Impaired power output and cardiac index with hypoplastic left heart syndrome: a magnetic resonance imaging study.
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.
Sundareswaran
Kartik S
KS
Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0535, USA.
Kanter
Kirk R
KR
Kitajima
Hiroumi D
HD
Krishnankutty
Resmi
R
Sabatier
Jennifer F
JF
Parks
W James
WJ
Sharma
Shiva
S
Yoganathan
Ajit P
AP
Fogel
Mark
M
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