Creation of Continuous and Transmural Radiofrequency Lesions

HomeCirculation: Arrhythmia and ElectrophysiologyVol. 11, No. 4Creation of Continuous and Transmural Radiofrequency Lesions Free AccessEditorialPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessEditorialPDF/EPUBCreation of Continuous and Transmural Radiofrequency Lesions Hiroshi Nakagawa, MD, PhD Hiroshi NakagawaHiroshi Nakagawa Heart Rhythm Institute, University of Oklahoma Health Sciences Center, Oklahoma City. Originally published13 Apr 2018https://doi.org/10.1161/CIRCEP.118.006378Circulation: Arrhythmia and Electrophysiology. 2018;11:e006378See Article by Whitaker et alContinuous and transmural ablation lesions are desired for pulmonary vein isolation and atrial linear ablation (such as the liner lesions across the left atrial roof and mitral isthmus) to reduce the recurrence of atrial fibrillation and atrial tachycardia after ablation.1–3 During radiofrequency ablation, active electrode cooling by saline irrigation allows the use of significant radiofrequency power for longer application times to produce deeper and wider lesions, while reducing the occurrence of thrombus formation and an impedance rise.4–6 Ablation lesion size (depth and diameter) increases with increasing 3 dominant variables: contact force, radiofrequency power, and radiofrequency application time.7–9In this issue of Circulation: Arrhythmia and Electrophysiology, Whitaker et al10 assessed the performance of the lesion index (LSI), a mathematical measure to predict radiofrequency lesion size based on contact force, radiofrequency current, and application time,11–14 to facilitate continuous, transmural lesions in the right atrium using a swine model. In isolated tissue preparations, a section of bovine right ventricular free wall was placed in a modified saline tank (37°C and electrical conductivity 6.5–7.0 mS/cm, similar to human blood). Ablation was performed at 20 or 25 W with the electrode positioned perpendicular to the endocardium at a contact force of 10, 20, or 30g with a target LSI of 4, 5, or 6 Units. Radiofrequency application time was variable, until the target LSI was achieved. Side-by-side radiofrequency lesions were created with a separation of equal to the achieved LSI (LSI+0 mm, LSI+2 mm, LSI+4 mm, or LSI+6 mm). With radiofrequency power at 25 W and the target LSI of 5 U, the incidence of gaps between the adjacent lesions significantly increased with increasing the interlesion distances (gap incidence: 13% for LSI+0 mm, 21% for LSI+2 mm, 59% for LSI+4 mm, and 96% for LSI+6 mm).10In previous studies on radiofrequency ablation (testing in vivo) using a contact force sensing catheter (Thermocool SmartTouch; Biosense-Webster, Inc)15–19 in the canine right and left ventricles, we found that lesion depth and diameter were described accurately by a logarithmic function of the product of contact force (grams), radiofrequency power (Watts), and application time (seconds), which is referred to as the Force–Power–Time Index Formula (Ablation Index; Biosense Webster, Inc).15,16 Using a wide range of contact force (5–50g) and radiofrequency power (25–45 W), the Force–Power–Time Index Formula prospectively predicts lesion depth (±1 mm accuracy) and diameter (±2 mm accuracy) in the beating canine hearts.15,16 The combination of greater contact force and higher radiofrequency power application rapidly reached the target lesion depth (predicted by the algorithm), whereas the combination of lower contact force and lower radiofrequency power application required a longer radiofrequency time.15 Radiofrequency ablation lesions usually exhibit an ellipsoid geometry with a diameter ≈40% to 70% greater than the depth, similar to the lesion geometry shown in the authors' Figure 2B and the Figure ID in the Data Supplement.10 The maximum lesion depth is usually located at the center of the