Phenotypic spectrum and patterns of left ventricular hypertrophy in hypertrophic cardiomyopathy: morphologic observations and significance as assessed by two-dimensional echocardiography in 600 patients.

OBJECTIVES: This study sought to achieve an understanding of the true structural heterogeneity of hypertrophic cardiomyopathy.
BACKGROUND: The diversity and clinical significance of the morphologic expression of hypertrophic cardiomyopathy have not been fully defined within this broad disease spectrum.
METHODS: Patterns of left ventricular hypertrophy were characterized by two-dimensional echocardiography in a large study cohort of 600 patients (7 to 79 years old, mean age 45; 393 [66%] men) consecutively studied at two referral centers.
RESULTS: Left ventricular wall thickness was 15 to 52 mm (mean [+/- SD] 22.3 +/- 5). A multitude of patterns of asymmetric left ventricular hypertrophy were identified, with the most common showing diffuse involvement of substantial portions of both ventricular septum and free wall. Of 16 possible patterns of left ventricular hypertrophy, 12 (78%) were identified among the 600 patients. Hypertrophy most commonly involved two left ventricular segments (228 patients [38%]) or three or more segments (202 patients [34%]), but was also localized to one segment in a substantial number of patients (170 [28%]). The anterior portion of the ventricular septum was the region of the left ventricle that most frequently showed thickening (573 patients [96%]), and was also the predominant site of hypertrophy in most patients (492 patients [83%]). Patterns of wall thickening that were either concentric (i.e., symmetric) or confined to the apex were particularly uncommon (in 1% each).
CONCLUSIONS: 1) In hypertrophic cardiomyopathy, the distribution of left ventricular hypertrophy is characteristically asymmetric and particularly heterogeneous, encompassing most possible patterns of wall thickening, from extensive and diffuse to mild and segmental, and with no single morphologic expression considered typical or classic. 2) A greater extent of left ventricular hypertrophy was associated with younger age and more marked mitral valve systolic anterior motion and outflow obstruction but showed no relation to either magnitude of symptoms or gender.