Idiopathic Hypertrophic Subaortic Stenosis with Split His Bundle Potentials

Electrophysiologic and Pathologic Correlations

BHARATI, SAROJA M.D.
MCANULTY, JOHN H. M.D.
LEV, MAURICE M.D.
RAHIMTOOLA, SHAHBUDIN H. M.B.

Department of Medicine, Division of Cardiology, University of Oregon Health Sciences Center, Portland, Oregon; the Congenital Heart Disease Research and Training Center, Hektoen Institute for Medical Research; Department of Pathology, Northwestern University Medical School; Pritzker School of Medicine, University of Chicago; Chicago Medical School, University of Health Sciences; Loyola University, Stritch School of Medicine; Section of Cardiology, Department of Medicine and Department of Pathology, Abraham Lincoln School of Medicine, University of Illinois; Departments of Pediatrics, Medicine and Pathology, Rush Medical College, Chicago, Illinois.

Supported by grants HL 07605-18 and HL 21727 from the NIH, NHLBI.

Dr. Lev is a Career Investigator and Educator, Chicago Heart Association.

Address for correspondence: S. Bharati, M.D., Hektoen Institute for Medical Research, 637 South Wood Street, Chicago, Illinois 60612.

Received January 21, 1980; revision accepted April 30, 1980.

Circulation 62(6):p 1373-1380, December 1980.

SUMMARY

A 25-year-old white female had idiopathic hypertrophic subaortic stenosis proved by catheterization. The ECG revealed left bundle branch block. Electrophysiologic studies revealed normal PA and AH intervals, but the HV interval was prolonged (70 msec). The width of the His spike was 20 msec. A clear, reproducible split His potential was demonstrated with the atrial extrastimulus technique. Because the patient was symptomatic, a permanent pacemaker was inserted. One week later the patient died suddenly. Autopsy revealed an enlarged heart with a markedly thickened and sigmoid ventricular septum and a small and coarsely trabeculated lumen. Histologically the common bundle was situated on the right side of the septum. It was intact at its origin, but showed fibrotic changes more distally. The beginning of the left bundle branch was markedly disrupted as it traversed the septum. The right bundle branch was moderately fibrosed. There was excellent correlation between the electrocardiographic and electrophysiologic findings and the findings in the conduction system. The cause of the sudden death was related either to the outflow obstruction or to an arrhythmia, or both.