Figure 40b

Morphologic compounds of the underlying disease process in HCM.
A. Gross heart specimen sectioned in a cross-sectional plane similar to that of the echocardiographic (parasternal) long axis. The pattern of left ventricular hypertrophy is asymmetrical, with wall thickening confined primarily to the anterior ventricular septum (VS), which bulges into the left ventricular outflow tract.
B. Heart specimen illustrating a different pattern of hypertrophy in which marked left ventricular wall thickening is localized to the posterior portion of the ventricular septum (Post. VS), while the anterior septum (Ant. VS) is only mildly thickened.
C, D. Histology characteristic of the left ventricle in HCM. In C, septal myocardium shows markedly disordered architecture with adjacent hypertrophied cardiac muscle cells arranged at perpendicular and oblique angles to each other. In D, bundles of hypertrophied cells show a disorganized, “interwoven “ arrangement.
E. Intramural coronary artery with apparently narrowed lumen and thickened wall due primarily to medial (M) hypertrophy. F. Extensive scarring of ventricular septum which is transmural in distribution. LV= left ventricular free wall.

From BJ Maron et al: N Engl J Med 316:780,