Identification of Human Ventricular Tachycardia Demarcated by Fixed Lines of Conduction Block in a 3-Dimensional Hyperboloid Circuit.

BACKGROUND: The circuit boundaries for reentrant ventricular tachycardia (VT) have been historically conceptualized within a 2-dimensional (2D) construct, with their fixed or functional nature unresolved. This study aimed to examine the correlation between localized lines of conduction block (LOB) evident during baseline rhythm with lateral isthmus boundaries that 3-dimensionally constrain the VT isthmus as a hyperboloid structure. METHODS: A total of 175 VT activation maps were correlated with isochronal late activation maps during baseline rhythm in 106 patients who underwent catheter ablation for scar-related VT from 3 centers (42% nonischemic cardiomyopathy). An overt LOB was defined by a deceleration zone with split potentials (≥20 ms isoelectric segment) during baseline rhythm. A novel application of pacing within deceleration zone (≥600 ms) was implemented to unmask a concealed LOB not evident during baseline rhythm. LOB identified during baseline rhythm or pacing were correlated with isthmus boundaries during VT. RESULTS: Among 202 deceleration zones analyzed during baseline rhythm, an overt LOB was evident in 47%. When differential pacing was performed in 38 deceleration zones without overt LOB, an underlying concealed LOB was exposed in 84%. In 152 VT activation maps (2D=53, 3-dimensional [3D]=99), 69% of lateral boundaries colocalized with an LOB in 2D activation patterns, and the depth boundary during 3D VT colocalized with an LOB in 79%. In VT circuits with isthmus regions that colocalized with a U-shaped LOB (n=28), the boundary invariably served as both lateral boundaries in 2D and 3D. Overall, 74% of isthmus boundaries were identifiable as fixed LOB during baseline rhythm or differential pacing. CONCLUSIONS: The majority of VT circuit boundaries can be identified as fixed LOB from intrinsic or paced activation during sinus rhythm. Analysis of activation while pacing within the scar substrate is a novel technique that may unmask concealed LOB, previously interpreted to be functional in nature. An LOB from the perspective of a myocardial surface is frequently associated with intramural conduction, supporting the existence of a 3D hyperboloid VT circuit structure. Catheter ablation may be simplified to targeting both sides around an identified LOB during sinus rhythm.

Acute procedural efficacy and safety of a novel expandable diameter cryoballoon in atrial fibrillation ablation: Early results from a multicenter ablation registry.

INTRODUCTION: The major limitation of the current cryoballoon (CB) system is a fixed 28 mm balloon-size. We sought to analyze real-world early experience with novel-sized adjustable CB. METHODS: This multicenter observational study included 140 consecutive atrial fibrillation patients (71 years, 94 men, 86 paroxysmal) who underwent pulmonary vein (PV) isolation using expandable diameter CB capable of ablation at 28 or 31 mm. RESULTS: Out of 544 targeted PVs, 526 (96.7%) were successfully isolated by a size-adjustable CB with a 770 [690-870] second median application dose, while the remaining 18 required touch-up ablation. Among them, 326 (62.0%) PVs were isolated by a 31 mm balloon, and the rate was significantly higher for upper than lower PVs (73.0% vs. 45.7%, p < .0001) and highest for right superior (78.5%) and lowest for right inferior (39.9%) PVs. The biophysical parameters and time to isolation were comparable between the 28 and 31 mm balloons, however, the real-time PV potential monitoring capability was significantly higher for 31 mm than 28 mm balloons for the left superior PV. The esophageal temperature reached 15°C during left inferior PV ablation significantly more often with 31 mm than 28 mm balloons (43.1% vs. 18.2%, p = .008). Right phrenic nerve injury (PNI) occurred in 9 (6.4%) patients during applications (6 right superior, 2 right inferior PVs), and most occurred with a 31 mm balloon. CONCLUSIONS: Our real-world early data demonstrated high acute efficacy and safety of the novel-sized adjustable CB. The biophysical parameters were similar between the 28 and 31 mm balloons. No marked decrease in the incidence of PNI was observed even with 31 mm balloons.

Validation of dual atrioventricular nodal physiology in dual atrioventricular nodal non-reentrant tachycardia via adenosine triphosphate injection during atrial pacing: A novel insight into the role of leftward inferior extension.

