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

Abstract

OBJECTIVESIn 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.BACKGROUNDMeasurement 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.METHODSIn 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.RESULTSAll 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 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 a control group of 39 patients undergoing EPS, all but one patient had normal cTnI or CK-MB.CONCLUSIONSThe 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.