Feasibility and safety assessment of RF double applications in very high power and short duration ablation.

BACKGROUND: The QDOT-MICRO catheter enables very high power and short duration (vHPSD) ablation. However, low first-pass isolation rates have been reported, possibly because of shallow lesion formation, necessitating deeper lesions to improve treatment outcomes. OBJECTIVE: This study aimed to confirm the safety and efficacy of double radiofrequency applications of vHPSD ablation in an in vivo beating swine heart model. METHODS: Eighteen swine were anesthetized and underwent vHPSD ablation using the QDOT-MICRO catheter at 90 W for 4 seconds, targeting a contact force of 10 g. Radiofrequency applications were performed as single application (SA) and double applications (DAs) with 4- to 8-second rest intervals. Lesion surface area and volume were measured postablation. RESULTS: A total of 337 atrial lesions and 74 ventricular lesions were created. Both 4- to 6-second DA and 7- to 8-second DA produced significantly larger and deeper lesions than did SA, with atrial surface lengths averaging 9.0 mm for 4- to 6-second DA, 9.2 mm for 7- to 8-second DA, and 8.0 mm for SA. Transmurality was observed at 100% for 4- to 6-second and 7- to 8-second DAs, while it was 94% for SA (P = .002). Ventricular lesion metrics followed similar trends. Except for 1 event of tiny char formation during 4-second DA in the ventricle, neither steam pops nor char formation was observed in either the atrium or the ventricle. CONCLUSION: In an in vivo swine heart model, DA with 4- to 6-second and 7- to 8-second intervals create deeper and wider lesions than does SA, suggesting its potential for clinical application in areas with thicker myocardial walls. However, DA with very short intervals may still pose a risk of excessive tissue heating.

Quantitative investigation of acute lesions created by ethanol infusion into the vein of Marshall.

BACKGROUND: Ethanol infusion into the vein of Marshall (EIVOM) has been performed as an adjunctive atrial fibrillation therapy. However, the time course change, quantitative lesion investigation, and effects on epicardial fat pads and fractionated atrial electrograms created by EIVOM have never been investigated. OBJECTIVE: This study aimed to perform a quantitative analysis of lesions created by EIVOM. METHODS: We created voltage maps using a 3-dimensional mapping system immediately before and 30 minutes and 60 minutes after performing EIVOM to study the time course change in the lesions. We compared differences in the average contact force value required for successful conduction block in the Marshall vein area of patients with and without EIVOM. We also investigated effects of EIVOM on the area of complex fractionated atrial electrograms before and after EIVOM. We measured the total epicardial fat pad volume before and after EIVOM by computed tomography. RESULTS: Voltage was significantly reduced after EIVOM, and there were significant differences in voltage reduction between the control status and 30 minutes and 60 minutes after EIVOM (P < .05). The average contact force value was significantly lower with vs without EIVOM (P < .05). The total epicardial fat volume and complex fractionated atrial electrogram area also significantly decreased after EIVOM (P < .05). CONCLUSION: EIVOM provided significant therapeutic effects on the left atrial tissue perpetuating atrial fibrillation, which was demonstrated by a quantitative analysis.

Distribution of peak frequency and omnipolar voltage in electrograms across the atrial body and thoracic veins in a normal heart.

BACKGROUND: The innovative peak frequency mapping facilitates the quantification of electrogram sharpness. However, reference values for normal atrial tissue are currently undefined. In this study, we explored the distribution of peak frequency and omnipolar peak-to-peak voltage (V-max) in a normal heart. METHODS: Twenty-two patients with structurally normal heart were included. Either the right atrium (RA) and superior vena cava (SVC) or the left atrium (LA) and pulmonary veins (PVs) were mapped during sinus rhythm. RESULTS: In total, 13,654 points in the RA and 4143 points in the SVC from 15 patients and 4662 points in the LA and 2761 points in PVs from 7 patients were analyzed. The correlation between peak frequency and V-max was weak (R = 0.223). The median peak frequency was larger in the SVC than in the RA (441 [358-524] Hz vs. 358 [291-441] Hz, P < 0.0001) and in PVs than in the LA (346 [253-441] Hz vs. 323 [262-397] Hz, P < 0.0001). Conversely, the median V-max was smaller in the SVC than in the RA (1.96 [0.77-3.75] mV vs. 4.11 [2.10-6.83] mV, P < 0.0001) and in PVs than in the LA (1.16 [0.33-3.17] mV vs. 4.42 [2.63-6.84] mV, P < 0.0001). More than 95% of peak frequencies were > 174 Hz in the RA and > 185 Hz in the LA, and > 95% of V-maxes were > 0.52 and > 1.07 mV in the RA and LA, respectively. CONCLUSION: Given the limited correlation between peak frequency and V-max, and recognizing their potential to provide distinct information, they can be used complementarily. Employing these parameters to extract varied insights can provide comprehensive understandings of tissue characteristics.

