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Systolic anterior motion begins at low left ventricular outflow tract velocity in obstructive hypertrophic

M V Sherrid1, D Z Gunsburg, S Moldenhauer

  • 1Division of Cardiology, St. Luke's-Roosevelt Hospital Center, Columbia University College of Physicians and Surgeons, New York, New York, USA. msherrid@slrhc.org

Journal of the American College of Cardiology
|October 12, 2000
PubMed

Insights

In obstructive hypertrophic cardiomyopathy, systolic anterior motion (SAM) is caused by flow drag, not the Venturi effect. This finding clarifies the hemodynamics of this condition.

Area of Science:

  • Cardiology
  • Fluid Dynamics
  • Medical Imaging

Background:

  • Obstructive hypertrophic cardiomyopathy (HCM) is associated with systolic anterior motion (SAM).
  • The underlying mechanism of SAM, whether Venturi or flow drag, remains debated.
  • Understanding SAM's cause is crucial for managing HCM.

Purpose of the Study:

  • To investigate the hydrodynamic mechanism responsible for systolic anterior motion (SAM) in obstructive hypertrophic cardiomyopathy (HCM).
  • To differentiate between the Venturi effect and flow drag as the primary cause of SAM.

Main Methods:

  • Echocardiography was used to study 25 patients with obstructive HCM.
  • Mitral valve M-mode and Doppler (CW and PW) tracings were analyzed.
  • Left ventricular outflow tract (LVOT) velocity at SAM onset was measured relative to Q-wave timing.

Main Results:

  • Systolic anterior motion (SAM) onset occurred at a mean of 71 ms after Q-wave.
  • Mean LVOT velocity at SAM onset was 89 cm/s, considered normal.
  • In 68% of cases, SAM initiated before LV ejection was detected by Doppler.

Conclusions:

  • Systolic anterior motion (SAM) begins at normal LVOT velocities.
  • The Venturi mechanism is insufficient to explain SAM due to low forces at onset.
  • Flow drag is identified as the dominant hydrodynamic force causing SAM in obstructive HCM.
Abstract

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