In-Hospital Outcomes of Ventricular Tachycardia Catheter Ablation in the Presence of Intra-Cardiac Thrombus.

BACKGROUND: Ventricular tachycardia (VT) catheter ablation in the presence of intracardiac thrombi was evaluated in very few studies. OBJECTIVES: To investigate in-hospital outcomes of VT ablation in the presence of an intracardiac thrombus, in a large inpatient US registry. METHODS: Using the National Inpatient Sample (NIS) database, patients who underwent non-elective VT catheter ablations in the United States between 2016 and 2019 were identified using ICD-10 codes. Sociodemographic, clinical data, in-hospital procedures, and outcomes as well as in-hospital mortality were collected. In-hospital outcomes were compared using propensity score (PS) matching analysis with a 1:3 ratio between patients with and without intracardiac thrombus. RESULTS: A weighted total of 15,725 admissions for non-elective VT ablation were included in the study, of which 190 (1.2%) had a discharge diagnosis of intracardiac thrombus. Patients with intracardiac thrombus had a higher comorbidity burden and were more likely to have ischemic cardiomyopathy and a diagnosis of cardiac aneurysm. In PS analysis, the presence of intracardiac thrombus was significantly associated with higher rates of any in-hospital complications (42.1% vs. 19.3%, p < 0.009), driven by higher periprocedural cerebrovascular accident and vascular injury events. In-hospital mortality rates were not significantly different between the groups. CONCLUSIONS: In patients undergoing non-elective VT ablation, intracardiac thrombus was associated with higher rates of in-hospital complications, but not higher in-hospital mortality. These findings suggest that intracardiac thrombus should not contraindicate VT ablation when deemed necessary, while efforts should be made to decrease potential complications.

A novel octaray multielectrode catheter for high-resolution atrial mapping: Electrogram characterization and utility for mapping ablation gaps.

INTRODUCTION: Multielectrode mapping catheters improve the ability to map within the heterogeneous scar. A novel Octaray catheter with eight spines and 48 electrodes may further improve the speed and resolution of atrial mapping. The aims of this study were to (1) establish the Octaray's baseline mapping performance and electrogram (EGM) characteristics in healthy atria and to (2) determine its utility for identifying gaps in a swine model of atrial ablation lines. METHODS AND RESULTS: The right atria of eight healthy swine were mapped with Octaray and Pentaray catheters (Biosense Webster, Irvine, CA) before and after the creation of ablation lines with intentional gaps. Baseline mapping characteristics including EGM amplitude, duration, number of EGMs, and mapping time were compared. Postablation maps were created and EGM characteristics of continuous lines and gaps were correlated with pathology. Compared with Pentaray, the Octaray collected more EGMs per map (2178 ± 637 vs 1046 ± 238; P < 0.001) at a shorter mapping duration (3.2 ± 0.79 vs 6.9 ± 2.67 minutes; P < 0.001). In healthy atria, the Octaray recorded lower bipolar voltage amplitude (1.96 ± 1.83 mV vs 2.41 ± 1.92 mV; P < 0.001) while ablation gaps were characterized by higher voltage amplitude (1.24 ± 1.12 mV vs 1.04 ± 1.27 mV; P < 0.001). Ablation gaps were similarly identified by both catheters (P = 1.0). The frequency of "false gaps," defined as intact ablation lines with increased voltage amplitude was more common with Pentaray (6 vs 2) and resulted from erroneous annotation of far-field EGMs. CONCLUSION: The Octaray increases the mapping speed and density compared with the Pentaray catheter. It is as sensitive for identifying ablation gaps and more specific for mapping intact ablation lines.

Time-to-first appropriate shock in patients implanted prophylactically with an implantable cardioverter-defibrillator: data from the Survey on Arrhythmic Events in BRUgada Syndrome (SABRUS).

