Usefulness of hyperventilation Tl-201 SPECT for detecting vasospasm in patients with myocardial infarction

To determine the involvement of vasospasm in the clinical process of myocardial infarction (MI), hyperventilation-loaded Tl-201 SPECT was performed in 25 patients one to 2 months after the onset of MI. Hyperventilation was loaded at the rate of 40 per minute, and SPECT images were obtained immediately and 3 hours after iv injection of Tl-201. SPECT images showed defect areas induced by vasospasm in 12 (48%) of the 25 patients. When these 12 patients were given calcium antagonisms widely used in the treatment of MI, subsequent SPECT images showed redistribution in 7 patients (58%). Thus, hyperventilation-loaded Tl-201 SPECT is considered useful for evaluating not only the involvement of vasospasm in MI and MI-related angina pectoris but also drug efficacy, as well as for diagnosing vasospastic angina pectoris. (N.K.)