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Electrocardiographic diagnosis of myocardial infarction in patients with complete left bundle branch block is often difficult. Most of the proposed diagnostic criteria have high specificity but low sensitivity; therefore, high clinical suspicion is crucial in this context. We present the case of a patient treated in the emergency department with severe hemodynamic instability and electrocardiographic abnormalities indicative of myocardial infarction with complete left bundle branch block; as well as other disorders suggestive of the aforementioned diagnosis, but poorly recognized in the scientific literature. [ABSTRACT FROM AUTHOR]

Arrhythmogenic right ventricular dysplasia is a heart muscle disease that predominantly affects the right ventricle, bringing about the replacement of normal myocardium with fatty or fibrofatty tissue and causing sudden death in young individuals. Ventricular tachycardia is an important clinical manifestation, although there are reports of right or global heart failure. The diagnosis is confirmed by echocardiography and magnetic resonance imaging. The case of a 65-year-old former smoker, with hypertension and ischemic heart disease, a history of effort syncope symptoms and proven non-sustained ventricular tachycardia, with morphology of left bundle branch block, is reported. Relevant diagnostic studies were performed, and echocardiographic elements which were compatible with arrhythmogenic right ventricular dysplasia were found. Therefore, an implantable cardioverter defibrillator was implanted, after which the patient has had a favorable outcome. [ABSTRACT FROM AUTHOR]

Introduction: Left bundle branch block is an important marker of poor prognosis in patients with heart failure. Resynchronization therapy can improve the function of the left ventricle in these cases. Objective: To describe electrocardiographic variables associated with a better response to cardiac resynchronization. Method: A total of 19 patients, 7 women and 12 men, with left bundle branch block and ejection fraction ≤ 35% were studied. An electrocardiogram was performed before and after resynchronization therapy, with QRS measurement in the twelve leads and calculation of its dispersion. Maximum QRS voltages were also measured. An echocardiogram was performed before and after the procedure. Results: The ejection fraction increased from 29.8±4.7 to 41.2±10.7 % (p=0.000). The linear correlation between ejection fraction and dispersion of QRS at six months of follow-up was significant (r=0.34 and p=0.02). Women showed a greater dispersion of QRS (48.0±24.0 ms vs. 37.14±13.8 ms; p=0.04). QRS voltages were predominantly negative in aVR (-0.52±0.58 vs. 0.28±0.42 mVolt; p=0.032) and positive in V5 (0.71±1.12 vs. -0.15±1.20 mVolt; p=0.023) for responders in relation to non-responders. Conclusions: The dispersion of QRS, increased in the electrocardiogram with left bundle branch block and decreased after resynchronization, showed a significant correlation with the ejection fraction. QRS narrowing after resynchronization was significant for responders. The predominantly positive voltages in aVR and negative in V5 could adequately predict which patients will not respond adequately to cardiac resynchronization therapy. [ABSTRACT FROM AUTHOR]