An optimized approach for increasing lesion size in temperature-controled setting using a catheter with a surface thermocouple and efficient irrigation.

Background: We explore an optimized approach for increasing lesion size using a novel ablation catheter with a surface thermocouple and efficient irrigation in a temperature-control setting. Methods: We conducted radiofrequency applications at various power levels (35 W, 40 W, and 45 W), contact forces (CFs, 10 g/20 g), and durations (60 s/120 s/180 s) in perpendicular/parallel catheter orientations, with normal saline irrigation (NS-irrigation) and Half NS-irrigation (HNS-irrigation) in an ex-vivo model (Step 1). In addition, we performed applications (35 W/40 W/45 W for 60 s/120 s/180 s in NS-irrigation and 35 W/40 W for 60 s/120 s/180 s in HNS-irrigation) in four swine (Step 2), evaluating lesion characteristics and the occurrence of steam pops. Results: In Step 1, out of 288 lesions, we observed 47 (16.3%) steam pops, with 13 in NS-irrigation and 34 in HNS-irrigation (p = .001). Although steam pops were mostly observed with the most aggressive setting (45 W/180 s, 54%) with NS-irrigation, they happened in less aggressive settings with HNS irrigation. Lesion size significantly increased with longer-duration ablation but not with HNS-irrigation. The optimal %impedance-drop cutoff to predict steam pops was 20% with a negative-predictive-value (NPV) = 95.1% including NS- and HNS-irrigation groups, and 22% with an NPV = 96.1% in NS-irrigation group. In Step 2, similar to the ex-vivo model, lesion size significantly increased with longer-duration ablation but not with HNS-irrigation. Steam pops were absent with NS-irrigation (0/35) even with the largest %impedance-drop reaching 31% at 45 W/180 s. All steam pops were observed with HNS-irrigation (6/21, 29%). The optimal %impedance-drop cutoff predicting steam pops was 24% with an NPV = 96.3% including both NS- and HNS-irrigation groups. Conclusions: Rather than using HNS-irrigation, very long-duration of radiofrequency applications up to 45 W/180 s may be recommended to safely and effectively increase lesion dimensions using this catheter with NS-irrigation.

Anatomical approach to suppression of para-Hisian ventricular arrhythmias with changes in QRS morphology after ablation at the earliest activation site.

BACKGROUND: The anatomical approach for the management of para-Hisian ventricular arrhythmias (VAs) with QRS morphological changes after catheter ablation (CA) has not been well investigated. OBJECTIVE: We aimed to evaluate the electrocardiographic and electrophysiological findings and ablation outcomes of para-Hisian VAs with QRS morphological changes after CA. METHODS: Of the 30 patients who underwent CA for para-Hisian VAs at 4 institutions, 10 (33%) had QRS morphological changes after ablation. All 10 patients underwent an anatomical approach, targeting the site anatomically opposite to the site where the QRS morphology had been changed by ablation. We investigated the safety and efficacy of the anatomical approach. RESULTS: Of the 10 patients evaluated, the approach was switched from the right ventricular septum to the left ventricular septum/aortic root in 7 (70%) (RL group) whereas 3 (30%) underwent left-to-right switches (LR group). After CA, the precordial transition zone tended to be earlier in the RL group and later in the LR group. In the RL group, successful VA suppression was achieved, despite suboptimal pace map concordance from the left side or a relatively delayed earliest activation time. Of the 10 patients who underwent an anatomical approach, 8 (80%) had procedural success, and ablation was discontinued in 1 (10%) because of the risk of atrioventricular block. CONCLUSION: The anatomical approach showed promising results regarding safety and efficacy. Therefore, it should be considered when QRS morphological changes are observed during or after CA of para-Hisian VAs.

