Multipolar Electrograms: A New Configuration That Increases the Measurement Accuracy of Intracardiac Signals.

BACKGROUND: Accurate measurements of intracardiac electrograms (EGMs) remain a clinical challenge because of the suboptimal attenuation of far-field potentials. Multielectrode mapping catheters provide an opportunity to construct multipolar instead of bipolar EGMs for rejecting common far-field potentials recorded from a multivectorial space. OBJECTIVES: The purpose of this study was to develop a multipolar EGM and compare its characteristics to those of bipolar EGMs METHODS: Using a 36-electrode array catheter (Optrell-36; Biosense Webster), a far-field component was mathematically constructed from clusters of electrodes surrounding each inspected electrode. This component was subtracted from the unipolar waveform to produce a local unipolar, referred to as a "multipolar EGM." The performance of multipolar EGMs was evaluated in 7 swine with healed anteroseptal infarction. RESULTS: Multipolar EGMs proved superior in attenuating far-field potentials in infarct border zones, increasing the near-field to far-field ratio from 0.92 ± 0.2 to 2.25 ± 0.3 (P < 0.001). Removal of far-field components reduced the voltage amplitude (P < 0.001) and enlarged the infarct surface area (P = 0.02), aligning more closely with histological findings. Of 379 EGMs with ≥20 ms activation time difference between bipolar and multipolar EGMs, 95.3% (361 of 379) were accurately annotated using multipolar EGMs, while annotation based on bipolar EGM was predominantly made on far-field components. CONCLUSIONS: Multielectrode array catheters provide a unique platform for constructing multipolar EGMs. This new EGM may be beneficial for "purifying" local potentials within a complex electrical field, resulting in more accurate voltage and activation maps.

In Vivo Findings of a Novel Focal Ablation Catheter: Focused Electric Field Catheter Tip.

Current catheter designs used for radiofrequency (RF) in cardiac tissue achieve limited ablation depth as lesion size is driven heavily by resistive heating at the tissue surface. A catheter with a truncated, dome-shaped tip with a toroidal surface designed for focal RF ablation was recently described. This in vivo study compares lesion characteristics between a second-generation focused electric field (FEF) catheter vs a standard irrigated catheter using RF energy in a beating heart model. We performed in vivo ablations using RF energy with the FEF ablation catheter tip (Focused Therapeutics) and an irrigated Blazer catheter (Boston Scientific) under identical power, duration, and irrigation rates. In addition, RF dosing at high power and duration was examined using the FEF catheter. Intracardiac echocardiography was used to evaluate steam pops and catheter tip angle relative to the tissue surface. Studies were terminal and lesion size was measured following 2,3,5-triphenyltetrazolium chloride staining. Ablations were performed in 6 swine (FEF, n = 31; control, n = 8). FEF ablation lesions (n = 7) were deeper (15.6 ± 2.6 mm vs 7.5 ± 1.9 mm; P < 0.001) and wider (18.4 ± 2.9 mm vs 12.6 ± 2.4 mm; P < 0.001) than lesions delivered with the control irrigated catheter (n = 8) under the same parameters. Thirty-two percent (n = 10 of 31) of lesions delivered from the left ventricle endocardial surface using the FEF catheter were transmural. No steam pops were observed with delivery of FEF lesions (n = 31). The angle of incidence did not significantly affect FEF lesion size. In this in vivo preclinical study, the FEF catheter, which provides focused energy delivery, resulted in significantly larger lesions than the irrigated control catheter without steam pops. Approximately one-third of ablations with the FEF catheter delivered from the endocardial left ventricular surface resulted in transmural lesions.

Efficacy of Pulsed Field vs Radiofrequency for the Reablation of Chronic Radiofrequency Ablation Substrate: Redo Pulsed Field Ablation.

