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Biphasic left ventricular outflow and its mechanism in hypertrophic obstructive cardiomyopathy

Heidi M Conklin1, Xiaoyan Huang, Crispin H Davies

  • 1Division of Cardiology, Oregon Health and Science University, Portland 97239, USA.

Journal of the American Society of Echocardiography : Official Publication of the American Society of Echocardiography
|March 27, 2004
PubMed

Insights

Biphasic systolic velocity in the left ventricular outflow tract (LVOT) in hypertrophic obstructive cardiomyopathy (HOCM) is linked to altered flow dynamics and mitral-septal separation. This finding may stem from "afterload mismatch" in HOCM patients.

Area of Science:

  • Cardiology
  • Cardiovascular Physiology

Background:

  • Biphasic systolic velocity in the left ventricular (LV) outflow tract (LVOT) is observed in hypertrophic obstructive cardiomyopathy (HOCM).
  • The underlying mechanisms and clinical significance of this phenomenon are not well understood.

Purpose of the Study:

  • To investigate the cause and implications of biphasic LVOT velocity in HOCM.
  • To correlate LVOT flow dynamics with the presence of biphasic velocity and mitral-septal separation.

Main Methods:

  • Matched case-control study comparing 25 HOCM patients with 30 controls.
  • Estimation of LVOT systolic flow rate using a derived function relating aortic and LVOT flow.
  • Grouping HOCM patients based on the presence or absence of biphasic LVOT velocity.

Main Results:

  • Biphasic LVOT velocity significantly correlated with biphasic estimated LVOT outflow (P =.002).
  • LVOT pressure gradient showed an inverse relationship with LV outflow rate at peak gradient (r = -.64, P <.001).
  • Dobutamine administration exacerbated the LVOT gradient and reduced outflow, while mitral-septal separation occurred in HOCM patients with biphasic velocity despite a gradient.

Conclusions:

  • Biphasic LVOT flow in HOCM is associated with "afterload mismatch."
  • Late systolic flow increase relates to mitral-septal separation.
  • Resolution of systolic anterior motion despite a persistent gradient suggests non-pressure-related forces are involved.
Abstract

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