Disparity between dobutamine stress and physical exercise magnetic resonance imaging in patients with an intra-atrial correction for transposition of the great arteries.

BACKGROUND In patients with an intra-atrial correction for transposition of the great arteries (TGA) an abnormal response to stress testing is common. However, hemodynamic responses may vary substantially when different stress tests are used. We compared the hemodynamic response to dobutamine stress with the response to physical exercise in patients and controls. METHODS Thirty-nine patients and 25 age/sex-matched control subjects underwent either dobutamine stress (15 microg/kg/min) or submaximal physical exercise cardiovascular magnetic resonance. End-systolic and end-diastolic right ventricular volumes (ESV; EDV) were determined. Five representative patients underwent both stress tests. For these patients, wall thickening reserve was calculated as systolic wall thickening during stress minus systolic wall thickening at rest. RESULTS In controls, dobutamine stress and physical exercise showed similar responses: stroke volume, cardiac output, and ejection fraction increased significantly, whereas ESV decreased significantly and EDV was unchanged. In patients, stroke volume did not increase with either dobutamine or exercise (-8.6% vs. 2.9%). Ejection fraction increased significantly with dobutamine (16%, p < 0.001) but tended to decrease during exercise (-2.1%, P = NS). EDV and ESV decreased during dobutamine but were unchanged during exercise. (-22% vs. 5.0%, P < 0.001; -36% vs. 9.0%, P < 0.01 respectively). Wall thickening reserve was higher with dobutamine than with exercise (0.9 mm vs. -0.6 mm, P = 0.02). CONCLUSION Dobutamine stress and physical exercise cannot be used interchangeably for assessment of systolic and diastolic function in patients with an intra-atrial correction for TGA. This may have consequences for the use of different stress CMR approaches in the clinical setting.