Objectives: This study investigated whether combining exercise with adenosine would reduce the adverse effects of adenosine vasodilation.
Background: Adenosine vasodilation is effective for perfusion imaging but causes frequent unpleasant noncardiac adverse effects, high noncardiac tracer uptake and occasional arrhythmias.
Methods: Of 500 consecutive patients referred for thallium-201 myocardial perfusion imaging, 407 were randomized to three study groups: 6 min of adenosine infusion alone; 6 min of adenosine with submaximal exercise; or symptom-limited exercise with continuous adenosine. Minimal detectable differences are presented; a significance level of 0.05 with a power of 80% is assumed.
Results: There was no difference among the three groups in sensitivity and specificity (overall 96% and 78%, minimal detectable differences 5.5% and 11%, respectively) for detection of coronary artery disease or stenosis in individual coronary arteries. There was a trend toward improved sensitivity in the combined exercise groups compared with that in the adenosine-only group (98% vs. 93%, p = 0.07, minimal detectable difference 6%). Noncardiac side effects were reduced by 43% in the exercise groups (p < 0.0001), and major arrhythmias were reduced by 90% (p < 0.0001). There was no effect on minor arrhythmias (25% vs. 22%, p = 0.6, minimal detectable difference 12%). The heart/background ratios were higher in the exercise groups (all p < 0.02). Each ratio was correlated with the exercise level achieved (all p < 0.001). The reversibility score increased with exercise (p = 0.04), as did the number of patients and segments with reversible defects (both p = 0.03).
Conclusions: Combining exercise with adenosine infusion reduced the noncardiac side effects of vasodilation and major arrhythmias while improving redistribution and heart/background ratios. These findings may be clinically important. Although maximal exercise with adenosine infusion produced optimal results, the improvement over the submaximal exercise protocol was minor, and this has the advantage of being simple and achievable within the normal 6-min duration of the adenosine infusion.