Ejection Fraction Calculator

How does this ejection fraction calculator work?

This health tool determines EF in percentage with the use of stroke volume and end diastolic volume for one patient at a time.

The ejection fraction refers to the outbound blood pumped during each heartbeat and is obtained by dividing stroke volume by the end diastolic volume (EDV).

EF (%) = SV / EDV * 100

Stroke volume can be obtained by:

1) SV = EDV – ESV (when end systolic volume is known)

2) Cardiac output in mL/min  /  Heart rate in bpm

Example calculation from the ejection fraction calculator: for a normal range stroke volume of 70 mL and a left ventricular EDV value of 120 mL, the ejection fraction is: 70/120 = 0.58, meaning in percentage 58%.

Normal EDV for the left ventricle is between 121 mL and 163 mL. Normal ejection fractions vary between 50% and 65%.

During exercise, individuals with a great physical condition can experience high increases in stroke volume which in turn result in EF exceeding 90%.

EF is a measure of cardiac function and indicates the severity of systolic heart failure which is the clinical manifestation of a low EF.

Low ejection fraction (below 40%):

■ Systolic congestive heart failure;

■ Myocardial damage caused by MI;

■ Atrial fibrillation;

■ Dilated cardiomyopathy;

■ Persistent hypertension.

EF vs. SV

The ejection fraction is the amount of blood that is pumped outside the heart and sent in the circulatory system with each heartbeat while stroke volume is the amount of blood pumped by the heart in a minute. 

Stroke volume depends on the difference between the end diastolic volume and end systolic volume while the EF depends on stroke volume and on the condition of the myocardial muscle and of the arteries.

Both are measured in mL of blood per unit, for SV the unit being a minute and for EF the unit being a heartbeat.

Factors that increase or decrease stroke volume, i.e exercise in healthy individuals, increased vascular resistance, sympathetic stimulation etc. action in turn of EF, however EF can be modified despite a normal stroke volume, due to conditions explained above.

Measuring ejection fraction

Echocardiograms are able to measure ejection fraction by measuring the volumes of heart chambers and their modification during the cardiac cycle. Other means of measuring EF include CT scan, MRI and cardiac catheterization.

During echocardiograms, the most commonly used method, sound waves produce images of the blood pumping function. Cardiovascular magnetic resonance imaging uses a magnetic field and radio waves to create cross sectional images of the heart.

Computerized tomography creates cross sectional images using x-rays while a nuclear medicine scan would inject radioactive material in the bloodstream to detect blood flow.

References

1) Bhatia RS, Tu JV, Lee DS, Austin PC, Fang J, Haouzi A, Gong Y, Liu PP. (2006) Outcome of heart failure with preserved ejection fraction in a population-based study. N Engl J Med. 2006 Jul 20; 355(3):260-9.

2) Roman V, Grigorian L, Barge E, Bassante P, de la Peña MG, Gonzalez-Juanatey JR. (2005) Heart failure in patients with preserved and deteriorated left ventricular ejection fraction. Heart. 2005 Apr; 91(4):489-94.

3) Wandt B, Bojo L, Tolagen K, Wranne B. (1999) Echocardiographic assessment of ejection fraction in left ventricular hypertrophy. Heart. 1999 Aug; 82(2): 192–198.