Biatrial enlargement

ECG 4A: Sinus rhythm with biatrial enlargement: P-wave amplitude increased in lead II (3 mm), with widened (> 40 ms) and deep (> 1.5 mm) negative component in V1, bifid pattern in lead I, P-wave duration of 115 ms in V4-V5; right ventricular hypertrophy (right axis, incomplete right bundle branch block, R/S ratio > 1 in V1); ultrasound revealed a significant dilation of both atria;

Patient: Young girl 13 years of age, with extremely severe dilated cardiomyopathy and major dilatation of both atria with predominance in the right atrium;

ECG 4B : Marked contrast between a major increase in atrial voltage and a decrease in ventricular voltage (low voltage); biatrial dilatation predominant in the right atrium with increased voltage in lead II, tall and wide positive atrial component (right atrial enlargement) and an increase in P-wave duration (left atrial enlargement);

Comments: Biatrial hypertrophy is reflected by combined signs of right and left atrial enlargement. The diagnosis is made on the basis of P-waves which have both a high amplitude and a duration greater than 110 ms. There are often dissociated signs with right atrial enlargement visible in the standard leads and left atrial enlargement visible in the precordial leads. Various abnormalities allow defining a biatrial enlargement:

• The P-wave is often bifid in lead II with an increase in the amplitude of its initial component and prolongation of its duration.
• In V1, the P-wave is often biphasic with significant initial positive deflection greater than 2 mm and wide rounded terminal negative deflection lasting at least 40 ms.

Each of these signs can be predominant depending on the patient. For example, in this particular patient, the left atrial enlargement is mainly reflected by a characteristic pattern in V1 with a widened and deep negative component but not by a significantly increased P-wave duration. The right ventricular hypertrophy is highlighted by the increase in P-wave voltages in lead II and by the associated signs of right ventricular hypertrophy, whereas the positive voltages of the P-wave are not increased in V1.

There is a biatrial enlargement in diseases causing biventricular hypertrophy: certain congenital heart diseases, hypertrophic cardiomyopathy, chronic cor pulmonale, aortic valve failure or mitral regurgitation associated with pulmonary hypertension.

Take-home message: The respective enlargement of each of the two atria predominantly affects a different component of the wave P. Biatrial enlargement is diagnosed when the criteria of right atrial enlargement and left atrial enlargement are fulfilled.