Which factors influence stroke volume (SV)?

Stroke volume (SV) refers to the volume of blood that the heart pumps with each beat, and it is influenced primarily by three key factors: afterload, preload, and contractility.

Afterload is the force or resistance against which the heart must pump to eject blood. An increased afterload can reduce stroke volume, as the heart must work harder to overcome this resistance. Conversely, a decreased afterload allows for more efficient ejection of blood, which can increase stroke volume.

Preload refers to the degree of stretch of the ventricular walls at the end of diastole, just before contraction. The amount of blood that fills the heart during diastole influences this stretch. According to the Frank-Starling law of the heart, a greater preload results in a greater stroke volume, up to a certain limit, due to enhanced myocardial contractility.

Contractility refers to the intrinsic ability of the heart muscle to contract. Factors that increase contractility will enhance stroke volume. This can be influenced by various physiological factors and the presence of certain hormones or medications.

Understanding these three components provides insight into how stroke volume is regulated and the physiological principles that underlie cardiac function. This knowledge is essential for anticipating how various clinical situations can affect a patient's cardiovascular health and