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Definition of Cardiac Output
Cardiologists measure cardiac output as the combination of heart rate and stroke volume (the amount of blood the left ventricle ejects into the aorta with each contraction). There are several methods for determining stroke volume, including dye injection and thermal differential.
In a person whose cardiovascular system is healthy, cardiac output increases with increased physical activity such as exercise, in which both heart rate and the force of the heart’s contractions increase.
Severe damage can result in cardiac output that is less than the body’s needs even at rest. Medications to strengthen the heart and focus the efforts of its contractions can often improve cardiac efficiency, though only mediating the underlying cause can restore adequate cardiac output.
People who have a high aerobic fitness level, such as athletes and those who regularly engage in aerobic exercise, can significantly increase their cardiac output to send more blood to their muscles. During intense aerobic activity, 60 percent or more of the cardiac output may go to the skeletal muscles.
High cardiac output is essential to get enough blood and oxygen to vital organs at the same time.