Short-duration Ablation Research Articles

High-power short-duration ablation of atrial fibrillation: A contemporary review.

Catheter ablation using radiofrequency (RF) energy has been widely used to treat patients with atrial fibrillation (AF). The optimal levels of power and duration to increase the success rate while minimizing complications have not been fully established. Different centers continue to use various power protocols for catheter ablation of AF. Herein, we present a comprehensive review of the impact of power output on efficacy and safety of RF ablation for AF. High-power short-duration (HPSD) ablation can be performed safely with similar procedural efficacy as low-power long-duration ablation strategy. HPSD ablation has the potential to shorten procedural and RF times and create more durable and localized lesions.

Incidence of ablation-induced esophageal injury associated with high-power short duration temperature-controlled pulmonary vein isolation using a specialized open-irrigated ablation catheter: A retrospective single-center study.

To evaluate short-term efficacy and incidence of ablation-induced endoscopically detected esophageal injury in patients undergoing high-power, short-duration (HPSD) pulmonary vein isolation using a novel irrigated radiofrequency ablation catheter and ablation generator setup. Atrial fibrillation (AF) patients, who underwent AF ablation using an irrigated radiofrequency ablation catheter specifically designed for a HPSD ablation approach (50 W, with a target Ablation Index of 350 at posterior wall), received postablation esophageal endoscopy after ablation. In total 45 consecutive patients (67 ± 10 years; 58% male; 42% paroxysmal AF) undergoing AF ablation using a specialized ablation catheter (QDOT) were included in the study. Thirty-one of 45 patients (69%) underwent a first-time pulmonary vein isolation (Group 1, 67 ± 11 years; 55% male; 48% paroxysmal AF). Fourteen patients (31%) underwent a redo AF procedure (Group 2, 66 ± 8 years; 64% male; 29% paroxysmal AF). Patients undergoing first-time pulmonary vein isolation were included in the final analysis. In these patients an endoscopically detected esophageal lesion (EDEL) was detected in 5 of 31 (16%) patients (erosion n = 2, ulcer n = 3). Mean contact force at posterior wall ablation sites was significantly lower in patients with postprocedural EDEL compared with patients without EDEL (11.9 ± 0.8 g vs. 15.6 ± 4.7 g). PVI using a specialized high-power ablation catheter in conjunction with a HPSD ablation approach results in a 16% incidence of EDEL in first AF ablation candidates. Future studies evaluating high-power short duration ablation strategies should include esophageal endoscopy to estimate the risk of clinically relevant esophageal complications.

High Power Ultra Short Duration Ablation with HD Grid Improves Freedom from Atrial Fibrillation and Redo Procedures Compared to Circular Mapping Catheter.

High power ultra-short duration (HPUSD) ablation has been advocated to prevent esophageal injuries during atrial fibrillation (AF) ablation procedures. Prior research using the standard circular mapping catheter (CMC) has shown that ultra-short ablations may compromise lesion durability resulting in an increased need for redo procedures. The purpose of this study was to determine if HD mapping of concealed pulmonary vein (PV) connections could improve freedom from atrial fibrillation and redo procedures compared to CMC guided AF ablation. A total of 472 consecutive first time AF ablation procedure patients with at least one year of follow up were included with an average follow-up of 18 months. HPUSD AF ablation consisted of 50 W for 2-3 seconds on the posterior wall and 5-15 seconds on the anterior wall of the left atrium. Acute pulmonary vein isolation (PVI) was defined as no concealed 1) PV signals, 2) activation into PVs, or 3) voltage into PVs with no intra-procedural waiting period utilizing the HD Grid catheter versus entrance/exit block with a 30-minute wait with the circular mapping catheter. Freedom from atrial fibrillation and all atrial arrhythmias following a 90-day blanking period were assessed. Acute pulmonary vein isolation was achieved in all 472 patients. HPUSD ablation using the HD Grid was associated with shorter procedure (70.2 vs 104.3 minutes, p<0.001) and fluoroscopy times (4.2 vs 15.0 minutes, p<0.001) when compared to CMC. The recurrence of any atrial arrhythmias at 1 year was 13% with HD Grid and 25% with CMC (p<0.001) with the need for redo procedures of 6% for HD Grid and 20% for CMC (p<0.001). No esophageal ulcerations/perforations were seen. No deaths, strokes, or TIAs were observed in either group. HPUSD AF Ablation, as guided by HD Grid mapping, may prevent esophageal injuries while at the same time improve freedom from any atrial arrhythmias and the need for redo procedures. Procedure and fluoroscopy times were also significantly decreased when compared to traditional CMC mapping.

