Left atrial hypertrophy on ECG

Main ECG criteria

Any myocardial chamber hypertrophy on the ECG is accompanied by a number of general signs: the amplitude of the corresponding waves (R or P) increases, signs of myocardial ischemia appear, conduction abnormalities may be recorded, and the electrical axis of the heart (EAH) deviates toward the hypertrophied chamber.

For left atrial hypertrophy (LAH), there is a specific set of changes:

• P-wave shape: becomes broad and notched. This is the most important diagnostic criterion, termed P-mitrale.
• Width: the duration of the P wave exceeds 0.10–0.12 seconds.
• Amplitude: unlike right heart hypertrophy, the height of the P wave in LAH increases only slightly.
• Localization of changes: the notched P wave is best visualized in standard and augmented limb leads (I, II, aVL), as well as in left precordial leads (V5, V6).

Hemodynamic causes of overload

Changes in the atrial complex on the ECG do not occur in isolation. They reflect structural myocardial remodeling in response to impaired intracardiac hemodynamics.

Key pathologies leading to LAH:

1. Left atrioventricular orifice stenosis. Impaired blood outflow into the left ventricle (LV) leads to increased pressure in the left atrium, its overload, and subsequent hypertrophy.
2. Chronic mitral regurgitation (MR). In response to constant blood regurgitation, the left atrium and left ventricle stretch (dilate). The atrium takes on the role of a reservoir for the regurgitant volume, which in the early stages protects the pulmonary vessels from pressure elevation.
3. Acute mitral regurgitation. Occurs in infective endocarditis or ruptured chordae tendineae (forming a flail leaflet). In this case, the non-compliant left atrium faces sudden volume overload, pressure rises sharply, frequently leading to acute pulmonary edema.

ECG dynamics and complications

As heart defects progress, the ECG picture becomes more complex. Isolated P-mitrale syndrome is eventually complemented by new signs:

• Rhythm disorders. Stretching (dilatation) and structural remodeling of the left atrial myocardium create conditions for arrhythmias. Atrial fibrillation is most frequently recorded.
• Addition of right ventricular (RV) hypertrophy. If mitral valve defects lead to the development of pulmonary hypertension, signs of RV overload appear on the ECG: rightward axis deviation, increased R wave in leads V1–V2 with a decreased S wave, and T-wave inversion.
• Biventricular hypertrophy. In late stages of decompensation, both ventricles are involved in the process, which is reflected by a mixed pattern of hypertrophy on the cardiogram.

Diagnosis confirmation

ECG data serve as an indication for imaging studies, which allow the assessment of the morphology and severity of hemodynamic disorders.

• Echocardiography (EchoCG). The main method. Reveals left atrial cavity dilatation. Doppler sonography (including color mapping) visualizes the regurgitation jet and allows calculation of the orifice area.
• Radiography. In chronic processes, enlargement of the left atrial appendage is visible, along with the formation of a "third arch" along the left heart border in the anteroposterior view. Subcardiac darkening with a slight upward displacement of the left main bronchus is noticeable.

Class and exam questions

What else to study on this topic

• ECG signs of right atrial hypertrophy (P-pulmonale)
• Criteria for left and right ventricular hypertrophy on ECG
• Hemodynamics and stages of mitral regurgitation
• Echocardiographic assessment of mitral valve prolapse
• Radiological signs of mitral valve defects

Other topics in the "Additional Topics" section

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