The clinical, hemodynamic, and pathologic diagnosis of muscular subvalvular aortic stenosis.

STENOSIS of the outflow tract of the left ventricle is a disease of serious and often of fatal consequence. The form of obstruction varies, but most commonly it is a discrete ridge of fibrous tissue that projects into the left ventricle completely encircling the out-flow tract.' In some instances this fibrous ridge may be accompanied by bulging and hypertrophy of the underlying interventricu-lar septum.2A Recently, several authors have reported muscular hypertrophy of the septum and left ventricle alone as a cause of subval-vular aortic stenosis.2' 5-10 They suggest that during systolic contraction this thickened muscle comes together, narrowing the outflow area and impeding ventricular ejection. In 1958 Teared reported postmortem findings in eight relatively young people who had had what he termed "asymmetrical cardiac hypertrophy." In each instance there was diffuse hypertrophy of the interventricular sep-tum and anterior left ventricle. Shortly thereafter, Brock5 described six cases of hy-pertrophy of the left ventricle and upper muscular septum with resultant functional obstruction to left ventricular outflow. Bereu and associates6 added a similar case in which a systolic gradient existed between the left ventricle and aorta and at necropsy only hypertrophy of the musculature of the outflow tract was evident. In early 1960 Brent and associates7 described a number of patients with this same entity. They emphasized the familial incidence of the disease, since all of their six patients having proved muscular subaortic ste-nosis were members of only two families. Brachfeld and Gorlin2 reviewed the subject of subaortic stenosis and reported two cases with predominantly muscular obstruction. Goodwin and associates8 suggested the name "obstructive myocardiopathy," stating that this massive muscular hypertrophy could obstruct the inflow and outflow of blood in both the right and left ventricles. Most recently, Braunwald and co-workers12 presented a study of 14 patients who had a condition that the authors called '"'idiopathic hypertrophic subaortic stenosis." Their recognition of the similarities in many previously reported cases, coupled with their own experience, enabled them to elucidate this entity. Recently, we have reviewed all the cases at the Mayo Clinic in which a diagnosis of sub-aortic stenosis was made either at operation or at necropsy. This is a report of those cases in which diffuse muscular thickening of the interventricular septum and wall of the left ventricle resulted in obstruction of left ven-tricular outflow. Materials and Methods Eight cases of proved muscular subvalvular aortic stenosis have been reviewed. In three cases necropsy …