Impact of contact force on the lesion characteristics of very high-power short-duration ablation using a QDOT-MICRO catheter.

Background: Lesion size is reported to become larger as contact force (CF) increases. However, this has not been systematically evaluated in temperature-guided very high-power short-duration (vHPSD) ablation, which was therefore the purpose of this study. Methods: Radiofrequency applications (90 W/4 s, temperature-control mode) were performed in excised porcine myocardium with four different CFs of 5, 15, 25, and 35 g using QDOT-MICRO™ catheter. Ten lesions for each combination of settings were created, and lesion metrics and steam-pops were compared. Results: A total of 320 lesions were analyzed. Lesion depth, surface area, and volume were smallest for CF of 5 g than for 15, 25, and 35 g (depth: 2.7 mm vs. 2.9 mm, 3.0 mm, 3.15 mm, p < .01; surface area: 38.4 mm2 vs. 41.8 mm2, 43.3 mm2, 41.5 mm2, p < .05; volume: 98.2 mm3 vs. 133.3 mm3, 129.4 mm3, 126.8 mm3, p < .01 for all pairs of groups compared to CF = 5 g). However, no significant differences were observed between CFs of 15-35 g. Average power was highest for CF of 5 g, followed by 15, 25, and 35 g (83.2 W vs. 82.1 W vs. 77.1 W vs. 66.1 W, p < .01 for all pairs), reflecting the higher incidence of temperature-guided power titration with greater CFs (5 g:8.8% vs. 15 g:52.5% vs. 25 g:77.5% vs. 35 g:91.2%, p < .01 for all pairs except for 25 g vs. 35 g). The incidence of steam-pops did not significantly differ between four groups (5 g:3.8% vs. 15 g:10% vs. 25 g:6.2% vs. 35 g:2.5%, not significant for all pairs). Conclusions: For vHPSD ablation, lesion size does not become large once the CF reaches 15 g, and the risk of steam-pops may be mitigated through power titration even in high CFs.

Effect of reference electrode on intracardiac electrograms: Close indifferent electrode vs Wilson central terminal.

BACKGROUND: Unipolar electrograms (uni-EGMs) are an essential part of intracardiac mapping. Although Wilson central terminal (WCT) is conventionally used as a reference for signals, avoidance of contamination by far-field and nonphysiologic signals is challenging. OBJECTIVE: The aim of the study was to explore the impact of an intracardiac indifferent reference electrode close to the recording electrodes, in lieu of WCT, on electrograms. METHODS: Sinus node activation was mapped in patients undergoing catheter ablation by a multielectrode array with a close indifferent electrode (CIE) embedded in the distal end of the catheter shaft. An equal number of points was sequentially acquired at each site with use of CIE as a reference first and subsequently with WCT. Uni-EGMs, bipolar EGMs, and the earliest activation area (defined as the area activated in the first 10 ms of the beat) were compared between CIE- and WCT-based activation maps. RESULTS: Seventeen patients (61 ± 18 years; 76% male) were studied. Uni-EGM voltages acquired with CIE were significantly larger than (n = 11) or comparable to (n = 4) those acquired with WCT. When points from the entire cohort were analyzed altogether, unipolar voltages and their maximum negative dV/dT and bipolar voltages recorded with CIE were significantly larger than those recorded with WCT (2.36 [1.42-3.79] mV vs 1.96 [1.25-3.03] mV, P < .0001; 0.40 [0.18-0.77] mV/s vs 0.35 [0.15-0.71] mV/s, P < .0001; and 1.46 [0.66-2.81] mV vs 1.33 [0.54-2.64] mV, P < .0001, respectively). The earliest activation area was significantly smaller in CIE-based activation maps than in WCT-based ones (0.3 [0.7-1.4] cm2 vs 0.6 [1.0-1.8] cm2, P = .01). CONCLUSION: CIE-based maps were associated with an approximately 20% increase in unipolar voltage and may highlight the origin of a focal activation more clearly than WCT-based ones.

Phrenic nerve injury after atrial fibrillation ablation: different recovery courses among cryoballoon, laser balloon, and radiofrequency ablation.