lesion. Therefore, to create continuous radiofrequency lesions with similar lesion depth (transmural lesions along the liner ablation), significant overlap of adjacent ablation lesions is required, as shown in their Figure 2C.10 Saline irrigation cools the electrode–tissue interface and significantly reduces the risk of thrombus formation during radiofrequency applications. However, the surface cooling by saline irrigation results in a smaller surface lesion diameter, and the maximum lesion diameter is usually located 2 to 3 mm below the surface.4–6 Insufficient overlap between 2 adjacent lesions may result in a gap located at the surface of the ablation lesions, because of a smaller surface diameter.To facilitate the continuous and transmural lesions, the extent of the lesion overlap between the adjacent lesions should be determined based on the lesion geometry. However, the authors did not provide the lesion size (maximum depth, maximum diameter, surface diameter, and depth of maximum diameter) for separate (notoverlapped) lesions with the target LSI of 4, 5, and 6 U. In the Figure IC in the Data Supplement, these lesions were classified as continuous.10 However, the lesion depth is shallow at the connection site of the 2 adjacent lesions, which may prevent transmural lesions along the entire length of linear lesions. Moreover, there is a gap located at the surface, resulting from the smaller surface diameter (the maximum diameter is located below the surface).The authors also performed an in vivo beating heart study using a contact force–sensing catheter (TactiCath; Abbott, Inc)10–14 in a swine model. Endocardial linear ablation was performed in the right atrium at 25 W (saline irrigation of 17 mL/min and contact force of 10–20g) with a target LSI of 5 U. The ablation electrode was moved to the adjacent site with a separation of LSI+0 mm (group 1), LSI+2 mm (group 2), or LSI+4 mm (group 3). In the 7 swine, 149 discrete radiofrequency lesions were created to form a total of 18 linear ablations (2–3 lines per animals). The mean lesion separation and ΔLSI (the difference between the interlesion distance and the mean LSI achieved adjacent lesions) were significantly greater in group 2 (6.32 and 1.45 mm, respectively) and group 3 (7.42 and 2.70 mm, respectively) than group 1 (4.24 and 0.12 mm, respectively). As expected, the incidence of histological gaps was significantly greater in group 3 (group 1: 4 gaps in 69 catheter movements, 5.8%; group 2: 7 gaps in 33 catheter movements, 21.2%; and group 3: 15 gaps in 23 catheter movements, 65.2%). In lines without gaps, the mean maximum ΔLSI per line was 1.50, which was significantly lower than in those lines with one or more gaps in which the mean maximum observed ΔLSI per line was 4.91 (P=0.008).To assess the wall thickness in the right atrium, ECG-gated, contract-enhanced cardiac computed tomography was obtained in each swine. There was a statistically significant relationship between the cardiac computed tomography–derived wall thickness and the histological measurement of wall thickness. In this study, the majority of atrial lesions were created along the thin wall (<3 mm). However, the target LSI of 5 U was utilized along the atrial linear lesions, which may be higher than desired, especially in the regions with <1 to 2 mm wall thickness. Ideally, to reduce or eliminate the risk of collateral damage (such as esophageal injury and phrenic nerve palsy), the target lesion depth should be selected based on the estimated wall thickness at each ablation site. In contrast, sites with thicker atrial myocardium (such as along the Buchman bundle, left atrial appendage ridge, or thick pectinate muscles within the sub-Eustachian isthmus), a greater LSI should be targeted. The ΔLSI to avoid gaps along the linear lesions may differ with different target LSI values. To facilitate the creation