The failing heart--an engine out of fuel.

Copyright © 2007 Massachusetts Medical Society. Heart failure is an enormous medical and societal burden.1,2 It is a common disease: more than 2% of the U.S. population, or almost 5 million people, are affected, and 30 to 40% of patients die from heart failure within 1 year after receiving the diagnosis.3 Heart failure can be disabling, and it can severely reduce a patient’s quality of life. It consumes approximately 2% of the National Health Service budget in the United Kingdom, and in the United States, the total annual cost of treatment for heart failure is approximately $28 billion. Moreover, the financial burden of heart failure will increase in coming decades because of the aging population and the improved treatments of its causes. Over the past 20 years, there has been considerable progress in the treatment of chronic heart failure with angiotensin-converting–enzyme (ACE) inhibitors,4,5 aldosterone antagonists,6 beta-receptor blockers,7,8 and resynchronization therapy.9,10 Even with the very best of modern therapy, however, heart failure is still associated with an annual mortality rate of 10%.10 The search for better treatments is one of the major challenges in cardiology. Chronic heart failure is multifactorial. There are many reasons why a human heart can fail,11 but the available evidence suggests that the failing heart is an engine out of fuel — that is, altered energetics play an important role in the mechanisms of heart failure. For this reason, the modulation of cardiac metabolism has promise as a new approach to the treatment of heart failure. This review describes cardiac energy metabolism, appraises the methods used for its assessment, evaluates the role of impaired energy metabolism in heart failure, and gives options for metabolic therapy.