BACKGROUND: Phrenic nerve injury (PNI) is one of the common complications in atrial fibrillation (AF) ablation, which often recovers spontaneously. However, the course of its recovery has not been examined fully, especially in regard to the different ablation methods. We sought to compare the recovery course of PNI in cryoballoon, laser balloon, and radiofrequency ablation. METHODS: This multicenter retrospective study analyzed 355 patients who suffered from PNI during AF ablation. PNI occurred during cryoballoon ablation (CB group) and laser balloon ablation (LB group) for a pulmonary vein isolation in 288 and 20 patients, and radiofrequency ablation for a superior vena cava (SVC) isolation (RF-SVC group) in 47 patients, respectively RESULTS: There was a significant difference in the estimated probability of PNI recovery after the procedure between the methods (p = 0.01). PNI recovered significantly earlier in the CB group, especially within 24 h and 3 months post-procedure (the percentage of the recovery within 24 h and 3 months: 49.7% and 71.5% in the CB group, 15.0% and 22.2% in the LB group, and 23.4% and 41.9% in the RF-SVC group, respectively). Persistent PNI after 12 months was observed in only seven patients in the CB group, one in the LB group, and four in the RF-SVC group, respectively. CONCLUSION: PNI rarely persists over 12 months after AF ablation; however, there is a difference in the timing of its recovery. PNI recovers quicker with cryoballoon ablation than with laser balloon ablation or radiofrequency ablation of the SVC.

Adjunctive posterior wall isolation for the treatment of persistent and longstanding persistent atrial fibrillation (CORNERSTONE AF) trial: Design and rationale.

BACKGROUND: A left atrial posterior wall isolation (LAPWI) is one of the atrial fibrillation (AF) ablation strategies. HYPOTHESIS: We hypothesized that an additional empirical LAPWI would increase the freedom from recurrent atrial arrhythmias as compared to standard AF ablation in persistent AF patients. METHODS: The CORNERSTONE AF study is a prospective, randomized, multicenter study investigating patients with AF persisting for >7 days and <3 years undergoing first-time AF ablation. They will be randomized to pulmonary vein isolation (PVI) or PVI + LAPWI in a 1:1 manner. Although PVI can be performed with either radiofrequency catheters or cryoballoons, only radiofrequency catheters will be permitted to achieve LAPWIs. Additional focal ablation targeting non-pulmonary vein triggers will be allowed. A total of 516 patients will be enrolled in 17 centers between August 2022 and February 2024 based on the calculation with 80% power, considering the assumption that 65% and 75% of the PVI and PVI + LAPWI group patients will be free from atrial arrhythmia recurrence 18-months postprocedure (10% of dropout). The primary endpoint is freedom from documented atrial arrhythmias 18 months postsingle procedures. Clinical follow-up will include 7-day ambulatory electrocardiograms and routine outpatient consultations by electrophysiologists at 1, 3, 6, 9, 12, and 18 months postprocedure. RESULTS: As of August 2023, a total of 331 patients (68 ± 9 years, 270 men, 43 longstanding persistent AF) have been enrolled. CONCLUSIONS: The CORNERSTONE AF study is a prospective, randomized, multicenter trial designed to evaluate the efficacy and safety of an adjunctive empirical LAPWI following standard AF ablation in persistent AF patients.

Novel method to avoid serious injurious effects on the atrioventricular nodal (AVN) conduction during catheter ablation of the AVN slow pathway utilizing cryofreezing energy.

BACKGROUND: Slow pathway elimination of the atrioventricular node (AVN) is essential to treat AVN reentrant tachycardia (AVNRT). However, injury to the AVN conduction (IAVN) is one of the serious complications. Cryofreezing energy is expected to reduce the incidence of IAVN. This study aimed to investigate the usefulness of a novel method to avoid IAVN during cryoablation of AVNRT. METHODS: A total of 157 patients (average age, 65.8 years; male, 71) suffering from AVNRT were included. Once the AVNRT terminated during cryo-ablation, then rapid atrial constant pacing (RACP) was performed during freezing at a rate lower 10 bpm than that inducing Wenchebach AV block in 74 (47.1 %) patients (Group A). The RACP rate was decreasingly reduced by 10 bpm in case of the occurrence of IAVN. When the RACP reached 100 bpm, the cryoablation was prematurely terminated. Group B patients (83 = 52.9 %) underwent cryoablation during sinus rhythm. All patients were allocated in a randomized fashion. We compared the severity of the IAVN between Groups A and B. RESULTS: There were no significant differences at 12 months regarding the freedom from the AVNRT between Groups A and B. However, the duration of the IAVN was significantly longer in Group B than A (p = 0.02). There were no significant differences regarding the distance between the His recording sites and successful ablation sites between Groups A and B. No permanent IAVN requiring pacemaker implantation was provoked in either group. CONCLUSION: RACP was useful to avoid sustained and serious IAVN during cryoablation of AVNRT.

