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Abstract & Commentary
Source: Petrov DB. Appearance of right bundle branch block in electrocardiograms of patients with pulmonary embolism as a marker for obstruction of the main pulmonary trunk. J Electrocardiol 2001;34:185-188.
The electrocardiogram (ECG) is clearly an imperfect test for diagnosing pulmonary embolism (PE); several findings have been associated with this entity, yet none offer adequate sensitivity or specificity. Nevertheless, ECG is a rapid, noninvasive test used early and frequently in patients with chest pain and/or dyspnea; therefore, familiarity with the various findings associated with PE is of clinical utility. Early suspicion, perhaps fueled by a characteristic ECG finding, may aid in the establishment of the proper diagnosis.
In this study, the ECGs of patients with autopsy-proven PE were examined; patients with pre-existing ECG criteria for right or left bundle branch block (BBB) or left ventricular hypertrophy were excluded (12 cases). The final study population included 50 patients; 20 had massive embolism of the pulmonary trunk, and the remainder had peripheral PE.
Eighty percent (16 of 20) of patients with PE involving the main pulmonary trunk demonstrated a new right bundle branch block (RBBB) pattern on ECG; in 10 cases it was complete, while in the remaining six it was incomplete. The other 20% (4 of 20) of patients with massive PE demonstrated ST depression and T-wave inversion in leads V1-V4, as well as right axis deviation. Interestingly, the S1Q3T3 finding was seen in 60% (12 of 20) of trunk embolism patients. With regard to the 30 cases of peripheral PE, an assortment of ECG findings were seen, including 12 cases (40%) with no abnormalities noted, and nine cases (30%) of sinus tachycardia. The authors concluded that although PE cannot be diagnosed solely on the basis of ECG, the clinician should have high suspicion for massive PE (i.e., complete obstruction of the pulmonary trunk) in cases of new RBBB in the presence of clinical evidence of acute right ventricular cardiac insufficiency.
Comment by Richard A. Harrigan, MD, FAAEM
The author hypothesizes that RBBB is a marker of acute right ventricular overload associated with massive PE. It is theorized that acute dilation of the right ventricle leads to inhibition of blood flow to subendocardial vessels in the right bundle, thus causing this ECG change. A variety of ECG changes have been associated with PE, including sinus tachycardia, atrial fibrillation, S1Q3T3, T-wave inversions, ST depression, P pulmonale, right axis deviation, RBBB, left axis deviation, clockwise rotation, and low voltage of the QRS complex in the limb leads.1-3 S1Q3T3 classically has been associated with PE, but has been reported—in four studies—to occur in only 12-50% of cases.1 Ferrari and colleagues found T-wave inversion in the precordial leads to be the most common ECG finding (68%) in their series of 80 cases, and also found it to correlate with the severity of the PE.1 This report of the high incidence of new RBBB in patients with massive trunk PE is an important addition to the list of telltale ECG findings associated with this disease entity.
1. Ferrari E, et al. The ECG in pulmonary embolism. Predictive value of negative T-waves in precordial leads—80 case reports. Chest 1997;111:537-543.
2. Stein P, et al. Clinical characteristics of patients with acute pulmonary embolism stratified according to their presenting syndromes. Chest 1997;112:974-979.
3. Manganelli D, et al. Clinical features of pulmonary embolism. Chest 1995;107:25S-32S.