Every beat of the heart moves blood from one part of the body to the other. The left ventricle, the lower chamber of the left side of the heart, pumps oxygenated blood to the rest of the body. Slightly half of the ventricle's volume pumps out with each heartbeat. This volume, called the ejection fraction, normally ranges between 55 and 70 percent, MayoClinic.com reports. Anything that damages the left ventricle and reduces the force of the heartbeat causes a drop in the ejection fraction. Cardiac ejection is determined by a formula that evaluates several factors.
Stroke Volume
Stroke volume is the amount of blood pumped by the left ventricle with each beat of the heart. Stroke volume is determined by subtracting the amount of blood left in the ventricle after each contraction, called the end-systolic volume, from the volume of end-diastolic volume, the amount of blood in each ventricle after diastole, the resting phase between beats. The ventricles fill with blood from the atria, the upper chambers of the heart, during the resting phase.
End-Diastolic Volume
End-diastolic volume usually averages between 120 to 130 milliliters, but sometimes goes as high as 200 to 250 ml, Dorland's Medical Dictionary for Health Consumers states. The end-diastolic volume can be affected by diseases of the heart that cause the muscles in the ventricle to stiffen and thicken. This restricts the amount of blood that can enter the ventricle, and causes blood to back up into the atria and then into the lungs. A low end-diastolic volume indicates diastolic heart failure. Poorly treated high blood pressure most commonly causes diastolic heart failure, along with increased age, diabetes and infection, the Merck Manual states.
End-Systolic Volume
The end-systolic volume ranges from as low as 10 to 30 ml to around 50 to 60 ml. Athletes may have a very low end-systolic volume due the pumping efficiency of their hearts. High end-systolic volume can indicate systolic heart failure. Conditions that cause dilation and weakness of the left ventricle such as coronary artery disease, heart attack, cardiomyopathy, myocarditis, inflammation of the heart or diseases that affect the heart valves cause the end-systolic volume to be high, because the heart doesn't pump blood efficiently. More blood than normal remains in the ventricle, which results in even more dilation and weakening of the ventricle over time.
Cardiac Ejection Fraction
The cardiac ejection fraction is figured by dividing the stroke volume by the end-diastolic volume and multiplying by 100. Cardiac ejection fraction is expressed as a percentage. Ejection fraction of 35 to 40 percent confirms a diagnosis of systolic heart failure, while ejection fraction of less than 35 percent puts a patient at risk for life-threatening irregular heartbeats, the Cleveland Clinic warns.
