Abstract. Viability studies are often performed in pa- tients receiving beta-blocking agents. However, the in- take of beta-blocking agents could influence the identifi- cation of viable myocardium when low-dose dobutamine is used to demonstrate inotropic reserve. The aim of this study was to quantify the effect of beta-blockade on global and regional left ventricular function in healthy volunteers using low-dose dobutamine gated single-pho- ton emission tomographic (SPET) myocardial perfusion scintigraphy. Ten subjects were studied once “on” and once “off” beta-blocker therapy (metoprolol succinate, 100 mg day –1 ). On each occasion four consecutive gated SPET acquisitions (of 7 min duration) were recorded af- ter injection of 925 MBq technetium-99m tetrofosmin on a triple-headed camera equipped with focussing (Cardio- focal) collimators. Acquisitions were made at rest (base- line 1 and 2) and 5 min after the beginning of the infu- sion of 5 and 10 μg kg –1 min –1 dobutamine. Wall thick- ening (WT) was quantified using a method based on cir- cumferential profile analysis. Left ventricular ejection fraction (LVEF) was obtained using the Cedars-Sinai al- gorithm. Blood pressure (BP) and heart rate (HR) were recorded at the end of each acquisition. At baseline LVEF, WT and systolic BP values under beta-blockade were not significantly different from those obtained in the non-beta-blocked state. The mean HR and diastolic BP at baseline were lower under beta-blockade. Dobuta- mine administration (at 5 and 10 μg kg –1 min –1 ) induced a significant increase in WT, LVEF and systolic BP in all subjects both on and off beta-blockade. The increases in WT, LVEF and systolic BP in the beta-blocked state were less pronounced but not significantly different. HR increased significantly at 10 μg kg –1 min –1 dobutamine without beta-blocker administration, while no increase in HR was observed in the beta-blocked state. Beta-blocker therapy in healthy subjects attenuates the inotropic and chronotropic myocardial response to low-dose dobuta- mine. At doses of 5 and 10 μg kg –1 min –1 dobutamine, however, significant increases in global and regional left ventricular function can still be measured using consecu- tive gated SPET myocardial perfusion scintigraphy ac- quisitions even under beta-blocker therapy. Key words: Gated single-photon emission tomography – Low-dose dobutamine – Beta-blocker Eur J Nucl Med (2000) 27:419–424 Introduction Patients referred for viability studies soon after myocar- dial infarction are often receiving beta-adrenergic block- ing agents [1, 2]. With their negative inotropic and chro- notropic effects, beta-blockers may prevent the contrac- tile response to low-dose dobutamine stress and may ad- versely affect the ability of dobutamine to detect viable tissue. Temporary discontinuation of beta-blockers may be hazardous, potentially exacerbating previous symp- toms of angina or precipitating unstable angina, acute myocardial infarction or sudden death [3]. In addition it can be anticipated that beta-blockers will increasingly be used in patients with chronic left ventricular dysfunction [4, 5]: many of the viability studies are performed in this class of patients. Electrocardiography gated single-photon emission tomographic (SPET) myocardial perfusion scintigraphy with technetium-99m labelled agents provides the oppor- tunity to assess regional perfusion and function simulta- neously. Gated SPET provides accurate information with regard to global and regional myocardial function at rest Correspondence to: H. Everaert, Division of Nuclear Medicine, University Hospital, Free University of Brussels (AZ VUB), Laarbeeklaan 101, 1090 Brussels, Belgium e-mail: nucgeth@az.vub.ac.be, Tel: +32-2-4775021 Fax: +32-2-4775017 Original article Effect of beta-blockade on low-dose dobutamine-induced changes in left ventricular function in healthy volunteers: assessment by gated SPET myocardial perfusion scintigraphy Hendrik Everaert, Christian Vanhove, Philippe R. Franken Division of Nuclear Medicine, University Hospital, Free University of Brussels (AZ VUB), Brussels, Belgium Received 4 September and in revised form 3 November 1999 European Journal of Nuclear Medicine Vol. 27, No. 4, April 2000 – ©Springer-Verlag 2000