BREATH-HOLD DOBUTAMINE MAGNETIC-RESONANCE MYOCARDIAL TAGGING - NORMALLEFT-VENTRICULAR RESPONSE

Analysis of the changes in myocardial deformation produced by adrenerg ic stress has been limited by the imaging techniques used, We used rap id magnetic resonance imaging (MRI) myocardial tagging to map the dose -dependent response to incremental dobutamine in the normal human left ventricle, Thirteen volunteers underwent breath-hold tagged cine MRI during dobutamine infusion, Images were acquired throughout systole to a peak dose of 20 mu g/kg/min. End-systolic percent circumferential s hortening (%S) was measured at 3 transmural locations and 4 circumfere ntial locations at 3 long-axis positions. Mean circumferential shorten ing velocity (CSV) was also calculated at each location and dose, Mean %S reached a maximum of 26 +/- 3% at 10 mu g/kg/min compared with 21 +/- 4% at baseline (p < 0.003), Peak %S was reached by 10 mu g/kg/min before a significant increase in heart rate or blood pressure and was unchanged at higher doses, In contrast, CSV increased linearly with do butamine dose from 4.4 +/- 0.9 mm/s at baseline to 9.8 +/- 1.4 mm/s at 20 mu g/kg/min (p < 0.0001), Breath-hold tagged dobutamine MRI is saf e and effective in detecting regional and transmural changes in functi on during incremental dobutamine. CSV increased continuously across th e dobutamine dose range, At low dose (less than or equal to 10 mu g/kg /min) %S increased without any change in blood pressure or heart rate. Maintenance of peak %S beyond 10 mu g/kg/min in the presence of decre asing systolic intervals resulted from a continued increase in CSV. Th us, CSV may be the preferred measure of contractile function during do butamine stimulation in human myocardium. (C) 1997 by Excerpta Medica, Inc.