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Effect of Left Ventricular Outflow Tract Obstruction on Left Atrial Mechanics in Hypertrophic Cardiomyopathy

Lynne K Williams1, Raymond H Chan2, Shemy Carasso3

  • 1Division of Cardiology, Toronto General Hospital, Toronto, ON, Canada M5G 2C4; Department of Cardiology, Papworth Hospital NHS Foundation Trust, Papworth Everard, Cambridge CB23 3RE, UK.

Biomed Research International
|January 21, 2016
PubMed

Insights

Hypertrophic cardiomyopathy (HCM) increases left atrial (LA) volumes and impairs LA function. Outflow tract obstruction further worsens these effects, but septal myectomy improves LA volumes and function in obstructive HCM patients.

Area of Science:

  • Cardiology
  • Cardiovascular Imaging
  • Biomedical Engineering

Background:

  • Left atrial (LA) enlargement in hypertrophic cardiomyopathy (HCM) predicts adverse outcomes.
  • LA dysfunction is typically attributed to left ventricular (LV) diastolic dysfunction, hypertrophy, and fibrosis.
  • The specific impact of outflow tract obstruction (LVOT obstruction) and mitral regurgitation on LA mechanics requires further elucidation.

Purpose of the Study:

  • To assess the incremental effect of LVOT obstruction and mitral regurgitation on LA function in HCM patients.
  • To quantify LA volumes and function using LA strain analysis via cardiovascular magnetic resonance (CMR).
  • To evaluate the impact of septal myectomy on LA volumes and function in obstructive HCM.

Main Methods:

  • Feature-tracking software applied to CMR images to calculate LA volumes and functional parameters.
  • Comparison of 50 obstructive HCM patients, 50 nonobstructive HCM patients, and 50 healthy controls.
  • Analysis of a subset of obstructive HCM patients before and after septal myectomy.

Main Results:

  • HCM patients exhibited significantly elevated LA volumes and reduced LA ejection fraction and strain compared to controls.
  • Obstructive HCM patients showed more severe LA volume and functional impairment than nonobstructive patients.
  • Septal myectomy significantly reduced LA volumes and improved LA function in obstructive HCM patients.

Conclusions:

  • LVOT obstruction and mitral regurgitation exacerbate LA mechanical impairment in HCM.
  • Septal myectomy effectively reduces LA volumes and improves LA function, suggesting a reversible component to LA dysfunction in obstructive HCM.
  • LA strain analysis is a valuable tool for assessing LA mechanics in HCM and the effects of interventions.

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