ASSESSMENT OF MAGNETIC-RESONANCE VELOCITY MAPPING OF GLOBAL VENTRICULAR-FUNCTION DURING DOBUTAMINE INFUSION IN CORONARY-ARTERY DISEASE

Background-Magnetic-resonance imaging (MRI) is a versatile technique f or examination of the cardiovascular system but only recently has asse ssment of myocardial ischaemia in coronary artery disease (CAD) become possible, for example by demonstrating abnormalities of regional vent ricular contraction during stress. Global ventricular function during stress was assessed by MRI of aortic flow, which has not been previous ly attempted. Design-Variables measured by MRI reflecting the effect o f ischaemia on global ventricular function during dobutamine stress we re correlated with thallium-201 myocardial perfusion tomography. Patie nts-10 normal controls and 25 patients with CAD. Setting-Tertiary card iac referral centre. Methods-Novel MRI sequences and analysis systems were used to measure the following variables during staged dobutamine infusion to 20 mu g/kg/min: stroke volume, cardiac output, cardiac pow er output, peak flow, peak flow acceleration, aortic back flow, and fl ow wave velocity. Heart rate, blood pressure, double product, and maxi mum tolerated dobutamine dose were also measured. Multiple regression analysis was used to compare changes during stress with (TI)-T-201 tom ography. Results-All parameters except for stroke volume and diastolic blood pressure increased in the controls. In the patients with CAD a significant relation was shown between the extent of reversible ischae mia and the change in peak flow acceleration (P < 0.00001), peak flow (P = 0.002), cardiac power output (P = 0.036), maximum dobutamine dose (P = 0.039), and systolic blood pressure (P = 0.04). flow acceleratio n accounted for of the variation in reversible ischaemia, and after al lowing for this, only cardiac power output remained independently pred ictive adding a further 4.2% to the model (adjusted r(2) = 0 626). A d ecrease in peak flow acceleration with an increase in dobutamine infus ion indicated moderate or severe ischaemia (chi(2) = 10.2, P = 0.017). Conclusion-MRI may be used to assess variables of aortic flow during stress, which includes acceleration with high temporal resolution. Pea k flow acceleration was the most sensitive indicator of the effect of ischaemia on global ventricular function.