Safety of intravenous dipyridamole thallium myocardial perfusion imaging: experience in 435 patients.

Dipyridamole stress 201Tl scintigraphy is widely used in the investigation of myocardial ischaemia. We report our experience of adverse effects observed during this diagnostic procedure. A prospective study was undertaken of 435 consecutive patients (mean age 59 years; 273 males) referred to two nuclear medicine departments for assessment of myocardial perfusion was undertaken. Patients were monitored prior to and following the infusion of dipyridamole. All symptomatic, haemodynamic and electrocardiographic changes were documented. No deaths occurred in this series. Adverse events were observed in 174 (40%) patients. Of these, three patients experienced 'major' adverse events (0.6%) requiring hospitalization (myocardial infarction = 1; chest pain = 1; simple partial seizure = 1). 'Moderate' adverse events occurred in 39 (8.9%) patients and required intravenous aminophylline to reverse effects (ST segment abnormalities = 26; nausea = 7 headache = 3; chest pain = 2; bronchospasm = 1; protracted vomiting = 1; diarrhoea = 1). 'Minor' adverse events were experienced by 132 (30.3%) patients and did not require aminophylline. Sixty per cent of our patients experienced no ill effects from dipyridamole given as an exercise substitute in conjunction with 201Tl imaging. The rest had symptoms which were mostly mild, although a few patients found the experience unpleasant. Only one patient experienced a life-threatening episode.