Usefulness of ambulatory radionuclide monitoring of left ventricular function early after acute myocardial infarction for predicting residual myocardial ischemia

Ambulatory radionuclide monitoring of left ventricular function was performed with the nuclear Vest device in 35 patients early after acute myocardial infarction. Patients were evaluated during post-infarction treadmill, other activities that included mental stress and cold pressor challenge, and with stress thallium imaging and cardiac catheterization. Of the 35 patients evaluated, 14 had ischemic responses on treadmill testing and 21 had negative responses. By contrast, 20 had redistribution by thallium imaging suggesting ischemia. Vest studies demonstrated 56 responses suggestive of ischemia in 23 patients. Twenty-two occurred during exercise and 13 with mental stress. Seventy-five percent were silent and only 39% had associated electrocardiographic changes. Vest responses were compared in patients whose thallium scan was indicative of ischemia (thallium-positive) and those without ischemia (thallium-negative). Ejection fraction was higher in the thallium-positive group (0.52 ± 0.11), as compared with thallium-negative patients (0.44 ± 0.1). With exercise, ejection fraction decreased for the thallium-positive patients from 0.52 ± 0.11 to 0.40 ± 0.09 at peak exercise. For thallium-negative patients, ejection fraction changes were not significant. During mental stress, ejection fraction decreased from 0.51 ± 0.11 to 0.45 ± 0.12 for thallium-positive patients while thallium-negative patients were unchanged. Vestmeasured decreases in ejection fraction of ≥5 units during exercise were highly sensitive (90%), specific (73%) and predictive (82%) of a positive thallium scan. The same response for mental stress was specific (87%) and predictive (85%) of a positive scan result. Ambulatory monitoring with Vest increased the sensitivity and specificity of the postinfarction treadmill and provided complementary information to thallium imaging.