Little is known about the effect of chronic beta-blockade on adenosine actions. We sought to investigate the effect of oral beta-blockers on the presence, extent, and severity of myocardial perfusion abnormality induced by adenosine in patients with coronary artery disease.
Methods: In this crossover study, 45 male patients with coronary artery disease on beta-blocker therapy with atenolol, bisoprolol, or metoprolol underwent adenosine myocardial perfusion imaging both on and off beta-blockade in a random order on separate days. Myocardial perfusion was assessed both qualitatively and quantitatively. Hemodynamic response, image analysis, and sensitivity for the detection of coronary stenosis (>or=50% luminal diameter reduction on x-ray coronary angiography) were compared between the on and off beta-blocker studies.
Results: Rate pressure product both at baseline and at peak adenosine infusion decreased by 23% +/- 15% and 21% +/- 18%, respectively, after beta-blockade (P < 0.001 for all). The median (interquartile range) summed difference score, a measure of defect reversibility, and quantitative defect size were both significantly lower after beta-blockade (median, 7.0 [interquartile range, 2.0-9.5] vs. median, 5.0 [interquartile range, 0-8.0], P = 0.002; and quantitative defect size, 18% [interquartile range, 9%-34%] vs. quantitative defect size, 6% [interquartile range, 0%-19%], P < 0.001, respectively). The overall sensitivity for the detection of coronary stenosis decreased from 0.76 (95% confidence interval, 0.65-0.88) to 0.58 (95% confidence interval, 0.45-0.71) after beta-blockade (P = 0.03).
Conclusion: beta-blockade causes a small but significant reduction in the extent and severity of perfusion abnormality by adenosine. This may reduce the diagnostic sensitivity of adenosine myocardial perfusion imaging for the detection of flow-limiting coronary stenosis.