Irrigated catheter ablation of intraatrial reentrant tachycardia and evaluation of new technology

Abstract

The problem of intraatrial reentrant tachycardia in patients who have undergone surgical repair or palliation of complex congenital heart disease is well known and has been the focus of much effort on the part of pediatric electrophysiologists and others interested in the problem. We have understood for some time that nearly all of these atrial arrhythmias are macroreentrant in nature, with longer cycle lengths than seen in typical isthmus-based flutter. We also know that it is feasible, in nearly all cases, to understand these circuits using a combination of entrainment pacing and three-dimensional electroanatomic mapping. Experience has shown that there is not an infinite variety in the circuits that are defined. Circuits in such patients tend to include the cavotricuspid isthmus or are related to atriotomy sites. Ablation sites that are successful usually address the cavotricuspid isthmus or corridors between atriotomy sites and adjacent anatomic features, such as the AV valve annulus, inferior vena cava, and superior vena cava. 1 Chan D.P. Van Hare G.F. Mackall J.A. Carlson M.M. Waldo A.L. Importance of atrial flutter isthmus in postoperative intra-atrial reentrant tachycardia. Circulation. 2000; 102: 1283-1289 Crossref PubMed Scopus (154) Google Scholar , 2 Collins K.K. Love B.A. Walsh E.P. Saul J.P. Epstein M.R. Triedman J.K. Location of acutely successful radiofrequency catheter ablation of intraatrial reentrant tachycardia in patients with congenital heart disease. Am J Cardiol. 2000; 86: 969-974 Abstract Full Text Full Text PDF PubMed Scopus (174) Google Scholar One exception, of course, is the situation of the atriopulmonary connection Fontan, in which circuits may not be macroreentrant but instead may involve small corridors of tissue within areas of myocardial scar, as shown by Nakagawa et al. 3 Nakagawa H. Shah N. Matsudaira K. Overholt E. Chandrasekaran K. Beckman K.J. Spector P. Calame J.D. Rao A. Hasdemir C. Otomo K. Wang Z. Lazzara R. Jackman W.M. Characterization of reentrant circuit in macroreentrant right atrial tachycardia after surgical repair of congenital heart disease isolated channels between scars allow “focal” ablation. Circulation. 2001; 103: 699-709 Crossref PubMed Scopus (346) Google Scholar Despite a rather good understanding of the anatomic basis for these reentrant rhythms, the results of catheter ablation have been disappointing when viewed through the lens of our current high success rates for ablation of simpler substrates. 4 Kugler J.D. Danford D.A. Houston K.A. Felix G. Pediatric radiofrequency catheter ablation registry success, fluoroscopy time, and complication rate for supraventricular tachycardia comparison of early and recent eras. J Cardiovasc Electrophysiol. 2002; 13: 336-341 Crossref PubMed Scopus (239) Google Scholar , 5 Van Hare G.F. Javitz H. Carmelli D. Saul J.P. Tanel R.E. Fischbach P.S. Kanter R.J. Schaffer M. Dunnigan A. Colan S. Serwer G. Pediatric Electrophysiology SocietyProspective assessment after pediatric cardiac ablation demographics, medical profiles, and initial outcomes. J Cardiovasc Electrophysiol. 2004; 15: 759-770 Crossref PubMed Scopus (292) Google Scholar One potential reason, addressed in Triedman et al 6 Triedman J.K. DeLucca J.M. Alexander M.E. Berul C.I. Cecchin F. Walsh E.P. Prospective trial of electroanatomically guided, irrigated catheter ablation of atrial tachycardia in patients with congenital heart disease. Heart Rhythm. 2005; 2: 700-705 Abstract Full Text Full Text PDF PubMed Scopus (70) Google Scholar in this issue of Heart Rhythm, is the difficulty in forming lesions in low-flow situations. When there is inadequate tip cooling by blood flow, the temperatures achieved with radiofrequency (RF) application may be very high despite very low power settings, limiting lesion size. 7 Blaufox A.D. Numan M.T. Laohakunakorn P. Knick B. Paul T. Saul J.P. Catheter tip cooling during radiofrequency ablation of intra-atrial reentry effects on power, temperature, and impedance. J Cardiovasc Electrophysiol. 2002; 13: 783-797 Crossref PubMed Scopus (30) Google Scholar Use of cooled-tip catheter technology allows for delivery of greater power in these situations, with concomitantly larger and deeper lesions. The study by Triedman et al is a randomized prospective trial comparing conventional RF ablation to irrigated-tip ablation. The study uses a crossover design. The results of this study are quite encouraging, demonstrating convincingly that it is possible to deliver more power at lower temperature using irrigated-tip ablation, with a higher overall success of ablation. Because this study was performed with strict adherence to a somewhat less aggressive protocol defined by the manufacturer, better results might be obtainable using higher tip temperatures, as the authors point out.