AIMS: Data on predictors of time-to-first appropriate implantable cardioverter-defibrillator (ICD) therapy in patients with Brugada Syndrome (BrS) and prophylactically implanted ICD's are scarce. METHODS AND RESULTS: SABRUS (Survey on Arrhythmic Events in BRUgada Syndrome) is an international survey on 678 BrS patients who experienced arrhythmic event (AE) including 252 patients in whom AE occurred after prophylactic ICD implantation. Analysis was performed on time-to-first appropriate ICD discharge regarding patients' characteristics. Multivariate logistic regression models were utilized to identify which parameters predicted time to arrhythmia ≤5 years. The median time-to-first appropriate ICD therapy was 24.8 ± 2.8 months. A shorter time was observed in patients from Asian ethnicity (P < 0.05), those with syncope (P = 0.001), and those with Class IIa indication for ICD (P = 0.001). A longer time was associated with a positive family history of sudden cardiac death (P < 0.05). Multivariate Cox regression revealed shorter time-to-ICD therapy in patients with syncope [odds ratio (OR) 1.65, P = 0.001]. In 193 patients (76.6%), therapy was delivered during the first 5 years. Factors associated with this time were syncope (OR 0.36, P = 0.001), spontaneous Type 1 Brugada electrocardiogram (ECG) (OR 0.5, P < 0.05), and Class IIa indication (OR 0.38, P < 0.01) as opposed to Class IIb (OR 2.41, P < 0.01). A near-significant trend for female gender was also noted (OR 0.13, P = 0.052). Two score models for prediction of <5 years to shock were built. CONCLUSION: First appropriate therapy in BrS patients with prophylactic ICD's occurred during the first 5 years in 76.6% of patients. Syncope and spontaneous Type 1 Brugada ECG correlated with a shorter time to ICD therapy.

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

INTRODUCTION: 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. METHODS AND RESULTS: 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/30 seconds) and in 3 other swine using HP-SD parameters (QDOT-MICRO™, 90 W/4 seconds). 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. CONCLUSIONS: HP-SD ablation strategy results in improved linear continuity, shorter ablation time, and a safety profile comparable to conventional ablation.

Cardiac MR Characterization of left ventricular remodeling in a swine model of infarct followed by reperfusion.

BACKGROUND: Myocardial infarction (MI) survivors are at risk of complications including heart failure and malignant arrhythmias. PURPOSE: We undertook serial imaging of swine following MI with the aim of characterizing the longitudinal left ventricular (LV) remodeling in a translational model of ischemia-reperfusion-mediated MI. ANIMAL MODEL: Eight Yorkshire swine underwent mid left anterior descending coronary artery balloon occlusion to create an ischemia-reperfusion experimental model of MI. FIELD STRENGTH/SEQUENCES: 1.5T Philips Achieva scanner. Serial cardiac MRI was performed at 16, 33, and 62 days post-MI, including cine imaging, native and postcontrast T1 , T2 and dark-blood late gadolinium enhanced (DB-LGE) scar imaging. ASSESSMENT: Regions of interest were selected on the parametric maps to assess native T1 and T2 in the infarct and in remote tissue. Volume of enhanced tissue, nonenhanced tissue, and gray zone were assessed from DB-LGE imaging. Volumes, cardiac function, and strain were calculated from cine imaging. STATISTICAL TESTS: Parameters estimated at more than two timepoints were compared with a one-way repeated measures analysis of variance. Parametric mapping data were analyzed using a generalized linear mixed model corrected for multiple observations. A result was considered statistically significant at P < 0.05. RESULTS: All animals developed anteroseptal akinesia and hyperenhancement on DB-LGE with a central core of nonenhancing tissue. Mean hyperenhancement volume did not change during the observation period, while the central core contracted from 2.2 ± 1.8 ml at 16 days to 0.08 ± 0.19 ml at 62 days (P = 0.008). Native T1 of ischemic myocardium increased from 1173 ± 93 msec at 16 days to 1309 ± 97 msec at 62 days (P < 0.001). Mean radial and circumferential strain rate magnitude in remote myocardium increased with time from the infarct (P < 0.05). DATE CONCLUSION: In this swine model of MI, serial quantitative cardiac MR exams allow characterization of LV remodeling and scar formation. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018.

