Atrial fibrillation in heart failure: epidemiology, pathophysiology, and rationale for therapy.

Heart failure (HF) affects almost 5 million patients in the United States and is a leading cause of morbidity and mortality. Atrial fibrillation (AF), like HF, affects millions of patients and markedly increases in prevalence with age. As the US population ages, the number of patients afflicted with HF and AF will continue to grow. HF with preserved ejection fraction is particularly common in the elderly population. The prevalence of AF in patients with HF increases from <10% in those with New York Heart Association (NYHA) functional class I HF to approximately 50% in those with NYHA functional class IV HF. The pathophysiologic changes that occur in patients with HF and AF are complex and incompletely understood. Alterations in neurohormonal activation, electrophysiologic parameters, and mechanical factors conspire to create an environment in which HF predisposes to AF and AF exacerbates HF. Mechanisms include atrial remodeling and tachycardia-induced myopathy. The development of AF in HF appears to independently predict death resulting from pump failure and total mortality. Although the currently available therapeutic options for AF in patients with HF are varied, their effect on prognosis remains unknown and is the subject of ongoing clinical trials. It will be critical to define and plan therapies specifically for those patients with AF, HF, and preserved ejection fraction in addition to the population with low ejection fraction that has dominated previous investigations.