title: Effect of beta-blockade on low-dose dobutamine-induced changes in left ventricular function in healthy volunteers: assessment by gated SPET myocardial perfusion scintigraphy.
abstract: Viability studies are often performed in patients receiving beta-blocking agents. However, the intake of beta-blocking agents could influence the identification 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-photon 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 after injection of 925 MBq technetium-99m tetrofosmin on a triple-headed camera equipped with focussing (Cardiofocal) collimators. Acquisitions were made at rest (baseline 1 and 2) and 5 min after the beginning of the infusion of 5 and 10 microg kg(-1) min(-1) dobutamine. Wall thickening (WT) was quantified using a method based on circumferential profile analysis. Left ventricular ejection fraction (LVEF) was obtained using the Cedars-Sinai algorithm. 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. Dobutamine administration (at 5 and 10 microg 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 microg 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 dobutamine. At doses of 5 and 10 microg kg(-1) min(-1) dobutamine, however, significant increases in global and regional left ventricular function can still be measured using consecutive gated SPET myocardial perfusion scintigraphy acquisitions even under beta-blocker therapy.
authors.affiliation: Division of Nuclear Medicine, University Hospital, Free University of Brussels (AZ VUB), Belgium. nucgeth@az.vub.ac.be
authors.forename: H
authors.initials: H
authors.lastname: Everaert
authors.forename: C
authors.initials: C
authors.lastname: Vanhove
authors.forename: P R
authors.initials: PR
authors.lastname: Franken
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000328:Adult; D001794:Blood Pressure / Q000187:drug effects; D004280:Dobutamine / Q000494:pharmacology*; D006321:Heart / Q000000981:diagnostic imaging*; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D008790:Metoprolol / Q000494:pharmacology; D009200:Myocardial Contraction / Q000187:drug effects; D009943:Organophosphorus Compounds; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; D013318:Stroke Volume / Q000187:drug effects; D015899:Tomography, Emission-Computed, Single-Photon; D016277:Ventricular Function, Left / Q000187:drug effects* / Q000502:physiology
chemical_list: D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D009943:Organophosphorus Compounds; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; D004280:Dobutamine; C078700:technetium tc-99m tetrofosmin; D008790:Metoprolol