BACKGROUND: The efficacy of pulsed field ablation (PFA) for redo procedures is unknown. OBJECTIVES: In this study, the authors aimed to evaluate the effectiveness of PFA when performing PFA over chronic RFA (redo environment). METHODS: This was a 3-step in vivo study. In step 1 (creation of redo environment), 6 swine underwent radiofrequency ablation (RFA) with a local impedance measuring catheter and a contact force-enabled catheter in 3 different sites: the right atrium (RA) (intercaval line with intentional gaps), the left atrium (LA) (pulmonary vein isolation [PVI] with intentional gaps and superficial posterior wall ablations), and the left ventricle (LV) (short RFA applications [chronic RFA]). In step 2 (re-ablation), following a survival period of ≈5 weeks, animals were retreated as follows: in the RA, a focal PFA catheter over the prior intercaval line; in the LA, PVI using a pentaspline PFA catheter; and in the LV, animals were randomized to focal PFA or RFA. In each arm, 2 types of lesions were performed: acute or acute over chronic. In step 3 (remapping and euthanization), following an additional 3 to 5 days, all animals were remapped and sacrificed. RESULTS: In the RA, re-ablation with PFA resulted in a complete intercaval block in all animals, expanding and homogenizing the disparate chronic RFA lesions from a width of 4 to 7 mm (chronic RFA) to a width of 16 to 28 mm (PFA over chronic RFA). In the LA, re-ablation with PFA resulted in complete PVI and transmural ablation of the PW. In the LV, the mean depth for acute RFA (post 2-5 days survival) was 7.6 ± 1.3 mm vs 3.9 ± 1.6 mm in the acute over chronic RFA lesions (P < 0.01). In contrast, the mean depth for acute PFA was 7.0 ± 1.6 mm, similar to when ablating with PFA over RFA (7.1 ± 1.3 mm; P = 0.94). CONCLUSIONS: PFA is highly efficient for ablation following prior RFA, which may be beneficial in patients presenting for redo procedures. In the ventricle, PFA resulted in lesions that are deeper than RFA when ablating over chronic superficial RFA lesions.

Effect of sodium glucose cotransporter 2 inhibitors on atrial tachy-arrhythmia burden in patients with cardiac implantable electronic devices.

INTRODUCTION: Use of sodium glucose cotransporter 2 inhibitors (SGLT2i) was associated with a reduction in atrial fibrillation hospitalizations. Therefore, we aim to evaluate the effects of SGLT2i on atrial tachy-arrhythmias (ATA) in patients with cardiac implantable electronic devices (CIEDs). METHODS: All 13 888 consecutive patients implanted with a CIED in two tertiary medical centers were enrolled. Treatment with SGLT2i was assessed as a time dependent variable. The primary endpoint was the total number of ATA. Secondary endpoints included total number of ventricular tachy-arrhythmias (VTA), ATA and VTA, and death. All events were independently adjudicated blinded to the treatment. Multivariable propensity score modeling was performed. RESULTS: During a total follow-up of 24 442 patient years there were 62 725 ATA and 10 324 VTA events. Use of SGLT2i (N = 696) was independently associated with a significant 22% reduction in the risk of ATA (hazard ratio [HR] = 0.78 [95% confidence interval {CI} = 0.70-0.87]; p < .001); 22% reduction in the risk of ATA/VTA (HR = 0.78 [95% CI = 0.71-0.85]; p < .001); and with a 35% reduction in the risk of all-cause mortality (HR = 0.65 [95% CI = 0.45-0.92]; p = .015), but was not significantly associated with VTA risk (HR = 0.92 [95% CI = 0.80-1.06]; p = .26). SGLT2i were associated with a lower ATA burden in heart failure (HF) patients but not among diabetes patients (HF: HR = 0.68, 95% CI = 0.58-0.80, p < .001 vs. Diabetes: HR = 0.95, 95% CI = 0.86-1.05, p = .29; p < .001 for interaction between SGLT2i indication and ATA burden). CONCLUSION: Our real world findings suggest that in CIED HF patients, those with SGLT2i had a pronounced reduction in ATA burden and all-cause mortality when compared with those not on SGLT2i.

Utility and Limitations of Ablation Index for Guiding Therapy in Ventricular Myocardium.

BACKGROUND: Ablation index (AI) is used for guiding therapy during pulmonary vein isolation. However, its potential utility in ventricular myocardium is unknown. OBJECTIVES: This study sought to examine the correlation between AI and lesion dimensions in healthy and infarcted ventricles. METHODS: In ex vivo experiments using healthy swine ventricles, the correlation between AI (400-1,200) and lesion dimensions was examined at fixed power (30 W) and contact force (CF) (15 g). To examine the accuracy of AI in predicting lesion dimensions created by different combinations of ablation parameters, applications with a similar prespecified AI value created using different power (30 vs 40 W), CF (15 vs 25 g) or impedance (130-170 Ω) were created. In in vivo experiments, the correlation between AI and lesion dimensions was examined in healthy and infarcted myocardium. RESULTS: Ex vivo experiments (247 lesions, 36 hearts) showed good correlation between AI and lesion depth (R = 0.93; P < 0.001). However, in vivo experiments (9 healthy swine and 10 infarcted swine) showed moderate correlation in healthy myocardium (R = 0.64; P < 0.01) and poor correlation in infarcted myocardium (R = 0.23; P = 0.61). AI values achieved using different combinations of power, CF, and baseline impedance resulted in different lesion depths: Ablation at 30 W produced deeper lesions compared with 40 W, ablation with CF of 15 g produced deeper lesions compared with CF of 25 g, and ablation at lower impedance produced larger lesions at similar prespecified AI values (P < 0.01 for all). CONCLUSIONS: AI has limited value for guiding ablation in ventricular myocardium, particularly scar. This may be related to small proportional significance of application duration and complex tissue architecture.

