Discontinuing of long-term beta-blocker therapy may falsely overestimate the fixed defects in dipyridamole myocardial perfusion imaging

摘要

Objectives: The previous studies suggest that acute beta-blocker administration may reduce the presence and severity of myocardial perfusion defects with dipyridamole stress. However, little information is available about chronic beta-blocker therapy. This study was designed to evaluate the effect of discontinuing beta-blocker drugs on dipyridamole myocardial perfusion imaging (DMPI) in patients who were on long-term beta-blocker therapy. Methods: One hundred twenty patients (103 male and 17 female) with angiographically proven coronary artery disease(CAD) who were being on long-term beta blocker therapy enrolled in a randomized clinical trial study. All patients were allocated in to group A(n=60) in whom beta-blocker was discontinued for 72 hours before DMPI and group B(n=60) with continuing beta-blocker therapy. Images were interpreted by three observers blinded to the patients' clinical data with scoring the perfusion status using a standard 20-segment model and 3-point scaling method (as normal, reversible and irreversible segments). Correspondingly, perfusion scores for territory of left anterior descending (LAD), left circumflex (LCx) and right coronary arteries (RCA) as well as for whole myocardium were calculated. The mean ranks of perfusion scores in group A were compared with group B by Mann-Whitney-U-test using SPSS software (12.0). Results: The mean rank of total perfusion scores for whole myocardium (irrespective of reversibility) in group B was more than that of group A, (65.75 vs. 55.25, p=0.096). Regarding the only irreversible perfusion defects, the mean rank of perfusion score in group B was substantially higher than that of group A for whole myocardium (72 vs. 49, p=0.0001), territory of LAD (65.25 vs. 55.75, p=0.098) and LCx (70.5 vs. 50.5, p<0.0001); however; no difference was noted between two groups for only reversible perfusion defects (61.0 vs. 60.0, p=0.898). Conclusions: Discontinuing long-term beta-blocker therapy several days before DMPI may overestimate the extent of irreversible perfusion defects but has no effect on reversible perfusion abnormalities. As a possible reason, beta-blocker withdrawal in patients with long-term beta-blocker therapy may decompensate myocardial perfusion in rest phase, reducing the difference between rest- and stress- regional perfusion ending in falsely appearing fixed defects in the case of severe ischemia.