Myocardial flow reserve (MFR) in human infants has not been reported. Infants with hypoplastic left-heart syndrome after Norwood reconstruction(NWD) may be at risk for diminished MFR because of: 1) the potential for obstruction to coronary flow in the neoaorta, 2) diminished coronary perfusion pressure from diastolic run-off into the aortopulmonary shunt, and 3) increased oxygen demand in the pressure and volume-loaded right ventricle. We therefore compared MFR utilizing positron emission tomography (PET) in patients with NWD with infants who had complete repair of a cardiac defect(Control). Methods: 5 infants with NWD, age 16d-26d (mean=21d) and five controls, age 9d-86d (mean=40d) underwent PET imaging (mean time from surgery=10.5d) with N-13 ammonia at rest and with adenosine (142ug/kg/min× 6 min). Infants were sedated, spontaneously breathing, and on no inotropic medications when studied. Myocardial flow was measured in 16 regions(4 regions in 4 contiguous short-axis slices) using compartmental modeling techniques and values were expressed in ml/min/gram tissue. Only myocardial flow in the systemic ventricle was analyzed for comparison between groups(MFR=Qstress/Qrest). Results:Table Conclusions: 1) Infants with NWD have less myocardial perfusion in their systemic ventricle at rest and with stress, but have similar MFR as infants with repaired structural heart disease, 2) Compared to adults, control infants may have slightly increased resting flows but a reduction in stress flows and MFR, and 3) PET may be a useful modality for studying myocardial perfusion in the newborn infant.

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