Detection of coronary disease patients at high risk for recurrent myocardial infarction by elevated plasma inactive creatine kinase B protein levels.

The diagnostic and prognostic significance of plasma inactive creatine kinase B protein (CK-Bi) levels measured by radioimmunoassay was determined in various ischemic myocardial syndromes. In 120 stable angina patients free of pain at time of blood sampling, mean CK-Bi level was 114 +/- 42 (SD) micrograms-equiv/ml; 195 micrograms-equiv/ml (95% confidence interval) represented upper limit of normal. In seven coronary artery disease (CAD) patients atrial pacing induced ischemia was not associated with increased coronary sinus CK-Bi. Of 201 consecutive patients with suspected acute infarction (AMI), 45 developed ECG criteria of transmural AMI with concomitant increased plasma CK-Bi levels (498 +/- 133, range 372-718 micrograms-equiv/ml). Elevated CK-Bi levels in evolving transmural AMI were detected before raised CK enzyme activity. Elevated plasma CK-Bi levels also occurred in acute pericarditis and in unstable angina. In the 84 patients not developing ECG changes or elevated plasma CK activity, their plasma CK-Bi levels were also normal and no coronary events occurred in the next 6 months. The remaining 55 patients had nontransmural AMI, with 15 also having elevated plasma CK and CK-Bi levels, of whom six developed re-AMI in the next 3 months. In the other 40 nontransmural AMI patients, plasma CK-Bi levels (350 +/- 65 micrograms/equiv/ml, range 228 to 445) increased significantly without associated CK activity rise, and 24 developed re-AMI (three fatal) in the next 6 months. These data suggest that: (1) plasma CK-Bi protein radioimmunoassay measurement provides a sensitive means for detecting myocardial necrosis or inflammation and (2) elevated plasma CK-Bi levels in coronary disease patients during myocardial ischemic pain may afford identification of a CAD clinical subset at high risk of subsequent AMI.