Left ventricular cavity obliteration: mechanism of the intracavitary
gradient and differentiation from hypertrophic obstructive
cardiomyopathy
Abstract
Controversy surrounds the cause of the pressure gradient in patients
with hypertrophic obstructive cardiomyopathy (HOCM). Left ventricular
cavity obliteration (LVCO) was first described as the cause of the
gradient but subsequently systolic anterior motion (SAM) of the mitral
valve has been established as the cause. Nevertheless, the two
gradients, though different in origin and significance, share similar
characteristics. They both have a similar “dagger” profile, are
obtained from the cardiac apex, are associated with a hyperdynamic left
ventricle, and the gradients are worsened by Valsalva. The distinction
has clinical relevance, because treating the intra cavitary gradient
(ICG) of LVCO as if it were a SAM associated gradient associated with
HOCM would be inappropriate and possibly harmful. To clarify the
cause and characteristics of the ICG in patients with LVCO in patients
without HOCM we assessed the extent and duration of cavity obliteration
and for differentiation we compared the spectral profiles with patients
with HOCM and severe aortic stenosis (AS). Higher ICG is associated with
greater extent and more prolonged apposition of LV walls. The spectral
profile of patients with AS, HOCM and LVCO are differentiated by the
peak/mean gradient ratios of 2 or less, 2-3, and 3 or greater,
respectively in > 90% of patients. Most patients with LVCO
without HOCM or severe LVH have an ICG < 36 mmHg. The
magnitude of ICG is quantitatively associated with extent and duration
of LVCO. Spectral profiles of severe AS, HOCM, and LVCO can be
differentiated by the peak/mean gradient ratio.