Arrhythmic Events in Brugada Syndrome: A Nationwide Israeli Survey of the Clinical Characteristics, Treatment; and Long-Term Follow-up (ISRABRU-VF).

BACKGROUND: Limited information exists about detailed clinical characteristics and management of the small subset of Brugada syndrome (BrS) patients who had an arrhythmic event (AE). OBJECTIVES: To conduct the first nationwide survey focused on BrS patients with documented AE. METHODS: Israeli electrophysiology units participated if they had treated BrS patients who had cardiac arrest (CA) (lethal/aborted; group 1) or experienced appropriate therapy for tachyarrhythmias after prophylactic implantable cardioverter defibrillator (ICD) implantation (group 2). RESULTS: The cohort comprised 31 patients: 25 in group 1, 6 in group 2. Group 1: 96% male, mean CA age 38 years (range 13-84). Nine patients (36%) presented with arrhythmic storm and three had a lethal outcome; 17 (68%) had spontaneous type 1 Brugada electrocardiography (ECG). An electrophysiology study (EPS) was performed on 11 patients with inducible ventricular fibrillation (VF) in 10, which was prevented by quinidine in 9/10 patients. During follow-up (143 ± 119 months) eight patients experienced appropriate shocks, none while on quinidine. Group 2: all male, age 30-53 years; 4/6 patients had familial history of sudden death age < 50 years. Five patients had spontaneous type 1 Brugada ECG and four were asymptomatic at ICD implantation. EPS was performed in four patients with inducible VF in three. During long-term follow-up, five patients received ≥ 1 appropriate shocks, one had ATP for sustained VT (none taking quinidine). No AE recurred in patients subsequently treated with quinidine. CONCLUSIONS: CA from BrS is apparently a rare occurrence on a national scale and no AE occurred in any patient treated with quinidine.

Contemporary rates and outcomes of single- vs. dual-coil implantable cardioverter defibrillator lead implantation: data from the Israeli ICD Registry.

AIMS: Dual-coil leads were traditionally considered standard of care due to lower defibrillation thresholds (DFT). Higher complication rates during extraction with parallel progression in implantable cardioverter defibrillator (ICD) technology raised questions on dual coil necessity. Prior substudies found no significant outcome difference between dual and single coils, although using higher rates of DFT testing then currently practiced. We evaluated the temporal trends in implantation rates of single- vs. dual-coil leads and determined the associated adverse clinical outcomes, using a contemporary nation-wide ICD registry. METHODS AND RESULTS: Between July 2010 and March 2015, 6343 consecutive ICD (n = 3998) or CRT-D (n = 2345) implantation patients were prospectively enrolled in the Israeli ICD Registry. A follow-up of at least 1 year of 2285 patients was available for outcome analysis. The primary endpoint was all-cause mortality. Single-coil leads were implanted in 32% of our cohort, 36% among ICD recipients, and 26% among CRT-D recipients. Secondary prevention indication was associated with an increased rate of dual-coil implantation. A significant decline in dual-coil leads with reciprocal incline of single coils was observed, despite low rates of DFT testing (11.6%) during implantation, which also declined from 31 to 2%. In the multivariate Cox model analysis, dual- vs. single-coil lead implantation was not associated with an increased risk of mortality [hazard ratio (HR) = 1.23; P= 0.33], heart failure hospitalization (HR = 1.34; P=0.13), appropriate (HR = 1.25; P= 0.33), or inappropriate ICD therapy (HR = 2.07; P= 0.12). CONCLUSION: Real-life rates of single-coil lead implantation are rising while adding no additional risk. These results of single-coil safety are reassuring and obtained, despite low and contemporary rates of DFT testing.

Atrial Fibrillation Catheter Ablation among Cancer Patients: Utilization Trends and In-Hospital Outcomes.

