Myocardial infarction: biochemical marker ratios help to detect successful reperfusion.

Clinical bottom line (level 3b)

  1. In patients who have had thrombolytic therapy after a myocardial infarction, assay of the before/after ratios of creatine kinase-MB mass, Troponin T or Myoglobin ratio helped to rule failed reperfusion out.
  2. The markers were less successful at ruling in failure to reperfuse.
Stewart et al: Journal of the American College of Cardiology 1998; 31 (7): 1499-1505
Expires March 2003

The study

Setting: multicentre, New Zealand

105 patients (aged mean 59 years, 78% male) presented with typical ischaemic chest pain >20 minutes in duration and > or = 1 mm ST segment elevation in two ECG leads
Aspirin (300 to 325 mg) and 1.5 million U of streptokinase by rapid infusion (over 30 to 60 minutes), followed by either heparin or Hirulog (as a bolus plus infusion).
Independent blinded reference standard, applied in some patients from a consecutive inappropriate spectrum.
Reference standard:
  • known TIMI flow grade
Diagnostic test: Ratios of serum cardiac enzymesCto baseline values. (creatine kinase-MB, assayed by the Status II immunoassay; myoglobin measured by immunoassay; cardiac troponin T measured by enzyme-linked immunoassay. Normal values used were creatine kinase-MB mass < or = 5 ng/ml; troponin T < or = 0.1 ng/ml; myoglobin < or =110 ng/ml. Ratios were examined for their ability to discriminate between patients with a TIMI grade 3 flow and those with lower TIMI flow grades, and to diagnose failed reperfusion.)
  • Patients were part of an RCT of reperfusion strategies.

The evidence


diagnostic test number of patients sensitivity for
failed reperfusion
(95% CI)		 specificity for
failed reperfusion
(95% CI)		 LR+ LR-
creatine kinase-MB mass ratio of 5, at 90 minutes 82%
(% to %) 		66%
(% to %) 		2.4 0.27
creatine kinase-MB mass ratio of 10, at 90 minutes 91%
(% to %) 		49%
(% to %) 		2.4 0.27
troponin T ratio of 5, at 90 minutes 82%
(% to %) 		67%
(% to %) 		2.5 0.27
troponin T ratio of 10, at 90 minutes 95%
(% to %) 		58%
(% to %) 		2.3 0.09
myoglobin ratio of 5, at 90 minutes 84%
(% to %) 		73%
(% to %) 		3.1 0.22
myoglobin ratio of 10, at 90 minutes 88%
(% to %) 		65%
(% to %) 		2.5 0.18
total 59

Comments

  1. No data is given on the additive utility of the three markers. It would be well to assume a very close relationship between the three, and therefore little added by testing more than one.

Citation

  1. Stewart JT, French JK, Theroux P, et al: Early noninvasive identification of failed reperfusion after intravenous thrombolytic therapy in acute myocardial infarction. Journal of the American College of Cardiology 1998; 31 (7): 1499-1505
Contributor: Clare Wotton and Bob Phillips, January 2000
Reviewer:

Clinical Question.
Patient myocardial infarction and thrombolytic therapy
Intervention or Exposure assay of creatine kinase-MB fraction
Comparison no assay
Outcome detection of reperfusion failure