Surgical pathology of subaortic septal myectomy associated with hypertrophic cardiomyopathy. A study of 204 cases (1996-2000).

BACKGROUND

No large surgical series have qualitatively examined all histopathologic features of hypertrophic cardiomyopathy (HCM).

METHODS

Medical records and microscopic slides were reviewed from 204 patients undergoing septal myectomy for HCM at Mayo Clinic Rochester.

RESULTS

The 108 females and 96 males (1-86 years old; mean, 48) included 133 patients <60 years old (Group 1) and 71 patients > or =60 years (Group 2). Clinical features more prevalent in Group 2 than in Group 1 included female gender (68% vs. 45%; P=.003), aortic valve disease (31% vs. 12%; P=.01) and severe coronary atherosclerosis (43% vs. 9%; P=.001). Overall, microscopic abnormalities included myocyte hypertrophy (100%), endocardial (96%) and myocardial (93%) fibrosis, myocyte disarray (79%) and vacuolization (60%), endocardial inflammation (48%), arterial thickening (46%), dilated venules (28%), arterial dysplasia (16%), left bundle branch tissue (12%), infarction (2%), endocardial (1%) and myocardial (<1%) calcium, and amyloid (1%; senile type in all three). Lesions more prevalent in Group 1 than Group 2 were vacuolization (68% vs. 45%; P=.002), disarray (87% vs. 65%; P=.0003) and dilated venules (33% vs. 18%; P=.02). In contrast, lesions more frequent in Group 2 than in Group 1 included left bundle branch (20% vs. 8%; P=.02) and amyloid and endocardial calcium (4% vs. 0%; P=.04, each).

CONCLUSIONS

Among patients undergoing septal myectomy for HCM, 53% were women and 35% were >/=60 years old. The most common microscopic features were hypertrophy, disarray, fibrosis, inflammation and vascular alterations. Disarray cannot be used as a morphologic hallmark for HCM in small surgical myectomy specimens because it was absent in 21% of the patients. Because amyloid unexpectedly affected three elderly patients, routine amyloid staining is recommended for patients >/=65 years old.