What causes a high ejection fraction (EF)?

High Ejection Fraction: Causes and Clinical Context

A high ejection fraction (EF >70%) is not a disease state but rather a physiological or pathophysiological response that typically occurs in conditions causing reduced ventricular cavity size, increased contractility, or altered loading conditions—most commonly seen with significant mitral regurgitation, hypertrophic states, or hyperdynamic circulation.

Primary Causes of Elevated Ejection Fraction

Mitral Regurgitation (Most Common Pathological Cause)

• In mitral regurgitation, the left ventricle ejects blood in two directions—forward into the aorta and backward into the left atrium, artificially elevating the measured ejection fraction 1
• The reduced afterload from regurgitant flow allows easier ventricular emptying, creating a falsely reassuring EF that masks underlying ventricular dysfunction 1
• An EF <60% in the setting of mitral regurgitation actually indicates left ventricular systolic dysfunction has already developed, making normal-appearing EF values (60-70%) potentially concerning in this context 1

Hypertrophic Cardiomyopathy and Ventricular Hypertrophy

• Severe left ventricular hypertrophy with small cavity size produces elevated EF through geometric changes rather than enhanced contractility 2
• In aortic stenosis with preserved EF, the hypertrophied ventricle maintains high relative wall thickness with reduced chamber volume, creating a high volume/mass ratio that preserves or elevates EF despite diastolic dysfunction 2
• This "paradoxical" pattern is particularly common in elderly patients with small, hypertrophied ventricles 2

Hyperdynamic States

• Tachycardia-induced states, hyperthyroidism, severe anemia, and sepsis can all produce supranormal EF through increased sympathetic tone and enhanced contractility 3
• These conditions reduce end-systolic volume through enhanced inotropy, mathematically elevating EF even without improved cardiac function 4

Important Clinical Context: EF as a Mathematical Construct

Understanding the Limitations

• EF is fundamentally a mathematical ratio (1 - ESV/EDV) that reflects relative volume changes rather than actual pumping function or cardiac output 4
• EF is strongly associated with mean cavity volume (the average of end-systolic and end-diastolic volumes), meaning it primarily reflects chamber size rather than contractile performance 4
• For patients across the heart failure spectrum, EF "borrows its attractiveness" from the linear correlation between ESV and EDV, not from reflecting underlying physiology 4

Clinical Pitfalls to Avoid

• Never assume high EF equals good cardiac function—patients with HFpEF (EF ≥50%) have severe exercise intolerance, frequent hospitalizations, and 15% annual mortality despite preserved EF 5
• In mitral regurgitation, waiting until EF drops to "normal" range (50-60%) means irreversible ventricular dysfunction has occurred; intervention should be considered when EF approaches 60% or end-systolic dimension reaches 40mm 1
• In aortic stenosis with small ventricles and high EF, reduced stroke volume index (<35 mL/m²) despite normal EF indicates severe hemodynamic compromise 2

When High EF Indicates Pathology

Valvular Disease

• Chronic mitral regurgitation with EF >70% represents compensated volume overload that will eventually progress to ventricular dysfunction 1
• The perpetual cycle of "mitral regurgitation begets mitral regurgitation" causes progressive LV dilatation and eventual EF decline 1
• Ventricular septal defects can similarly produce elevated EF through left-to-right shunting 1

Restrictive Physiology

• Small, stiff ventricles from infiltrative disease, constrictive pericarditis, or severe hypertrophy may show elevated EF due to reduced cavity size rather than enhanced function 2
• These patients have severe diastolic dysfunction with elevated filling pressures despite high EF 2

Clinical Approach to High EF

Essential Diagnostic Steps

• Assess for valvular regurgitation (especially mitral) with comprehensive echocardiography including color Doppler 1
• Measure absolute stroke volume and cardiac output, not just EF—high EF with low stroke volume indicates pathology 2
• Evaluate for left ventricular hypertrophy, cavity size, and wall thickness to identify restrictive or hypertrophic patterns 2
• Screen for hyperdynamic states: check thyroid function, assess for anemia, evaluate heart rate and rhythm 3

Key Measurements Beyond EF

• End-systolic and end-diastolic volumes provide more physiological information than EF alone 4
• Stroke volume index <35 mL/m² despite normal or high EF indicates hemodynamic compromise 2
• Diastolic parameters (E/e' ratio, left atrial size, pulmonary pressures) are critical in patients with preserved or elevated EF 3, 5