title: Impaired power output and cardiac index with hypoplastic left heart syndrome: a magnetic resonance imaging study.
abstract: BACKGROUND
  Unfavorable cardiac mechanics in children with hypoplastic left heart syndrome (HLHS) when compared with other single-ventricle defects may affect long-term morbidity and outcome. Using noninvasive phase contrast magnetic resonance imaging (PC MRI), we examined cardiac mechanics in children with HLHS and compared the results to other single-ventricle defects.
  
  
  METHODS
  Eighteen children with HLHS and 18 children with other single-ventricle defects were studied after the Fontan operation. Phase contrast MRI scans were obtained perpendicular to the ascending aorta, and flow was quantified using an in-house segmentation and reconstruction scheme. The total power output was determined using the modified Bernoulli equation along with cardiac output and systemic vascular resistance index.
  
  
  RESULTS
  Compared with non-HLHS congenital heart defects, children with HLHS had significantly lower power output (1.40 +/- 0.39 versus 1.78 +/- 0.38 W/m2, p < 0.004) and cardiac index (3.15 +/- 0.97 versus 4.09 +/- 1.23 L x Min(-1) x m(-2), p < 0.009) with a concomitant higher systemic vascular resistance index (28.94 +/- 11.5 versus 22.7 +/- 8.53 WU, p < 0.03) despite generating similar systolic blood pressures (112.9 +/- 22.4 versus 115.2 +/- 23 mm Hg, p > 0.05).
  
  
  CONCLUSIONS
  Minimally invasive measurements with PC MRI in children with HLHS showed significantly lower power output and cardiac index when compared with other single-ventricle physiologies. Abnormal aortic flow patterns may contribute to power loss and may have long-term survival and morbidity implications associated with the Fontan procedure. Elevated systemic vascular resistance index despite similar blood pressure opens avenues for therapeutic intervention for afterload reduction.
authors.affiliation: Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0535, USA.
authors.forename: Kartik S
authors.initials: KS
authors.lastname: Sundareswaran
authors.forename: Kirk R
authors.initials: KR
authors.lastname: Kanter
authors.forename: Hiroumi D
authors.initials: HD
authors.lastname: Kitajima
authors.forename: Resmi
authors.initials: R
authors.lastname: Krishnankutty
authors.forename: Jennifer F
authors.initials: JF
authors.lastname: Sabatier
authors.forename: W James
authors.initials: WJ
authors.lastname: Parks
authors.forename: Shiva
authors.initials: S
authors.lastname: Sharma
authors.forename: Ajit P
authors.initials: AP
authors.lastname: Yoganathan
authors.forename: Mark
authors.initials: M
authors.lastname: Fogel
mesh_terms: D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena; D002302:Cardiac Output; D002648:Child; D002675:Child, Preschool; D006801:Humans; D018636:Hypoplastic Left Heart Syndrome / Q000175:diagnosis* / Q000503:physiopathology*; D007223:Infant; D008279:Magnetic Resonance Imaging; D014655:Vascular Resistance