title: Loss of pace capture after radiofrequency application predicts the formation of uniform transmural lesions.
abstract: OBJECTIVE
  Lesion transmurality is critical to procedural success in radiofrequency catheter ablation. We sought to determine whether loss of pace capture (PC) with high-output unipolar and/or bipolar pacing predicts the formation of uniform transmural lesions.
  
  
  RESULTS
  Ten juvenile swine were anaesthetized and prepped under sterile conditions. Seventy-seven isolated radiofrequency applications (RFAs) using a 3.5 mm tip-irrigated catheter were available for analysis. Pace capture was assessed before and after RFA at 10 mA/2 ms and catheter stability verified with a three-dimensional mapping system. Pace capture was defined as 1 : 1 or intermittent local capture per paced beat. Myocardial contact and catheter orientation were assessed using intracardiac echo. Endocardial and epicardial lesion areas were measured after sacrifice using 2,3,5-triphenyltetrazolium chloride staining. A uniform transmural lesion was defined as an epicardial-to-endocardial surface ratio (epi/endo) ≥ 76%. Seventy-four per cent of lesions were transmural and 55.8% of lesions had an epi/endo ratio ≥ 76%. In all, 79.2% of lesions associated with loss of bipolar PC were uniform whereas 20.8% of lesions with loss of bipolar PC were non-uniform (P = 0.006). Loss of bipolar PC was associated with higher mean epicardial/endocardial ratio compared with lesions with persistent PC (P = 0.019). Echocardiographic evidence of optimal catheter contact during RFA improved the predictive accuracy of uniform lesion formation when loss of bipolar PC was noted after RFA.
  
  
  CONCLUSIONS
  Loss of bipolar PC after RFA is associated with the formation of uniform lesions in atrial tissue. Optimal catheter contact further improves the predictive accuracy associated with loss of PC.
authors.affiliation: Department of Cardiology, Brigham and Women's Hospital, 75 Francis Street, Boston, MA 02115, USA. ioanna.kosmidou@piedmont.org
authors.forename: Ioanna
authors.initials: I
authors.lastname: Kosmidou
authors.forename: Haley
authors.initials: H
authors.lastname: Houde-Walter
authors.forename: Lori
authors.initials: L
authors.lastname: Foley
authors.forename: Gregory
authors.initials: G
authors.lastname: Michaud
mesh_terms: D000818:Animals; D062906:Cardiac Catheters; D002304:Cardiac Pacing, Artificial; D017115:Catheter Ablation / Q000295:instrumentation; D022062:Electrophysiologic Techniques, Cardiac; D006325:Heart Atria / Q000503:physiopathology / Q000601:surgery; D006329:Heart Conduction System / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D023421:Models, Animal; D011237:Predictive Value of Tests; D013194:Staining and Labeling; D013552:Swine; D016896:Treatment Outcome; D014463:Ultrasonography