Cardiac Markers in Myocarditis

cTnI and CK-MB levels were examined from 53 patients with biopsy-verified myocarditis lasting for less than 2 years and from 35 control patients with cardiac insufficiency with some other aetiology 1. cTnI levels were elevated (> = 3.1 mg/mL) in 18 of the examined patients with myocarditis (34%) but CK-MG was elevated (> = 6.7 ng/mL) in only three (6%) (p = 0.001). Four of the control patients (11%) had an elevated cTnI, while none had elevated CK-MB. cTnI levels were highest in patients whose infection had continued for less than one month. The blood samples were collected on biopsy. The effect of biopsy on the results is not discussed.

cTnI was determined in 69 consequent patients with idiopathic acute pericarditis 2. A measurable concentration was found in 48%, and in 22% of the patients the level exceeded the reference value for infarction (1.5 ng/mL). Seven of these 15 patients underwent coronary angiography. The result was normal in all. Elevated cTnI levels were found particularly in younger patients and in those with a recent infection. ST elevation was observed in 93% of the patients with a cTnI concentration above 1.5 ng/mL and in 57% of those with a concentration below this level.

In children, the cutoff point of cTnT level to diagnose acute myocarditis was 0.052 ng/ml (sensitivity, 71%; specificity, 86%) in a group of 43 children with primary myocardial dysfunction, of which 24 patients were diagnosed as acute myocarditis, 19 were idiopathic chronic DCM, and 21 patients had moderate to large ventricular septal defect and congestive heart failure 3.

Eighty patients with clinically suspected myocarditis were screened for creatine kinase (CK) activity, MB isoform of CK (CK-MB) activity and cTnT 4. Endomyocardial biopsy specimens were examined histologically and immunohistologically. cTnT was elevated in 28 of 80 patients with clinically suspected myocarditis, CK in 4 and CK-MB in 1. Histologic analysis alone of the endomyocardial biopsy specimen revealed evidence of myocarditis in only five patients, all with elevated cTnT levels. Twenty-three of 28 patients with elevated cTnT levels had histologically negative findings for myocarditis. Additional immunohistologic analysis revealed evidence of myocarditis in 26 (93%) of 28 patients with elevated cTnT levels and in 23 (44%) of 52 patients with normal cTnT levels. Mean cTnT levels were higher in patients with myocarditis proved histologically or immunohistologically, or both, than in patients without myocarditis (0.59 +/- 1.68 vs. 0.04 +/- 0.05, p < 0.001).

Comment: The quality of evidence is upgraded by strong association.

The following decision support rules contain links to this evidence summary:

• Increased cardiac troponins in young people http://www.ebmeds.org/ebmeds/ebmeds_home.asp?mode=scripts&submode=view&id=scr00467&country=UK

References

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• Soongswang J, Durongpisitkul K, Nana A, Laohaprasittiporn D, Kangkagate C, Punlee K, Limpimwong N. Cardiac troponin T: a marker in the diagnosis of acute myocarditis in children. Pediatr Cardiol 2005 Jan-Feb;26(1):45-9. [PubMed]
• Lauer B, Niederau C, Kühl U, Schannwell M, Pauschinger M, Strauer BE, Schultheiss HP. Cardiac troponin T in patients with clinically suspected myocarditis. J Am Coll Cardiol 1997 Nov 1;30(5):1354-9. [PubMed]