Stroke volume
Stroke Volume[edit]
Stroke volume (SV) is the volume of blood pumped from the left ventricle of the heart with each beat. It is a critical component of cardiac output, which is the total volume of blood the heart pumps per minute. Stroke volume is influenced by several factors, including preload, afterload, and contractility.
Determinants of Stroke Volume[edit]
Stroke volume is determined by three primary factors:
Preload[edit]
Preload refers to the initial stretching of the cardiac myocytes prior to contraction. It is related to the ventricular filling and is influenced by the venous return to the heart. The greater the preload, the greater the stroke volume, according to the Frank-Starling law of the heart.
Afterload[edit]
Afterload is the pressure against which the heart must work to eject blood during systole. It is primarily determined by the systemic vascular resistance and the condition of the aortic valve. An increase in afterload can decrease stroke volume.
Contractility[edit]
Contractility refers to the intrinsic ability of cardiac muscle fibers to contract at a given fiber length. It is influenced by factors such as sympathetic nervous system activity and circulating catecholamines. Increased contractility enhances stroke volume.
Clinical Significance[edit]
Stroke volume is an important parameter in assessing cardiac function. It can be affected in various pathological conditions such as heart failure, myocardial infarction, and valvular heart disease. Understanding stroke volume and its determinants is crucial for diagnosing and managing these conditions.
Measurement[edit]
Stroke volume can be measured using several techniques, including echocardiography, cardiac catheterization, and magnetic resonance imaging (MRI). These methods provide insights into the heart's pumping efficiency and help guide treatment decisions.