Background: Atrial fibrillation (AF) catheter ablation in cancer patients has been evaluated in very few studies. We aimed to investigate utilization trends and in-hospital outcomes of AF catheter ablation among cancer patients in a large US inpatient registry. Methods: Utilizing the National Inpatient Sample (NIS) database, patients who underwent AF catheter ablation between 2012 and 2019 were identified. Sociodemographic, clinical data, in-hospital procedures and outcomes were collected. Baseline characteristics and in-hospital outcomes were compared between patients with and without cancer. Results: An estimated total of 67,915 patients underwent AF catheter ablation between 2012 and 2019 in the US. Of them, 950 (1.4%) had a cancer diagnosis. Patients with a cancer diagnosis were older and had higher Charlson Comorbidity Index, CHA2DS2-VASc and ATRIA bleeding indices scores. A higher rate of total complications was observed in cancer patients (10.5% vs. 7.9, p < 0.001), driven mainly by more bleeding and infectious complications. However, no significant differences in cardiac or neurological complications as well as in-hospital mortality rates were observed and were relatively low in both groups. Conclusions: AF catheter ablation in cancer patients is associated with higher bleeding and infectious complication rates, but not with increased cardiac complications or in-hospital mortality in a US nationwide, all-comer registry.

The Trends in Atrial Fibrillation-Related Mortality before, during, and after the COVID-19 Pandemic Peak in the United States.

Background: During the first months of the COVID-19 outbreak, an increase was observed in atrial fibrillation (AF)-related mortality in the United States (U.S). We aimed to investigate AF-related mortality trends in the U.S. before, during, and after the COVID-19 pandemic peak, stratified by sociodemographic factors. Methods: using the Wide-Ranging Online Data for Epidemiologic Research database of the Centers for Disease Control and Prevention, we compared the AF-related age-adjusted mortality rate (AAMR) among different subgroups in the two years preceding, during, and following the pandemic peak (2018-2019, 2020-2021, 2022-2023). Result: By analyzing a total of 1,267,758 AF-related death cases, a significant increase of 24.8% was observed in AF-related mortality during the pandemic outbreak, followed by a modest significant decrease of 1.4% during the decline phase of the pandemic. The most prominent increase in AF-related mortality was observed among males, among individuals younger than 65 years, and among individuals of African American and Hispanic descent, while males, African American individuals, and multiracial individuals experienced a non-statistically significant decrease in AF-related mortality during the pandemic decline period. Conclusions: Our findings suggest that in future healthcare crises, targeted healthcare policies and interventions to identify AF, given its impact on patients' outcomes, should be developed while addressing disparities among different patient populations.

Atrial fibrillation in young hospitalized patients: Clinical characteristics, predictors of new onset, and outcomes.

BACKGROUND: Atrial fibrillation (AF) in young adults is an uncommon and not well studied entity. METHODS: Consecutive patients aged 18-45 years admitted to internal or cardiology services in a large tertiary medical center (January 1, 2009 through December 31, 2019) were included. Clinical, electrocardiographic, and echocardiographic data were compared between patients with and without AF at baseline. Predictors of new-onset AF in the young were identified using multivariate Cox regression model among patients free of baseline AF. RESULTS: Final cohort included 16,432 patients with median age of 34 (IQR 26-41) years of whom 8914 (56 %) were men. Patients with AF at baseline (N = 366; 2 %) were older, more likely to be men, and had higher proportion of comorbidities and electrocardiographic conduction disorders. Male sex, increased age, obesity, heart failure, congenital heart disease (CHD) and the presence of left or right bundle branch block were all independently associated with baseline AF in a multivariate model (p < 0.001 for all). Sub-analysis of 10,691 (98 %) patients free of baseline AF identified 85 cases of new-onset AF during a median follow up of 3.5 (IQR 1.5-6.5) years. Multivariate model identified increased age, heart failure, and CHD as independent predictors of new-onset AF. Finally, the CHARGE-AF risk score outperformed the CHA2DS2-VASc score in AF prediction [AUC of ROC 0.75 (0.7-0.8) vs. 0.56 (0.48-0.65)]. CONCLUSIONS: AF among hospitalized young adults is not rare. Screening for new-onset AF in young post hospitalization patients may be guided by specific clinical predictors and the CHARGE-AF risk score.

