941

Regional Difference of Optimal Contact Force to Prevent Acute Pulmonary Vein Reconnection During Radiofrequency Catheter Ablation for Atrial Fibrillation YOHEI SOTOMI, M.D.,∗ TAKAYUKI KIKKAWA,† KOICHI INOUE, M.D., Ph.D.,∗ KOJI TANAKA, M.D.,∗ YUKO TOYOSHIMA, M.D.,∗ TAKAFUMI OKA, M.D., Ph.D.,∗ NOBUAKI TANAKA, M.D.,∗ YOICHI NOZATO, M.D.,∗ YOSHIYUKI ORIHARA, M.D.,∗ KATSUOMI IWAKURA, M.D., Ph.D.,∗ YASUSHI SAKATA, M.D., Ph.D.,‡ and KENSHI FUJII, M.D., Ph.D.∗ From the ∗ Department of Cardiology, Sakurabashi-Watanabe Hospital, Osaka, Japan; †Department of Medical Engineering, Sakurabashi-Watanabe Hospital, Osaka, Japan; and ‡Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Osaka, Japan

Optimal Contact Force for AF Ablation. Background: Regional differences in optimal contact force (CF) to prevent acute pulmonary vein reconnection (APVR) during catheter ablation for atrial fibrillation (AF) remain unclear. Objective: The purpose of this study was to evaluate regional difference in optimal CF during AF ablation. Methods: This single-center observational study evaluated data from 57 consecutive drug-refractory AF patients (mean age, 62 ± 11 years; 43 males) who underwent initial pulmonary vein isolation (PVI) using R the THERMOCOOL SMARTTOUCHTM (Biosense Webster, Diamond Bar, CA, USA) catheter from June to August 2013. APVR was defined as the time-dependent reconnection >20 minutes after initial PVI and/or reconnection evoked by intravenous adenosine administration (20 mg). Point-by-point relationships between the reconnected points and their CF values were evaluated. Results: Total 72 gaps causing APVR were observed. Of a total of 4,421 ablation points, 285 (6.4%) were associated with APVR. The average CF value of the points with APVR was significantly lower than that of those without (APVR vs. no APVR; 7.5 ± 6.7 g vs. 9.9 ± 8.4 g; P < 0.0001). The areas under the curve and optimal CF values differed between segments (range 0.593–0.761 and 10–22 g, respectively). The optimal CF value was highest in bottom of the right PV and posterosuperior right PV segments (22 g) and lowest in posteroinferior right PV segment (10 g). Conclusions: There was a regional difference in optimal CF values to prevent APVR, and the optimal CF value to prevent APVR with >95% probability was 10–22 g, depending on the individual peri-PV segments. (J Cardiovasc Electrophysiol, Vol. 25, pp. 941-947, September 2014) acute pulmonary vein reconnection, atrial fibrillation, catheter ablation, contact force, pulmonary vein isolation Introduction Pulmonary vein isolation (PVI) has become the cornerstone of contemporary catheter ablation procedures for both paroxysmal and persistent atrial fibrillation (AF) and has evolved into an increasingly safe and efficacious procedure.1 Despite significant improvements made in catheter ablation strategies to treat AF in recent years, recurrent arrhythmia remains a concern. Insufficient radiofrequency (RF) ablation of lesions results in electrical PV reconnection, which is the primary cause of recurrent arrhythmia after ablation for AF.2-4 A large number of factors, including respiration, RF power and duration, electrode temperature and size, irrigation, local No disclosures. Address for correspondence: Koichi Inoue, M.D., Ph.D., Department of Cardiology, Sakurabashi Watanabe Hospital, 2-4-32, Umeda, Kita-ku, Osaka 530-0001, Japan. Fax: 8-166-341-0785; E-mail: [email protected] Manuscript received 26 February 2014; Revised manuscript received 10 April 2014; Accepted for publication 17 April 2014. doi: 10.1111/jce.12443

