Stroke volume
Encyclopedia
In cardiovascular physiology
, stroke volume (SV) is the volume of blood
pumped from one ventricle of the heart
with each beat. SV is calculated using measurements of ventricle volumes from an echocardiogram
and subtracting the volume of the blood in the ventricle at the end of a beat (called end-systolic volume
) from the volume of blood just prior to the beat (called end-diastolic volume
). The term stroke volume can apply to each of the two ventricles of the heart, although it usually refers to the left ventricle. The stroke volumes for each ventricle are generally equal, both being approximately 70 ml in a healthy 70-kg man.
Stroke volume is an important determinant of cardiac output
, which is the product of stroke volume and heart rate
, and is also used to calculate ejection fraction
, which is stroke volume divided by end-diastolic volume. Because stroke volume decreases in certain conditions and disease states, stroke volume itself correlates with cardiac function.
(ESV) from end-diastolic volume
(EDV) for a given ventricle.
In a healthy 70-kg man, EDV is approximately 120 mL and ESV is approximately 50 mL, giving a difference of 70 mL for the stroke volume.
"Stroke work" refers to the work, or pressure of the blood ("P") multiplied by the stroke volume.
, duration of contraction, preload (end-diastolic volume
), and afterload
.
training may also increase stroke volume, which frequently results in a lower (resting) heart rate. Reduced heart rate prolongs ventricular diastole
(filling), increasing end-diastolic volume, and ultimately allowing more blood to be ejected.
(commonly measured as the aortic pressure during systole) reduces stroke volume. Though not usually affecting stroke volume in healthy individuals, increased afterload will hinder the ventricles in ejecting blood, causing reduced stroke volume. Increased afterload may be found in aortic stenosis and arterial hypertension.
, is a method of relating the stroke volume to the size of the person.
Cardiovascular physiology
Cardiovascular physiology is the study of the circulatory system. More specifically, it addresses the physiology of the heart and blood vessels ....
, stroke volume (SV) is the volume of blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
pumped from one ventricle of the heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
with each beat. SV is calculated using measurements of ventricle volumes from an echocardiogram
Echocardiography
An echocardiogram, often referred to in the medical community as a cardiac ECHO or simply an ECHO, is a sonogram of the heart . Also known as a cardiac ultrasound, it uses standard ultrasound techniques to image two-dimensional slices of the heart...
and subtracting the volume of the blood in the ventricle at the end of a beat (called end-systolic volume
End-systolic volume
End-systolic volume is the volume of blood in a ventricle at the end of contraction, or systole, and the beginning of filling, or diastole.ESV is the lowest volume of blood in the ventricle at any point in the cardiac cycle....
) from the volume of blood just prior to the beat (called end-diastolic volume
End-diastolic volume
In cardiovascular physiology, end-diastolic volume is the volume of blood in the right and/or left ventricle at end Load or filling in . Because greater EDVs cause greater distention of the ventricle, EDV is often used synonymously with preload, which refers to the length of the sarcomeres in...
). The term stroke volume can apply to each of the two ventricles of the heart, although it usually refers to the left ventricle. The stroke volumes for each ventricle are generally equal, both being approximately 70 ml in a healthy 70-kg man.
Stroke volume is an important determinant of cardiac output
Cardiac output
Cardiac output is the volume of blood being pumped by the heart, in particular by a left or right ventricle in the time interval of one minute. CO may be measured in many ways, for example dm3/min...
, which is the product of stroke volume and heart rate
Heart rate
Heart rate is the number of heartbeats per unit of time, typically expressed as beats per minute . Heart rate can vary as the body's need to absorb oxygen and excrete carbon dioxide changes, such as during exercise or sleep....
, and is also used to calculate ejection fraction
Ejection fraction
In cardiovascular physiology, ejection fraction is the fraction of Blood pumped out of the Right Ventricle of the heart to the Pulmonary Circulation and Left Ventricle of the heart to the Systemic Circulation with each Heart beat or Cardiac cycle...
, which is stroke volume divided by end-diastolic volume. Because stroke volume decreases in certain conditions and disease states, stroke volume itself correlates with cardiac function.
Calculation
Its value is obtained by subtracting end-systolic volumeEnd-systolic volume
End-systolic volume is the volume of blood in a ventricle at the end of contraction, or systole, and the beginning of filling, or diastole.ESV is the lowest volume of blood in the ventricle at any point in the cardiac cycle....
(ESV) from end-diastolic volume
End-diastolic volume
In cardiovascular physiology, end-diastolic volume is the volume of blood in the right and/or left ventricle at end Load or filling in . Because greater EDVs cause greater distention of the ventricle, EDV is often used synonymously with preload, which refers to the length of the sarcomeres in...
(EDV) for a given ventricle.
In a healthy 70-kg man, EDV is approximately 120 mL and ESV is approximately 50 mL, giving a difference of 70 mL for the stroke volume.
"Stroke work" refers to the work, or pressure of the blood ("P") multiplied by the stroke volume.
Determinants
Men, on average, have higher stroke volumes than women due to the larger size of their hearts. However, stroke volume depends on several factors such as heart size, contractilityContractility
Myocardial contractility is the intrinsic ability of the heart to contract independent of preload and afterload. Changes in the ability to produce force during contraction result from different degrees of binding between myosin and actin filaments...
, duration of contraction, preload (end-diastolic volume
End-diastolic volume
In cardiovascular physiology, end-diastolic volume is the volume of blood in the right and/or left ventricle at end Load or filling in . Because greater EDVs cause greater distention of the ventricle, EDV is often used synonymously with preload, which refers to the length of the sarcomeres in...
), and afterload
Afterload
Afterload is the tension or stress developed in the wall of the left ventricle during ejection. Following Laplace's law, the tension upon the muscle fibers in the heart wall is the product of the pressure within the ventricle, multiplied by the volume within the ventricle, divided by the wall...
.
Exercise
Prolonged aerobic exerciseAerobic exercise
Aerobic exercise is physical exercise of relatively low intensity that depends primarily on the aerobic energy-generating process. Aerobic literally means "living in air", and refers to the use of oxygen to adequately meet energy demands during exercise via aerobic metabolism...
training may also increase stroke volume, which frequently results in a lower (resting) heart rate. Reduced heart rate prolongs ventricular diastole
Diastole
Diastole is the period of time when the heart fills with blood after systole . Ventricular diastole is the period during which the ventricles are relaxing, while atrial diastole is the period during which the atria are relaxing...
(filling), increasing end-diastolic volume, and ultimately allowing more blood to be ejected.
Preload
Stroke volume is intrinsically controlled preload (the degree to which the ventricles are stretched prior to contracting). An increase in the volume or speed of venous return will increase preload and, through the Frank–Starling law of the heart, will increase stroke volume. Decreased venous return has the opposite effect, causing a reduction in stroke volume.Afterload
Elevated afterloadAfterload
Afterload is the tension or stress developed in the wall of the left ventricle during ejection. Following Laplace's law, the tension upon the muscle fibers in the heart wall is the product of the pressure within the ventricle, multiplied by the volume within the ventricle, divided by the wall...
(commonly measured as the aortic pressure during systole) reduces stroke volume. Though not usually affecting stroke volume in healthy individuals, increased afterload will hinder the ventricles in ejecting blood, causing reduced stroke volume. Increased afterload may be found in aortic stenosis and arterial hypertension.
Stroke Volume Index
Similar to cardiac indexCardiac index
Cardiac index is a vasodynamic parameter that relates the cardiac output to body surface area , thus relating heart performance to the size of the individual...
, is a method of relating the stroke volume to the size of the person.