Can notched P waves on an electrocardiogram (ECG) indicate mitral regurgitation?

Notched P Waves and Mitral Regurgitation

Notched P waves on ECG can indicate mitral regurgitation, but they reflect left atrial abnormality caused by the hemodynamic consequences of the valve disease rather than directly indicating the regurgitation itself. 1

Understanding the ECG-Mitral Regurgitation Connection

The American College of Cardiology explicitly recommends that P waves with an M-like structure (bifid or notched P waves) be evaluated for underlying cardiac conditions including mitral valve disease, hypertension, or heart failure. 1 This establishes a clear clinical link between notched P waves and mitral regurgitation as one of the key differential diagnoses to consider.

Mechanism of P Wave Changes in Mitral Regurgitation

The notched P wave reflects left atrial abnormality that develops secondary to mitral regurgitation through several pathophysiological mechanisms:

• Elevated left atrial pressure from chronic volume overload causes atrial remodeling 1
• Delayed intraatrial conduction through Bachmann's bundle creates the characteristic double-peaked morphology 2
• Left atrial enlargement from chronic regurgitant flow produces structural changes detectable on ECG 3

Research confirms that patients with mitral valve disease demonstrate P wave changes including increased duration, increased bipeak interval, and increased P terminal force, though these changes correlate imperfectly with the degree of left atrial pressure elevation. 4

Specific ECG Criteria to Identify

When evaluating for mitral regurgitation-related left atrial abnormality, look for these specific findings:

• P wave duration ≥120 ms (the most consistent finding for left atrial abnormality) 1, 5
• Widely notched P wave with ≥40 ms separation between peaks creating the characteristic M-like or bifid appearance 2, 1
• Increased P terminal force in lead V1 (product of amplitude and duration of terminal negative component) 2, 1
• Left axis of terminal P wave (−30° to −90°) 1, 5

The American Heart Association emphasizes that P wave duration ≥120 ms or widely notched P wave ≥40 ms appear to have equal diagnostic value for detecting left atrial abnormality. 2

Clinical Significance and Diagnostic Approach

The American College of Cardiology recommends measuring P wave duration when a bifid P wave is identified, with ≥120 ms suggesting left atrial abnormality, and evaluating the notch width, with ≥40 ms between peaks being significant. 1

Recent research demonstrates that notched P waves (defined as peak-to-peak distance ≥20 ms in lead II) are associated with:

• Significantly larger left atrial diameter (38.8 vs 36.8 mm, p=0.001) 3
• Increased left ventricular mass index 3
• Higher risk of cardiovascular events in patients with cardiovascular risk factors 3

In patients with moderate or severe mitral regurgitation specifically, P-wave peak time correlates with left ventricular end-diastolic pressure and can predict left ventricular diastolic dysfunction. 6

Critical Pitfalls to Avoid

• Do not rely solely on P wave morphology—the American College of Cardiology emphasizes correlating ECG findings with clinical context and cardiac imaging 1
• Avoid outdated terminology like "P-mitrale," "atrial hypertrophy," or "atrial enlargement"—use "left atrial abnormality" instead 2, 1, 5
• Recognize that P wave changes reflect multiple factors including atrial dilatation, muscular hypertrophy, elevated pressure, and conduction delay—not just anatomic enlargement 1, 5
• Remember that interatrial conduction delay can cause bifid P waves even without significant atrial enlargement 1
• Use multiple electrocardiographic criteria rather than single findings to increase diagnostic confidence 2, 5

Next Steps in Evaluation

When notched P waves are identified in the context of suspected mitral regurgitation:

• Obtain echocardiography to assess left atrial size, function, and severity of mitral regurgitation 1, 7
• Assess for arrhythmia risk, particularly atrial fibrillation, as P wave abnormalities predict new onset AF in mitral stenosis and likely other mitral valve diseases 1, 8
• Evaluate underlying cardiac conditions including hypertension and heart failure that may coexist 1
• Consider cardiac catheterization if hemodynamic assessment is needed, as LVEDP correlates with P wave abnormalities in mitral regurgitation 6