Transcoronary mapping with an over-the-wire multielectrode catheter in scar-related ventricular tachycardia patients.

AIMS: The usefulness of coronary venous system mapping has been reported for assessing intramural and epicardial substrates in patients with scar-related ventricular tachycardia (VT). However, there has been little data on mapping from coronary arteries. We investigated the safety and utility of mapping from coronary arteries with a novel over-the-wire multielectrode catheter in scar-related VT patients. METHODS AND RESULTS: Ten consecutive scar-related VT patients with non-ischaemic cardiomyopathy who underwent mapping from a coronary artery were analysed. Six patients underwent simultaneous coronary venous mapping. High-density maps were created by combining the left ventricular endocardium and coronary vessels. Substrate maps were created during the baseline rhythm with 2438 points (IQR 2136-3490 points), including 329 (IQR 59-508 points) in coronary arteries. Abnormal bipolar electrograms were successfully recorded within coronary arteries close to the endocardial substrate in seven patients. During VT, isthmus components were recorded within the coronary vessels in three patients with no discernible isthmus components on endocardial mapping. The ablation terminated the VT from an endocardial site opposite the earliest site in the coronary arteries in five patients. CONCLUSION: The transcoronary mapping with an over-the-wire multielectrode catheter can safely record abnormal bipolar electrograms within coronary arteries. Additional mapping data from the coronary vessels have the potential to assess three-dimensional ventricular substrates and circuit structures in scar-related VT patients.

The effect of half-normal saline irrigation on lesion characteristics in temperature-flow-controlled ablation.

PURPOSE: Radiofrequency (RF) ablation with half-normal saline (HNS) irrigation is reported to potentially enlarge local lesion compared to normal saline (NS) in power-controlled ablation (PC-Abl). However, the effect of HNS-irrigation in temperature-flow-controlled ablation (TFC-Abl) on lesion characteristics is unknown. We compared this between TFC-Abl with QDOT-Micro™ catheter and PC-Abl with Thermocool SmartTouch SF™ catheter (STSF). METHODS: RF-application with NS (n = 480) and HNS (n = 480) irrigation were performed on swine myocardium placed in a circulating saline bath. Lesion characteristics without steam-pops under various conditions (target AI, 400/550; ablation power, 30/50 W; contact force, 10/20/30 g; catheter orientation, perpendicular/parallel) were assessed and compared between two irrigants. RESULTS: After matching, 343 lesions without steam-pops in each group were evaluated. In PC-Abl, lesion size did not differ between two groups (NS, 188 ± 97 vs. HNS, 200 ± 95 mm3, p = 0.28 in volume; 33.9 ± 7.3 vs. 34.8 ± 9.5 mm2, p = 0.34 in surface area; and 4.0 ± 1.0 vs. 4.0 ± 1.0 mm, p = 0.81 in depth), but steam-pops were more frequently observed with HNS-irrigation (23.8% vs. 37.9%, p = 0.001). Contrary, in TFC-Abl, HNS-irrigation produced significantly larger (214 ± 106 vs. 243 ± 128 mm3, p = 0.017) and deeper (4.0 ± 1.0 vs. 4.3 ± 1.1 mm, p = 0.002) lesions without increasing the risk of steam-pops (15.0% vs 15.0%, p = 0.99). Automatic temperature-guided titration was more frequently observed in HNS-irrigation (54.8% vs. 78.5%, p < 0.001). CONCLUSIONS: TFC-Abl with QDOT-Micro™ catheter utilizing HNS-irrigation might increase volume and depth of local lesion without increasing the risk of stem-pops compared to NS-irrigation. Power-controlled ablation with HNS-irrigation showed similar focal lesion with higher incidence of steam-pops (SPs) compared to normal saline (NS) irrigation. Contrary, temperature-flow-controlled ablation with HNS-irrigation provided larger and deeper lesion than NS-irrigation with similar incidence of SPs. ns, p > 0.05; *, 0.01 < p ≤ 0.05; **, 0.005 < p ≤ 0.01. HNS, half-normal saline; NS, normal saline.

