title: Isometric cardiac contraction. a possible cause of the disorganized myocardial pattern of idiopathic hypertrophic subaortic stenosis.
abstract: The bizarre septal architecture of idiopathic hypertrophic subaortic stenosis (IHSS) may be secondary to a small systolic cavity with late systolic isometric contraction. We examined ventricular muscle for IHSS-type muscle-fiber disarray in infant hearts in which isometric contraction would occur during development-namely, pulmonary or aortic-valve atresia with intact ventricular septum and normal atrio-ventricular valves. Fifteen patients with aortic atresia and 10 with pulmonary atresia were compared to 25 normal controls of matched age and heart weight. Aortic atresia showed disorganization of muscle-fiber alignment of left ventricle, particularly septum, and intramural coronary-artery changes virtually identical to IHSS. Pulmonic atresia had similar right ventricular  disarray and vessel changes, again most marked in the septum. Thus, cardiac muscle-cell disorientation similar to IHSS occurs in infant ventricles with outflow-tract obstruction. This IHSS-type myocardial-fiber disarray may result from altered wall stresses related to isometric systolic contraction.
mesh_terms: D000328:Adult; D002312:Cardiomyopathy, Hypertrophic / Q000473:pathology* / Q000503:physiopathology; D003331:Coronary Vessels / Q000473:pathology; D005260:Female; D006330:Heart Defects, Congenital / Q000473:pathology; D006346:Heart Septum / Q000473:pathology*; D006352:Heart Ventricles; D006801:Humans; D006984:Hypertrophy; D007223:Infant; D007231:Infant, Newborn; D009200:Myocardial Contraction; D009206:Myocardium / Q000473:pathology*