Combined Tc-99m sestamibi first-pass radionuclide angiography and cardiac SPECT imaging during arbutamine infusion delivered by a computerized closed-loop system.

Abstract

This study evaluated the feasibility, hemodynamic responses, and relation of combined Tc-99m sestamibi SPECT imaging and first-pass radionuclide angiography during the infusion of a new beta agonist arbutamine. Arbutamine was administered to 15 patients and constantly adjusted by a closed-loop computerized system. Rest and arbutamine Tc-99m sestamibi radionuclide angiography was performed with a multicrystal gamma camera followed by SPECT imaging with a rotating triple-head, single-crystal gamma camera. The mean differences (paired t-test) between rest and arbutamine studies for heart rate (HR), end-diastolic volume (EDV), stroke volume (SV), cardiac output (CO), and ejection fraction (EF) were as follows: 55 bpm for HR (P < 0.001), 5 ml for EDV (P=ns), 7.5 ml for SV (P=0.04), 4.4 l/min for CO (P < 0.001), and 6.4% for EF (P < 0.001), respectively. The results of SPECT studies were abnormal in six patients and normal in nine. Findings of radionuclide angiography were normal in 12 patients and abnormal in three. Interpretation of the perfusion and functional studies were concordant in 10 and discordant in five patients. Simultaneous cardiac radionuclide angiography and SPECT imaging are feasible during arbutamine infusion. This potent beta agonist increases cardiac output through a chronotropic effect with no significant changes in EDV. The discordance in SPECT and radionuclide angiography results may represent incremental diagnostic and prognostic information provided by both studies.