still of concern.”
Recommendations for using clopidogrel and dronedarone in the management of AF were also provided in the updated guidelines. Research has shown that the addition of clopidogrel to aspirin is beneficial and more effective than taking either agent alone to reduce the risk of major vascular events among patients with AF who cannot or will not take warfarin. However, this regimen is still not as efficacious as warfarin, according to the guidelines. Dronedarone, a newer antiarrhythmic agent, also has beneficial effects on AF. It has been approved by the FDA to reduce the need for rehospitalization for cardiovascular events related to AF. Dronedarone shares certain properties with amiodarone, but it appears to be better tolerated and can be initiated in the outpatient setting. The agent should not, however, be administered to AF patients with class IV heart failure or to patients who have had an episode of decompensated heart failure in the past 4 weeks, especially if they have depressed left ventricular function (left ventricular ejection fraction less than or equal to 35%).
“Another change of interest to physicians is that the level of evidence on catheter ablation has been increased to a Class Ia indication,” Dr. Wann says. “Our evidence on the efficacy of catheter ablation for AF is much more robust now than it was in 2006. Catheter ablation performed in experienced centers helps maintain sinus rhythm in patients with symptomatic persistent AF. That said, patients should be treated with antiarrhythmic drugs prior to considering catheter ablation.”
Dabigatran: A New Alternative
Dabigatran (Pradaxa, Boehringer Ingelheim), an oral anticoagulant, was approved by the FDA in 2010 for the prevention of stroke and systemic embolism in patients with non-valvular AF. After releasing the guideline update, the committee released a focused update specifically on dabigatran in the March 2011 issue of Circulation (Table 2). In pre-clinical studies, dabigatran was shown to be as effective as warfarin in preventing strokes and blood clots in patients with either paroxysmal or permanent AF, and in those with risk factors for stroke or blood clots who do not have a prosthetic heart valve, significant heart valve disease, severe renal failure, or advanced liver disease.
“Dabigatran has several very desirable characteristics that may be useful in treating patients with AF to prevent stroke,” says Dr. Wann. “Adherence issues, which are common for patients taking warfarin, may be minimized because dabigatran use doesn’t necessitate frequent office visits for repeated monitoring of INR. The agent also has an immediate onset of action, as opposed to the 3 days that warfarin takes to establish anticoagulation.”
The Future in Atrial Fibrillation
New treatments for AF are continuing to emerge as new anticoagulants and novel procedures and devices are being explored in clinical trials. “Efforts will be made to ensure that the guidelines are evidence-based and address emerging treatments for AF,” Dr. Wann says. “Until more data materialize, it’s important that physicians employ these guidelines judiciously and balance the recommendations with their experience and knowledge when managing AF patients. We should be sure to match diagnostic and treatment plans to patient preferences whenever possible.”
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