Immunoscintigraphy for detecting acute myocardial infarction without electrocardiographic changes.

OBJECTIVE To establish whether immunoscintigraphy with antibody to myosin may detect acute myocardial infarction without electrocardiographic changes. DESIGN Prospective study of patients with suspected acute myocardial infarction or unstable angina with cardiac imaging with 111indium myosin antibody, estimation of cardiac enzyme concentrations, electrocardiography, 201thallium imaging, and radionuclide ventriculography. SETTING Coronary care unit in a district general hospital. PATIENTS 119 Consecutive patients with suspected acute myocardial infarction or unstable angina. Patients with cardiomyopathy, myocarditis, valvular heart disease, myocardial infarction or cardiac surgery in the previous two weeks or with left bundle branch block and women of childbearing age were excluded. RESULTS Of 75 patients with suspected acute myocardial infarction, seven had no diagnostic electrocardiographic changes despite normal conduction patterns. Immunoscintigraphy with myosin antibody disclosed necrosis in all seven patients, which was localised in regions supplied by diseased coronary arteries in all but one. Six patients had abnormal images on 201thallium imaging, and all seven had abnormal wall motion at the site of antibody uptake. One patient with minimal left main stem and right coronary artery atheroma had uptake of antibody at two discrete sites. CONCLUSIONS Immunoscintigraphy with antibody to myosin confirms myocardial infarction in the absence of electrocardiographic changes and discloses the site of infarction.