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

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 RF may underestimate the degree of myocardial injury due to its thermal inactivation by RFA. Cardiac troponin I is 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 RF for 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 RF 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 RF and to 2.19 ± 2.46 at 4–24 h later. Creatine kinase isoenzyme was found to be elevated (>6 μg/l) in 32 patients (27%), while cTnI levels were increased (≥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 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 RF 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 RF and the approach to the mitral annulus.