Improved Detection of Radiofrequency Current- Induced Minor Myocardial Injury by Cardiac Troponin T Measurement

KOSIT SRIBHEN, M.D.*, KIERTUAI BHURIPANYO, M.D.**, ONGKARN RAUNGRATANAAMPORN, M.D.**, SUDCHAREE KIARTIVICH, M.Sc.*, WATTANA LEOWATTANA, M.D.*, SUPHACHAI CHAITHIRAPHAN, M.D., F.A.C.P., F.R.A.C.P., F.A.C.C.**

Affiliation : * Department of Clinical Pathology, ** Her Majesty's Cardiac Centre, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok l 0700. Thailand.

AbstractTranscatheter radiofrequency current application in patients with cardiac arrhythmias was reported to be associated with a low rate of an increase in the activity of enzyme creatine kinase (CK) and CK-MB isoenzyme. As the novel heart-specific protein troponin T (cTnT) was shown to be superior to CK and CK-MB in detecting small damage to myocardial tissue in various clinical situations including unstable angina, a comparison of the diagnostic efficiency of these marker proteins to detect myocardial damage was made in 34 patients (mean age 38.3 ± 15.6 years) undergoing radiofrequency (RF) catheter ablation of accessory pathways (n = 17) and atrio- ventricular nodal reentrant tachycardia (n = 17). Serial measurements of total CK and CK-MB activity before and every 8 hours for 24 hours after ablative procedure were performed with enzymatic and immunoinhibition method, respectively, using automated chemical analyLer Hitachi 717. Serum concentration of cTnT was determined by one-step sandwich ELISA performed on ES 300 analyzer (Boehringer Mannheim).
With a median of 7.0 (range 1-39) RF current pulses only 12 (35Gk) and I 0 (2Q'7c) of 34 patients showed an increase above the upper limit of normal CK and CK-MB activity, respec- tively. The peak activity of CK (mean peak= 285.8 ± 517.7 lUlL) occurred at a variable time that infrequently coincided with those of peak CK-MB activity (23.1 ± 8.0 IU/L). By contrast. all except 4 (88%) of 34 patients exhibited a distinct elevation of cTnT concentration (mean peak = 0.56 ± 0.63 ng/ml), with almost all (33) of these 34 patients showed an early peak value at 8 hours postprocedural. There was, on the average, a small but distinct higher relative increase (5.6 times) in cTnT concentration from the upper limit of reference range compared with those of CK (1.5 times) and CK-MB peak activity (0.9 time).
In conclusion, cTnT exhibited a minor but distinst elevation in its concentration and demonstrated a higher rate and magnitude of increase following radiofrequency current applica- tion than the conventional CK and CK-MB isoenzyme. Measurements of cTnT serum concentra- tion may thus provide a useful test method for assessing the effect of the new transcatheter ablation procedures on myocardial tissue.

Keywords : Cardiac Troponin T Measurement, Minor Myocardial Injury, Radiofrequency Current- Induction, Improved Detection

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