The ECG in Ebstein’s anomaly: a 1987 historical case series on right fascicular blocks

José J. Ortega-Cerda, Mexican Faculty of Medicine, Universidad La Salle México; Direction of Teaching and Research, Hospital Ángeles Health System; Department of Cardiology, Hospital Ángeles Pedregal; Mexico City, Mexico
Gustavo A. Medrano, Department of Electrocardiography, Instituto Nacional de Cardiología Ignacio Chávez, Mexico City, Mexico
Santiago Obregón-Rosas, Mexican Faculty of Medicine, Universidad La Salle México; Department of Medical Education, Instituto Nacional de Cardiología Ignacio Chávez. Mexico City, Mexico

Objectives: To recover an invaluable 1987 historical case series of 51 patients to highlight the prevalence of right fascicular blocks (RFB) – a subtle and historically underrecognized intraventricular conduction disturbance – in Ebstein’s anomaly, and to document the clinical diagnostic insight of the Mexican School of Electrocardiography in an era before the advent of three-dimensional electroanatomical mapping. Methods: Patients were originally divided into two groups based on the diagnostic methodology available at the time. After confirming statistical homogeneity (p > 0.05 in all comparisons), a unified population analysis of the surface electrocardiograms was performed, relying heavily on rigorous deductive vector analysis. Results: The most frequent finding was third degree right bundle branch block (54.9%), followed by Wolff-Parkinson-White syndrome (33.3%). Fascicular blocks were identified in 15.7% of cases, with the right posterior fascicular block being the most common (7.8%). Conclusions: RFB may be more prevalent in this population than previously believed. To our knowledge, this is the first systematic characterization of RFB in patients with Ebstein’s anomaly, serving as a historical document that preserves the legacy of pure electrocardiographic vector analysis.

Keywords: Ebstein’s anomaly. Bundle-branch block. Fascicular block. Ventricular pre-excitation. Cardiac conduction system. Wolff-Parkinson-White syndrome.