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Whereas the heart rate is simply the number of times your heart beats in a minute, the stroke volume is the volume of blood pumped out by your heart's left ventricle with each beat. It is measured in millilitres and is much more complicated to determine that your heart rate. A special test called an echocardiogram (aka echo) is used to determine your heart's stroke volume. An echocardiogram uses radio waves to create a picture of your heart so the volume of blood passing through it can be measured. An echocardiogram makes it possible to make the measurements of the heart that are required to calculate stroke volume. Using the echocardiogram, you will be able to determine the numbers needed for the following calculations. The left ventricle outflow tract is the portion of your heart through which blood passes to enter your arteries. In order to calculate the stroke volume you will need to determine the area the left ventricular outflow tract (LVOT), and the velocity time integral of the left ventricular outflow tract (LVOT VTI). These calculations need to be done by a professional reading an echocardiogram. An expert may use the following equation to determine the area of the left ventricle's outflow tract: Area = 3.14 (LVOT diameter/2)^2 This way of calculating the area is now beginning to be superseded by more advanced imaging technology. To determine stroke volume, the amount of the blood in a ventricle just before a beat (end-diastolic volume, EDV) is subtracted from the amount of the blood in a ventricle (heart chamber) at the end of a beat (end-systolic volume, ESV). Stroke Volume = EDV ESV. While stroke volume usually refers to the left ventricle, it can also refer to the right ventricle. The stroke volume of both ventricles is usually equal. To determine your stroke volume index, take the velocity time integral, which is the amount of blood being pumped with each heartbeat and divide it by the body surface area of the left ventricle (in square meters). This formula allows direct analysis of the stroke volume for a patient of any size. Finally, to determine your cardiac output, multiply your heart rate by your stroke volume. This is a relatively simple calculation which identifies the amount of blood your heart pumps in one minute. The formula is Heart Rate x Stroke Volume = Cardiac Output. For example, if your heart rate is 60 bpm and your stroke value is 70 ml, the equation looks like this: 60 bpm x 70 ml = 4200 ml/min or 4.2 liters (1.1USgal) a minute.
Have an echocardiogram. Calculate the area of the left ventricle's outflow tract (aka LVOT). Assess stroke volume. Determining your cardiac output.