Contractility

Contractility refers to the ability of a muscle or tissue to contract or shorten in response to a stimulus. In the context of cardiology, contractility often refers to the ability of the heart's muscle tissue to contract and thus pump blood throughout the body.

Overview

Contractility is an intrinsic property of cardiac muscle and is influenced by a number of factors, including the heart rate, the degree of myocardial stretch (known as the Frank-Starling mechanism), and the influence of certain hormones and neurotransmitters.

Factors affecting contractility

Several factors can affect the contractility of the heart. These include:

• Heart rate: An increase in heart rate can increase contractility, up to a certain point. Beyond this point, however, contractility may decrease due to insufficient time for the heart to fill with blood between contractions.
• Preload: This refers to the degree of stretch of the heart muscle prior to contraction. According to the Frank-Starling mechanism, an increase in preload (i.e., an increase in the volume of blood in the heart before it contracts) can increase contractility.
• Afterload: This refers to the pressure against which the heart must work to eject blood. An increase in afterload can decrease contractility.
• Neurotransmitters and hormones: Certain neurotransmitters and hormones, such as adrenaline and noradrenaline, can increase contractility. Conversely, other substances, such as acetylcholine, can decrease contractility.

Clinical significance

Abnormalities in contractility can lead to a variety of cardiovascular diseases, including heart failure, cardiomyopathy, and arrhythmias. Assessment of contractility is therefore an important part of the clinical evaluation of patients with suspected or known heart disease.

See also

• Cardiac output
• Stroke volume
• Ejection fraction
• Cardiac cycle