Paradoxical hypotension during dobutamine infusion for myocardial perfusion scintigraphy

Aim: Dobutamine as a predominant beta-1 agonist increases heart rate and my ocardial contractility and at sufficient high doses, it also increases syst olic blood pressure. This study was undertaken to describe instances of par adoxical hypotension during dobutamine infusion for Tl-201 myocardial perfu sion SPECT study and the relationship between scintigraphic findings and hy potension occurred during dobutamine infusion. Methods: In 201 consecutive patients unable to perform adequate exercise, dobutamine Tl-201 myocardial SPECT was performed. Dobutamine was infused starting from 10 mu g/kg/min in creasing to 40 mu g/kg/min. Paradoxical hypotension was defined as a decrea se in systolic blood pressure greater than or equal to 20 mmHg compared wit h baseline study. Results: Paradoxical hypotension was observed in 40 patie nts (Group A) out of 201 (19.9%) while no significant change in systolic bl ood pressure was detected in the remaining 161 patients (Group B). Mean max imum fall in systolic blood pressure was 39 +/- 18 mmHg (range: 20-90). In 33 of 40 patients (83%) with paradoxical hypotension, scintigraphy was norm al compared to 131 (81%) of the remaining 161 patients. In patients of Grou p A, angiography, echocardiography and tilt table tests were performed in 1 3, 11 and 6 patients respectively. Nine of 13 angiographic evaluations (69% ), 10 of 11 echocardiographic evaluations (91%), all of the tilt table test s were normal. Additionally, all of the patients of Group A were clinically followed up at least 6 months after the myocardial perfusion scintigraphy. None of the patients had a cardiac event except one patient during the fol low-up period. Conclusion: Paradoxical hypotension during dobutamine infusi on for myocardial scintigraphy is not an uncommon finding and up to 19.9% p atients may develop such hypotension. To maximize test safety, precautions should be taken during dobutamine myocardial stress test, since remarkable decrease in systolic blood pressure may occur. Unlike hypotension occurring with exercise test, hypotension response to dobutamine is not always a mar ker for coronary artery disease.