of continuous and transmural atrial lesions, target lesion depth and diameter (including the extent of overlap lesions) should be selected based on the estimated wall thickness at each ablation site.Sources of FundingDr Nakagawa has received research grant support from Biosense Webster, Inc, Boston Scientific Corporation, and Affera, Inc.DisclosuresDr Nakagawa served as a consultant for Biosense Webster, Inc, Boston Scientific Corporation, and Affera, Inc.FootnotesThe opinions expressed in this article are not necessarily those of the editors or of the American Heart Association.http://circep.ahajournals.orgHiroshi Nakagawa, MD, PhD, Heart Rhythm Institute, University of Oklahoma Health Sciences Center, 800 Stanton L Young Blvd, Suite 5400, AAT Room 5466, Oklahoma City, OK 73104. E-mail [email protected]References1. Ouyang F, Tilz R, Chun J, Schmidt B, Wissner E, Zerm T, Neven K, Köktürk B, Konstantinidou M, Metzner A, Fuernkranz A, Kuck KH. Long-term results of catheter ablation in paroxysmal atrial fibrillation: lessons from a 5-year follow-up.Circulation. 2010; 122:2368–2377. doi: 10.1161/CIRCULATIONAHA.110.946806.LinkGoogle Scholar2. Hussein AA, Saliba WI, Martin DO, Bhargava M, Sherman M, Magnelli-Reyes C, Chamsi-Pasha M, John S, Williams-Adrews M, Baranowski B, Dresing T, Callahan T, Kanj M, Tchou P, Lindsay BD, Natale A, Wazni O. Natural history and long-term outcomes of ablated atrial fibrillation.Circ Arrhythm Electrophysiol. 2011; 4:271–278. doi: 10.1161/CIRCEP.111.962100.LinkGoogle Scholar3. Medi C, Sparks PB, Morton JB, Kistler PM, Halloran K, Rosso R, Vohra JK, Kumar S, Kalman JM. Pulmonary vein antral isolation for paroxysmal atrial fibrillation: results from long-term follow-up.J Cardiovasc Electrophysiol. 2011; 22:137–141. doi: 10.1111/j.1540-8167.2010.01885.x.MedlineGoogle Scholar4. Nakagawa H, Yamanashi WS, Pitha JV, Arruda M, Wang X, Ohtomo K, Beckman KJ, McClelland JH, Lazzara R, Jackman WM. Comparison of in vivo tissue temperature profile and lesion geometry for radiofrequency ablation with a saline-irrigated electrode versus temperature control in a canine thigh muscle preparation.Circulation. 1995; 91:2264–2273.LinkGoogle Scholar5. Nakagawa H, Wittkampf FH, Yamanashi WS, Pitha JV, Imai S, Campbell B, Arruda M, Lazzara R, Jackman WM. Inverse relationship between electrode size and lesion size during radiofrequency ablation with active electrode cooling.Circulation. 1998; 98:458–465.LinkGoogle Scholar6. Wittkampf FH, Nakagawa H. RF catheter ablation: lessons on lesions.Pacing Clin Electrophysiol. 2006; 29:1285–1297. doi: 10.1111/j.1540-8159.2006.00533.x.CrossrefMedlineGoogle Scholar7. Avitall B, Mughal K, Hare J, Helms R, Krum D. The effects of electrode-tissue contact on radiofrequency lesion generation.Pacing Clin Electrophysiol. 1997; 20(12pt 1):2899–2910.CrossrefMedlineGoogle Scholar8. Yokoyama K, Nakagawa H, Shah DC, Lambert H, Leo G, Aeby N, Ikeda A, Pitha JV, Sharma T, Lazzara R, Jackman WM. Novel contact force sensor incorporated in irrigated radiofrequency ablation catheter predicts lesion size and incidence of steam pop, and thrombus.Circ Arrhyth Electrophysiol. 2009; 2:41–49.LinkGoogle Scholar9. Ikeda A, Nakagawa H, Lambert H, Shah DC, Fonck E, Yulzari A, Sharma T, Pitha JV, Lazzara R, Jackman WM. Relationship between catheter contact force and radiofrequency lesion size and incidence of steam pop in the beating canine heart: electrogram amplitude, impedance, and electrode temperature are poor predictors of electrode-tissue contact force and lesion size.Circ Arrhythm Electrophysiol. 2014; 7:1174–1180. doi: 10.1161/CIRCEP.113.001094.LinkGoogle Scholar10. Whitaker J, Fish J, Harrison J, Chubb H, Williams SE, Fastl T, Corrado C, Zaen JV, Gibbs J, O'Neill L, Mukherjee R, Rittey D, Thorsten J, Donskoy E, Sohal M, Rajani R, Niederer S, Wright M, O'Neill MD. Lesion index–guided ablation facilitates continuous, transmural, and durable lesions in a porcine recovery model.Circ Arrhythm Electrophysiol. 