Stroke Volume

Stroke volume is the amount of blood pumped by the heart from its left side ventricle. Stroke volume is the most important constraint of the heart, which describes its overall functioning and its health. It is the quantity of blood passed or released into the left ventricle of blood in one beat. Stroke volume is directly interlinked with the function of the heart. If the functioning of the heart gets disturbed due to diseases, then it also hinders the stroke volume. It either increases or decreases, resulting in the blockage of nerves and other severe conditions.

Stroke volume meaning 

Let’s learn about the stroke volume’s meaning. 

Stroke volume is part of cardiovascular physiology. It is the total volume of blood pumped by the heart’s left ventricle on every beat. It can be measured by subtracting the volume of blood at the endpoint of the ventricle from the volume of the heart at echocardiogram (opening of the left ventricle from the heart). Although we can use the stroke volume for both left and right ventricles, it is mainly used for the left ventricle. It is the important constraint of knowing the total cardiac output of any individual. Cardiac output of the heart is the product of heart rate with stroke volume. Along with this, stroke volume is also used to determine the ejection fraction. Ejection fraction is obtained by dividing stroke volume with the end-diastolic volume. 

Stroke volume cardiac output equation

Let’s learn about the stroke volume cardiac output equation. 

We can calculate stroke volume by subtracting the blood volume in the end beat from the blood volume in the beat, which is just before it. It can be calculated by mining the value of the last beat’s end-systolic volume from the value of the previous beat’s end-diastolic volume. It can be written as, 

SV = EDV – ESV

SV = Value of stroke volume 

EDV = Value of end-diastolic volume

ESV =  Value of end-systolic volume

The end-systolic volume remains equal to 50 ml, and the end-diastolic volume remains 120 ml in an average person of 70 kg weight. Hence, the average stroke volume of a normal person is 70ml. 

The factor which determines the stroke volume in a human being 

According to some biological reasons, the stroke volume of males remains slightly higher than that of females. This is basically due to larger heart sizes in males. The stroke volume of any person determines by  the following factors:

Size of heart 

The size of the heart is the foremost factor that influences the stroke volume of individuals. The larger the heart’s size, the larger quantity of blood is pumped at one time. Due to this, individuals with large heart sizes have high stroke volume. That’s why the stroke volume of infants and children remains less in comparison to the adults. 

Contractility 

The contraction of muscles of the heart is called contractility. If muscles’ contraction rate is high, it means more blood is pumping at a time. So, in this way, the heart’s contraction directly influences the stroke volume of any individual. 

Duration of contraction 

The heart’s contraction duration is the time period that the heart takes in contracting and regaining its size. It depends on the beat. If the contraction is high, the value of beats per minute is also high. If the person’s beat is high, then a large quantity of blood is supplied to the body and heart, pumping faster.

Factors that influence the rate of stroke volume 

The rate of stroke differs in different ages. The infants and children have less stroke volume, while adults have high. The men have higher stroke volume while females have less. These are biological factors. Let’s learn about some other factors that directly impact the stroke volume of any person. 

Exercises 

If done for a longer time, exercise increases the overall stroke volume. When the person performs a heavy workout, his heart’s beating increases simultaneously. This increases the rate of stroke volume. Along with this, it also increases the end-diastolic volume of the heart, due to which the heart starts pumping blood at fast rates, and results in the increase of stroke volume. 

Preload and afterload

Preload is the degree to which the ventricles of the heart stretch before contracting. According to the  Frank-Starling law of the heart, if the preload increases, the volume of blood in the heart increases, consequently increasing the stroke volume. 

Afterload is the measurement of aortic pressure during systole. It results in decreasing stroke volume in an individual. If the afterload increases, it hinders the functioning of ventricles, and ventricles eject less blood, resulting in a decrease in stroke volume. An increase in the afterload may result in arterial hypertension and aortic stenosis. 

Conclusion 

The heart is the most vital organ of the human body, which is responsible for the body’s overall functioning. It plays a major role in purifying the body’s impure blood. The heart’s stroke volume determines the rate at which it is pumping the blood. The stroke volume of the individual also describes the overall health. If the stroke volume of any person is normal according to his age, it means he is living a healthy life. The stroke volume can be maintained by performing exercises daily. Although, a good diet also affects the stroke volume in a person.