Single- Versus Dual-Chamber Implantable Cardioverter-Defibrillator for Primary Prevention of Sudden Cardiac Death in the United States.

Background Routine addition of an atrial lead during an implantable cardioverter-defibrillator (ICD) implantation for primary prevention of sudden cardiac death, in patients without pacing indications, was not shown beneficial in contemporary studies. We aimed to investigate the use and safety of single- versus dual-chamber ICD implantations in these patients. Methods and Results Using the National Inpatient Sample database, we identified patients with no pacing indications who underwent primary-prevention ICD implantation in the United States between 2015 and 2019. Sociodemographic and clinical characteristics, as well as in-hospital complications, were analyzed. Multivariable logistic regression was used to identify predictors of in-hospital complications. An estimated total of 15 940 patients, underwent ICD implantation for primary prevention of sudden cardiac death during the study period, 8860 (55.6%) received a dual-chamber ICD. The mean age was 64 years, and 66% were men. In-hospital complication rates in the dual-chamber ICD and single-chamber ICD group were 12.8% and 10.7%, respectively (P<0.001), driven by increased rates of pneumothorax/hemothorax (4.6% versus 3.4%; P<0.001) and lead dislodgement (3.6% versus 2.3%; P<0.001) in the dual-chamber ICD group. Multivariable analyses confirmed atrial lead addition as an independent predictor for "any complications" (odds ratio [OR], 1.1 [95% CI, 1.0-1.2]), for pneumo/hemothorax (odds ratio, 1.1 [95% CI, 1.0-1.4]), and for lead dislodgement (odds ratio, 1.3 [95% CI, 1.1-1.6]). Conclusions Despite lack of evidence for clinical benefit, dual-chamber ICDs are implanted for primary prevention of sudden cardiac death in a majority of patients who do not have pacing indication. This practice is associated with increased risk of periprocedural complications. Avoidance of routine implantation of atrial leads will likely improve safety outcomes.

Can the Norton Scale Score Be Used as an Adjunct Tool for Implantable Defibrillator Patient Selection? A Retrospective Single-Center Cohort Study.

(1) Background: Implantable cardioverter defibrillators (ICDs) have become the standard of care in the prevention of sudden cardiac death, yet studies have shown that competing causes of death may limit ICD benefits. The Norton scale is a pressure ulcer risk score shown to have prognostic value in other fields. The purpose of this study was to assess the use of the Norton scale as an aid for ICD patient selection; (2) Methods: The study was comprised of consecutive patients who underwent defibrillator implantation at Sheba Medical Center between 2008 and 2016. A competing risk analysis was performed to assess the likelihood of death prior to device therapy; (3) Results: 695 patients were included. A total of 59 (8.5%) patients had low admission Norton scale score (ANSS) (≤14), 81 (11.7%) had intermediate ANSS (15−17), and the remainder (79.8%) had high (18−20) ANSS. The cumulative probability of all-cause mortality within one year of ICD implantation in patients with low ANSS was 30%, compared with 20% and 7% among the intermediate- and high-ANSS groups, respectively. Moreover, the one-year mortality rate without ICD therapy in low-ANSS patients was over four-fold compared with that of high-ANSS patients (33% versus 7%, p < 0.0001); (4) Conclusions: The Norton scale could be a useful additional tool in predicting the life expectancy of ICD candidates, thereby improving patient selection.

Occluded vein as a predictor for complications in non-infectious transvenous lead extraction.

