Biventricular diastolic function is unaffected by chronically elevated left ventricular afterload in fetal sheep

  • Dr Paul Brooks, The Royal Children's Hopsital, Murdoch Children's Research Institute, University of Melbourne, Australia
  • Mr Andrew Hattam, Murdoch Children's Research Institute, Department of Paediatrics University of Melbourne, Australia
  • Dr Michael Cheung, The Royal Children's Hopsital, Murdoch Children's Research Institute, University of Melbourne, Australia
  • Prof Daniel Penny, The Royal Children's Hopsital, Murdoch Children's Research Institute, University of Melbourne, Australia
  • A/Prof Joseph Smolich, Murdoch Children's Research Institute, Department of Paediatrics University of Melbourne

    • Aims: In contrast to the mature heart, fetal ventricular diastolic dysfunction is a late and ominous finding in conditions accompanied by long-standing elevated ventricular afterload. Little is known, however, about longitudinal changes in fetal diastolic function occurring in this setting. The aim of this study was to assess biventricular diastolic properties using echocardiography in a fetal sheep model of chronically elevated left ventricular (LV) afterload.

    Methods: In 17 twin ovine pregnancies, one fetus had a surgical non-constrictive ascending aortic band placed at mid-gestation (range 90-98 days, term=147 days), whilst the other served as an un-operated control. Echocardiograms of both fetuses were performed under maternal sedation at ~2 weekly intervals until near term, with biventricular assessment of color tissue Doppler (cTDI) early relaxation (E’) and late filling (A’) myocardial velocities at their respective atrioventricular valve annulus, along with pulsed wave Doppler early (E) and late (A) inflow velocities and deceleration time.

    Results: Although a moderate peak ascending aortic gradient was present in the banded fetuses near term (23.9±11.5mmHg), neither cTDI myocardial velocities nor pulsed wave Doppler E and A wave velocities or their ratio (E/A) were significantly different for either ventricle between groups. However, mitral inflow deceleration time in the banded fetuses tended to be shorter with advancing gestation after adjustment for heart rate (p=0.06).

    Conclusion: Isolated moderate and chronically increased LV afterload in fetal sheep produces no significant change in biventricular diastolic function. The contribution of chronically elevated afterload to fetal diastolic dysfunction requires further investigation.