A COMPARISON OF ADENOSINE AND ARBUTAMINE FOR MYOCARDIAL PERFUSION IMAGING

We have compared our standard stress protocol (adenosine combined with exercise) with the new stress agent arbutamine, for thallium-201 myoc ardial perfusion imaging (MPI) in order to assess the comparative valu e of arbutamine. We studied 23 patients referred for MPI, and each pat ient had two studies (18 males, median age 66 years, five with previou s myocardial infarction). Uptake scores were assigned to each of nine segments, and the extent and severity of defects were measured using a polar plot. Haemodynamic changes were greater with arbutamine (rate-p ressure product increase 78% vs 51%, P = 0.003). Symptoms were experie nced by 21 patients with arbutamine and 16 with adenosine (P = 0.07). Agreement between the techniques for classification of patients as nor mal or as having reversible, fixed or mixed defects was good (19 of 23 studies, 83%, kappa = 0.76). Agreement for similar classification of segments was also good (82%, kappa = 0.71). Segmental agreement for st ress scores was good (86%, kappa = 0.77). However, mean size of stress defect was larger with adenosine (83 +/- 52 pixels vs 65 +/- 48 pixel s, P < 0.05), though severity and reversibility were similar (P = NS). We conclude that arbutamine provides comparable results to those obta ined with adenosine and exercise and that the observed differences are not clinically significant.