Atrial Endocardial Unipolar Voltage Mapping for Detection of Viable Intramural Myocardium: A Proof-of-Concept Study.

BACKGROUND: Endocardial bipolar voltage amplitude is largely derived from endocardial and subendocardial wall layers. This may result in situations of low bipolar voltage amplitude despite the presence of mid-myocardial including epicardial (ie, intramural-epicardial) viable myocardium. This study examined the utility of endocardial unipolar voltage mapping for detection of viable intramural-epicardial atrial myocardium. METHODS: In 15 swine, an atrial intercaval ablation line with an intentional gap was created. Animals survived for 6 to 8 weeks before electroanatomical mapping followed by sacrifice. Gaps were determined by the presence of electrical conduction and classified based on the histopathologiclly layer(s) of viable myocardium into the following: (1) transmural, (2) endocardial, and (3) intramural-epicardial. Voltage data from healthy, scar, and gap points were exported into excel. The sensitivity and specificity of bipolar and unipolar voltage amplitude to detect intramural-epicardial gaps were compared using receiver operating characteristic analysis. RESULTS: In 9 of 15 (60%) swine, a focal ablation gap was detected in the intercaval line, while in the remainder 6 of 15 (40%), the line was complete without gaps. Gaps were classified into transmural (n=3), endocardial (n=3), or intramural-epicardial (n=3). Intramural-epicardial gaps were characterized by very low bipolar voltage amplitude that was similar to areas with transmural scar (P=0.91). In comparison, unipolar voltage amplitude in intramural-epicardial gaps was significantly higher compared to transmural scar (P<0.001). Unipolar voltage amplitude had higher sensitivity (93% versus 14%, respectively) and similar specificity (95% versus 98%, respectively) to bipolar voltage for detection of intramural-epicardial gaps. CONCLUSIONS: Atrial unipolar voltage mapping may be a useful technique for identifying viable intramural-epicardial myocardium in patients with endocardial scar.

Lattice-tip catheter for single-shot pulmonary vein isolation with pulsed field ablation.

BACKGROUND: A compressible lattice-tip catheter designed for focal ablation using radiofrequency or pulsed-field energies has been recently described. The objective of this study is to describe a new lattice catheter designed for single-shot pulmonary vein isolation (PVI). METHODS: This 8F catheter consists of a compressible lattice tip that is delivered over the wire and is expandable up to 34 mm (SpherePVI™, Affera Inc.). Pulsed field ablation (PFA) was applied from 6 elements using a biphasic waveform of microsecond scale (± 1.3-2.0 kV, 5 s per application). In 12 swine, the superior vena cava (SVC) and right superior pulmonary vein (RSPV) were targeted for isolation. Animals were survived for 12-24 h (n = 6) or 3 weeks (n = 6) for evaluation of short and long-term safety and efficacy parameters. PVI was evaluated immediately after ablation and at the terminal procedure. Ablation-related microbubbles were examined using intracardiac echocardiography and phrenic nerve function by pacing. The tissue was examined by histopathology. RESULTS: In all 12 animals, PFA resulted in successful acute isolation of the SVC and RSPV using 2.8 ± 1.1 and 3.2 ± 1.2 applications per vein, respectively. After a survival period of 23 ± 5.9 days, all targeted veins remained isolated, and the level of isolation persisted without significant regression or expansion. In one animal, SVC isolation at the level of the right atrial appendage resulted in sinus node arrest. PFA did not affect phrenic nerve function, and it was associated with a few isolated bubbles formation. CONCLUSIONS: In this pre-clinical study, a new expandable lattice catheter designed for single-shot PVI was able to achieve rapid and durable isolation.

Effect of Pulsed-Field and Radiofrequency Ablation on Heterogeneous Ventricular Scar in a Swine Model of Healed Myocardial Infarction.

