Factors influencing exercise tolerance in patients with myocardial infarction as elucidated by Tl-201 myocardial scintigraphy

Measurements of O2 consumption during treadmill exercise tests and Tl-201 myocardial scintigraphy were performed in 17 cases of myocardial infarction to elucidate O2 consumption at an anaerobic threshold ATVO2 as an adequate index of exercise tolerance, and the scintigraphic indices influencing the exercise tolerance. ATVO2 was obtained using the method of Wasserman and Davisand corracted by body weight. The scintigraphic indiced such as the location, extent (residual myocardium), and severity (% uptake) of myocardial infarction were obtained from SPECT and bull's eye displays on Tl-201 myocardial scintigraphy. ATVO2 was correlated with theoretical VO2max as obtained by the predicted maximal heart rate (r=0.56, P<0.01) and with left ventricular ejection fraction as obtained by radionuclide left ventriculography (r=0.59, p<0.01). There was no significant difference between ATVO2 in cases of anterior wall infarction and those of inferior (and/or lateral wall) infarction. There was no significant correlation between % uptake and ATVO2. However, the residual myocardium showed a significant correlation with ATVO2 (r=0.61, p<0.01). In conclusion, 1) ATVO2 is an adequate index of exercise tolerance and reflects cardiac function. 2)The extent of the residual myocardium is most strongly influenced by ATVO2 among the indices of myocardial damage as obtained by Tl-201 myocardial scintigraphy. (author)