P mitrale

P mitrale (left atrial abnormality) is an ECG finding of a P wave shaped like an M.

Diagnostic criteria

• there is notched or double peaked P wave in lead II. The notch is due to the delay of left atrial activation
• the P wave duration is generally > 120ms (normal P wave duration should be < 120ms)
• observation of completely negative P wave in lead C1 (V1) supports the diagnosis of left atrial abnormality.
  

It is indicative of a bulky left atrium, most commonly in left atrial hypertrophy.

Clinical importance

Left atrial dilatation favours the development of atrial fibrillation

Click for more detailed information and ECG examples

Notes:

• In the past, several terms like P mitrale, left atrial dilatation, left atrial hypertrophy, atrial overload were also used. However, the above described ECG findings are not limited to subjects with atrial muscle hypertrophy, but may also be observed in the presence of atrial pressure overload, ventricular diastolic dysfunction or intraatrial conduction delay. Therefore, the term left atrial abnormality should be used (1)
  
  

Reference:

• Alpaslan M. Left atrial abnormality. doctorecg.com (accessed 12/6/2020)