Temperature- and flow-controlled ablation/very-high-power short-duration ablation vs conventional power-controlled ablation: Comparison of focal and linear lesion characteristics

The QDOT MICRO catheter allows temperature- and flow-controlled (TFC) ablation and very-high-power short-duration (vHPSD) ablation. The purpose of this study was to compare lesion characteristics between TFC/vHPSD ablation and standard power-controlled (PC) ablation. Lesion characteristics in the right atrium, left atrium, and right ventricle (RV) of 6 sheep were compared between vHPSD (90 W/4 seconds, TC mode with 60°C target using QDOT) and standard radiofrequency settings (PC mode, 30 W/30 seconds with ThermoCool SmartTouch SF). Lesions in the left ventricle (LV) were compared, targeting 50 W for 60-second applications. Forty-six focal atrial lesions, 50 RV focal lesions, and 12 linear lesions were created by vHPSD ablation and PC ablation in each group of 6 animals. vHPSD ablation produced significantly larger focal atrial lesions in length (8.3 [6.4-9.7] mm vs 6.3 [5.2-7.4] mm; P = .0002), width (6.0 [5.3-6.9] mm vs 4.6 [3.8-5.4] mm; P <.0001), and surface area (39.4 [25.4-52.4] mm2 vs 23.6 [16.0-31.1] mm2; P = .0001), with superior transmurality (89.1% vs 69.6%; P = .04) compared to PC ablation. vHPSD ablation produced significantly larger RV lesions in length (7.7 [7.0-8.7] mm vs 6.0 [4.8-6.9] mm; P <.0001), width (6.4 [5.4-7.5] mm vs 4.3 [3.6-5.2] mm; P <.0001), and area (39.4 [29.1-50.1] mm2 vs 19.9 [14.7-25.2] mm2; P <.0001) but similar volume (P = .97) with shallower lesions (2.7 [2.2-3.4] mm vs 3.8 [3.0-4.4] mm; P <.0001). Atrial linear lesions were more homogeneous (P = .02), with fewer gaps in each line (P = .003) with vHPSD ablation. LV focal lesions (15 TFC mode; 21 PC mode) were similar in volume and depth, but lesion size showed less deviation (P <.05) in TFC than PC mode. Fewer steam pops were observed in TFC mode (0% vs 28.6%; P = .03). Hemorrhagic rings around the lesion core were generally smaller with TFC/vHPSD ablation (P <.05). TFC/vHPSD ablation produces larger, shallower, more homogeneous, and less hemorrhagic lesions. vHPSD Ablation produces more transmural and contiguous linear lesions compared to PC ablation. LV lesions are more homogeneous with fewer steam pops in TFC ablation.

The procedural efficiency, efficacy and safety of high power and short duration ablation in patients with atrial fibrillation: A systemic review and meta-analysis

Catheter ablation has been established as an effective treatment for symptomatic atrial fibrillation (AF) [1]. Radiofrequency catheter ablation (RFCA) was performed using a point-by-point mode, but its' process is time-consuming, especially when compared with cyroballoon ablation and pulse field ablation [2,3]. The RF power, duration, catheter stability and contact force (CF) during RFCA are crucial parameters to achieve the lesion transmurality and linear continuity for durable pulmonary vein isolation (PVI) [4,5].

Efficacy of high-power and short-duration ablation in patients with atrial fibrillation: a prospective randomized controlled trial.

The formation of radiofrequency lesions depends on the power and duration of ablation, and the contact force (CF). Although high power (HP) creates continuous and transmural lesions, most centres still use 25-30 W for 30-40 s for safety reasons. We evaluated the clinical efficacy and safety of a HP and short-duration (HPSD) strategy for atrial fibrillation (AF) ablation. One hundred and fifty patients [58.2 ± 10.0 years, 48% with paroxysmal AF (PAF)] scheduled for index AF ablation using a CF-sensing catheter were randomly assigned to three groups [30 W, 40 W, and 50 W at ablation sites of anterior, roof, and inferior segments of pulmonary vein (PV) antra and roof line between each upper PV]. In 25-30 W for ≤20 s was applied at posterior wall ablation site in all subjects. Compared with the 30 W and 40 W groups, procedure (P < 0.001) and ablation times (P < 0.001) were shorter and ablation number for PV isolation (P < 0.001) was smaller in the 50 W group. There were no significant differences in the CF and ablation index (AI) among the three groups. There were no significant differences in the procedure-related complication rates. During the 12-month follow-up, AF recurred in 24 (16%) patients with no significant difference among the groups (P = 0.769). In the multivariate analysis, non-PAF [hazard ratio (HR) 2.836, P = 0.045] and AI (HR 0.983, P = 0.001) were independent risk factors for AF recurrence. Radiofrequency ablation with HPSD is a safe and effective strategy with reduced ablation number and shortened procedure time compared to conventional ablation.

