COMPARISON OF ADENOSINE AND HIGH-DOSE DIPYRIDAMOLE BOTH COMBINED WITHLOW-LEVEL EXERCISE STRESS FOR TC-99(M)-MIBI SPET MYOCARDIAL PERFUSIONIMAGING

Intravenously administered adenosine and high-dose dipyridamole, both combined with low-level exercise stress, were compared in a head-to-he ad fashion using Tc-99(m)-methoxyisobutyl isonitrile (Tc-99(m)-MIBI) s ingle photo emission tomography (SPET) myocardial perfusion imaging. T hirty-nine consecutive patients who had undergone coronary arteriograp hy underwent Tc-99(m)-MIBI (740 Mbq) SPET after dipyridamole (0.84 mg kg(-1)) and after adenosine (0.84 mg kg(-1)), both combined with low-l evel exercise (30 W load), and under resting conditions. Our results d emonstrate that adenosine and dipyridamole combined with exercise have comparable haemodynamic effects, with a low incidence of side-effects . The time of recovery from the stress protocol was not significantly different: adenosine, 5.7 +/- 3.9 min; dipyridamole, 6.6 +/- 4.9 min. However, aminophylline was significantly (P < 0.05) more often adminis tered to reverse side-effects using the dipyridamole protocol (36% of patients) compared with the adenosine protocol (8% of patients). The r esults of Tc-99(m)-MIBI SPET imaging were highly concordant and demons trated a high diagnostic accuracy for identifying coronary artery dise ase (CAD). The sensitivity was 90% (95% confidence intervals 79-100%) with adenosine SPET and 93% (95% confidence intervals 84-100%) with di pyridamole SPET for identifying patients with CAD (i.e. luminal stenos is > 50%); their specificities were both 100% (95% confidence interval s 66-100%). The sensitivity of identifying angiographically diseased v essels was 81% (95% confidence intervals 70-92%) using adenosine SPET and 85% (95% confidence intervals 75-95%) using dipyridamole; the spec ificity for both stress modalities was 94% (95% confidence intervals 8 9-100%). The combination of exercise with adenosine and high-dose dipy ridamole appears to be a feasible and safe method to alleviate some of the undesirable A1-receptor-mediated side-effects of adenosine. The c hoice of the pharmacological stress will depend on local expertise and availability.