Effect of dobutamine on myocardial blood flow in patients with coronary artery disease - a quantitative analysis using O-15 H2O positron emission tomography

Background and objective: Although dobutamine is currently widely used for stress testing, only little is known about the effects of dobutamine on myo cardial blood flow. The purpose of the present study was therefore to analy ze quantitatively the regional changes in myocardial blood flow during rest and stress. Patients and methods: In order to assess these effects 17 patients (12 men, five women, mean age 57 +/- 8 years) with symptomatic single vessel corona ry artery disease (>70% stenosis) scheduled for coronary angioplasty underw ent dobutamine stress testing with a maximum dose of 40 mu g/kg/min. Myocar dial blood flow was measured using O-15 H2O positron emission tomography at rest and during maximum stress in ischemic and non-ischemic myocardial reg ions. Results: Dobutamine stress (median dose 30 mu g/kg/min) increased the Fate pressure product significantly (from rest 8697 [95% confidence interval 795 9-9435] to stress 16 512 [15 208-17 815] mmHg/min (p < 0.007). Myocardial b lood flow during rest was similar in non-ischaemic and ischaemic regions (0 ,91 [0.93; 0.83-1.28] vs. 1.10 [1.23; 0.91-1.28] ml/min/g, n.s.). During do butamine stress myocardial blood flow increased in non-ischaemic regions to 2.17 (2.15; 1.77-2.57) ml/min/g, while myocardial blood flow did not incre ase in ischaemic regions (1.06 [0.97; 0.83-1.28], p < 0.001). Accordingly, dobutamine coronary reserve was 2.42 (2,55; 2,10-2,74) for non-ischaemic re gions and 0.98 (1.05; 0.84-1.13) for ischemic regions (p < 0.001). Rate pre ssure product and myocardial blood flow were significantly correlated(r = 0 .79, p < 0.001). Conclusion:A dobutamine-induced increase in rate pressure product was propo rtional to an increase in myocardial blood flow in non-ischaemic regions. I n contrast, myocardial blood flow did not increase in myocardial regions su pplied by a severely stenosed coronary artery.