1247Similar rate of thermal esophageal lesions are found in patients alternatively assigned to high power short duration (70W, 8s) vs. lesion index guided (35W) ablation for atrial fibrillation

Abstract Background wide antral pulmonary vein (PV) catheter ablation (CA) in patients with atrial fibrillation (AF) is safe and effective when permanent trans-mural lesions are achieved without causing harm to surrounding anatomical structures. Atrio-esophageal fistula, due to its high mortality, is the most dreadful complication related to CA for AF, therefore alternative radiofrequency (RF) approaches to reduce or eliminate this complication are currently studied. The shallower but wider lesions of high power short duration (HPSD) ablation might represent a safe alternative. Purpose to compare the rate of thermal esophageal lesions in patients with paroxysmal and persistent AF undergoing CA assigned to the 2 different RF modality. Methods one-hundred patients with paroxysmal and 100 with persistent AF will be alternatively assigned to undergo CA with the FlexAbility™ (HPSD group: 70W, 41°, 8 seconds) or the TactiCath™ (LSI-group: 35W, 41°, LSI: 5-5.5 posterior wall, up to 6 anywhere else) catheter. A 3-D mapping system, a steerable sheath and adenosine-test (30mg) were used in all patients. Posterior wall (PW) isolation in addition to PV isolation was performed in all, and patients with persistent AF were additionally treated with mitral and cavotricuspid isthmus ablation. Insertion of an esophageal probe was always attempted, and all patients underwent upper endoscopy 24 to 48 hours after CA. Results between June and October 2019, 71 patients (68 ± 10 years old, 32 (45%) female, 44 (60%) paroxysmal AF, AF duration 58 ± 81 months) were alternatively assigned to HPSD (36, 51%) or LSI-guided (35, 49%) ablation. No differences in clinical characteristics were found between groups. After 45 ± 18min and 30 ± 14 min of procedural and RF time, all PVs were isolated, and all spontaneous and adenosine-induced reconnections treated. Successful PW isolation was achieved with an additional 8 ± 3 and 7 ± 3 min of procedural and RF time. When HPSD and LSI-guided groups are compared, a similar rate of clinically non-relevant and self-healing thermal lesions at endoscopy was found (10, 27.8% vs. 10, 28.6%). Independent of the treatment group, a higher peak temperature identified patients with esophageal lesions (43.2° vs. 42°; P=.0065). A peak temperature value of 43.1° best identify patients most likely to develop thermal lesions (AUC 0.71, SE 84%, SP 39%). Interestingly, none of the 11 patients in whom esophageal probe insertion was not possible or attempted developed thermal lesions in comparison to 20 (33%) patients who underwent esophageal temperature monitoring (P=.0046). Conclusions: no difference in thermal induced esophageal lesions were found when the two different RF approach (HPSD vs. LSI guided) were compared. Interestingly, lack of temperature monitoring with an esophageal probe is associated with no thermal lesions at endoscopy.

1249Acute efficacy and safety of pulmonary vein isolation for atrial fibrillation in patients alternatively assigned to high power short duration (70W, 8s) vs lesion index guided (35W) ablation