Background: The use of cardiovascular implantable electronic device (CIED) is steadily increasing, and complications include venous occlusion and fractured leads. Transvenous lead extraction (TLE) can facilitate the re-implantation of new leads. Aims: This study aims to explore predictors and complications of non-infectious TLE. Methods: This study involves a retrospective analysis and comparison of characteristics, complications, and outcomes of patients with and without occluded veins (OVs) undergoing TLE at our center. Results: In total, eighty-eight patients underwent TLE for non-infectious reasons. Indications for TLE were lead malfunction (62; 70.5%) and need for CIED upgrade (22; 25%). Fourteen patients referred due to lead malfunction had an OV observed during venography. The OV group (36 patients) were significantly older (65.7 ± 14.1 vs. 53.8 ± 15.9, p = 0.001) and had more comorbidities. Ejection fraction (EF) was significantly lower for the OV group (27.5 vs. 57.5%, p = 0.001) and had a longer lead dwelling time (3,226 ± 2,324 vs. 2,191 ± 1,355 days, p = 0.012). Major complications were exclusive for the OV group (5.5% vs. none, p = 0.17), and most minor complications occurred in the OV group as well (33.3 vs. 4.1%, p < 0.001). Laser sheath and mechanical tools for TLE were frequently used for OV as compared to the non-occluded group (94.4 vs. 73.5%, respectively, p = 0.012). Procedure success was higher in the non-occluded group compared to the OV group (98 vs. 83.3%, respectively, p = 0.047). Despite these results, periprocedural mortality was similar between groups. Conclusion: Among the TLE for non-infectious reasons, vein occlusion appears as a major predictor of complex TLE tool use, complications, and procedural success. Venography should be considered prior to non-infectious TLE to identify high-risk patients.

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.

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.

Temperature-Controlled Radiofrequency Ablation Using Irrigated Catheters: Maximizing Ventricular Lesion Dimensions While Reducing Steam-Pop Formation.

OBJECTIVES: The goal of this study was to examine the safety and efficacy of radiofrequency ablation (RFA) with irrigated catheters operated in a temperature-controlled mode for ventricular ablation. BACKGROUND: Techniques to increase RFA dimensions are associated with higher risk for steam-pops. A novel irrigated catheter with circumferential thermocouples embedded in its ablation surface provides real-time surface temperature data. This study hypothesized that RFA operated in a temperature-controlled mode may allow maximizing lesion dimensions while reducing the occurrence of steam-pops. METHODS: RFA with an irrigated catheter incorporating surface thermocouples was examined in 6 swine thigh muscle preparations and 15 beating ventricles at higher (50 W/60 s, Tmax50oC) and lower (50 W/60 s, Tmax45oC) temperature limits. Biophysical properties, lesion dimensions, and steam-pop occurrence were compared versus RFA with a standard catheter operated in power-control mode at higher (50 W/60 s) and lower (40W/60 s) power, and additionally at high power with half-normal saline (50 W/60 s). RESULTS: In the thigh muscle preparation, lesion depth and width were similar between all groups (p = 0.90 and p = 0.17, respectively). Steam-pops were most frequent with power-controlled ablation at 50 W/60 s (82%) and least frequent with temperature-controlled ablation at 50 W/60 s, Tmax45oC (0%; p < 0.001). In the beating ventricle, lesion depth was comparable between all RFA settings (p = 0.09). Steam-pops were most frequent using power-controlled ablation at 50 W/60 s (37%) and least frequent with temperature-controlled ablation at 50 W/60 s, Tmax45oC (7%; p < 0.001). Half-normal saline had no incremental effect on lesion dimensions at 50 W in either the thigh muscle or the beating heart. CONCLUSIONS: RFA using a novel irrigated catheter with surface thermocouples operated in a temperature-controlled mode can maximize lesion dimensions while reducing the risk for steam-pops.

Ablation of Reentry-Vulnerable Zones Determined by Left Ventricular Activation From Multiple Directions: A Novel Approach for Ventricular Tachycardia Ablation: A Multicenter Study (PHYSIO-VT).