BACKGROUND: Pulsed-field ablation (PFA) is a nonthermal energy with higher selectivity to myocardial tissue in comparison to radiofrequency ablation (RFA). We compared the effects of PFA and RFA on heterogeneous ventricular scar in a swine model of healed infarction. METHODS: In 9 swine, myocardial infarction was created by balloon occlusion of the left anterior descending artery. After a survival period of 8 to 10 weeks, ablation with PFA or RFA was performed at infarct border zones identified by abnormal electrograms. In the PFA group (4 swine), ablation was performed with a lattice catheter (Sphere-9, Affera, Inc). In the RFA group (5 swine), ablation was performed using a 3.5-mm tip catheter (Thermocool ST-SF; Biosense Webster). To further investigate the effect of RFA on temperature development in scar tissue, intramyocardial temperature was measured in healthy and infarcted myocardium using an ex vivo bath model. RESULTS: A total of 11 PFA and 15 RFA lesions were created at infarct border zones with heterogeneous scar. PFA produced uniform and well-demarcated lesions exhibiting irreversible injury characterized by cardiomyocyte death, contraction bands, and lymphocytic infiltration. This effect of PFA extended from the subendocardium through collagen and fat to the epicardial layers. In contrast, the effect of RFA is less uniform and largely limited to the subendocardium with minimal effect on viable myocardium deeper to separating layers of collagen and fat. PFA produced deeper and more transmural lesions (6.4 [interquartile range, 5.5-7.5) versus 5.4 [interquartile range, 4.8-5.9]), 72% versus 30%, respectively; P≤0.02 for each comparison). The limited effect of RFA on viable myocardium at deeper infarct layers was related to a lower intramyocardial maximal temperature compared with healthy myocardium (P=0.01). CONCLUSIONS: PFA may be advantageous for ablation in ventricular scar, producing lesions that unlike RFA are not limited to the subendocardium, but also eliminate viable myocardium separated from the catheter by collagen and fat.

Reduction in Ventricular Tachyarrhythmia Burden in Patients Enrolled in the RAID Trial.

BACKGROUND: The RAID (Ranolazine Implantable Cardioverter-Defibrillator) randomized placebo-controlled trial showed that ranolazine treatment was associated with reduction in recurrent ventricular tachycardia (VT) requiring appropriate implantable cardioverter-defibrillator (ICD) therapy. OBJECTIVES: This study aimed to identify groups of patients in whom ranolazine treatment would result in the highest reduction of ventricular tachyarrhythmia (VTA) burden. METHODS: Andersen-Gill analyses were performed to identify variables associated with risk for VTA burden among 1,012 patients enrolled in RAID. The primary endpoint was VTA burden defined as VTA episodes requiring appropriate treatment. RESULTS: Multivariate analysis identified 7 factors associated with increased VTA burden: history of VTA, age ≥65 years, New York Heart Association functional class ≥III, QRS complex (≥130 ms), low ejection fraction (<30%), atrial fibrillation (AF), and concomitant antiarrhythmic drug (AAD) therapy. The effect of ranolazine on VTA burden was seen among patients without concomitant AAD therapy (HR [HR]: 0.68; 95% CI: 0.55-0.84; P < 0.001), whereas no effect was seen among those who are concomitantly treated with other AADs (HR: 1.33; 95% CI: 0.90-1.96; P = 0.16); P = 0.003 for interaction. In patients with cardiac resynchronization therapy (CRT) ICDs, ranolazine treatment was associated with a 36% risk reduction for VTA recurrence (HR: 0.64; 95% CI: 0.47-0.86; P < 0.001), whereas among patients with ICDs without CRT no significant effect was noted (HR: 0.94; 95% CI: 0.74-1.18; P = 0.57); P = 0.047 for interaction. CONCLUSIONS: In patients with high risk for VTA, ranolazine is effective in reducing VTA burden, with significantly greater effect in CRT-treated patients, those without AF, and those not treated with concomitant AADs. In patients already on AADs or those with AF, the addition of ranolazine did not affect VTA burden. (Ranolazine Implantable Cardioverter-Defibrillator Trial [RAID]; NCT01215253).

Increasing Lesion Dimensions of Bipolar Ablation by Modulating the Surface Area of the Return Electrode.