2018; 11:e005892. doi: 10.1161/CIRCEP.117.005892.LinkGoogle Scholar11. Shah DC, Lambert H, Nakagawa H, Langenkamp A, Aeby N, Leo G. Area under the real-time contact force curve (force-time integral) predicts radiofrequency lesion size in an in vitro contractile model.J Cardiovasc Electrophysiol. 2010; 21:1038–1043. doi: 10.1111/j.1540-8167.2010.01750.x.CrossrefMedlineGoogle Scholar12. Lambert H, Olstad SJ, Fremont OB. Prediction of atrial wall electrical reconnection based on contact force measured during RF ablation.US Patent US20120209260A1. 2012.Google Scholar13. Kuck KH, Reddy VY, Schmidt B, Natale A, Neuzil P, Saoudi N, Kautzner J, Herrera C, Hindricks G, Jaïs P, Nakagawa H, Lambert H, Shah DC. A novel radiofrequency ablation catheter using contact force sensing: toccata study.Heart Rhythm. 2012; 9:18–23. doi: 10.1016/j.hrthm.2011.08.021.CrossrefMedlineGoogle Scholar14. Kautzner J, Neuzil P, Lambert H, Peichl P, Petru J, Cihak R, Skoda J, Wichterle D, Wissner E, Yulzari A, Kuck KH. EFFICAS II: optimization of catheter contact force improves outcome of pulmonary vein isolation for paroxysmal atrial fibrillation.Europace. 2015; 17:1229–1235. doi: 10.1093/europace/euv057.CrossrefMedlineGoogle Scholar15. Nakagawa H, Ikeda A, Govari A, Papaioannou T, Constantine G, Bar-Tal M, Silberschein E, Saba-Karen E, Rubissa A, Sharma T, Pitha J, Lazzara R, Jackman WM. Prospective study to test the ability to create RF lesions at predicted depth and diameter using a new formula incorporating contact force, radiofrequency power and application time (Force-Power-Time Index) in the beating canine heart.Heart Rhythm. 2014: 11:S548.Google Scholar16. Bar-Tal M, Silberschein E, Rubissa A, Constantine GF, Nakagawa H. Estimation of lesion size.US Patent US 2017/0014181 A1.Google Scholar17. El Haddad M, Taghji P, Phlips T, Wolf M, Demolder A, Choudhury R, Knecht S, Vandekerckhove Y, Tavernier R, Nakagawa H, Duytschaever M. Determinants of acute and late pulmonary vein reconnection in contact force - guided pulmonary vein isolation. Identifying the weakest link in the ablation chain.Circ Arrhythmia Electrophysiol. 2017; 10:e004867. doi: 10.1161/CIRCEP.116.004867.LinkGoogle Scholar18. Natale A, Reddy VY, Monir G, Wilber DJ, Lindsay BD, McElderry HT, Kantipudi C, Mansour MC, Melby DP, Packer DL, Nakagawa H, Zhang B, Stagg RB, Boo LM, Marchlinski FE. Paroxysmal AF catheter ablation with a contact force sensing catheter: results of the prospective, multicenter SMART-AF trial.J Am Coll Cardiol. 2014; 64:647–656. doi: 10.1016/j.jacc.2014.04.072.CrossrefMedlineGoogle Scholar19. Jarman JWE, Panikker S, DAS M, Wynn GJ, Ullah W, Kontogeorgis A, Haldar SK, Patel PJ, Hussain W, Markides V, Gupta D, Schilling RJ, Wong T. Relationship between contact force sensing technology and medium-term outcome of atrial fibrillation ablation: a multicenter study of 600 patients.J Cardiovasc Electrophysiol. 2015; 26:378–384. doi: 10.1111/jce.12606.CrossrefMedlineGoogle Scholar Previous Back to top Next FiguresReferencesRelatedDetailsCited By Mujović N, Marinković M, Marković N, Kocijančić A, Kovačević V, Vučićević V, Mujović N and Potpara T (2023) Risk factors for late reconnections after circumferential pulmonary vein isolation guided by lesion size index – Data from repeat invasive electrophysiology procedure, Frontiers in Cardiovascular Medicine, 10.3389/fcvm.2022.986207, 9 April 2018Vol 11, Issue 4 Advertisement Article InformationMetrics © 2018 American Heart Association, Inc.https://doi.org/10.1161/CIRCEP.118.006378PMID: 29654135 Originally publishedApril 13, 2018 Keywordscatheter ablationtachycardia, ventricularEditorialsatrial fibrillationpulmonary veinPDF download Advertisement SubjectsAtrial FibrillationCatheter Ablation and Implantable Cardioverter-Defibrillator