heart failure

Heart failure can be caused by factors originating from within the heart (i.e., intrinsic disease or pathology) or from external factors that place excessive demands upon the heart. Intrinsic disease includes conditions such as dilated cardiomyopathy and hypertrophic cardiomyopathy. External factors that can lead to heart failure include long-term, uncontrolled hypertension, increased stroke volume (volume load; arterial-venous shunts), hormonal disorders such as hyperthyroidism, and pregnancy.

Acute heart failure develops rapidly and can be immediately life threatening because the heart does not have time to undergo compensatory adaptations. Acute failure (hours/days) may result from cardiopulmonary by-pass surgery, acute infection (sepsis), acute myocardial infarction, valve dysfunction, severe arrhythmias, etc. Acute heart failure can often be managed successfully by pharmacological or surgical interventions. Chronic heart failure is a long-term condition (months/years) that is associated with the heart undergoing adaptive responses (e.g., dilation, hypertrophy) to a precipitating cause. These adaptive responses, however, can be deleterious in the long-term and lead to a worsening condition.

The number one cause of heart failure is coronary artery disease (CAD). CAD reduces coronary blood flow and oxygen delivery to the myocardium. This leads to myocardial hypoxia and impaired function. Another common cause of heart failure is myocardial infarction, with is the final and often fatal culmination of CAD. Infarcted tissue does not contribute to the generation of mechanical activity so overall cardiac performance is diminished. Furthermore, non-infarcted regions must compensate for the loss of function and this extra burden can precipitate changes that lead to failure. Valvular disease and congenital defects place increased demands upon the heart that can precipitate failure. Cardiomyopathies, of known origin (e.g., bacterial or viral) or idiopathic (unknown origin), can lead to failure. Myocarditis can have a similar effect. Arrhythmias such as severe bradycardia or tachycardia can also precipitate failure.

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Pathophysiology of Heart Failure

Revised 04/23/07

DISCLAIMER: These materials are for educational purposes only, and are not a source of medical decision-making advice.