BETHESDA, MD-The American College of Cardiology, the American Heart Association, and the European Society of Cardiology have joined forces to issue new guidelines for atrial fibrillation (AF).[1] The guidelines, which are also endorsed by the North American Society of Pacing and Electrophysiology, reconcile the latest scientific evidence and expert opinion from both sides of the Atlantic on classification, evaluation, and treatment of this common and complex arrhythmia.

AF is the cardiac arrhythmia encountered most often in clinical practice and is common in patients with chronic obstructive lung disease. AF affects an estimated 2.2 million persons in the United States. Its prevalence increases with age; less than 1% of adults younger than 60 years have AF, compared with more than 6% of those older than 80 years. Perhaps the most dreaded consequence of AF is ischemic stroke. The annual rate of brain ischemia (including strokes, clinically occult strokes, and transient ischemic attacks) in patients with non-valvular AF exceeds 7%.[1]

What makes AF so challenging to treat is the wide variety of associated conditions (Table 1). “Pulmonary disease is itself a trigger for atrial fibrillation,” said Valentin Fuster, MD, PhD, Director of the Cardiovascular Institute at Mt. Sinai School of Medicine in New York City. Dr. Fuster, who cochaired the guidelines writing committee (with Lars E. Rydèn, MD, of the Karolinska Hospital in Stockholm), noted that “abnormalities in blood gases and abnormalities in pulmonary function can lead to atrial fibrillation. But what is most important is that the drugs given for chronic obstructive lung disease can predispose the patients to atrial fibrillation.”

ß-Adrenergic agonists and theophylline, agents commonly used to relieve bronchospasm in patients with obstructive pulmonary disease, can precipitate AF and make it difficult to control the ventricular response. Furthermore, certain agents that are often used to treat AF (eg, ß-blockers, sotalol, and propafenone) are contraindicated in patients with wheezing or bronchospasm.

“One must always balance what is gained with certain drugs and what may be lost, depending on the age of the patient and other predisposing factors for atrial fibrillation,” said Dr. Fuster. “One has to really understand all the triggers of the disease and all the benefits and risks of the medications used to treat it.”

Thus, the guidelines include detailed recommendations for managing AF in patients with pulmonary disease and in other groups of patients. “There are about 15 different drugs that can be given for the rhythm abnormalities,” Dr. Fuster noted.

The guidelines prioritize drug selection based on each patient’s risk profile. For example, “You wouldn’t give a calcium channel blocker to a patient with atrial fibrillation in the context of heart failure,” he explained. “You cannot give a ß-blocker to a patient who has significant chronic obstructive lung disease.”

SIMPLIFYING AF CLASSIFICATIONS

One of the achievements of the new guidelines is simplified classification for the heterogeneous presentations of AF based on clinical relevance. The classifications apply to episodes that last for longer than 30 seconds and that are not related to a reversible cause.

When AF is first detected, the duration of the episode and whether it has been preceded by other episodes may be uncertain, particularly if the patient has minimal or no symptoms. Thus, it should be designated as newly discovered AF. If a patient has had at least two episodes of AF, the arrhythmia should be classified as recurrent, and as paroxysmal if it terminates spontaneously or persistent if it is sustained. AF is designated as permanent if cardioversion does not result in sustained sinus rhythm or if the arrhythmia has persisted for longer than one year.

STREAMLINING THE WORK-UP

The initial clinical evaluation for AF is directed at characterizing the arrhythmia (eg, as paroxysmal or persistent), determining the underlying cause, and defining the associated cardiac or extracardiac factors. The minimum evaluation should include:

• A careful history and physical examination.
• An electrocardiogram (at least a single-lead recording).
• A chest film (primarily for evaluating the lung parenchyma and pulmonary vasculature).
• Two-dimensional transthoracic echocardiogram.
• Blood tests of thyroid function.

TAILORING TREATMENT

The hallmark of the new guidelines is a tailored approach to AF management (eg, based on AF symptoms and symptom severity and comorbidities). The two major treatment issues are how to manage the arrhythmia (ie, with rhythm control or heart rate control) and how to prevent thromboembolism.

Neither cardioversion and maintenance of sinus rhythm nor heart rate control has a clear advantage over the other, based on the available evidence. Theoretically, cardioversion may provide symptomatic relief, prevent thromboembolism (and thus the need for antithrombotic therapy), and avoid cardiomyopathy. However, the potential for adverse effects is generally greater with antiarrhythmic agents than it is with drugs used to control heart rate.

In general, the guidelines recommend:

• Using electrical cardioversion in patients with acute paroxysmal AF and a rapid ventricular response who have electrocardiographic evidence of acute myocardial infarction or symptomatic hypotension, angina, or heart failure that does not respond to drug therapy.
• Considering cardioversion (electrical or pharmacologic) for patients who are not hemodynamically unstable but have unacceptable AF symptoms.
• Treating precipitating or reversible causes of AF before starting antiarrhythmic drug therapy.
• Selecting drug therapy for maintaining sinus rhythm in patients with disabling or troublesome AF symptoms based on the safety profile of the agent.
• Measuring the heart rate response both at rest and during exercise in patients with persistent or permanent AF and using drug therapy to control the rate within the physiological range.
• Administering antithrombotic therapy to all AF patients except those with lone AF (ie, AF in patients younger than 60 years who have no echocardiographic evidence of cardiopulmonary disease).
• Individualizing the selection of an antithrombotic agent based on the absolute risks of stroke and bleeding complications, as well as the relative risk and benefit.

--Christine M. Olsen, PhD