HEART FAILURE - PATHOPHYSIOLOGY

Heart failure, also sometimes referred to as congestive heart failure, is a chronic progressive disorder in which the heart's normal pumping mechanism is altered and cardiac output is inadequate to meet the body’s metabolic needs. Certain conditions, such as coronary artery disease (narrowing of cardiac arteries) or elevated blood pressure, can result in a heart too weak or rigid to fill and pump efficiently. Other disorders associated with heart failure include obesity and diabetes.

The ventricles are the pumping chambers of the heart. With each heartbeat, the heart contracts and relaxes. Every contraction pushes blood out of the two ventricles and during relaxation the ventricles are refilled with blood.

A regular heartbeat enables the heart to pump sufficiently to maintain blood flow, thereby meeting the body's needs. The amount of blood pumped out or ejected from the ventricle in a single heartbeat is known as the ejection fraction (EF). The EF is a parameter that is used to indicate how efficiently the heart is pumping. In a healthy heart, the EF is 50 percent or above, i.e. at least half of the blood that fills the ventricle is pumped out with each heartbeat.

Systolic and diastolic dysfunction can also result in heart failure. Systolic heart failure occurs due to the stretching and thinning of ventricular chambers, after which the heart loses its ability to contract normally and hence cannot pump out the required amount of blood.

Diastolic heart failure occurs when the left ventricle cannot relax or fill adequately, indicating a filling difficulty. The stiffening and thickening of the ventricular walls results in a back up of blood into the left atrium and pulmonary blood vessels and prevents the normal filling of the heart. Diastolic dysfunction alters cardiac output and causes blood returning from the systemic circulation to back up, resulting in fluid build-up in other parts of the body as well.

The G protein-coupled receptor (GPCR)-mediated transcription of hypertrophic genes in certain cardiac disorders can also cause contractile dysfunction, leading to heart failure. Cardiac overload or cardiac injury due to other conditions such as myocardial infarction, coronary artery disease and cardiomyopathy can also result in cardiac remodeling, leading to heart failure.

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HEART FAILURE - PATHOPHYSIOLOGY

BIBLIOGRAPHY AND RECOMMENDED READING

Federmann, M., Hess, O.M. Differentiation between systolic and diastolic dysfunction. European heart journal 1994, 15 Suppl D: 2-6.

Konstam, M.A. et al. Left ventricular remodeling in heart failure: current concepts in clinical significance and assessment. JACC Cardiovascular imaging 2011, 4(1): 98-108.

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