title: Phased-array intracardiac echocardiography for defining cavotricuspid isthmus anatomy during radiofrequency ablation of typical atrial flutter.
abstract: BACKGROUND
  Cavotricuspid isthmus (CTI) topography includes ridges, pouches, recesses, and trabeculations. These features may limit the success of radiofrequency ablation (RFA) of typical atrial flutter (AFL). The aim of this study was to assess the utility of phased-array intracardiac echocardiography (ICE) for imaging the CTI and monitoring RFA of AFL.
  
  
  RESULTS
  Fifteen patients (mean age 64 +/- 9 years) underwent ICE assessment (imaging frequency 7.5-10 MHz) before and after RFA of AFL. The ICE catheter was positioned at the inferior vena cava-right atrial junction and the following parameters were measured: (1) CTI length from the tricuspid valve to the eustachian ridge; (2) extent of CTI pouching; and (3) thickness pre/post RFA of the anterior, mid, and posterior CTI. CTI length was 35 +/- 6 mm at end-ventricular systole but shorter (30 +/- 6 mm) and more pouched at end-ventricular diastole (P = 0.02). A pouch or recess was seen in 11 of 15 patients (mean depth 6 +/- 2 mm). The septal CTI was more pouched than the lateral CTI, but the latter had more prominent trabeculations. Trabeculations were seen in 10 of 15 patients, and at these locations the CTI was 4.6 +/- 1 mm thick. Anterior, mid, and posterior CTI thickness pre-RFA was 4.1 +/- 0.8, 3.3 +/- 0.5, and 2.7 +/- 0.9 mm, respectively (P < 0.001 by analysis of variance). ICE guided RFA away from unfavorable CTI features (recesses/thick trabeculations). RFA applications created discrete CTI lesions that coalesced, forming diffuse CTI swelling. Post-RFA thickness was as follows: anterior 4.8 +/- 0.8 mm (P = NS vs pre); mid 3.8 +/- 0.8 mm (P = 0.05 vs pre); and posterior 3.8 +/- 0.8 mm (P = 0.02 vs pre).
  
  
  CONCLUSIONS
  Phased-array ICE permits novel real-time CTI imaging with excellent endocardial resolution and may facilitate RFA of AFL.
authors.affiliation: Department of Cardiology, The Royal Melbourne Hospital, Melbourne, Australia.
authors.forename: Joseph B
authors.initials: JB
authors.lastname: Morton
authors.forename: Prashanthan
authors.initials: P
authors.lastname: Sanders
authors.forename: Neil C
authors.initials: NC
authors.lastname: Davidson
authors.forename: Paul B
authors.initials: PB
authors.lastname: Sparks
authors.forename: Jitendra K
authors.initials: JK
authors.lastname: Vohra
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Kalman
mesh_terms: D000368:Aged; D001158:Arteries / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000473:pathology; D001282:Atrial Flutter / Q000601:surgery*; D017115:Catheter Ablation; D003331:Coronary Vessels / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000473:pathology; D004452:Echocardiography; D022062:Electrophysiologic Techniques, Cardiac; D004699:Endocardium / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000473:pathology; D005260:Female; D006325:Heart Atria / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000473:pathology; D006329:Heart Conduction System / Q000033:anatomy & histology* / Q000000981:diagnostic imaging* / Q000473:pathology; D006346:Heart Septum / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000473:pathology; D006352:Heart Ventricles / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000473:pathology; D006801:Humans; D007430:Intraoperative Care; D008297:Male; D008875:Middle Aged; D016896:Treatment Outcome; D014261:Tricuspid Valve / Q000033:anatomy & histology* / Q000000981:diagnostic imaging* / Q000473:pathology