BACKGROUND: The optimal method to identify the arrhythmogenic substrate of scar-related ventricular tachycardia (VT) is unknown. Sites of activation slowing during sinus rhythm (SR) often colocalize with the VT circuit. However, the utility and limitations of such approach for guiding ablation are unknown. METHODS: We conducted a multicenter study in patients with infarct-related VT. The left ventricular (LV) was mapped during activation from 3 directions: SR (or atrial pacing), right ventricular, and LV pacing at 600 ms. Ablation was applied selectively to the cumulative area of slow activation, defined as the sum of all regions with activation times of ≥40 ms per 10 mm. Hemodynamically tolerated VTs were mapped with activation or entrainment. The primary outcome was a composite of appropriate implanted cardioverter-defibrillator therapies and cardiovascular death. RESULTS: In 85 patients, the LV was mapped during activation from 2.4±0.6 directions. The direction of LV activation influenced the location and magnitude of activation slowing. The spatial overlap of activation slowing between SR and right ventricular pacing was 84.2±7.1%, between SR and LV pacing was 61.4±8.8%, and between right ventricular and LV pacing was 71.3±9.6% (P<0.05 between all comparisons). Mapping during SR identified only 66.2±8.2% of the entire area of activation slowing and 58% critical isthmus sites. Activation from other directions by right ventricular and LV stimulation unmasked an additional 33% of slowly conducting zones and 25% critical isthmus sites. The area of maximal activation slowing often corresponded to the site where the wavefront first interacted with the infarct. During a follow-up period of 3.6 years, the primary end point occurred in 14 out of 85 (16.5%) patients. CONCLUSIONS: The spatial distribution of activation slowing is dependent on the direction of LV activation with the area of maximal slowing corresponding to the site where the wavefront first interacts with the infarct. This data may have implications for VT substrate mapping strategies.

Expandable Lattice Electrode Ablation Catheter: A Novel Radiofrequency Platform Allowing High Current at Low Density for Rapid, Titratable, and Durable Lesions.

BACKGROUND: High-current short-duration radiofrequency energy delivery has potential advantages for cardiac ablation. However, this strategy is limited by high current density and narrow safety-to-efficacy window. The objective of this study was to examine a novel strategy for radiofrequency energy delivery using a new electrode design capable of delivering high power at a low current density to increase the therapeutic range of radiofrequency ablation. METHODS: The Sphere9 is an expandable spheroid-shaped lattice electrode design with an effective surface area 10-fold larger than standard irrigated electrodes (lattice catheter). It incorporates 9 surface temperature sensors with ablation performed in a temperature-controlled mode. Phase I: in 6 thigh muscle preparations, 2 energy settings for atrial ablation were compared between the lattice and irrigated-tip catheters (low-energy: Tmax75°C/5 s versus 25 W/20 s; high-energy: Tmax75°C/7 s versus 30 W/20 s). Phase II: in 8 swine, right atrial lines were created in the posterior and lateral walls using low- and high-energy settings, respectively. Phase III: the safety, efficacy, and durability at 30 days were evaluated by electroanatomical mapping and histopathologic analysis. RESULTS: In the thigh model, the lattice catheter resulted in wider lesions at both low- and high-energy settings (18.7±3.3 versus 12.2±1.7 mm, P<0.0001; 19.4±2.4 versus 12.3±1.7 mm, P<0.0001). Atrial lines created with the lattice were wider (posterior: 14.7±3.4 versus 9.2±4.0 mm, P<0.0001; lateral: 15.8±4.2 versus 5.7±4.2 mm, P<0.0001) and required 85% shorter ablation time (12.4 versus 79.8 s/cm-line). While current squared (I2) was higher with Sphere9 (7.0±0.04 versus 0.2±0.002 A2; P<0.0001), the current density was lower (9.6±0.9 versus 16.9±0.09 mA/mm2; P<0.0001). At 30 days, 100% of ablation lines created with the lattice catheter remained contiguous compared with only 14.3% lines created with a standard irrigated catheter. This was achieved without steam pops or collateral tissue damage. CONCLUSIONS: In this preclinical model, a novel, high-current low-density radiofrequency ablation strategy created contiguous and durable ablation lines in significantly less ablation time and a comparable safety profile.