INTRODUCTION: Dual atrioventricular nodal non-reentrant tachycardia (DAVNNT) is a rare and challenging-to-diagnose arrhythmia, without previous reports associating it with a leftward inferior extension (LIE). METHODS: Diagnosis was made using adenosine triphosphate (ATP) injection during atrial pacing in a suspected DAVNNT patient. RESULTS: Ablation of the rightward inferior extension was unsuccessful in eliminating DAVNNT; however, subsequent ablation of the LIE successfully eradicated the arrhythmia. CONCLUSION: This unique case, marked by the first instance of DAVNNT caused by LIE, diagnosed through ATP injection, underscores the utility of this diagnostic approach and broadens the spectrum of our understanding and management of this condition.

Raise-up technique for the creation of left atrial roof lesion: A useful technique with cryoballoon for persistent atrial fibrillation.

INTRODUCTION: Recent studies have reported the efficacy of the cryoballoon (CB)-guided left atrial roof block line (LARB) creation in patients with persistent atrial fibrillation (AF). However, it can be technically challenging to attach the balloon to the left atrial (LA) roof due to its anatomical variations. We designed a new procedure called the "Raise-up Technique," which may facilitate the firm adhesion of the CB to the LA roof during freezing. This study aimed to evaluate the efficacy of the Raise-up technique in LARB creation. METHODS AND RESULTS: In total, 100 consecutive patients with persistent AF who underwent CB-LARB creation were enrolled. Fifty-seven patients underwent LARB creation using the Raise-up technique (Raise-up group), and the remaining 43 did not use it (control group). The Raise-up technique was performed as follows: An Achieve catheter was inserted as deeply as possible into the upper branch of the right superior pulmonary vein to anchor the CB. The balloon was placed below the targeted site on the LA roof and frozen. When the temperature of the CB reached approximately -10°C and the CB was easier to attach to the LA tissue, the CB was raised and pressed against the LA roof immediately by sheath advancement. Then the balloon could be in firm contact with the target site on the roof. If necessary, additional sheath advancement after sufficient freezing (-20°C to -30°C) was allowed the CB to have more firm and broad contact with the target site. LARB creation without touch-up ablation was achieved in 54 of 57 patients (94.7%) in the Raise-up group and 33 of 43 patients (76.7%) in the control group (p < .05). The lesion size of the LARB in the Raise-up group was significantly larger than that in the control group (15.2 cm2 vs. 12.8 cm2, p < .05). Moreover, the width of the LARB lesion in the Raise-up group was wider than that in the control group (32.0 mm vs. 26.6 mm, p < .05). CONCLUSION: The Raise-up technique enabled the creation of seamless and thick LARB lesions with a single stroke. In addition, the CB-LARB lesions created using the Raise-up technique tended to be large, resulting in extensive debulking of the LA posterior wall arrhythmia substrates. In CB ablation for persistent AF, the Raise-up technique can be considered one of the key strategies for LARB creation.

Incidence of phrenic nerve injury during pulmonary vein isolation using different cryoballoons: data from a large prospective ablation registry.

AIMS: Phrenic nerve injury (PNI) is the most common complication during cryoballoon ablation. Currently, two cryoballoon systems are available, yet the difference is unclear. We sought to compare the acute procedural efficacy and safety of the two cryoballoons. METHODS: This prospective observational study consisted of 2,555 consecutive atrial fibrillation (AF) patients undergoing pulmonary vein isolation (PVI) using either conventional (Arctic Front Advance) (AFA-CB) or novel cryoballoons (POLARx) (POLARx-CB) at 19 centers between January 2022 and October 2023. RESULTS: Among 2,555 patients (68.8 ± 10.9 years, 1,740 men, paroxysmal AF[PAF] 1,670 patients), PVIs were performed by the AFA-CB and POLARx-CB in 1,358 and 1,197 patients, respectively. Touch-up ablation was required in 299(11.7%) patients. The touch-up rate was significantly lower for POLARx-CB than AFA-CB (9.5% vs. 13.6%, p = 0.002), especially for right inferior PVs (RIPVs). The touch-up rate was significantly lower for PAF than non-PAF (8.8% vs. 17.2%, P < 0.001) and was similar between the two cryoballoons in non-PAF patients. Right PNI occurred in 64(2.5%) patients and 22(0.9%) were symptomatic. It occurred during the right superior PV (RSPV) ablation in 39(1.5%) patients. The incidence was significantly higher for POLARx-CB than AFA-CB (3.8% vs. 1.3%, P < 0.001) as was the incidence of symptomatic PNI (1.7% vs. 0.1%, P < 0.001). The difference was significant during RSPV (2.5% vs. 0.7%, P < 0.001) but not RIPV ablation. The PNI recovered more quickly for the AFA-CB than POLARx-CB. CONCLUSIONS: Our study demonstrated a significantly higher incidence of right PNI and lower touch-up rate for the POLARx-CB than AFA-CB in the real-world clinical practice.

