Left ventricular ejection fraction (LVEF) indicates how much blood the left ventricle pumps out with each contraction. A more clinical definition of LVEF is the percentage of blood ejected during systole in relation to the total end-diastolic volume (Srichai, Danias & Lima, 2019). Knowing how to calculate LVEF helps practitioners assess the strength of the heart as well as diagnose and monitor heart failure.
Stroke Volume
Before you can calculate the LVEF, you need to know the stroke volume. Stroke volume (SV) is the volume of blood ejected from the left ventricle with each cardiac cycle or heartbeat. SV is calculated by subtracting the left ventricular end systolic volume (ESV) from the left ventricular end diastolic volume (EDV). Not all the blood that fills the heart by the end of diastole (EDV) can be ejected from the heart during systole. Therefore, the volume of blood left in the heart at the end of systole is the ESV.
For an average-sized man, the end-diastolic volume is about 120 milliliters (mL) of blood and the end-systolic volume is about 50 mL of blood. Thus, the average stroke volume is approximately 70 milliliters (mL). These values can be calculated using diagnostic tests such as a left-heart catheterization, transesophageal echocardiogram (TEE) or transthoracic echocardiogram (TTE).
Calculating Ejection Fraction
Left ventricular ejection fraction (LVEF) can also be obtained using a variety of diagnostic tests. Non-invasive assessment methods include echocardiography, magnetic resonance imaging (MRI), computed tomography (CT), gated equilibrium radionuclide angiography or gated myocardial perfusion imaging with either single-photon emission computed tomography (SPECT) or positron emission tomography (PET). One invasive method to assess LVEF is left ventricular contrast ventriculography performed during cardiac catheterization.
If these diagnostic tests are not available, LVEF can be calculated by dividing the SV by the end-diastolic volume. Multiply this by 100 to get the percentage.
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What is a normal LVEF?
Clinicians use LVEF to evaluate cardiovascular disease. LVEF can help assess both systolic and diastolic heart failure and predict adverse outcomes in patients with heart failure, after myocardial infarction, and after revascularization (Kosaraju et al., 2021). However, it’s possible to have a normal ejection fraction and still have heart failure, known as heart failure with preserved ejection fraction (HFpEF).
The American College of Cardiology classifies LVEF into the following categories (Kosaraju et al., 2021):
- Hyperdynamic = LVEF greater than 70%
- Normal = LVEF 50% to 70%
- Mild dysfunction = LVEF 40% to 49%
- Moderate dysfunction = LVEF 30% to 39%
- Severe dysfunction = LVEF less than 30%
Indications for measuring LVEF include (Kosaraiu et al., 2021):
- Evaluating the anatomy and function of the left ventricle
- Assessing qualitative and quantitative left ventricular function
- Assessing patients with signs of cardiovascular disease
- Identifying the category of heart failure
- Heart failure with preserved ejection fraction (HFpEF): LVEF greater than or equal to 50%
- HFpEF, borderline: LVEF 41 to 49%
- HFpEF, improved: LVEF greater than 40%
- Heart failure with reduced ejection fraction (HFrEF): LVEF less than or equal to 40%
- Ventricular arrhythmias to assess for structural abnormalities
- Exposure to cardiotoxic therapy
- Assessing congenital heart disease
- Assessing valvular disorders
Example
A TEE was performed on a patient to evaluate his recent complaints of shortness of breath and mild chest discomfort. His ESV was 85 and his EDV was 128. Calculate your patient’s LVEF.
Step 1: Calculate the SV
Step 2: Calculate LVEF
According to this quick calculation, your patient has moderate LV dysfunction. A complete work-up is needed to determine if he has HFrEF, valvular disease, ventricular dysrhythmias, structural abnormalities, other cardiovascular disease or underlying condition.
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