Safety verification of a novel irrigation catheter with flexible tip of laser-cut kerfs and contact force sensor.

BACKGROUND AND AIMS: The safety evaluation of TactiFlex, a novel contact-force sensing catheter with a flexible 4-mm tip irrigated through laser-cut kerfs, has been ongoing. This study aimed to verify the safety of this type of catheter. METHODS: Study 1: Radiofrequency (RF) applications at a range of powers (30-50 W), contact forces (10-20 g), and durations (10-60 s) using perpendicular/parallel catheter orientation with half-normal (HNS) or normal saline irrigation were compared between TactiFlex (4-mm tip) and TactiCath (3.5-mm tip) with temperature-controlled mode in excised porcine hearts. Study 2: The relation between RF applications using TactiFlex and the incidence of steam-pops in the real clinical cases were examined. RESULTS: Study-1: 576 RF lesions were examined. TactiFlex demonstrated a significantly lower risk of steam-pops (5[1.7%] vs. 59[20.5%], p < .0001). Compared to 3.5-mm-tip catheter (TactiCath), 4-mm-tip catheter (TactiFlex) produced smaller lesion volume at perpendicular (193[98-554]mm3 vs. 263[139-436]mm3 , p < .0001), but relatively similar lesion volume at parallel contact (243[105-443]mm3 vs. 278[180-440]mm3 , p = .06). HNS-irrigation tended to increase the lesion volume in both catheters and to increase the incidence of steam-pops with TactiCath, but not with TactiFlex. The cut-off value of %impedance-drop ( = absolute impedance-drop/initial impedance) of 20% predicted steam-pops with a sensitivity = 100% and specificity = 89.6% in TactiFlex. Study-2: 5496 RF applications in 84 patients (51AFs/8ATs/3AVNRTs/4AVRTs/17PVCs/4VTs) using TactiFlex were analyzed. Four steam-pops (0.07%) in three patients with pericardial effusion were observed (%impedance-drop = 24%/26%/29%/35%, respectively). The cut-off value of %impedance-drop = 20%, derived from ex-vivo study, showed sensitivity = 100% and specificity = 90.1% in detecting steam-pops. CONCLUSION: TactiFlex reduced the risk of steam-pops than TactiCath. %impedance-drop ≤ 20% may be reasonable for safely use with a sufficient safety margin. For 4-mm-tip catheter, parallel-contact may be recommended for larger lesion creation.

Superiority of the Combination of Input and Output Parameters to the Single Parameter for Lesion Size Estimation.

BACKGROUND: For lesion size prediction, each input parameter, including ablation energy (AE), and output parameter, such as impedance, is individually used. We hypothesize that using both parameters simultaneously may be more optimal.Methods and Results: Radiofrequency applications at a range of power (30-50 W), contact force (10 g and 20 g), duration (10-60 s), and catheter orientation with normal saline (NS)- or half-normal saline (HNS)-irrigation were performed in excised porcine hearts. The correlations, with lesion size of AE, absolute impedance drop (∆Imp-drop), relative impedance drop (%Imp-drop), and AE*%Imp-drop were examined. Lesion size was analyzed in 283 of 288 lesions (NS-irrigation, n=142; HNS-irrigation, n=141) without steam pops. AE*%Imp-drop consistently showed the strongest correlations with lesion maximum depth (NS-irrigation, ρ=0.91; HNS-irrigation, ρ=0.94), surface area (NS-irrigation, ρ=0.87; HNS-irrigation, ρ=0.86), and volume (NS-irrigation, ρ=0.94; HNS-irrigation, ρ=0.94) compared with the other parameters. Moreover, compared with AE alone, AE*%Imp-drop significantly improved the strength of correlation with lesion maximum depth (AE vs. AE*%Imp-drop, ρ=0.83 vs. 0.91, P<0.01), surface area (ρ=0.73 vs. 0.87, P<0.01), and volume (ρ=0.84 vs. 0.94, P<0.01) with NS-irrigation. This tendency was also observed with HNS-irrigation. Parallel catheter orientation showed a better correlation with lesion depth and volume using ∆Imp-drop, %Imp-drop, and AE*%Imp-drop than perpendicular orientation. CONCLUSIONS: The combination of input and output parameters is more optimal than each single parameter for lesion prediction.