OBJECTIVES: This study sought to examine the effect of the return electrode's surface area on bipolar RFA lesion size. BACKGROUND: Bipolar radiofrequency ablation (RFA) is typically performed between 2 3.5-mm tip catheters serving as active and return electrodes. We hypothesized that increasing the surface area of the return electrode would increase lesion dimensions by reducing the circuit impedance, thus increasing the current into a larger tissue volume enclosed between the electrodes. METHODS: In step 1, ex vivo bipolar RFA was performed between 3.5-mm and custom-made return electrodes with increasing surface areas (20, 80, 180 mm2). In step 2, ex vivo bipolar RFA was performed between 3.5-mm and 3.5-mm or 8-mm electrode catheters positioned perpendicular or parallel to the tissue. In step 3, in vivo bipolar RFA was performed between 3.5-mm and either 3.5-mm or 8-mm parallel electrode at the: 1) left ventricular summit; 2) interventricular septum; and 3) healed anterior infarction. RESULTS: In step 1, increasing the surface area of the return electrode resulted in lower circuit impedance (R = -0.65; P < 0.001), higher current (R = +0.80; P < 0.001), and larger lesion volume (R = +0.88; P < 0.001). In step 2, an 8-mm return electrode parallel to tissue produced larger and deeper lesions compared with a 3.5-mm return electrode (P = 0.014 and P = 0.02). Similarly, in step 3, compared with a 3.5-mm, bipolar RFA with an 8-mm return electrode produced larger (volume: 1,525 ± 871 mm3 vs 306 ± 310 mm3, respectively; P < 0.001) and more transmural lesions (88% vs 0%; P < 0.001). CONCLUSIONS: Bipolar RFA using an 8-mm return electrode positioned parallel to the tissue produces larger lesions in comparison with a 3.5-mm return electrode.

How to use bipolar and unipolar electrograms for selecting successful ablation sites of ventricular premature contractions.

BACKGROUND: Local activation time is often determined by the maximal negative of the extracellular unipolar potential (-dV/dTmax). While this is accurate in 2-dimensional uniform tissue, propagation through nonuniform or 3-dimensional structures have shown discordance between -dV/dTmax and local activation time. OBJECTIVE: The purpose of this study was to examine the relationship between bipolar and unipolar electrograms for selecting successful ablation sites of endocardial (superficial) vs intramural (deep) ventricular premature contractions (VPCs). METHODS: This cohort consisted of 66 patients with VPCs presenting for ablation in a bigeminy, trigeminy, or quadrigeminy pattern. VPCs were classified as endocardial if ablation at the earliest endocardial site resulted in immediate suppression (<10 seconds) or as intramural if ablation resulted in delayed suppression (≥10 seconds), required multiple applications, or was not achieved. Unipolar and bipolar electrograms were analyzed. RESULTS: In endocardial VPCs, the first rapid bipolar deflection corresponded with unipolar -dV/dTmax, occurring 20.5 ms (17.8-26.0 ms) and 16.0 ms (6.8-22.0 ms), respectively, before the QRS onset. In successfully ablated intramural VPCs, the first rapid bipolar deflection preceded the QRS onset by 14.0 ms (11.2-22.6 ms) and coincided with the first rapid unipolar deflection, although -dV/dTmax occurred 10.5 ms (0.0-20.8 ms) after the QRS onset and often coincided with far-field activity. In unsuccessfully ablated intramural VPCs, the first rapid bipolar deflection to QRS onset interval was shorter in comparison to successfully ablated intramural VPCs (1.5 ms vs 14.0 ms; P < .001) while the unipolar -dV/dTmax to QRS onset interval was similar (P = .095). CONCLUSION: Mapping of VPCs should be guided by the first rapid bipolar deflection that corresponds to a similarly early unipolar deflection but not with -dV/dTmax.

Direction-aware mapping algorithms have minimal impact on bipolar voltage maps created using high-resolution multielectrode catheters.

INTRODUCTION: Direction-aware mapping algorithms improve the accuracy of voltage mapping by measuring the maximal voltage amplitude recorded in the direction of wavefront propagation. While beneficial for stationary catheters, its utility for roving catheters collecting electrograms (EGMs) at multiple angles is unknown. OBJECTIVE: To compare the directional dependence of bipolar voltage amplitude between stationary and roving catheters. METHODS: In 10 swine, a transcaval ablation line with a gap was created. The gap was mapped using an array catheter (Optrell™; Biosense Webster). In Step 1, the array was kept stationary over the gap, and four voltage maps were created during activation of the gap from superior, inferior, septal, and lateral directions. In Step 2, four additional maps were created; however, the catheter was allowed to move with points acquired at multiple angles. In Step 3, the gap was remapped; however, bipoles were computed using a direction-aware mapping algorithm. RESULTS: In a stationary catheter position, bipolar voltage distribution was influenced by the direction of activation with maximal differences obtained between orthogonal directions 32% (13%-53%). However, roving the catheter produced similar bipolar voltage maps irrespective of the direction of activation 11% (5%-18%). A direction-aware mapping algorithm was beneficial for reducing the directional dependence of voltage maps created by stationary catheters but not by roving catheters. CONCLUSION: The directional dependency of bipolar voltage amplitude is greatest when the catheter is stationary. However, when the catheter is allowed to rove and collect EGMs at multiple angles as occurs clinically, the directional dependence of bipolar voltage is minimal.

