Severe pulmonary embolism and evolution of tracings

ECG 3A: Sinus tachycardia (129 bpm); limit PR interval, slightly increased QRS duration (104 ms); SIQ3T3 pattern (negative T-wave in lead III); narrow and shallow Q-wave in the other inferior leads; deviation to the left (between V5 and V6) of the transition (R/S pattern > 1); absence of major repolarization disorders; ventricular extrasystole visible at the beginning of the tracing in precordial leads; Given the presence of shock, hypotension and signs of strain on the right ventricle (acute cor pulmonale), this patient was treated with fibrinolysis to improve the symptomatology (return to systemic arterial pressure > 100 mmHg);

ECG 3B: Tracing recorded 2 hours after the initiation of fibrinolysis; slowing of the sinus rate (117 bpm); decrease in the size of the S wave in lead I; T-wave inversion in V3-V4;

ECG 3C: Tracing recorded 4 hours after the initiation of fibrinolysis; slowing of the sinus rate (108 bpm); disappearance of the S1Q3 pattern;

ECG 3D: Tracing recorded 3 days after fibrinolysis; slowing of the sinus rate (75 bpm); negative T-waves in the lower territory and throughout the precordium; slightly prolonged QT interval (QTc at 460 ms);

ECG 3E: Tracing recorded 10 days later; persistence of major repolarization disorders;

Comments: The tracings of this patient allow to detail the electrical abnormalities observed during a pulmonary embolism and their evolution over time. In a pulmonary embolism, one can observe:

• A sinus tachycardia which is common but not obligatory (absent, for example, in patients receiving beta-blocking treatment or in the presence of a small embolus with no hemodynamic strain); the heart rate usually slows down rapidly within a few hours or days; the incidence of supraventricular rhythm disorders (atrial fibrillation preferentially) is approximately 10%;
• Unlike the chronic cor pulmonale, changes in the morphology of the P-wave and the pulmonary P-wave pattern (increase in P-wave amplitude in  lead II, rotation of the P-wave to the right of the frontal axis) are rare in pulmonary embolism;
• A discrete prolongation of the PR interval is exceptionally observed;
• Changes in the pattern of  the QRS-complexes are relatively frequent, early and transient (they disappear within a few hours to a few days); their detection sometimes requires comparison with previous or subsequent electrocardiograms; in addition to the S1Q3 pattern, one can observe: 1) an incomplete right bundle branch block with a rSr’ or rsR’ pattern, possible notching of the upward branch of the S wave and modest widening of the width of the QRS; this modification is precocious and fleeting; the observation of a complete right bundle branch block reflects the presence of a massive pulmonary embolism; 2) an often limited rotation of the axis in the clockwise direction (from the normal axis to the vertical axis); 3)  displacement toward the left of the QRS transition zone in precordial leads by the recoiling of the left ventricle posteriorly and to the left;
• Repolarization disorders with inversion of the T-wave in leads III, V1, V2, V3 sometimes with an “ischemic” appearance (peaked and symmetrical T-waves, more or less deep); these modifications are sometimes more discreet, asymmetrical and limited to V1; the inversion of the wave T in right precordial leads is the most common electrical sign; it appears slightly delayed compared to changes in the QRS but persists longer (up to several weeks); the T-wave is often unequivocally negative in lead III (S1Q3D3 pattern) whereas it is rather weakly positive or biphasic in lead II; in left precordial leads, repolarization remains mostly normal even if negative T-waves can also be observed; the ST-segment is mostly isoelectric, although changes in the T-wave can sometimes be associated with an ST-segment depression and exceptionally with an elevation;

Take-home message: Inversion of T-waves in right precordial leads and/or in lead III is the most common of the electrical abnormalities (after sinus tachycardia) observed during pulmonary embolism; the occurrence of peaked and symmetrical T-waves is often later than the changes in the QRS-complex, although persisting longer.