Abstract 10606: The Increase of Myocardial Echogenicity Using Intracardiac Echography During Radiofrequency Ablation is an Effective Ablation Indicator

Abstract

Introduction: The increase of myocardial echogenicity (iME) is sometimes observed by intracardiac echography (ICE) during radiofrequency ablation (RFA), and the phenomenon has also been reported as a predictor of steam pop. However, the mechanism of iME caused by RFA remains unclear. Methods: We retrospectively studied 112 consecutive patients (age 70±9 years, 74 male) who underwent cavotricuspid isthmus (CTI) ablation. The changes in myocardial tissue during RFA were observed using ICE in 5.3 ± 1.4 points in each patient. 415 out of 590 ablation points were evaluable with ICE, and the iME during RFA were classified into three degrees (grade I: no change, II: mild, III: high brightness) by three independent observers who did not know clinical data. The voltage of myocardial amplitude and the myocardial wall thickness before and after RFA, and the lesion size index (LSI) incorporating contact force were measured at all RFA points. Results: RFA points were classified into 128 grade I of iME, 150 grade II, and 137 grade III. The iME during RFA were associated with reduced voltage of myocardial amplitude (grade I -0.22±0.44mV, II -0.29±0.47mV, III -0.38±0.47mV, P=0.0147), decreased rate of the voltage (grade I -14%, II -25%, III -44%, P=0.0131), and higher LSI (grade I 4.5±0.8mV, II 4.7±0.8mV, III 4.8±0.8, P=0.0207) (Figure). The higher LSI was associated with the decreased rate of the voltage (P=0.0491), but not with the voltage change of myocardial amplitude. On multivariate analysis, the iME during RFA was independently associated with the decreased rate of the voltage (P=0.0214). The iME was not related to the change in myocardial wall thickness before and after RFA, ablation sites (near tricuspid annulus side, middle part, or inferior vena cava side), and morphology of cavo-tricuspid isthmus. No steam pop phenomenon was observed. Conclusions: The iME during RFA is related to the decrease in myocardial amplitude due to RFA, and possibly be an effective ablation indicator.