Basal Coronary Microvascular Resistance Predicting Death and Heart Failure in Patients Without Functional Coronary Stenosis.

BACKGROUND: Abnormal coronary microcirculation is linked to poor patient prognosis, so the aim of the present study was to assess the prognostic relevance of basal microvascular resistance (b-IMR) in patients without functional coronary stenosis.Methods and Results: Analyses of 226 patients who underwent intracoronary physiological assessment of the left anterior descending artery included primary endpoints of all-cause death and heart failure, as well as secondary endpoints of cardiovascular death and atherosclerotic vascular events. During a median follow-up of 2 years, there were 12 (5.3%) primary and 21 (9.3 %) secondary endpoints. The optimal b-IMR cutoff for the primary endpoints was 47.1 U. Kaplan-Meier curve analysis demonstrated worse event-free survival of the primary endpoints in patients with a b-IMR below the cutoff (χ2=21.178, P<0.001). b-IMR was not significantly associated with the secondary endpoints (P=0.35). A low coronary flow reserve (CFR; <2.5) had prognostic value for both endpoints (primary endpoints: χ2=11.401, P=0.001; secondary endpoints: (χ2=6.015; P=0.014), and high hyperemic microvascular resistance (≥25) was associated only with the secondary endpoints (χ2=4.420; P=0.036). Incorporating b-IMR into a clinical model that included CFR improved the Net Reclassification Index and Integrated Discrimination Improvement for predicting the primary endpoints (P<0.001 and P=0.034, respectively). CONCLUSIONS: b-IMR may be a specific marker of the risk of death and heart failure in patients without functional coronary stenosis.

Association of Coronary Computed Tomography-Defined Myocardial Bridge With Pre- and Post-Procedural Fractional Flow Reserve in Patients Undergoing Elective Percutaneous Coronary Intervention.

BACKGROUND: Myocardial bridge (MB) is a common coronary anomaly characterized by a tunneled course through the myocardium. Coronary computed tomography angiography (CCTA) can identify MB. The impact of MB detected by CCTA on coronary physiological parameters before and after percutaneous coronary intervention (PCI) is unknown.Methods and Results: We investigated 141 consecutive patients who underwent pre-PCI CCTA and fractional flow reserve (FFR)-guided elective PCI for de novo single proximal lesions in the left anterior descending artery (LAD). We compared clinical demographics and physiological parameters between patients with and without CCTA-defined MB. MB was identified in 46 (32.6%) patients using pre-PCI CCTA. The prevalence of diabetes was higher among patients with MB. Median post-PCI FFR values were significantly lower among patients with than without MB (0.82 [interquartile range 0.79-0.85] vs. 0.85 [interquartile range 0.82-0.89]; P=0.003), whereas pre-PCI FFR values were similar between the 2 groups. Multivariable linear regression analysis revealed that the presence of MB and greater left ventricular mass volume in the LAD territory were independently associated with lower post-PCI FFR values. Multivariable logistic regression analysis also revealed that the presence of MB and lower pre-PCI FFR values were independent predictors of post-PCI FFR values ≤0.80. CONCLUSIONS: CCTA-defined MB independently predicted both lower post-PCI FFR as a continuous variable and ischemic FFR as a categorical variable in patients undergoing elective PCI for LAD.

Predictors of Optical Coherence Tomography-Defined Calcified Nodules in Patients With Acute Coronary Syndrome　- A Substudy From the TACTICS Registry.

