Hypertrophic cardiomyopathy and sudden death in the young: Pathologic evidence of myocardial ischemia

The mechanism underlying cardiac arrest in patients with hyper-trophic card iomyopathy (HC) is intriguing. In the clinical setting myocardial ischemia has long been incriminated, particularly in the young. Among 274 cardiovasc ular sudden deaths in the young (less than or equal to 35 years), 19 (7.0%) , 14 males and 5 females, median age 23 years, had HC. Familial occurrence of HC was ascertained in 3 (16%). SD occurred on effort in 6 (31%). Previou s syncope occurred in 5 and palpitations in 3. Basal electrocardiogram (ECG ) was abnormal in 7 of 8 available cases. Hypertrophy was septal asymmetric in 14. Gross examination showed large isolated or multiple septal scars in 11 (58%); at histomorphometry, the mean percent area of fibrosis of the se ptal myocardium was 18.6 +/- 6. Four showed a deep intramyocardial course o f the left anterior descending coronary artery. At histology, myocardial di sarray involved 30 +/- 16% of the septal myocardium; evidence of acute-suba cute myocardial necrosis was present in 14 (74%), 1 of them with a regional acute myocardial infarction. By comparing hearts with (n = 11) and without (n = 8) areas of scar-type fibrosis, we found a statistically significant difference in terms of age (25.5 +/- 5.4 v 15.5 +/- 12.4 years, P = .01), s eptal thickness (25.4 +/- 5.4 v 15.4 +/- 4.9 mm, P < .001), percent increas e of septal thickness versus normal value for age and sex (46.2 +/- 15 2, 2 5.2 +/- 13.6%, P < .01) and mean score of small vessel disease (1.7 +/- 0.4 v 1.2 0.4, P = .04). Linear regression analysis showed a positive correlat ion of percent area of replacement fibrosis with septal thickness (P = .01) and with mean score of small vessel disease (P < .01). In conclusion, our pathologic findings of ischemic damage, either acute-subacute or in the for m of fibrotic scars, support the clinical evidence that ischemia occurs in the natural history of HC and may contribute to life-threatening electrical instability. Copyright (C) 2000 by W.B. Saunders Company.