Atrial Fibrillation and Heart Failure: Treatment Considerations for a Dual Epidemic

Atrial fibrillation (AF) and heart failure have emerged as new cardiovascular epidemics over the last decade.1 Heart failure affects 5 million patients in the United States, and 550 000 patients are diagnosed with new heart failure each year.2 Although the incidence of heart failure remained stable over the past 50 years, the prevalence of heart failure in the United States has steadily increased. Heart failure is the primary reason for 12 to 15 million office visits and 6.5 million hospital days yearly.3 From 1990 to 1999, the annual number of hospitalizations increased from 800 000 to 1 million for heart failure as a primary diagnosis and from 2.4 to 3.6 million for heart failure as a primary or secondary diagnosis.4 The steadily increasing number of patients with heart failure is due partially to better treatment and “salvage” of patients with acute myocardial infarctions earlier in life.2 As a consequence, heart failure carries a significant economic burden on our society because it is the most common discharge diagnosis and because more Medicare dollars are spent for the diagnosis and treatment of heart failure than for any other diagnosis.5 In 2007, the American Heart Association estimated that $33 billion was spent on heart failure alone.6 AF is the most common arrhythmia in clinical practice, accounting for approximately one third of admissions resulting from cardiac rhythm disturbances. An estimated 2.3 million people in North America have AF. During the last 20 years, hospital admissions for AF have increased by 66% for a number of reasons, including the aging of the population, the rising prevalence of chronic heart disease, and more frequent diagnosis as a result of increased monitoring.7 The recent Anticoagulation and Risk Factors in Atrial Fibrillation (ATRIA) study projected that the prevalence of AF will increase 2.5-fold by the year 2050, affecting nearly 5.6 million Americans, an estimate based on the growing proportion of elderly individuals in the United States.8 The predicted future prevalence of AF was even greater in a communitybased study by Miyasaka and colleagues.9 They observed that the age-adjusted incidence of AF increased by 12.6% over the period from 1980 to 2000. Assuming the rate of increase in incidence remains unabated and assuming that these incidence rates can be applied to the entire US population, the projected number of persons with AF in the United States could reach 15.9 million by 2050. The Association Between AF and Heart Failure The association between AF and heart failure was appreciated almost a century ago10; Paul Dudley White noted, “Since auricular fibrillation so often complicates very serious heart disease, its occurrence may precipitate heart failure or even death, unless successful therapy is quickly instituted. ”11 The reported prevalence of AF in modern heart failure series ranges from 13% to 27%. 12–16 In the Framingham Heart Study, 1470 participants developed either new AF or heart failure between the years 1948 and 1995. Among these participants, a total of 383 individuals (26%) developed both AF and heart failure.17 Moreover, the prevalence of AF in patients with heart failure increased in parallel with the severity of the disease, ranging from 5% in patients with mild to 10% to 26% among patients with moderate up to 50% in patients with severe heart failure.18 Although the causative relationship between the 2 conditions has not been fully determined, their coexistence can be explained to some degree by the presence of common risk factors such as age, hypertension, diabetes, and obesity, as well as valvular, ischemic, and nonischemic structural heart disease. These factors are associated with myocardial cellular and extracellular alterations, electrophysiological and neurohormonal changes that combine to create an environment that predisposes the heart to both myocardial failure and AF.19