QTc interval prolongation during infusion with dipyridamole or adenosine.

The aim of our study was to discover whether there was a relationship between the QTc interval prolongation on the standard 12-lead electrocardiogram (ECG) and provoked myocardial ischemia. Since the increase of adenosine plasma levels, obtained either with adenosine or dipyridamole (an adenosine reuptake inhibitor) infusion, has been used to test the coronary artery reserve in patients affected by coronary artery disease, the QTc interval modifications during dipyridamole or adenosine echocardiographic stress test were evaluated. Twenty-five patients admitted to our Institute for evaluation of chest pain of suspected myocardial origin underwent an echocardiographic dipyridamole stress test (0.84 mg/kg over 10 min) after discontinuation of antianginal treatment. Of these patients, 10 underwent an echocardiographic adenosine stress test (scalar doses of 50, 75, 100, 140 micrograms/kg/min) after 48-72 h. The Bazett formula was used to evaluate the QTc interval. After dipyridamole and adenosine administration, a significant prolongation of the QTc interval was observed only in those patients who had positive test results. Our data suggested that QTc interval prolongation during pharmacological stress tests might be considered a marker of myocardial ischemia.