How to perform effective cryoballooon ablation of the left atrial roof: Considerations after experiencing more than 1000 cases.

INTRODUCTION: Cryoballoon ablation (CBA) of the left atrial (LA) roof in addition to a pulmonary vein isolation has been expected to improve the clinical outcomes post-atrial fibrillation (AF) ablation. We demonstrated the characteristics and efficacy of CBA of the LA roof through our experience with a large volume of procedures. METHODS: Among 1036 AF ablation procedures with CBA of the LA roof, 834 patients who underwent a de novo ablation were analyzed. RESULTS: Complete LA roof line conduction block was obtained in 767 patients (92.0%) solely by CBA (Group A). Compared with the other patients (Group B), the mean nadir balloon temperature during CBA of the LA roof (-44.5 ± 5.6°C for Group A vs. -40.5 ± 7.5°C for Group B, p < .01) and number of cryoballoon applications during the LA roof ablation with a circular mapping catheter located in the left superior pulmonary vein (1.3 ± 0.8 for Group A vs. 1.6 ± 1.0 for Group B, p = .02) were significantly lower in Group A. A multivariate analysis revealed that those were predictors of a complete LA roof conduction block after only CBA. The 1-year Kaplan-Meier atrial arrhythmia free rate estimates were 80.6% for Group A and 59.0% for Group B (p < .01). CONCLUSION: Complete LA roof line conduction block could be obtained with a cryoballoon without touch-up ablation in most cases. The LA roof CBA with a circular mapping catheter located in the right superior pulmonary vein was preferable to obtaining complete LA roof conduction block, which was important with regard to the clinical outcomes.

Detailed analysis of tachycardia cycle length aids diagnosis of the mechanism and location of atrial tachycardias.

AIMS: Although the mechanism of an atrial tachycardia (AT) can usually be elucidated using modern high-resolution mapping systems, it would be helpful if the AT mechanism and circuit could be predicted before initiating mapping. OBJECTIVE: We examined if the information gathered from the cycle length (CL) of the tachycardia can help predict the AT-mechanism and its localization. METHODS: One hundred and thirty-eight activation maps of ATs including eight focal-ATs, 94 macroreentrant-ATs, and 36 localized-ATs in 95 patients were retrospectively reviewed. Maximal CL (MCL) and minimal CL (mCL) over a minute period were measured via a decapolar catheter in the coronary sinus. CL-variation and beat-by-beat CL-alternation were examined. Additionally, the CL-respiration correlation was analysed by the RhythmiaTM system. : Both MCL and mCL were significantly shorter in macroreentrant-ATs [MCL = 288 (253-348) ms, P = 0.0001; mCL = 283 (243-341) ms, P = 0.0012], and also shorter in localized-ATs [MCL = 314 (261-349) ms, P = 0.0016; mCL = 295 (248-340) ms, P = 0.0047] compared to focal-ATs [MCL = 506 (421-555) ms, mCL = 427 (347-508) ms]. An absolute CL-variation (MCL-mCL) < 24 ms significantly differentiated re-entrant ATs from focal-ATs with a sensitivity = 96.9%, specificity = 100%, positive predictive value (PPV) = 100%, and negative predictive value (NPV) = 66.7%. The beat-by-beat CL-alternation was observed in 10/138 (7.2%), all of which showed the re-entrant mechanism, meaning that beat-by-beat CL-alternation was the strong sign of re-entrant mechanism (PPV = 100%). Although the CL-respiration correlation was observed in 28/138 (20.3%) of ATs, this was predominantly in right-atrium (RA)-ATs (24/41, 85.7%), rather than left atrium (LA)-ATs (4/97, 4.1%). A positive CL-respiration correlation highly predicted RA-ATs (PPV = 85.7%), and negative CL-respiration correlation probably suggested LA-ATs (NPV = 84.5%). CONCLUSION: Detailed analysis of the tachycardia CL helps predict the AT-mechanism and the active AT chamber before an initial mapping.

Impact of baseline pool impedance on lesion metrics and steam pops in catheter ablation.

