Left ventricular ejection dynamics and outflow obstruction in hypertrophic cardiomyopathy

Abstract

Despite more than 25 years of investigation, the physiologic and clinical significance of the systolic pressure gradient measured across the left ventricular outflow tract in many patients with hypertrophic cardiomyopathy remains a subject of controversy and seemingly endless debate. This controversy appears destined to continue into the foreseeable future. Several aspects of the complex interplay between left ventricular morphologic and functional abnormalities during systolic ejection in hypertrophic cardiomyopathy have been scrutinized and debated. These include the high velocity of blood ejected in early systole by the hyperdynamic left ventricle, the anatomic narrowing of the outflow tract and the importance of systolic anterior motion of the mitral valve leaflets in the genesis of the gradient. At the core of this debate, however, are the timing and completeness of left ventricular ejection; whether the left ventricle ejects against a true impediment to emptying (l-3), with forward flow continuing for the duration of systole (and for the duration of the pressure gradient), or whether the pressure gradient arises from cavity obliteration after the superejecting left ventricle has emptied its contents very rapidly in early systole, with continued isovolumic contraction during the remainder of systole (4-7). Relation between the pressure gradient and ejection time. The findings of Sasson et al. (8) reported in this issue of the Journal provide additional compelling data in support of the concept that the pressure gradient in hypertrophic cardiomyopathy represents a true obstruction to left ventricular ejection. These investigators demonstrated highly significant correlations between the magnitude of the pressure gradient and prolongation of left ventricular ejection time under conditions at rest and during drug interventions to raise or