[Thallium and echo- dipyridamole in the early selection of patients at risk after acute myocardial infarction. Which test? What dose?].

UNLABELLED

The optimal iv dose of Dipyridamole (Dip) in echocardiography (echo) or Thallium scintigraphy (Tl) remains undetermined. To select the high-risk patients (pts) subset, we performed echo and Tl with standard dose (SD) and high dose (HD) Dip infusion (0.56 mg/Kg/4'-0.84 mg/Kg/10' respectively) in 40 pts 9 +/- 3 days after admission for acute myocardial infarction (AMI). Of these, 38 pts had coronary artery disease at angiography and 2 had no significant lesions. Worsening in regional wall motion on echo and reversible perfusion defects on Tl were considered abnormal patterns. SD had no side effects; only in one pt was ischemic ventricular dysfunction detected on echo, whereas Tl redistribution was found in 24 pts (12 had multivessel disease and 12 had one coronary stenosis greater than or equal to 70%). HD caused adverse reaction in 24 pts, did not enhance SD-Tl sensitivity, but induced abnormal echo in 18/24 pts with transient defects on SD-Tl. Eleven of the 16 Tl negative pts had occlusive disease, 3 had one vessel disease and 2 showed no evidence of coronary artery disease.

IN CONCLUSION

SD is safe but often provokes a submaximal coronary vasodilation. Failure to detect ischemia on echo may be explained by this. SD-Tl is, however, able to identify high-risk pts who may benefit from early myocardial revascularization. HD does not enhance SD-Tl sensitivity, but it is necessary to induce echo abnormalities which are all too often undetectable at SD.