Background: Failure of the systemic right ventricle (RV) often complicates adult survival in unoperated or physiologically repaired congenitally corrected transposition of the great arteries (CCTGA). Healthy controls schematically represent an optimal outcome of anatomic repair, which is increasingly performed to treat CCTGA. Magnetic resonance imaging dobutamine stress testing measures cardiac reserve, and sets to compare the left ventricle of controls with the systemic RV of unoperated and physiologically repaired patients with CCTGA.
Methods: Baseline and stress magnetic resonance imaging (maximum dobutamine dose, 15 microg/kg/min) assessed systemic RV function in 13 minimally or asymptomatic adult patients with CCTGA (unoperated, n = 7; physiologically repaired, n = 6). The left ventricles of 11 healthy age-matched adults served as controls.
Results: Baseline and stress end-diastolic volumes similar between the systemic RV of unoperated patients and the left ventricle of controls, as well as base end-systolic volumes. Stress ejection fraction was lower in unoperated and physiologically repaired patients (70 +/- 6% and 60 +/- 5%, respectively, vs healthy controls (84 +/- 8%). However, comparable with healthy controls, both subsets of CCTGA patients responded appropriately to dobutamine stress, as illustrated by similar RV stroke volume, heart rate, mean blood pressure, and cardiac index.
Conclusions: Compared with the left ventricles of healthy controls, both patient groups had larger systemic RV volumes, diminished ejection fraction, but an appropriate response to dobutamine stress. Values of unoperated patients are closer to normal than physiologically repaired patients. Magnetic resonance imaging dobutamine may help to define the subgroups of CCTGA patients with favorable anatomy, whereby asymptomatic adult survival could be anticipated without the need for an operation.