title: Development of a noninvasive ultrasound color M-mode means of estimating pulmonary vascular resistance in pediatric pulmonary hypertension: mathematical analysis, in vitro validation, and preliminary clinical studies.
abstract: BACKGROUND
  Accurate determination of pulmonary vascular resistance (PVR) is an important component in the evaluation and treatment of pediatric patients with pulmonary hypertension. We developed a novel technique, based on the concept of flow propagation, to estimate PVR noninvasively. The hypothesis is that changes in PVR cause changes in the velocity propagation (Vel(prop)) within the main pulmonary artery and that Vel(prop) can be quantified using color M-mode imaging.
  
  
  RESULTS
  We tested the hypothesis using mathematical modeling, in vitro experiments, and preliminary clinical studies. The mathematical model showed that pressure and velocity tracings are closely correlated in time and that 6 to 18 ms time resolution was needed to resolve propagation times within typical main pulmonary artery lengths (2 to 5 cm). The in vitro experiments demonstrated that it was feasible to use color M-mode to measure Vel(prop) and that Vel(prop) correlated well with downstream resistance [y=(-1.01x)+22.77; R=0.96]. The method was then evaluated on patients undergoing acute pulmonary reactivity testing (n=22 measurements). Good correlation between Vel(prop) and PVR was found [y=(-1.71x)+26.0; R=0.90; SEE=2.41].
  
  
  CONCLUSIONS
  This newly developed method promises to be useful in the noninvasive evaluation of adults and children with pulmonary hypertension.
authors.affiliation: Children's Hospital/University of Colorado Health Sciences Center, Denver, CO 80219, USA. shandas.robin@tchden.org
authors.forename: R
authors.initials: R
authors.lastname: Shandas
authors.forename: C
authors.initials: C
authors.lastname: Weinberg
authors.forename: D D
authors.initials: DD
authors.lastname: Ivy
authors.forename: E
authors.initials: E
authors.lastname: Nicol
authors.forename: C G
authors.initials: CG
authors.lastname: DeGroff
authors.forename: J
authors.initials: J
authors.lastname: Hertzberg
authors.forename: L
authors.initials: L
authors.lastname: Valdes-Cruz
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D004452:Echocardiography; D005260:Female; D006330:Heart Defects, Congenital / Q000150:complications* / Q000503:physiopathology; D006801:Humans; D006976:Hypertension, Pulmonary / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology; D007223:Infant; D016014:Linear Models; D008297:Male; D008955:Models, Cardiovascular; D015588:Observer Variation; D011237:Predictive Value of Tests; D011651:Pulmonary Artery / Q000000981:diagnostic imaging / Q000503:physiopathology; D011652:Pulmonary Circulation; D015203:Reproducibility of Results; D018615:Ultrasonography, Doppler, Color; D014655:Vascular Resistance