- contraindications to dipyridamole SPECT including : i)severe reactive airway disease; ii) less than 3 days post Myocardial Infarction - Acute Coronary Syndrome (MI-ACS); iii) high-grade Atrioventricular block (AV block); iv)allergy to dipyridamole or theophylline; v) caffeine within 12 hours; vi) theophylline use within 48 hours; vii) severe claustrophobia; or viii) women who may be pregnant