Is echocardiographic ejection fraction measurement accurate in a patient with atrial fibrillation?

Ejection Fraction Assessment in Atrial Fibrillation

Echocardiographic ejection fraction measurement in atrial fibrillation is feasible and clinically useful, but requires averaging approximately 10 consecutive cardiac cycles to account for beat-to-beat variability, and clinicians must recognize that measurements may underestimate true LVEF compared to sinus rhythm. 1

Technical Approach for Accurate Measurement

The key to accurate LVEF assessment during AF is proper averaging technique:

• Average at least 10 consecutive cardiac cycles (some guidelines suggest ≥13 beats) when measuring LVEF in AF to account for the irregular rhythm and beat-to-beat changes in preload and contractility 1
• The European Association of Cardiovascular Imaging specifically recommends this averaging approach for both systolic and diastolic function parameters in AF 1
• An alternative "index beat" method uses measurements from the cardiac cycle following a pair of equal preceding cardiac cycles, though averaging remains the gold standard 1

Use biplane Simpson's method as the standard 2D technique for LVEF measurement, as recommended by the European Society of Cardiology, regardless of rhythm 2

Critical Clinical Pitfalls

Timing of measurement matters significantly in AF:

• A reduced ejection fraction measured during or immediately after rapid AF (particularly rates ≥130 bpm) may not accurately reflect true ventricular function once rate control is achieved 1
• In tachycardia-induced cardiomyopathy from AF, median LVEF can increase dramatically from 25% to 52% with rate control alone 1
• Wait until consistent rate control is achieved before using LVEF measurements for major therapeutic decisions such as ICD implantation 1

AF systematically causes underestimation of LVEF by echocardiography:

• Recent artificial intelligence analysis demonstrated that multicycle averaging during AF increases measured LVEF by approximately 8.2% compared to standard single-beat measurements 3
• This AI-based reassessment reclassified 28.2% of patients initially thought to have reduced LVEF as actually having preserved function 3
• The beat-to-beat variability in AF creates measurement challenges that can lead to misdiagnosis of reduced LVEF 3

When Echocardiography May Be Particularly Problematic

Consider alternative imaging in specific scenarios:

• When acoustic windows are suboptimal, global longitudinal strain (GLS) may be more reliable than visual LVEF estimation, with GLS ≥-14% detecting LVEF ≤40% with 95% sensitivity and 86% specificity 4
• Interestingly, one study found correlation between LVEF and GLS was actually stronger in AF patients (r=-0.86) than in sinus rhythm (r=-0.51), though this was a small subset 4
• Cardiac MRI provides superior accuracy compared to echocardiography in AF, with excellent correlation (r=0.90 for ejection fraction) to invasive measurements and no systematic underestimation 5

Alternative Imaging Modalities

Cardiac MRI is the gold standard when precision is critical:

• MRI measurements of LVEF, stroke volume, and cardiac output correlate excellently with invasive catheterization measurements in AF patients (r=0.85-0.95) 5
• The mean difference between MRI and catheterization measurements is similar in AF and sinus rhythm, indicating MRI is not affected by rhythm irregularity 5
• In real-world practice, CMR upwardly reclassifies approximately 42.3% of patients with severely impaired LVEF by echocardiography as less severely impaired 6

Clinical Decision-Making Framework

For routine clinical management:

• Transthoracic echocardiography with proper 10-beat averaging is adequate for most clinical decisions in AF 1
• Ensure heart rate is controlled (ideally around 70 bpm) before definitive LVEF assessment 1

Consider cardiac MRI when:

• Therapeutic decisions hinge on precise LVEF thresholds (e.g., ICD implantation at LVEF ≤35%) 5, 6
• Echocardiographic windows are poor 4
• There is discordance between clinical presentation and echocardiographic LVEF 6
• Initial echocardiography shows severely reduced LVEF during or shortly after rapid AF, and you need to determine true baseline function after rate control 3, 6

The bottom line: Echocardiography can accurately assess LVEF in AF when proper technique is used (10-beat averaging, adequate rate control), but clinicians must recognize it tends to underestimate LVEF compared to both sinus rhythm measurements and MRI, particularly when rate control is suboptimal. 1, 3, 5