Abstract Background permanent trans-mural lesions not affecting surrounding anatomical structures is the goal of safe and effective wide antral pulmonary vein (PV) isolation in patients with paroxysmal and persistent atrial fibrillation (AF) undergoing catheter ablation (CA). Time, energy and contact force are parameters related to lesion goodness and incorporated in a complex formula (i.e. the lesion index, LSI™, Abbott). This parameter is emerging as the gold standard for PV isolation. Recently, the shallower but wider lesions created by high power short duration (HPSD) ablation has came to attention. Purpose to compare acute reconnection rate, procedural parameters, and complication rates in patients with paroxysmal or persistent AF undergoing CA. Methods one-hundred patients with paroxysmal and 100 with persistent AF will be alternatively assigned to undergo PV isolation with the FlexAbility™ (HPSD group, 70W, 41°, 8 seconds) or the TactiCath™ (LSI-group: 35W, 41°, LSI: 5-5.5 posterior wall, up to ≥6 anywhere else) catheter. A 3-D mapping system (Ensite Precision™) and a steerable sheath (Agilis™, both Abbott) were always used. Adenosine (30mg) is given after PV isolation and ≥ 20 minutes waiting time. Posterior wall isolation was added in all, and patients with persistent AF were additionally treated with mitral and cavotricuspid isthmus ablation. Results: between June and October 2019, 71 patients (68 ± 10 years old, 32 (45%) female, 44 (60%) paroxysmal AF, AF duration 58 ± 81 months) were alternatively assigned to HPSD (36, 51%) or LSI-guided (35, 49%) ablation. No difference in clinical characteristics was found between groups. After 44 ± 18 and 30 ± 14min of procedural and RF time, all PVs were isolated, and all 17 (24%) reconnections treated with an additional 4 ± 3 and 3 ± 2min, respectively. In 8 ± 3 and 7 ± 3 min of procedural and RF time, the PW was successfully isolated in all. PV isolation (34 ± 12min vs. 56 ± 16min; P&amp;lt;.0001), RF (18 ± 5min vs. 41 ± 9min; P&amp;lt;.0001), and total procedural (138 ± 34min vs. 162 ± 34min; P=.0026) time were shorter in the HPSD group. X-Ray time and effective dose did not differ. A similar rate of acute reconnections (9, 25% vs. 8 23%) was found when HPSD and LSI were compared. A higher, although statistically not significant, number of steam pops was observed in the HPSD (14, 39%) vs. LSI (8, 23%) group, possibly related to the higher incidence of moderate pericardial effusion (&amp;gt;0.5mm, &amp;lt;20mm) found the day following the ablation (10, 28% vs. 2, 6%; P=.0238). No further complications related to CA were detected. Conclusions in patients with paroxysmal and persistent AF undergoing their first CA, HPSD ablation is faster than an LSI-guided approach. Acute efficacy (reconnection rate) is similar. Although a higher rate of haemodynamically non-relevant pericardial effusions were seen in the HPSD group, these were all treated medically and the general safety profile of this approach is excellent and comparable to LSI ablation.

Catheter ablation of atrial fibrillation using ablation index–guided high power (50 W) for pulmonary vein isolation with or without esophageal temperature probe (the AI-HP ESO II)

High-power, short-duration ablation for pulmonary vein isolation (PVI) in the treatment of atrial fibrillation (AF) facilitates the procedure and improve effectiveness; however, esophageal injury remains a safety concern. The purpose of this study was to investigate the role of luminal esophageal temperature (LET) monitoring during high-power ablation for PVI in terms of endoscopic esophageal lesion. Patients with symptomatic AF underwent ablation index-guided high-power (AI-HP) PVI (50 W; AI anterior wall/posterior wall: 550/400). In the first consecutive set of patients, an insulated esophageal temperature probe was used for LET monitoring (cutoff LET >39°C) (group A). In the second consecutive set of patients, the probe was not used (group B). All patients were scheduled to undergo esophageal endoscopy 1-3 days after ablation. A total of 120 patients (60 group A; 60 group B) were included in the study (mean age 67.8 years; 64% male). Baseline characteristics and procedural outcomes were similar between the 2 groups. Procedural PVI was achieved in all patients. First-pass PVI rate was 96.6%. Mean procedural radiofrequency (RF) time was 11.5 minutes, mean procedural time was 55.5 minutes, and fluoroscopic time was 5.6 minutes. Mean contact force at the LA posterior wall was 23 g, and mean RF ablation time at the LA posterior wall was 3.2 minutes. Two patients in group A and 1 patient in group B had endoscopic small esophageal lesions (P = .99). No serious procedural adverse events were observed. Among patients undergoing AI-HP (50 W) PVI, the incidences of ablation-related endoscopic esophageal lesion in patients with and those without use of a temperature probe for LET monitoring (cutoff 39°C) were comparably low.

Esophageal temperature evolution during high power short duration ablation: Numerical simulations and clinical suggestions

In recent times electrophysiologists started considering the possibility of performing Radiofrequency (RF) ablation for the treatment of atrial fibrillation by delivering shorter pulses of larger power (e.g. 60W, 6s applications).

