What does an ejection fraction (EF) of 64% indicate?

Understanding Ejection Fraction (EF) of 64%

An ejection fraction (EF) of 64% indicates normal left ventricular systolic function, as it falls within the normal range of 50-70%. 1

What is Ejection Fraction?

Ejection fraction is a measurement that represents the percentage of blood that leaves the left ventricle when it contracts compared to the total amount of blood in the left ventricle when it's filled. It is calculated using the formula:

EF = (EDV - ESV) / EDV × 100%

Where:

• EDV = End-diastolic volume (volume when the heart is filled)
• ESV = End-systolic volume (volume when the heart has contracted)

Interpretation of EF Values

According to established guidelines, EF values are categorized as follows:

• Hyperdynamic: greater than 70%
• Normal: 50% to 70% (midpoint 60%)
• Mild dysfunction: 40% to 49% (midpoint 45%) - now termed "mildly reduced EF" (HFmrEF)
• Moderate dysfunction: 30% to 39% (midpoint 35%)
• Severe dysfunction: less than 30% 1

Clinical Significance of EF 64%

An EF of 64% has the following implications:

1. Normal Systolic Function: This value indicates that the left ventricle is contracting normally and efficiently pumping blood to the body 1.

2. Heart Failure Classification: If a patient with this EF has symptoms of heart failure, they would be classified as having heart failure with preserved ejection fraction (HFpEF), defined as EF ≥50% 1.

3. Valvular Disease Considerations: In patients with valvular heart disease, particularly mitral regurgitation, an EF of 64% is reassuring. Guidelines indicate that intervention for mitral regurgitation should be considered when EF falls below 60% 1.

4. Diagnostic Context: It's important to note that EF is just one parameter of cardiac function. A normal EF doesn't exclude other cardiac abnormalities, particularly diastolic dysfunction 1.

Measurement Considerations

When interpreting an EF of 64%, several important factors should be considered:

1. Measurement Variability: There is inherent variability in EF measurements. For example, the same patient might have an EF of 62% on one study and 55% on another due to measurement variability 1.

2. Method of Calculation: The method used to determine EF (visual estimation vs. quantitative measurement) can affect the reported value 1.

3. Imaging Modality: Different imaging techniques (echocardiography, cardiac MRI, nuclear imaging) may yield slightly different EF values for the same patient 1.

4. Clinical Context: EF should always be interpreted in the context of the patient's symptoms, other cardiac parameters, and overall clinical picture 1.

Important Caveats

• Not a Binary Measure: Ventricular function is a continuous variable, not binary. Small differences in EF (e.g., 64% vs. 66%) are not clinically significant 1.

• Serial Measurements: Changes in EF over time are often more clinically meaningful than a single measurement 1.

• Limitations of EF: EF primarily reflects systolic function and doesn't capture diastolic function, which can be abnormal even with a normal EF 1.

• Geometric Assumptions: Traditional EF calculations make geometric assumptions about the left ventricle that may not accurately reflect true ventricular function in all patients 2.

In summary, an EF of 64% represents normal left ventricular systolic function, but should be interpreted within the broader clinical context and alongside other cardiac parameters for comprehensive assessment of cardiac health.