Impact of High-Power Short-Duration Radiofrequency Ablation on Esophageal Temperature Dynamic.

BACKGROUND: High-power short-duration (HP-SD) radiofrequency ablation (RFA) has been proposed as a method for producing rapid and effective lesions for pulmonary vein isolation. The underlying hypothesis assumes an increased resistive heating phase and decreased conductive heating phase, potentially reducing the risk for esophageal thermal injury. The objective of this study was to compare the esophageal temperature dynamic profile between HP-SD and moderate-power moderate-duration (MP-MD) RFA ablation strategies. METHODS: In patients undergoing pulmonary vein isolation, RFA juxtaposed to the esophagus was delivered in an alternate sequence of HP-SD (50 W, 8-10 s) and MP-MD (25 W, 15-20 s) between adjacent applications (distance, ≤4 mm). Esophageal temperature was recorded using a multisensor probe (CIRCA S-CATH). Temperature data included magnitude of temperature rise, maximal temperature, time to maximal temperature, and time return to baseline. In swine, a similar experimental design compared the effect of HP-SD and MP-MD on patterns of esophageal injury. RESULTS: In 20 patients (68.9±5.8 years old; 60% persistent atrial fibrillation), 55 paired HP-SD and MP-MD applications were analyzed. The esophageal temperature dynamic profile was similar between HP-SD and MP-MD ablation strategies. Specifically, the magnitude of temperature rise (2.1 °C [1.4-3] versus 2.0 °C [1.5-3]; P=0.22), maximal temperature (38.4 °C [37.8-39.3] versus 38.5 °C [37.9-39.4]; P=0.17), time to maximal temperature (24.9±7.5 versus 26.3±6.8 s; P=0.1), and time of temperature to return to baseline (110±23.2 versus 111±25.1 s; P=0.86) were similar between HP-SD and MP-MD ablation strategies. In 6 swine, esophageal injury was qualitatively similar between HP-SD and MP-MD strategies. CONCLUSIONS: Esophageal temperature dynamics are similar between HP-SD and MP-MD RFA strategies and result in comparable esophageal tissue injury. Therefore, when using a HP-SD RFA strategy, the shorter application duration should not prompt shorter intervals between applications.

Pulsed-Field Ablation in Ventricular Myocardium Using a Focal Catheter: The Impact of Application Repetition on Lesion Dimensions.

[Figure: see text].

Propagation Vectors Facilitate Differentiation Between Conduction Block, Slow Conduction, and Wavefront Collision.

[Figure: see text].

Epicardial fat and the risk of atrial tachy-arrhythmia recurrence post pulmonary vein isolation: a computed tomography study.

Epicardial and Pericardia fat have been hypothesized to exert local and systemic pathogenic effects on nearby cardiac structures. The present study aimed to evaluate the impact of epicardial and pericardial fat volumes on the outcome of patients that underwent a first pulmonary vein isolation (PVI) with cryoablation. We included 130 consecutive patients with atrial fibrillation (AF) that underwent contrast enhanced ECG-gated cardiac computed tomography (CCT) before a PVI. The control group included 50 patients in normal sinus rhythm that underwent ECG-gated CT to rule out coronary artery disease. Epicardial and pericardial fat volumes were quantified with CCT. Patients with AF compared to patients with normal sinus rhythm (control group) had significantly larger epicardial (140.3 ± 58.1 vs. 55.9 ± 17.7 ml; respectively, P < 0.001) and pericardial (77.0 ± 35.5 ml vs. 27.2 ± 9.5 ml; respectively, P < 0.001) fat volumes. Among patients that underwent PVIs, those with AF recurrence had a greater epicardial (175.0 ± 54.4 ml vs. 130.7 ± SD 54.2 ml; respectively, P < 0.001) and pericardial (93.7 ± SD 42.8 vs. 72.5 ± SD 31.9 ml; respectively, P < 0.001) fat volumes, compared to patients with no AF recurrence. Multivariate analyses revealed that epicardial fat was an independent predictor of recurrence post-ablation (HR = 1.08, 95% CI 1.02-1.16 per 10-ml increase in volume; P = 0.009). Pericardial fat was associated with 7% increase in risk of recurrent AF (HR = 1.07, 95% CI 0.98-1.18; P = 0.117). Epicardial fat, assessed with contrast enhanced CCT, is an independent predictor of AF recurrence after PVI ablation.