Continuous ablation improves lesion maturation compared with intermittent ablation strategies.

Interrupted ablation is increasingly proposed as part of high-power short-duration radiofrequency ablation (RFA) strategies and may also result from loss of contact from respiratory patterns or cardiac motion. To study the extent that ablation interruption affects lesions. In ex vivo and in vivo experiments, lesion characteristics and tissue temperatures were compared between continuous (group 1) and interrupted (groups 2 and 3) RFA with equal total ablation duration and contact force. Extended duration ablation lesions were also characterized from 1 to 5 minutes. In the ex vivo study, continuous RFA (group 1) produced larger total lesion volumes compared with each interrupted ablation lesion group (273.8 ± 36.5 vs 205.1 ± 34.2 vs 174.3 ± 32.3 mm3 , all P < .001). Peak temperatures for group 1 were higher at 3 and 5 mm than groups 2 and 3. In vivo, continuous ablation resulted in larger lesions, greater lesion depths, and higher tissue temperatures. Longer ablation durations created larger lesion volumes and increased lesion depths. However, after 3 minutes of ablation, the rate of lesion volume, and depth formation decreased. Continuous RFA delivery resulted in larger and deeper lesions with higher tissue temperatures compared with interrupted ablation. This study may have implications for high-power short duration ablation strategies, motivates strategies to reduce variations in ablation delivery, and provides an upper limit for ablation duration beyond which power delivery has diminishing returns.

Safety and outcome of very high-power short-duration ablation using 70 W for pulmonary vein isolation in patients with paroxysmal atrial fibrillation.

Pulmonary vein isolation (PVI) using radiofrequency ablation (RFA) in patients with paroxysmal atrial fibrillation (PAF) is effective but hampered by pulmonary vein reconnection due to insufficient ablation lesions. High-power delivery over a short period of time (HPSD) in RFA is stated to create more efficient lesions. The aim of this study was to compare intraprocedural safety and outcome of HPSD ablation to conventional power settings in patients undergoing PVI for PAF. We included 197 patients with PAF that were scheduled for PVI. An ablation protocol with 70 W and a duration cut-off of 7 s at the anterior left atrium (LA) and 5 s at the posterior LA (HPSD group; n = 97) was compared to a conventional power protocol with 30-40 W for 20-40 s (standard group; n = 100) in terms of periprocedural complications and a 1-year outcome. The HPSD group showed significantly less arrhythmia recurrence during 1-year follow-up with 83.1% of patients free from atrial fibrillation compared to 65.1% in the standard group (P < 0.013). No pericardial tamponade, periprocedural thromboembolic complications, or atrio-oesophageal fistula occurred in either group. Mean radiofrequency time (12.4 ± 3.4 min vs. 35.6 ± 12.1 min) and procedural time (89.5 ± 23.9 min vs. 111.15 ± 27.9 min) were significantly shorter in the HPSD group compared to the standard group (both P < 0.001). High-power short-duration ablation demonstrated a comparable safety profile to conventional ablation. High-power short-duration ablation using 70 W for 5-7 s leads to significantly less arrhythmia recurrences after 1 year. Radiofrequency and procedural time were significantly shortened.

Atrial fibrillation : Recent studies and new treatment options

Catheter ablation by pulmonary vein isolation (PVI) is established in patients suffering from drug-refractory symptomatic atrial fibrillation (AF). According to recent guidelines, it can also be offered to AF patients as afirst-line treatment. The CASTLE-AF study randomized AF patients with severely impaired left ventricular (LV) function to catheter ablation or drug therapy. The patients in the ablation group experienced asignificantly lower all-cause mortality and hospitalization rate compared to the conservatively managed group. This result is supported by the CAMERA-MRI trial. The benefit of AF ablation in heart failure was not reproducible in the large randomized CABANA trial. Due to ahigh cross-over rate, the results are vigorously being discussed and the consequences for clinical practice remain unclear. The DECAAF study described apositive correlation with left atrial fibrosis and the risk for recurrence following PVI. Whether those fibrotic areas should be targeted during the first ablation attempt is now part of the ongoing DECAAF-II trial. Its results might affect the preprocedural planning phase and future ablation strategies. Finally, new ablation techniques are being investigated. In this context, high-power short-duration ablation (HPSD) is of growing interest. In the QDOT-FAST trial, the procedure and fluoroscopy times could be significantly reduce using HPSD catheter technology. However, future studies are still required to evaluate the long-term performance of this novel ablation approach.

