DETECTION OF MICROINFARCTION IN PATIENTS WITH UNSTABLE ANGINA - STUDYBY IN-111-ANTIMYOSIN IMAGING

To examine the incidence of a positive indium-111 antimyosin scintigra phy in patients with unstable angina, we prospectively examined 25 pat ients with unstable angina and 11 patients with stable angina. All pat ients were injected with 2 mCi of indium-111 on admission and planar s cintigraphy was performed 48 h later. Symptoms and signs of ischemia i ndicating severity of ischemia were monitored during the period betwee n injection and scanning. None of the patients developed a rise in car diac enzymes suggesting myocardial necrosis. Seven (28%) of the 25 pat ients with unstable angina had positive antimyosin scanning; no stable patients had positive scanning. All seven patients with unstable angi na and positive scanning had signs of severe ischemia (four patients h ad multiple episodes of >2/day, three patients had prolonged episodes of >15 min, three patients had ST depression in >3 EKG leads) while on ly one of the eighteen unstable patients with negative scannings had s igns of severe ischemia (P < 0.001). In conclusion, (1) a significant number of unstable angina patients present positive antimyosin scannin g without an elevation of cardiac enzymes and (2) these patients usual ly present multiple or severe episodes of ischemia indicating that dur ing these episodes, minor myocardial necrosis, undetected by enzymes, may occur.