Severe pulmonary embolism and surgical embolectomy

ECG 4: Increased heart rate (91 bpm); sinus P-wave of normal size and morphology; couplet of atrial extrasystoles (modification of the pattern of the T-wave); normal PR interval; wide QRS with complete right bundle branch block pattern (QRS duration > 120 ms, rSR’ pattern in V1 with delayed intrinsicoid deflection, qRs pattern in V6 with wide and slurred S wave); SIq3 pattern; negative T-waves in V1-V3 and in lead III;

Comments: The term acute cor pulmonale refers to the acute manifestations resulting from the strain of lung, pleural or pulmonary circulatory diseases on the right heart. Massive pulmonary embolism is the most common cause of acute cor pulmonale. In a massive pulmonary embolism with shock (present in less than 5% of cases), the clinical picture is often evocative and the electrocardiographic pattern more or less characteristic, especially when occurring on a healthy heart. Occlusion of the pulmonary vascular bed by one or more large emboli leads to acute pressure overload, sudden pulmonary arterial hypertension and right ventricular dilatation. Perturbation of hematosis may also result in ischemia.

The electrical signs are dependent on the following 2 factors:

1. Acute overload of the right ventricle: abrupt closure of the trunk or of several branches of the pulmonary artery leads to a sudden rise in pulmonary arterial pressure and total pulmonary resistance of varying degrees depending on the size of the embolus and the extent of the obliterated territory. The right ventricle is therefore subjected to a sudden overload causing its cavity to expand, particularly at the level of the pulmonary infundibulum which is very sensitive to variations in pressure, and a rotation of the heart as a whole in a clockwise direction, the left ventricle being more or less pushed posteriorly. This pressure increase can be shown on the electrocardiogram by the so-called clockwise S1Q3 pattern, the displacement to the left of the QRS transition zone in the precordial leads and the incomplete right block by delayed activation of the pulmonary infundibulum. A complete right bundle branch block can be caused by compression or mechanical traction secondary to pulmonary arterial hypertension and acute dilatation of the right ventricle. The increase in pressure can also favor the occurrence of ventricular repolarization disorders (negative T-waves). The acute increase in pressure rarely results in atrial electrical changes (pulmonary P-wave), more frequently the occurrence of supra-ventricular rhythm disorders.
2. Myocardial ischemia: the sudden decrease in cardiac output can lead to the occurrence of functional coronary insufficiency and predominant ischemia in the left ventricular septum or anterior wall explaining in part the negativity of T-waves in the right precordium (V1 to V3) and the “ischemic” pattern of the T-waves (peaked, symmetrical and deep);

Take-home message: The occurrence of a complete right bundle branch block is rare during a pulmonary embolism, represents a sign of severity and is secondary to the sudden increase in right ventricular pressure.