P2841Atrial fibrillation ablation using ablation index guided high power (50W) smart touch technology for quantifiable and efficient circumferential pulmonary vein lesions (the FAFA power-touch study)

Abstract Background High-power short-duration ablation appears a promising concept. The so-called ablation index (AI) integrating power, contact force and time have demonstrated increased pulmonary vein isolation (PVI) durability. However, feasibility and safety of AI guided high-power ablation is unknown. Methods and results Symptomatic AF patients (n=50) underwent circumferential PVI using AI guided high-power point-by-point ablation (CARTO Smart-Touch). Ablation was set to 50W targeting AI values (550: anterior wall/roof, 400: posterior wall) with an inter-lesion distance of 6mm using a non-steerable sheath. An esophageal probe monitored luminal temperature rises (limit: 39°C). Acute PVI was obtained in all patients; first-pass efficacy was 92%. Mean ablation time per procedure was 11.2±2.2 min, mean procedure time was 55.6±6.6 min. A total of 2105 lesions were analyzed, comparing left anterior wall vs. left posterior wall and right anterior wall vs. right posterior wall, the mean ablation time (sec.) was 20.5±8.2 vs. 8.6±3.2, and 12.2±4 vs 9.3±3.4; the mean contact force (g): 17.1±12 vs 25.4±14.2 and 33.7±13.1 vs 21.0±10.5, the mean AI: 546.8±48.2 vs 444.6±55 and 554.8±56 vs. 439.8±47.1 (all P&lt;0.0001). Audible steam pops were noted in in 4 (8%) patients. Esophageal temperature rise &gt;39°C were noted in 25 (50%) patients. In 1/50 (2%) patient a minor esophageal lesion after ablation was observed without requiring specific therapy. No major complications such as death, stroke, tamponade or atria-esophageal -fistula occurred. Conclusion The novel AI guided high power ablation appears to be a feasible, safe, quantifiable and efficient strategy for PVI.

High-power and short-duration ablation for pulmonary vein isolation: Safety, efficacy, and long-term durability.

PV reconnection is often the result of catheter instability and tissue edema. High-power short-duration (HP-SD) ablation strategies have been shown to improve atrial linear continuity in acute pre-clinical models. This study compares the safety, efficacy, and long-term durability of HP-SD ablation with conventional ablation. In 6 swine, 2 ablation lines were performed anterior and posterior to the crista terminalis, in the smooth and trabeculated right atrium, respectively; and the right superior PV was isolated. In 3 swine, ablation was performed using conventional parameters (Thermocool-Smarttouch® SF; 30 W/30seconds) and in 3 other swine using HP-SD parameters (QDOT-MICRO™, 90 W/4seconds). After 30 days, linear integrity was examined by voltage mapping and pacing, and the heart and surrounding tissues were examined by histopathology. Acute line integrity was achieved with both ablation strategies; however, HP-SD ablation required 80% less RF time compared with conventional ablation (P≤0.01 for all lines). Chronic line integrity was higher with HP-SD ablation: all 3 posterior lines were continuous and transmural compared to only 1 line created by conventional ablation. In the trabeculated tissue, HP-SD ablation lesions were wider and of similar depth with 1 of 3 lines being continuous compared to 0 of 3 using conventional ablation. Chronic PVI without stenosis was evident in both groups. There were no steam-pops. Pleural markings were present in both strategies, but parenchymal lung injury was only evident with conventional ablation. HP-SD ablation strategy results in improved linear continuity, shorter ablation time, and a safety profile comparable to conventional ablation.

High-Power and Short-Duration Ablation for Pulmonary Vein Isolation: BiophysicalCharacterization.