INTRODUCTION: Little is known about the impact of blood-pool local impedance (LI) on lesion characteristics and the incidence of steam pops. METHODS: Radiofrequency applications at a range of powers (30, 40, and 50 W), contact forces (CF) (5, 15, and 25 g), and durations (15, 30, 45, and 120 s) using perpendicular/parallel catheter orientation were performed in 40 excised porcine preparations, using a catheter capable of monitoring LI (StablePoint©, Boston Scientific). To simulate the variability in blood-pool impedance, the saline-pool LI was modulated by calibrating saline concentrations. Lesion characteristics were compared under three values of saline-pool LI: 120, 160, and 200 Ω. RESULTS: Of 648 lesions created, steam pops occurred in 175 (27.0%). When power, CF, time, and catheter orientation were adjusted, ablation at a saline-pool impedance of 160 or 200 Ω more than doubled the risk of steam pops compared with a saline-pool impedance of 120 Ω (Odds ratio = 2.31; p = .0002). Lesions in a saline-pool impedance of 120 Ω were significantly larger in surface area (50 [38-62], 45 [34-56], and 41 [34-60] mm2 for 120, 160, and 200 Ω, p < .05), but shallower in depth (4.0 [3-5], 4.4 [3.2-5.3], and 4.5 [3.8-5.5] mmfor 120, 160, and 200 Ω, respectively, p < .05) compared with the other two settings. The correlation between the absolute LI-drop and lesion size weakened as the saline-pool LI became higher (e.g., 120 Ω group (r2 = .30, r2 = .18, and r2 = .16, respectively for 120, 160, and 200 Ω), but the usage of %LI-drop (= absolute LI-drop/initial LI) instead of absolute LI-drop may minimize this effect. CONCLUSIONS: In an experimental model, baseline saline-pool impedance significantly affects the lesion metrics and the risk of steam pops.

Delineation of the right ventricular septal activation during a right bundle branch origin accelerated idioventricular rhythm.

Accelerated idioventricular rhythm (AIVR) originating from the right bundle branch (RBB) (RBB-AIVR) is a rare ventricular arrhythmia. We delineated RBB and myocardial activation separately during RBB-AIVR, which revealed the spatial relationship of the AIVR origin, preferential pathway, and breakout site. Radiofrequency ablation to the preferential pathway successfully eliminated this arrhythmia.

Comparison of lesion characteristics using temperature-flow-controlled versus conventional power-controlled ablation with fixed ablation index.

INTRODUCTION: The QDOT-MicroTM catheter is a novel irrigated contact force (CF) sensing catheter which benefits from thermocouples for temperature monitoring, allowing temperature-flow-controlled (TFC) ablation. We compared lesion metrics at fixed ablation index (AI) value during TFC-ablation and conventional power-controlled (PC)-ablation. METHODS: A total of 480 RF-applications were performed on ex-vivo swine myocardium with predefined AI targets (400/550) or until steam-pop occurred, using the QDOT-MicroTM (TFC-ablation) and Thermocool SmartTouch SFTM (PC-ablation). RESULTS: Both TFC-ablation and PC-ablation produced similar lesions in volume (218 ± 116 vs. 212 ± 107 mm3 , p = .65); however, lesions using TFC-ablation were larger in surface area (41.3 ± 8.8 vs. 34.8 ± 8.0 mm2 , p < .001) and shallower in depth (4.0 ± 1.0 vs. 4.2 ± 1.1 mm, p = .044). Average power tended to be lower in TFC-alation (34.2 ± 8.6 vs. 36.9 ± 9.2, p = .005) compared to PC-ablation due to automatic regulation of temperature and irrigation-flow. Although steam-pops were less frequent in TFC-ablation (24% vs. 15%, p = .021), they were particularly observed in low-CF (10 g) and high-power ablation (50 W) in both PC-ablation (n = 24/240, 10.0%) and TFC-ablation (n = 23/240, 9.6%). Multivariate analysis revealed that high-power, low-CF, long application time, perpendicular catheter orientation, and PC-ablation were risk factors for steam-pops. Furthermore, activation of automatic regulation of temperature and irrigation-flow was independently associated with high-CF and long application time while ablation power had no significant relationship. CONCLUSIONS: With a fixed target AI, TFC-ablation reduced the risk of steam-pops, producing similar lesions in volume, but with different metrics in this ex-vivo study. However, lower CF and higher power in fixed-AI ablation may increase the risk of steam-pops.