Contact Force During VT Ablation

Abstract

O ur understanding of ventricular tachycardia (VT) substrate and mapping has evolved considerably over the past 3 decades. Nonetheless, the outcomes of catheter ablation of scar-mediated VT continue to remain far from perfect. 1 There is no doubt that new advances in VT mapping may help improve the outcomes of catheter ablation. But ultimately it will be the quality of the ablation lesions delivered to the VT substrate that will determine the clinical outcomes. This is important because radiofrequency, the principal source of energy used in VT ablation has been presumed to be a suboptimal energy modality for catheter ablation of scar tissue. A recent study found that in experienced hands using the standard 3.5-mm tip irrigated ablation catheter, elimination of late potentials occurred during only one-third of the radiofrequency applications and electrogram reduction with impedance drop >10 Ω in just half of the radiofrequency lesions during VT ablation.2 Yet, experimental data suggest that presence of scar by itself does not significantly impact lesion size or intramural temperatures when stable ablation catheter-tissue contact is maintained during radiofrequency energy delivery through a needle electrode.3 As such, there seems to be a paradox-scar by itself does not significantly affect radiofrequency lesion size or intramural temperature during ablation, however, the efficacy of ablating scar tissue seems poorer than anticipated! Because tissue contact by way of a needle electrode seems most optimal, one may simply ask whether lack of a stable catheter-tissue contact could provide a plausible explanation for our disappointing clinical outcomes. Article see p 1168Although no concrete data are presently available to support a direct relationship between contact force (CF) and successful elimination of abnormal ventricular electrograms or VT recurrence after catheter ablation, it is conceivable that poor or unstable contact between the ablation catheter tip and myocardial tissue could gravely impact VT ablation outcomes. Sacher et al 4 have previously shown that lesion formation during radiofrequency ablation could significantly improve in nearly one quarter of the applications with the aid of CF feedback. CF also seems to be the principal determinant of epicardial radiofrequency lesion size, steam pops, acute coronary artery, and phrenic nerve injury.5 In fact, ablation using sufficiently high CF has even been shown to create small myocardial radiofrequency lesions at sites covered by thick epicardial fat (>3.5 mm) 5 -that is, epicardial sites at which the heavy fat layer would otherwise seriously impede radiofrequency lesion formation.Although the optimal CF for ventricular mapping and ablation has yet to be determined, in this issue of Circulation: Arrhythmia and Electrophysiology, Jesel et al 6 provide important insights into regional variations in CF and catheter orientation relating to epicardial and endocardial mapping. Briefly, the authors evaluated CF variability using a cooled-tip mapping/ablation cathe...

Epicardial approach for cardiac electrophysiology procedures

“…As such, suboptimal catheter orientation during epicardial mapping was frequently associated with higher CF measurements (ie, 16 g when pointing away from the epicardial surface vs 8 g when directed toward the myocardium). Consequently, this suggests that increased CF during epicardial mapping does not necessarily imply adequate myocardial contact . On the contrary, the application of higher CF epicardially can in fact redirect the ablation catheter away from the myocardium toward extracardiac structures (ie, parietal pericardium, lungs) which could in fact result in undesired complications .…”

“…It is also plausible that such differences could account for certain lesion characteristics considered more typical of epicardial ablation (ie, shallower and wider radiofrequency lesions). Hence, these findings are of key importance indicating that while CF is more relevant to endocardial ablation, catheter orientation is, in fact, more pertinent to the efficacy and safety of epicardial mapping/ablation …”

Bipolar ablation with contact force‐sensing of swine ventricles shows improved acute lesion features compared to sequential unipolar ablation

“…These features are particularly important when ablating thick ventricular myocardium. Electroanatomical mapping allows more precise localization of arrhythmic foci, 5 while contact force (CF)‐sensing technology leads to further improvements in terms of reliability of lesion creation and safety 6 …”

Can Fat Deposition After Myocardial Infarction Alter the Performance of RF Catheter Ablation of Scar‐Related Ventricular Tachycardia?: Results from a Computer Modeling Study

“…The outcomes of catheter ablation of scar-mediated ventricular tachycardia (VT) remain far from perfect. 1 The quality of the ablation lesions delivered to the VT substrate is likely one of the most important factors determining the clinical outcome. One reason may be that radiofrequency (RF) energy represents a suboptimal energy modality for catheter ablation of scar tissue.…”

“…The outcomes of catheter ablation of scar‐mediated ventricular tachycardia (VT) remain far from perfect . The quality of the ablation lesions delivered to the VT substrate is likely one of the most important factors determining the clinical outcome.…”