The definition of stroke volume is the volume of blood pumped out of the left ventricle of the heart during each systolic cardiac contraction.
|Ventricular volumes view talk edit|
|Measure||Right ventricle||Left ventricle|
|Stroke volume||94 mL (± 15 mL)||95 mL (± 14 mL)|
Stroke volume index is determined by three factors: Preload: The filling pressure of the heart at the end of diastole. Contractility: The inherent vigor of contraction of the heart muscles during systole. Afterload: The pressure against which the heart must work to eject blood during systole.
Stroke Volume (SV) is the volume of blood in millilitres ejected from the each ventricle due to the contraction of the heart muscle which compresses these ventricles. SV is the difference between end diastolic volume (EDV) and end systolic volume (ESV).
The EDV is the filled volume of the ventricle prior to contraction and the ESV is the residual volume of blood remaining in the ventricle after ejection. In a typical heart, the EDV is about 120 mL of blood and the ESV about 50 mL of blood.
Cardiac output is the product of heart rate (HR) and stroke volume (SV) and is measured in liters per minute. HR is most commonly defined as the number of times the heart beats in one minute. SV is the volume of blood ejected during ventricular contraction or for each stroke of the heart.
For an average-sized man, the end-diastolic volume is 120 milliliters of blood and the end-systolic volume is 50 milliliters of blood. This means the average stroke volume for a healthy male is usually about 70 milliliters of blood per beat. Total blood volume also affects this number.
Insert the value of stroke volume into the algebraic equation EDV = SV + ESV. In this equation, EDV stands for "end-diastolic volume," SV stands for "stroke volume," and ESV stands for "end-systolic volume." For instance, if the stroke volume has a value of 65, the equation becomes EDV = 65 + ESV.
Preload is related to the ventricular end-diastolic volume; a higher end-diastolic volume implies a higher preload. However, the relationship is not simple because of the restriction of the term preload to single myocytes.
The ejection fraction, as mentioned earlier, is calculated by dividing the stroke volume by the end diastolic volume. It is literally the fraction of the end diastolic ventricular volume that is ejected with each beat.
Preload is defined as the stretch of myocardium or end-diastolic volume of the ventricles and most frequently refers to the volume in a ventricle just before the start of systole.
A reduced stroke volume at the same end-diastolic volume results in reduced ejection fraction. If afterload is reduced by decreasing aortic pressure, the opposite occurs - stroke volume and ejection fraction increase, and end-systolic volume decreases (green loop in figure).
An increase in right ventricular stroke volume increases pulmonary venous blood flow to the left ventricular, thereby increasing left ventricular preload and stroke volume. An increase in stroke volume then increases cardiac output and arterial blood pressure.
Consequently, an increase in end-diastolic volume will result in a decrease in end-systolic pressure and SV (with respect to their values predicted under constant LV elastance), whereas a decrease in end-diastolic volume will result in an increase in end-diastolic pressure and SV (again, with respect to their values ...
An increase in afterload, for example, in individuals with long-standing high blood pressure, generally causes a decrease in stroke volume.  In summary, stroke volume may be increased by increasing the contractility or preload or decreasing the afterload.
The systemic pulse pressure is approximately proportional to stroke volume, or the amount of blood ejected from the left ventricle during systole (pump action) and inversely proportional to the compliance (similar to Elasticity) of the aorta.
Widening of pulse pressure was associated with increased stroke volume in the young and reduced arterial compliance in the older patients. The age-related decrease in stroke volume resulted in a parallel narrowing of pulse pressure up to age 50 years.
Results: From rest to exercise at a heart rate of 160 beats min(-1) end-diastolic volume increased by 18% (P < 0.001) and end-systolic volume decreased by 21% (P = 0.002). Stroke volume showed an almost linear increase during exercise (45% increase, P < 0.001).
During moderate, upright, whole body exercise (e.g., running, bicycling) increased venous return to the heart by the muscle and respiratory pump systems generally causes a small increase in end-diastolic volume (shown in figure); however, if heart rate increases to very high rates, reduced diastolic filling time can ...
Pulse pressure is the difference between the upper and lower numbers of your blood pressure. This number can be an indicator of health problems before you develop symptoms. Your pulse pressure can also sometimes that you're at risk for certain diseases or conditions.
When heart rate or stroke volume increases, cardiac output is likely to increase also. Conversely, a decrease in heart rate or stroke volume can decrease cardiac output.