Catenoidal shape of the interventricular septum acquired secondary to myocardial infarction.

A catenoidal, or saddle-shaped, configuration of the interventricular septum, concave toward the left ventricular cavity in the transverse plane, but convex toward the left ventricular cavity in the apex to base plane, occurs in idiopathic hypertrophic subaortic stenosis and possibly may lead to septal hypertrophy and immobility. The authors also have observed catenoidal shape of the interventricular septum in hearts with myocardial infarcts. They reviewed 1,415 hearts examined after postmortem arteriography and fixation in distention from patients autopsied at The Johns Hopkins Hospital. Among 586 hearts with myocardial infarcts, there were 54 (9%) with a catenoidal shape of the interventricular septum. The infarcts, 45 anterior septal and 9 inferior and lateral, appeared to account for the reversal of normal apex to base curvature, although coexistent idiopathic hypertrophic subaortic stenosis could not be excluded in 3 patients. There was moderate or marked infarct expansion in 25/54 (46%) and septal or free wall rupture in 8 (15%) hearts. Reduced average net septal curvature in the 54 hearts, highly significant compared with that in 80 hearts without infarcts (P less than 0.001), would reduce the septum's contribution to left ventricular function and may contribute to the observed postinfarct congestive failure, 30/54 (56%), and hypoperfusion, 7/54 (13%). The results suggest that some myocardial infarcts may produce a catenoidal shape of the interventricular septum that could reduce the functional activity of the surviving uninfarcted basilar portion of the septum and thereby contribute to postinfarction cardiac dysfunction.