Pseudoblock of the Posterior Mitral Line With Epicardial Bridging Connections Is a Frequent Cause of Complex Perimitral Tachycardias.

BACKGROUND: The mitral isthmus is the critical element of perimitral reentrant tachycardias. Prolongation in transisthmus conduction time and differential pacing techniques are commonly used to determine block. However, these may not distinguish block from slow conduction or conduction via epicardial bridging connections. The aim of this study was to examine these standard criteria for mitral line block with endocardial and epicardial activation mapping. METHODS: In 56 patients, posterior mitral line was performed using radiofrequency ablation. Conduction block was defined as transisthmus time (≥100 ms) and reversal of coronary sinus activation during pacing from the left atrial appendage. These results were compared with high-resolution activation mapping (Rhythmia) of the endocardium and epicardium via the coronary sinus. RESULTS: Mitral block determined by pacing was achieved in 51 out of 56 (91%) patients. In 11 out of 51 (21.6%), activation mapping demonstrated residual endocardial (3/11; 27.2%) or epicardial (8/11; 72.7%) connections. Epicardial bridging connections were distant from the line (2.4±1.6 cm), inserting laterally at the proximal-middle coronary sinus and septally at the left atrial ridge. Patients with residual conduction were prone to complex circuits involving the epicardium (7/11; 63.6%). Mitral line block was achieved in 75% by targeting these insertion site(s). The transisthmus conduction time had limited predictive value for distinguishing block from pseudoblock. CONCLUSIONS: Standard criteria for posterior mitral line block may not distinguish block from pseudoblock. In particular, epicardial bridging connections can result in prolonged transisthmus conduction time and reversal in coronary sinus activation to falsely suggest block. These connections are a frequent cause for complex circuits, and their insertion site(s) can be targeted for ablation.

Histopathological Characterization of Radiofrequency Ablation in Ventricular Scar Tissue.

OBJECTIVES: This study sought to characterize the histopathological features of radiofrequency ablation (RFA) in heterogeneous ventricular scar in comparison to those in healthy myocardium. BACKGROUND: The histopathological features of RFA have been studied largely in normal myocardium. However, its effect on clinically relevant heterogeneous scar is not well understood. METHODS: Five swine with chronic infarction underwent RFA using 35-W, 45-s, 10-20 g (Biosense Webster, Irwindale, California) in heterogenous scar tissue (voltage ≤1.5 mV) and healthy myocardium (≥3.0 mV). The location of each application was marked using the electroanatomical mapping system. Histological sections at intervals of 0.5 mm with hematoxylin and eosin and Masson's trichrome stained intervals were created. A pathologist blinded to the myocardium type characterized the extent of RF injury in cellular, extracellular, and vascular structures. RESULTS: In healthy myocardium, 23 of 23 lesions (100%) were well demarcated and could be precisely measured (width: 11.3 ± 3.3 mm; depth: 7.3 ± 2.0 mm). In scar tissue, only 3 of 30 lesions (10%) were identified, and none could be measured due to a lack of defined borders. Lesions in healthy myocardium had a distinctive architecture showing a coagulative necrosis core surrounded by an outer rim of contraction band necrosis. Lesions in scar had ill-defined tissue injury without a distinct architecture. In all ablated regions, viable myocytes remained interspersed between necrotic myocytes exhibiting characteristics of both coagulative and contraction band necrosis. Connective tissue was more resistant to thermal injury in comparison to cardiomyocytes. CONCLUSIONS: RFA in scarred myocardium results in irregular tissue injury and unpredictable effect on surviving cardiomyocytes. This may be related to biophysical differences between healthy and scarred myocardium.