In cardiovascular physiology, stroke volume 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 from the volume of blood just prior to the beat. 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.
Calculation
Its value is obtained by subtracting end-systolic volume from end-diastolic volume 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 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, contractility,
duration of contraction, preload, and afterload. Exercise
Prolonged aerobic exercise training may also increase stroke volume, which frequently results
in a lower heart rate. Reduced heart rate prolongs ventricular diastole, increasing
end-diastolic volume, and ultimately allowing more blood to be ejected.
Preload Stroke volume is intrinsically controlled
by preload. 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 afterload 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 index, is a method of relating
the stroke volume to the size of the person.
References ^ a b c d Schlosser, Thomas; Pagonidis, Konstantin;
Herborn, Christoph U.; Hunold, Peter; Waltering, Kai-Uwe; Lauenstein, Thomas C.; Barkhausen,
Jörg. "Assessment of Left Ventricular Parameters Using 16-MDCT and New Software for Endocardial
and Epicardial Border Delineation". Am J Roentgenol 184: 765–773. doi:10.2214/ajr.184.3.01840765.
Values: End-diastolic volume – average 118 and a
range of 68 – 239mL and End-systolic volume – average 50.1 and range,
16 – 143 mL: Also, ejection fraction was estimated in this
study to be average 59.9% ± 14.4%; range, 18 – 76%, but secondary source is used in
this article instead.
^ O'Connor, Simon. Examination Medicine. Edinburgh: Churchill Livingstone. p. 41. ISBN 0-7295-3911-3.
^ Normal ranges for heart rate are among the narrowest limits between bradycardia and tachycardia.
See the Bradycardia and Tachycardia articles for more detailed limits.
^ Edwards Lifesciences LLC > Normal Hemodynamic Parameters – Adult 2009
^ Katz, Arnold M.. Physiology of the heart. Hagerstwon, MD: Lippincott Williams & Wilkins.
p. 337. ISBN 0-7817-5501-8. Berne, Robert M., Levy, Matthew N.. Cardiovascular
Physiology. Philadelphia, PA: Mosby. ISBN 0-323-01127-6. Boron, Walter F., Boulpaep, Emile L.. Medical
Physiology: A Cellular and Molecular Approach. Philadelphia, PA: Elsevier/Saunders. ISBN 1-4160-2328-3.
External links The Gross Physiology of the Cardiovascular
System The Determinants of Cardiac Output