BACKGROUND: Recent studies suggest that the presence of calcified nodules (CN) is associated with worse prognosis in patients with acute coronary syndrome (ACS). We investigated clinical predictors of optical coherence tomography (OCT)-defined CN in ACS patients in a prospective multicenter registry.Methods and Results: We investigated 695 patients enrolled in the TACTICS registry who underwent OCT assessment of the culprit lesion during primary percutaneous coronary intervention. OCT-CN was defined as calcific nodules erupting into the lumen with disruption of the fibrous cap and an underlying calcified plate. Compared with patients without OCT-CN, patients with OCT-CN (n=28) were older (mean [±SD] age 75.0±11.3 vs. 65.7±12.7 years; P<0.001), had a higher prevalence of diabetes (50.0% vs. 29.4%; P=0.034), hemodialysis (21.4% vs. 1.6%; P<0.001), and Killip Class III/IV heart failure (21.4% vs. 5.7%; P=0.003), and a higher preprocedural SYNTAX score (median [interquartile range] score 15 [11-25] vs. 11 [7-19]; P=0.003). On multivariable analysis, age (odds ratio [OR] 1.072; P<0.001), hemodialysis (OR 16.571; P<0.001), and Killip Class III/IV (OR 4.466; P=0.004) were significantly associated with the presence of OCT-CN. In non-dialysis patients (n=678), age (OR 1.081; P<0.001), diabetes (OR 3.046; P=0.014), and Killip Class III/IV (OR 4.414; P=0.009) were significantly associated with the presence of OCT-CN. CONCLUSIONS: The TACTICS registry shows that OCT-CN is associated with lesion severity and poor clinical background, which may worsen prognosis.

Can phrenic nerve injury be anticipated by larger cryoballoons?

Recently, a novel size-adjustable cryoballoon has been introduced in clinical practice, which can be inflated to two different diameters (28 and 31 mm). The 31 mm cryoballoon is specifically designed to achieve better contact with remodeled pulmonary veins (PVs) that have wider ostia while avoiding deep cannulation, thereby potentially reducing the risk of phrenic nerve injury (PNI) associated with deep balloon cannulation. However, we encountered two cases of PNI during cryoballoon ablation using the novel system among our initial 25 consecutive case series. Herein, we present two cases that exhibited PNI during freezing of the right superior PV with a size-adjustable balloon. While larger balloons are expected to create a larger area of isolation, the safety of this novel balloon system needs to be evaluated in a large-scale clinical study.

PCSK9 inhibitor use during pregnancy in a case of familial hypercholesterolemia complicated with coronary artery disease.

Limited data have been reported on the use of proprotein convertase subtilisin/kexin type 9 (PCSK 9) inhibitors during pregnancy in women with familial hypercholesterolemia (FH). Here, we present the first case of initiating evolocumab (PCSK9 inhibitor) in a compound heterozygous FH mother. The patient was a 34-year-old primipara with severe dyslipidemia and a history of coronary artery bypass surgery. An elevated low-density lipoprotein cholesterol (LDL-C) level of 420 mg/dL was detected in the first trimester and persistently increased throughout pregnancy. Evolocumab was administered at 31 and 35 weeks of gestation, showing a positive effect on stabilizing LDL-C levels. Planned delivery with labor analgesia was performed at 38 + 4 weeks. Both the mother and infant were discharged without any notable complications. Hence, evolocumab, an IgG2 monochromatic antibody with little placental permeability, may be an alternative medication with limited influence on infants. Further studies are needed to assess the safety of evolocumab administration during pregnancy.

Detection of unrecognized myocardial infarction by preprocedural transthoracic echocardiography in patients undergoing elective percutaneous coronary intervention.