blood flow, and catheter–tissue contact, collectively interact to influence the volume of RF lesions during ablation.5-7 Among these factors, catheter–tissue contact force (CF) is a critical determinant of RF ablation lesion size, and insufficient CF can lead to ineffective RF delivery and nonuniform lesion formation.8-10 A novel CF-sensing ablation catheter is now available, which allows real-time CF assessment between the catheter tip and target tissue by integrating a force sensor at the distal tip of an open-irrigated RF catheter.11-13 Recent results with this technology showed that low catheter–tissue CF resulted in gap formation and PV reconnection in acute- and medium-term follow-up after AF ablation.12,14-17 According to these reports, arrhythmia control is best achieved when lesion ablation is performed with an average CF >16–20 g. However, the regional difference of optimal CF to prevent acute pulmonary vein reconnection (APVR) was not evaluated. Our hypothesis proposes that optimal CF varies regionally because of anatomical differences. To evaluate this hypothesis, we analyzed the point-by-point relationship between APVR and CF and calculated the optimal CF to prevent APVR in each peri-PV segment.

942

Journal of Cardiovascular Electrophysiology

Vol. 25, No. 9, September 2014

Figure 1. Prevalence of acute pulmonary vein (PV) reconnection and average contact force (CF) in the segmented PV model. Each ipsilateral pair of PV antra was divided into 7 segments: roof, anterosuperior, anteroinferior, bottom, posteroinferior, posterosuperior, and carina. For a high quality, full color version of this figure, please see Journal of Cardiovascular Electrophysiology’s website: www.wileyonlinelibrary.com/journal/jce

Methods Study Design A total of 96 consecutive drug-refractory AF patients (age 20–80 years) who underwent only PVI for AF with the R THERMOCOOL SMARTTOUCHTM catheter (Biosense Webster, Diamond Bar, CA, USA) at Sakurabashi-Watanabe Hospital from June to August 2013 were enrolled in this study. Patients who underwent ablation of linear lesions in the left atrium (LA) or ablation of atrial premature complexes were not enrolled. Of these, 16 patients who underwent repeated ablation and 23 others with insufficient data were excluded from this study. Written informed consent for AF ablation was obtained from all patients. The study protocol was approved by the institution’s ethic committee. The AF ablation procedure was conducted using the R THERMOCOOL SMARTTOUCHTM (Biosense Webster) catheter following standard clinical practice guidelines with conventional power and temperature settings by 5 experienced operators. We reconfirmed PV potential 20 minutes or more after initial success of PVI, and if PV potential reappeared, we defined it as positive for time-dependent PV reconnection. We also checked adenosine triphosphate (ATP)-dependent PV reconnection, which was evoked by intravenous administration of 20 mg of adenosine. In this study, APVR was defined as both a time- and ATP-dependent PV reconnection. The point-by-point relationship between APVR and average CF was evaluated. Each ipsilateral pair of PV antrum was divided into 7 segments: roof, anterosuperior, anteroinferior, bottom, posteroinferior, posterosuperior, and

Figure 2. Definition of the electrically reconnected area. Electrically reconnected points were defined as all of the ablation points of the initial pulmonary vein isolation (PVI), with a center located within 6.0 mm from the center of additional ablation points for re-PVI (indicated by gray zone). Red tag: ablation points during initial PVI. Blue tag: additional ablation points for re-PVI. Each tag is a circle with a 6.0-mm diameter. For a high quality, full color version of this figure, please see Journal of Cardiovascular Electrophysiology’s website: www.wileyonlinelibrary.com/journal/jce

carina (Fig. 1). Re-PVI was performed by ablation of the initial ablation line for PVI or its adjunct points. Electrically reconnected points were defined as all ablation points for initial PVI with a center located within 6.0 mm from the center of additional ablation points for re-PVI (Fig. 2). The average CF was defined as the average of CF values during 1.0 second just before location tagging using the CARTO 3 three-dimensional mapping platform (Biosense Webster) (Fig. 3). CF data of all ablation sites for PVI were analyzed offline after the procedure.

