Improved detection of myocardial infarction with technetium-99m stannous pyrophosphate and serum MB creatine phosphokinase

Abstract

The relative sensitivity and combined value of myocardial technetium99m stannous pyrophosphate imaging and determinations of serum MB creatine phosphokinase (the “myocardial” CPK isoenzyme) in detecting acute myocardial infarction were evaluated in 41 patients with suspected infarction and 23 patients recovering from cardiac surgery. In the patients with suspected infarction, myocardial infarction was confirmed in 25 and was consistently associated with increased serum MB CPK. Abnormal radionuclide images were obtained in 23 of 25 patients (92 percent) with definite myocardial infarction and in 2 of 16 patients without confirmed infarction. Although the localization of infarction by imaging correlated well with the localization by electrocardiogram, infarct size estimated by imaging did not correlate well with estimates based on peak total serum CPK activity or serial changes in CPK activity. Serum MB CPK activity increased after cardiac surgery in 6 patients undergoing valve replacement and in 17 patients undergoing coronary arterial bypass surgery. However, no patient with valve replacement and only 1 of the 17 with bypass surgery had an abnormal radionuclide image. These results suggest that (1) abnormal radionuclide images in patients without infarction can be distinguished from abnormal images indicative of ischemic necrosis by consideration of MB CPK activity and (2) interpretation of elevated MB CPK activity, particularly in patients undergoing cardiac surgery, is facilitated by evaluation with imaging.