Pressure gradients without obstruction. A new concept of "hypertrophic subaortic stenosis".

Abstract

Summary and Conclusions Significant outflow tract obstruction was notseen byleft ventricular cineangiocardiography in seven patients with hypertrophic subaorticstenosis.Catheter withdrawals through the leftventricle, recorded cinefluorographically, lo-calized the high pressure areas to portions ofthe left ventricle which emptied completely in early systole. Sustained systolic contractionin empty portions of the left ventricle pro-vides an explanation for the pressure gradi-entsinthesepatients.Isoproterenol infusions increased the rate and degree of left ventricular emptying, ob-literating portions of the cavity earlier andincreasingthepressure gradient.Themechanismof gradient production with- out obstruction was similar to the phenome-non observed in dogs receiving isoproterenol infusions. The cardiac muscle in these patients is ab-normally thick and the left ventricle emptiesmorerapidly than normal; therefore a hyper- trophic hyperkinetic cardiomyopathy is present.The nonobstructive