What Factors Affect Ejection Fraction Values?

Since ejection fraction values deal with the pumping action of the ventricles, any condition that reduces this activity affects the values. Ineffective blood circulation to the heart or ineffective ventricle filling combined with faulty valves, weakened muscle tissue, or tissue death all contribute to the amount of blood leaving the heart. Cardiologists generally use imaging studies to evaluate heart action and ejection fraction values. Treatment depends on the cause of the low values.

Physicians determine ejection fraction values by dividing the stroke volume by the end diastolic volume of primarily the left ventricle. The stroke volume is the amount of blood ejected from the heart with each heartbeat. The end diastolic volume is the total volume contained within the left ventricle between heartbeats, or before a beat occurs. A healthy left ventricle filling to a total volume of 120 milliliters is an example of end diastolic volume. During the beat, the stoke volume leaving the heart might be 75 milliliters of blood.

The calculation for the ejection fraction value is then stroke volume divided by end diastolic volume, or 75/120, which equals 0.62 or 62%. Normal ejection fraction values range from 50% to 75% and vary depending on time of day or physical activity. Problems arise when this percentage drops below 50%. When the ventricle does not fill properly, the heart is not pumping an adequate blood supply to the body. This might occur in the presence of valve disease in which ineffective closure between the chambers causes blood to back up into the atria.

Physicians refer to ineffective valve closure as mitral valve regurgitation, for which patients may require valve repair or replacement surgery. Tachycardic rhythms, or heart rates exceeding 100 beats per minute, cause the heart to beat so fast that the ventricles do not have sufficient time to fill. This dysrhythmia may occur because of overstimulation by the sympathetic nervous system or a malfunction of the heart's electrical system, known as ventricular dyssynchrony. Patients who have this problem may require resynchronization with defibrillator implants.

Under normal circumstances, heart tissue fibers expand to accommodate filling of the ventricle. Fiber weakening caused by hypertension eventually causes enlargement in the left ventricle to a degree that pumping action becomes ineffective. Once again, ejection fraction values decrease. Patients having this condition, known as left ventricular hypertrophy, often require lifestyle and diet modifications. Health care providers may also prescribe medications that reduce excess fluid, relax vascular tissue, and slow the heart.