NONINVASIVE DIAGNOSIS OF INFARCT ARTERY PATENCY AFTER ACUTE MYOCARDIAL-INFARCTION BY USE OF SERIAL PLASMA TROPONIN-T CONCENTRATIONS - IMPORTANCE OF MEASUREMENT OF PEAK LEVELS

Objective-To confirm the validity of a previously described method for assessment of infarct artery patency involving serial measurements of creatine kinase activity by use of troponin T concentration as an ind ependent plasma marker. Design-Streptokinase (1.5 x 10(6) units) was g iven intravenously to 60 patients within 6 h of onset of prolonged che st pain and ST segment elevation, and blood was taken for measurement of troponin T concentration at baseline and at 1, 2, 3, 4, 8, 12, 16, 20, and 24 h after starting treatment. Coronary arteriography was perf ormed at 2 6 (SD 0 3) h. Plasma troponin T concentration was assessed by two methods: (1) as the absolute rise between 0 and 3 h; and (2) as the proportion of the total rise (from baseline to peak) over the sam e period. Accuracy for prediction of infarct artery patency, assessed by receiver operating characteristic curves, was compared for both met hods of assessment using troponin T and was in turn compared with prev iously reported results on the same patients using serial measurements of creatine kinase activity. Results-Sufficient values for prediction of patency using troponin T were available in 53 patients. A rise in troponin T between 0 and 3 h to greater than or equal to 9% of peak co ncentration predicted angiographic patency with sensitivity of 94% and specificity of 100%. By contrast, at the optimum cutoff for absolute rate of rise (0.5 mu g/1/h) sensitivity was only 66% and specificity 8 6%. Comparable figures for creatine kinase were 92% and 91% (greater t han or equal to 20% of peak by 3 h) and 62% and 78% (150 IU/1/h). Rece iver operating curves confirmed better predictive accuracy for proport ions over absolute rates of rise for both markers (P < 0.01). Conclusi ons-For accurate diagnosis of infarct artery patency using plasma mark ers it is necessary to express the rate of rise as a proportion of the peak level. Analysed in this way, both creatine kinase and troponin T are suitable for use in randomised trials of new thrombolytic or adju vant drugs.