Effects of low-dose dobutamine on left ventricular function in normal subjects as assessed by gated single-photon emission tomography myocardial perfusion studies

Electrocardiography gated single-photon emission tomography (gated SPET) al lows the assessment of regional perfusion and function simultaneously and i n full spatial congruency. In this study changes in global and regional lef t ventricular function in response to dobutamine infusion were assessed in ten healthy volunteers using sequential gated SPET myocardial perfusion acq uisitions. Four consecutive gated SPET images were recorded 60 min after in jection of 925 MBq technetium-99m tetrofosmin on a three-head camera equipp ed with focussing collimators. Two acquisitions were made at rest (baseline 1 and 2), and the third and fourth acquisitions were started 5 min after t he beginning of the infusion of 5 and 10 mu g kg(-1) min(-1) dobutamine, re spectively. Systolic wall thickening (WT) was quantified using a method bas ed on circumferential profile analysis. Left ventricular ejection fraction (LVEF) and volumes were calculated automatically using the Cedars-Sinai pro gram. Nine of the ten subjects presented a definite increase in WT during d obutamine infusion. WT increased on aver age from 46%+/-14% at baseline to 71%+/-23% (range: 37%-106%: P<0.05) during 5 mu g kg(-1) min(-1) dobutamine infusion and to 85%+/-25% (range: 62%-123%; P<0.05 with respect to WT at 5 mu g kg(-1) min(-1)) during 10 mu g kg(-1) min(-1) dobutamine infusion. Ap ical segments showed the largest WT at baseline. The average WT response to dobutamine was similar for all parts of the myocardium. It is concluded th at changes in WT induced by infusion of low-dose dobutamine can be assessed by sequential gated SPET myocardial perfusion studies. The "stress gated S PET" protocol proposed in this study might be helpful to distinguish viable from scar tissue in patients with coronary artery disease, by demonstratin g a preserved inotropic response in hypoperfused myocardium.