[Role of pharmacologic stimulation with myocardial perfusion scintigraphy in the evaluation of patients with ischemic cardiopathy]

Abstract

Exercise myocardial-thallium scintigraphy plays a fundamental role in the diagnosis of coronary artery disease. Once exercise is not always feasible, pharmacological stress became a possible alternative. The authors review the mechanism of action, administrations protocols, indications and side effects of the drugs used for this purpose: dipyridamole, adenosine and dobutamine. Dipyridamole causes coronary hyperemia by increasing the interstitial levels of endogenous adenosine. Perfusion defects result from the mismatch of coronary reserve in different coronary territories. The drug administration is classically performed with a 0.142 mg/kg/min dosage e.v. for 4 minutes, total of 0.56 mg/kg. It is possible to use a greater dose of 0.84 mg/kg e.v. for 10 minutes, increasing sensitivity without loss of specificity for diagnosis of coronary artery disease. Oral dipyridamole protocols with 300 and 400 mg were used with similar results for sensitivity and specificity. The oral protocol has the disadvantage of delayed onset and longer action. Including several dipyridamole studies, 87% was obtained for sensitivity and 84% for specificity, in the diagnosis of CAD. Dipyridamole scintigraphy has been applied to myocardial infarction risk stratification, cardiac risk evaluation of patients proposed to noncardiac surgery and therapeutic efficacy evaluation of reperfusion techniques (angioplasty and surgery). The secondary effects of dipyridamole are frequent, however mild and well tolerated. They occur in half the patients, the most frequent, facial flushing (2%), dizziness (5%), nausea (4%), vomiting (1%), headaches (11%) and chest pain (26%). Some important complications were reported although rare: myocardial infarction, ventricular fibrillation and bronchospasm.(ABSTRACT TRUNCATED AT 250 WORDS)