Sotomi et al. Optimal Contact Force for AF Ablation

943

Figure 3. Average contact force (CF) during pulmonary vein isolation. Average CF was defined as the average of CF values during a 1.0-second period just before location tagging using the CARTO 3 system. For a high quality, full color version of this figure, please see Journal of Cardiovascular Electrophysiology’s website: www.wileyonlinelibrary.com/journal/jce

Electrophysiological Study and RF Catheter Ablation A 6-Fr decapolar catheter was placed in the coronary sinus through the median antebrachial vein, while a 7-Fr decapolar catheter was placed in the superior vena cava and right atrium through the femoral vein. Two long sheaths were introduced into the LA using a single transseptal puncture technique. An initial intravenous bolus of heparin (150 IU/kg) was followed by continuous infusion to maintain an activated clotting time of >300 seconds. Pulmonary angiography was performed by injecting contrast medium through the transseptal long sheaths into the LA. After catheter placement, electrical cardioversion was performed in cases with persistent AF. PVI was guided by fluoroscopy or the CARTO 3 threedimensional mapping system. We used the open irrigated-tip R RF THERMOCOOL SMARTTOUCHTM ablation catheter (Biosense Webster) for all procedures. Catheter ablation was basically performed using a conventional electrophysiological and anatomical approach. We monitored CF values just to avoid excessive catheter contact. All patients underwent extensive PVI using the single lasso technique. We performed point-by-point ablation, not with dragging technique, with an interlesion distance 404 g*s had excellent sensitivity and specificity (>80%) for identifying an effective lesion. Neuzil et al.14 evaluated 40 AF patients who underwent PVI in a 3-month follow-up procedure. Invasive electrophysiological assessment of conduction gaps at PVI ablation sites

Sotomi et al. Optimal Contact Force for AF Ablation

945

Figure 4. Optimal contact force (CF) to prevent acute pulmonary vein (PV) reconnection. The optimal CF range to prevent acute PV reconnection with a probability of >95% was 10–22 g depending on the peri-PV segments. A significant association between CF and acute PV reconnection could not be detected in 8 segments (indicated by N.S.), which may be partially due to the small number of reconnected points. For a high quality, full color version of this figure, please see Journal of Cardiovascular Electrophysiology’s website: www.wileyonlinelibrary.com/journal/jce

at the 3-month follow-up showed that the minimum CF and minimum force–time integral values during initial procedures in the reconnected segments, which were revealed in the follow-up procedures, were strongly correlated to subsequent gap formation. Reddy et al.20 evaluated 32 patients with paroxysmal AF undergoing PVI and reported that the CF during catheter ablation for AF was correlated with clinical outcome at a 12month follow-up. Arrhythmia control is best achieved when lesion ablation is performed with an average CF of >20 g, and clinical failure is universally noted with an average CF of 6 ࣘ11 >5 ࣘ3 ࣘ9 >7 ࣘ7 ࣘ3 ࣘ6 >7 ࣘ14 >8 >6 >5 >9 0.161 0.4931 0.1994 0.5234 0.6936 0.4769 0.1338 0.2495 0.1502 0.4366 0.2812 0.3127 0.3209 0.1809 0.2687 0.0165 0.128 0.0318 0.0676 0.0513 0.0656 0.0766 0.0779 0.0687 0.054 0.072 0.0643 0.0358 0.0439 0.111 4136 288 616 342 235 332 244 94 236 423 379 233 313 334 67 Overall segments LPV

Roof Anterosuperior Anteroinferior bottom Posteroinferior Posterosuperior Carina Roof Anterosuperior Anteroinferior Bottom Posteroinferior Posterosuperior Carina

4421 292 687 348 237 344 255 105 254 442 395 248 358 383 73

285 4† 71 6† 2† 12 11 11 18 19 16 15 45 49 6†

0.59 0.767 0.593 0.744 0.768 0.726 0.51 0.578 0.537 0.761 0.597 0.645 0.669 0.608 0.647

0.575–0.604 0.715–0.815 0.555–0.630 0.695–0.789 0.709–0.820 0.675–0.772 0.446–0.572 0.478–0.674 0.473–0.599 0.719–0.800 0.546–0.645 0.582–0.704 0.618–0.718 0.557–0.657 0.526–0.755