This study sought to examine the biophysical properties of high-power and short-duration (HP-SD) radiofrequency ablation for pulmonary vein isolation. Pulmonary vein isolation is the cornerstone of atrial fibrillation ablation. However, pulmonary vein reconnection is frequent and is often the result of catheter instability, tissue edema, and a reversible nontransmural injury. We postulated that HP-SD ablation increases lesion-to-lesion uniformity and transmurality. This study included 20 swine and a novel open-irrigated ablation catheter with a thermocouple system able to record temperature at the catheter-tissue interface (QDOT Micro Catheter). Step 1 compared 3 HP-SD ablation settings:90 W/4 s, 90 W/6 s, and 70 W/8 s in a thigh muscle preparation. Ablation at 90 W/4 s was identified as the best compromise between lesion size and safety parameters, with no steam-pop or char. In step 2, a total of 174 single ablation applications were performed in the beating heart and resulted in 3 (1.7%) steam-pops, all occurring at catheter-tissue interface temperature≥85°C. Additional 233 applications at 90 W/4 s and temperature limit of 65°C were applied without steam-pop. Step 3 compared the presence of gaps and lesion transmurality in atrial lines and pulmonary vein isolation between HP-SD (90 W/4 s, T≤65°C) and standard (25 W/20 s) ablation. HP-SD ablation resulted in 100% contiguous lines with all transmural lesions, whereas standard ablation had linear gaps in 25% and partial thickness lesions in 29%. Ablation with HP-SD produced wider lesions (6.02 ± 0.2 mm vs. 4.43 ± 1.0 mm; p= 0.003) at similar depth (3.58 ± 0.3 mm vs. 3.53 ± 0.6 mm; p= 0.81) and improved lesion-to-lesion uniformity with comparable safety end points. In a preclinical model, HP-SD ablation (90 W/4 s, T≤65°C) produced an improved lesion-to-lesionuniformity, linear contiguity, and transmurality at a similar safety profile of conventional ablation.

Durable lesion formation while avoiding esophageal injury during ablation of atrial fibrillation: Lessons learned from late gadolinium MR imaging

Adequate catheter/atrial tissue contact is critical for lesion formation during radiofrequency (RF) ablation of atrial fibrillation (AF). Late gadolinium enhancement magnetic resonance imaging (LGE-MRI) is a unique tool for the evaluation of lesion formation and detection of acute esophageal injury. LGE-MRIs were obtained prior, within 24hours of, and at 115 ± 62 days after first AF ablation in 36 patients. The Visitag module of CARTO3 was used to collect contact force (CF) and duration from a CF sensing ablation catheter for each registered ablation point. The minimum CF resulting in permanent lesions was determined. Esophageal enhancement detected by acute LGE-MRI was classified as mild, moderate, and severe. The CF resulting in esophageal enhancement was determined. A total of 4,642 registered ablation tags at 50 W power were analyzed. The mean RF duration (5.9 ± 3.7vs. 5.6 ± 3.2 seconds, P<0.05), CF (11.5 ± 5.6vs. 10.9 ± 5.4g, P<0.001), and force time integral (FTI) (67.3 ± 54.5vs. 62.2 ± 52.7 gs, P<0.01) were significantly higher between ablation tags with and without associated LGE-MRI detected scar. The mean CF (15.7 ± 6.1vs. 12.6 ± 5.9g, P<0.05, n=17 patients) in areas of esophageal enhancement was greater than areas without. Left atrial short duration ablation lesions with a CF greater than 12 g are more likely to be associated with permanent lesion formation. Ablating on top of the esophagus, CF less than 15g would help minimize esophageal wall injury.

Effect of variable heat transfer coefficient on tissue temperature next to a large vessel during radiofrequency tumor ablation

BackgroundOne of the current shortcomings of radiofrequency (RF) tumor ablation is its limited performance in regions close to large blood vessels, resulting in high recurrence rates at these locations. Computer models have been used to determine tissue temperatures during tumor ablation procedures. To simulate large vessels, either constant wall temperature or constant convective heat transfer coefficient (h) have been assumed at the vessel surface to simulate convection. However, the actual distribution of the temperature on the vessel wall is non-uniform and time-varying, and this feature makes the convective coefficient variable.MethodsThis paper presents a realistic time-varying model in which h is a function of the temperature distribution at the vessel wall. The finite-element method (FEM) was employed in order to model RF hepatic ablation. Two geometrical configurations were investigated. The RF electrode was placed at distances of 1 and 5 mm from a large vessel (10 mm diameter).ResultsWhen the ablation procedure takes longer than 1–2 min, the attained coagulation zone obtained with both time-varying h and constant h does not differ significantly. However, for short duration ablation (5–10 s) and when the electrode is 1 mm away from the vessel, the use of constant h can lead to errors as high as 20% in the estimation of the coagulation zone.ConclusionFor tumor ablation procedures typically lasting at least 5 min, this study shows that modeling the heat sink effect of large vessels by applying constant h as a boundary condition will yield precise results while reducing computational complexity. However, for other thermal therapies with shorter treatment using a time-varying h may be necessary.