title: Development of Australian reference ranges for the left fetal modified myocardial performance index and the influence of caliper location on time interval measurement.
abstract: OBJECTIVE
  To construct gestational age-adjusted reference ranges of the left fetal modified myocardial performance index (Mod-MPI) in the Australian population and assess the influence of valve click caliper position on constituent time intervals and the Mod-MPI.
  
  
  METHODS
  This is a prospective longitudinal study of 117 normal singleton fetuses undergoing 318 ultrasound scans at 4-6 weekly intervals between 18 and 38 weeks of gestation. The isovolumetric contraction time (ICT), isovolumetric relaxation time (IRT), and ejection time (ET) were measured at 3 different caliper positions in each fetus: beginning of the original valve clicks ('original'), beginning of the reflected valve clicks ('reflected'), and peak of valve clicks ('peak'). The Mod-MPI was calculated as (ICT + IRT)/ET.
  
  
  RESULTS
  The Mod-MPI increased throughout gestation with means ± SD of 0.42 ± 0.05 'reflected' and 'peak' versus 0.49 ± 0.03 'original' at 19 weeks, and means of 0.46 ± 0.05 'reflected and peak' versus 0.51 ± 0.08 'original' at 36 weeks. Throughout gestation, ICT remained fairly constant and IRT increased, while ET decreased with 'original' click and remained constant for 'reflected' and 'peak' clicks. A modest increase in Mod-MPI was seen with increasing fetal heart rate. Analysis of repeatability for the 3 methods showed the following ICCs: 'original', 0.797 (95% CI 0.762-0.829); 'reflected', 0.809 (95% CI 0.775-0.839), and 'peak', 0.799 (95% CI 0.764-0.831).
  
  
  CONCLUSIONS
  Detailed exploration of the morphology of mitral and aortic valve closure and opening clicks shows how selection of different phases of these clicks may significantly influence the Mod-MPI. We recommend that the peak of the valve clicks be standardized between research groups.
authors: Department of Obstetrics and Gynaecology, King Saud University, Riyadh, Saudi Arabia.
authors: N
authors: N
authors: Meriki
authors: A W
authors: AW
authors: Welsh
mesh_terms: D000465:Algorithms; D001021:Aortic Valve / Q000000981:diagnostic imaging / Q000196:embryology / Q000502:physiology; D001315:Australia; D015150:Echocardiography, Doppler; D005260:Female; D047109:Fetal Development; D005865:Gestational Age; D006340:Heart Rate, Fetal; D006352:Heart Ventricles / Q000000981:diagnostic imaging* / Q000196:embryology*; D006801:Humans; D008137:Longitudinal Studies; D008943:Mitral Valve / Q000000981:diagnostic imaging / Q000196:embryology / Q000502:physiology; D009200:Myocardial Contraction; D011247:Pregnancy; D011446:Prospective Studies; D012016:Reference Values; D015203:Reproducibility of Results; D013997:Time Factors; D016216:Ultrasonography, Prenatal / Q000295:instrumentation / Q000379:methods*; D016276:Ventricular Function