Circular Multielectrode Pulsed Field Ablation Catheter Lasso Pulsed Field Ablation: Lesion Characteristics, Durability, and Effect on Neighboring Structures.

BACKGROUND: Pulsed field ablation (PFA) is a nonthermal energy with potential safety advantages over radiofrequency ablation. This study investigated a novel PFA system-a circular multielectrode catheter (PFA lasso) and a multichannel generator designed to work with Carto 3 mapping system. METHODS: A 7.5F bidirectional circular catheter with 10 electrodes and variable expansion was designed for PFA (biphasic, 1800 Volts). This study included a total of 16 swine used to investigate the following 3 experimental aims: Aim 1 examined the feasibility to create a right atrial ablation line of block from the superior vena cava to the inferior vena cava. Aim 2 examined the effect of PFA on lesion maturation including durability after a 30-day survival period. Aim 3 examined the effect of high-intensity PFA (10 applications) on esophageal and phrenic nerve tissue in comparison to normal intensity radiofrequency ablation (1-2 applications). Histopathologic analysis of all cardiac, esophageal, and phrenic nerve tissue was performed. RESULTS: Acute line of block was achieved in 12/12 swine (100%) and required a total PFA time of 14 seconds (interquartile range [IQR], 9-24.5) per line. Ablation line durability after 28±3 days was maintained in 11/12 (91.7%) swine. PFA resulted in transmural lesions in 179/183 (97.8%) sections and a median lesion width of 14.2 mm. High-intensity PFA (9 [IQR, 8-14] application) had no effect on the esophagus while standard intensity radiofrequency ablation (1.5 [IQR, 1-2] applications) resulted in deep esophageal tissue injury involving the muscularis propria and adventitia layers. High-intensity PFA (16 [IQR, 10-28] applications) has no effect on phrenic nerve function and structure while standard dose radiofrequency ablation (1.5 [IQR, 1-2] applications) resulted in acute phrenic nerve paralysis. CONCLUSIONS: In this preclinical model, a multielectrode circular catheter and multichannel generator produced durable atrial lesions with lower vulnerability to esophageal or phrenic nerve damage.

Discordance in Scar Detection Between Electroanatomical Mapping and Cardiac MRI in an Infarct Swine Model.

OBJECTIVES: This study sought to investigate the sensitivity of electroanatomical mapping (EAM) to detect scar as identified by late gadolinium enhancement (LGE) cardiac magnetic resonance (CMR). BACKGROUND: Previous studies have shown correlation between low voltage electrogram amplitude and myocardial scar. However, voltage amplitude is influenced by the distance between the scar and the mapping surface and its extent. The aim of this study is to examine the reliability of low voltage EAM as a surrogate for myocardial scar using LGE-derived scar as the reference. METHODS: Twelve swine underwent anterior wall infarction by occlusion of the left anterior descending artery (LAD) (n = 6) or inferior wall infarction by occlusion of the left circumflex artery (LCx) (n = 6). Subsequently, animals underwent CMR and EAM using a multielectrode mapping catheter. CMR characteristics, including wall thickness, LGE location and extent, and EAM maps, were independently analyzed, and concordance between voltage maps and CMR characteristics was assessed. RESULTS: LGE volume was similar between the LCx and LAD groups (8.5 ± 2.2 ml vs. 8.3 ± 2.5 ml, respectively; p = 0.852). LGE scarring in the LAD group was more subendocardial, affected a larger surface area, and resulted in significant wall thinning (4.88 ± 0.43 mm). LGE scarring in the LCx group extended from the endocardium to the epicardium with minimal reduction in wall thickness (scarred: 5.4 ± 0.67 mm vs. remote: 6.75 ± 0.38 mm). In all the animals in the LAD group, areas of low voltage corresponded with LGE and wall thinning, whereas only 2 of 6 animals in the LCx group had low voltage areas on EAM. Bipolar and unipolar voltage amplitudes were higher in thick inferior walls in the LCx group than in thin anterior walls in the LAD group, despite a similar LGE volume. CONCLUSIONS: Discordances between LGE-detected scar areas and low voltage areas by EAM highlighted the limitations of the current EAM system to detect scar in thick myocardial wall regions.

