Detection of myocardial injury during radiofrequency catheter ablation by measuring serum cardiac troponin I levels: procedural correlates.

ABSTRACT

OBJECTIVES: In the present prospective controlled study, we measured blood levels of cardiac troponin I (cTnI) in patients undergoing radiofrequency (RF) catheter ablation (RFA), and we sought to investigate the degree of myocardial injury incurred by the application of RF energy and determine its procedural correlates. BACKGROUND: Measurement of serum creatine kinase (CK) levels after RFA may underestimate the degree of myocardial injury due to its thermal inactivation by RFA. Cardiac troponin I is a newer, more specific marker of myocardial injury, which may circumvent this limitation; its use in this setting has rarely been studied. METHODS: In 118 consecutive patients, 67 men and 51 women aged 38 +/- 19 years undergoing RFA for a variety of arrhythmias, cTnI and creatine kinase isoenzyme (CK-MB) levels were measured before, immediately after and 4 to 24 h after RFA. Cardiac troponin I was also measured in 39 patients (control group) having only electrophysiologic studies (EPS) without RFA. RESULTS: All RFA procedures were uncomplicated, lasted 3.2 +/- 2.0 h and included delivery of 16 +/- 22 (median 9) RF current applications. Baseline cTnI levels averaged 0.17 +/- 0.18 ng/ml, rose to 0.88 +/- 1.12 at the end of RFA and to 2.19 +/- 2.46 at 4-24 h later. Creatine kinase isoenzyme was found to be elevated (>6 microg/l) in 32 patients (27%), while cTnI levels were increased (> or =1 ng/ml) in 80 patients (68%) (p = 0.0001). Cardiac troponin I levels correlated with the number of RF lesions applied (r = 0.53, p < 0.0001), the site of RFA, being higher with ventricular > atrial > annular lesions (p = 0.012) and the approach to the mitral annulus (transaortic > transseptal, p = 0.004). In a control group of 39 patients undergoing EPS, all but one patient had normal cTnI or CK-MB. CONCLUSIONS: The degree of myocardial injury incurred by RFA is far more accurately assessed by cTnI levels rather than by CK-MB measurements. Cardiac troponin I levels correlate with the number of RF lesions applied, the site of RFA and the approach to the mitral annulus.