Impact of High-Power Short-Duration Radiofrequency Ablation on Long-Term Lesion Durability for Atrial Fibrillation Ablation.

OBJECTIVES: The goal of this study was to compare lesion durability between high-power short-duration (HP-SD) and moderate-power moderate-duration (MP-MD) ablation strategies. BACKGROUND: HP-SD radiofrequency ablation (RFA) was developed to improve pulmonary vein isolation (PVI) by reducing the effect of catheter instability inherent to MP-MD ablation strategies. However, its long-term effect on lesion durability for the treatment of atrial fibrillation is unknown. METHODS: Patients with atrial fibrillation (n = 112) underwent PVI using HP-SD ablation (45 to 50 W, 8 to 15 s) with contact force-sensing open irrigated catheter. Cavotricuspid isthmus, mitral annular, and roof lines were permitted. A control group (n = 112) underwent ablation using MP-MD ablation (20 to 40 W, 20 to 30 s) with similar technology. Chronic PV reconnection was examined in patients who required a redo procedure (HP-SD ablation, n = 18; MP-MD ablation, n = 23). RESULTS: The rate of PVI at the completion of the initial encirclement was similar between the HP-SD and MP-MD ablation strategies (90.2% vs. 83.0%; p = 0.006). The HP-SD strategy required shorter RFA time (17.2 ± 3.4 min vs. 31.1 ± 5.6 min; p < 0.001). The incidence of chronic PV reconnection was lower with HP-SD ablation (16.6% vs. 52.2%; p = 0.03). Areas of chronic reconnection were associated with catheter motion ≥1 mm for ≥50% application duration. In a higher proportion of HP-SD applications, catheter motion was <1 mm during ≥50% duration (88.6% vs. 72.8%; p < 0.001), allowing energy delivery with greater stability. Both ablation strategies were effective for cavotricuspid isthmus; however, the HP-SD strategy was less effective for mitral annular lines, requiring ablation at lower power for longer duration to avoid steam pops. CONCLUSIONS: HP-SD ablation may improve PVI durability, and it shortens RFA time. However, ablation in thicker myocardium often requires lower power applied for longer duration, allowing deeper lesions without tissue overheating.

Pulsed Field Ablation Using a Lattice Electrode for Focal Energy Delivery: Biophysical Characterization, Lesion Durability, and Safety Evaluation.

BACKGROUND: Pulsed field ablation (PFA) is a nonthermal energy that may provide safety advantages over radiofrequency ablation (RFA). One-shot PFA catheters have been developed for pulmonary vein isolation, but they do not permit flexible lesion sets. This study investigated a novel lattice-tip catheter designed for focal RFA or PFA ablation. METHODS: The effects of PFA (biphasic, 24 amperes) were investigated in 25 swine using a lattice-tip catheter and system (Affera Inc). Step 1 (n=14) examined the feasibility to create atrial line of block and described its acute effects on the phrenic nerve and esophagus. Step 2 (n=7) examined the subacute effects of PFA on block durability, phrenic nerve, and esophagus ≥2 weeks. Step 3 compared the effects of PFA and RFA on the esophagus using a mechanical deviation model approximating the esophagus to the right atrium (n=4) and by direct ablation within its lumen (n=4). The effects of endocardial PFA and RFA on the phrenic nerve were also compared (n=10). Histological analysis was performed. RESULTS: PFA produced acute block in 100% of lines, achieved with 2.1 (1.3-3.2) applications/cm line. Histological analysis following (35 [18-37]) days showed 100% transmurality (thickness range 0.4-3.4 mm) with a lesion width of 19.4 (10.9-27.4 mm). PFA selectively affected cardiomyocytes but spared blood vessels and nervous tissue. PFA applied from the posterior atria (23 [21-25] applications) to the approximated esophagus (6 [4.5-14] mm) produced transmural lesions without esophageal injury. PFA (16.5 [15-18] applications) applied inside the esophageal lumen produced mild edema compared with RFA (13 [12-14] applications) which produced epithelial ulcerations. PFA resulted in no or transient stunning of the phrenic nerve (<5 minutes) without histological changes while RFA produced paralysis. CONCLUSIONS: PFA using a lattice-tip ablation catheter for focal ablation produced durable atrial lesions and showed lower vulnerability to esophageal or phrenic nerve damage compared with RFA.