BACKGROUND: Previous studies showed that unrecognized myocardial infarction (UMI) identified on cardiac magnetic resonance (CMR) was related to worse prognosis. We aimed to investigate the efficacy of preprocedural transthoracic echocardiography (TTE) to detect the presence of UMI in patients undergoing percutaneous coronary intervention (PCI). METHODS: A total of 138 patients with chronic coronary syndrome (CCS) and preserved left ventricular ejection fraction (LVEF) without history of myocardial infarction or revascularization were retrospectively studied. UMI was evaluated with pre-PCI late gadolinium enhancement (LGE)-CMR. TTE and two-dimensional speckle-tracking echocardiography (2D-STE) were performed before PCI. All patients were divided into two groups according to the presence or absence of UMI, and clinical and echocardiographic findings were compared between these two groups. RESULTS: UMI was detected in 43 patients (31.2%). Multivariable logistic regression analysis revealed that higher SYNTAX score, the presence of wall motion abnormalities (WMAs) and lower global longitudinal strain (GLS) were independent predictors of the presence of UMI. Furthermore, GLS provided incremental efficacy for the detection of UMI over abnormal Q waves, SYNTAX score and WMAs. CONCLUSIONS: Preprocedural TTE in combination with 2D-STE could help identify patients with UMI regardless of the presence or absence of ECG findings and WMAs.

Higher power achieves greater local impedance drop, shorter ablation time, and more transmural lesion formation in comparison to lower power in local impedance guided radiofrequency ablation of atrial fibrillation.

BACKGROUND: Since the local impedance (LI) of the ablation catheter reflects tissue characteristics, the efficacy of higher power (HP) compared to lower power (LP) in LI-guided ablation may differ from other index-guided ablations. OBJECTIVE: This study aimed to assess the efficacy of HP ablation in LI-guided ablation of atrial fibrillation (AF). METHODS: A prospective observational study was conducted, enrolling patients undergoing de novo ablation for AF. Pulmonary vein isolation was performed using point-by-point ablation with a RHYTHMIA HDxTM Mapping System and an open-irrigated ablation catheter with mini-electrodes (IntellaNav MIFI OI). Ablation was stopped when the LI drop reached 30 ohms, three seconds after the LI plateaued, or when ablation time reached 30 s. To balance the baseline differences, a unique method was used in which the power was changed between HP (45 W to anterior wall/40 W to posterior wall) and LP (35 W/30 W) alternately for each adjacent point. RESULTS: A total of 551 ablations in 10 patients were analyzed (HP, n = 276; LP, n = 275). The maximum LI drop was significantly larger (HP: 28.3 ± 5.4 vs. LP: 24.8 ± 6.3 ohm), and the time to minimum LI was significantly shorter (HP: 15.0 ± 6.3 vs. LP: 19.3 ± 6.6 s) in the HP setting. The unipolar electrogram analysis of three patients revealed that the electrogram indicating transmural lesion formation was observed more frequently in the HP setting. CONCLUSION: In LI-guided ablation, the HP could achieve a larger LI drop and shorter time to minimum LI, which may result in more transmural lesion formation compared to a LP setting.

Comparison of three different approaches to very high-power short-duration ablation using the QDOT-MICRO catheter.

BACKGROUND/OBJECTIVES: The QDOT-MICRO™ catheter allows very high-power and short-duration (vHPSD) ablation. This study aimed to investigate lesion characteristics using different ablation settings. METHODS: Radiofrequency applications (90 W/4 s, temperature-control mode with 55°C or 60°C target) were performed in excised porcine myocardium using three different approaches: single (SA), double nonrepetitive (DNRA), and double repetitive applications (DRA). Applications were performed with an interval of 1 min for DNRA, and without interval for DRA. RESULTS: A total of 480 lesions were analyzed. Lesion depth and volume were largest for DRA followed by DNRA and SA regardless of catheter direction (depth: 3.8 vs. 3.3 vs. 2.6 mm, p < .001 for all comparisons; volume: 176.6 vs. 145.1 vs. 97.0 mm3 , p < .001 for all comparisons). Surface area was significantly larger for DRA than for SA (45.1 vs. 38.3 mm2 , p < .001) and larger for DNRA than for SA (44.5 vs. 38.3 mm2 , p < .001), but was similar between DRA and DNRA (45.1 vs. 44.5 mm2 , p = .54). Steam-pops more frequently occurred for DRA than for SA (15.6% vs. 4.4%, p = .004) and DNRA (15.6% vs. 6.9%, p = .061), but the incidence was similar between SA and DNRA (4.4% vs. 6.9%, p = 1). Although surface area and lesion volume were larger in lesions with steam-pops than without steam-pops (46.5 vs. 38.1 mm2 , p = .018 and 128.3 vs. 96.8 mm3 , p = .068, respectively), lesions were not deeper (pop(+): 2.5 mm vs. pop(-): 2.6 mm, p = .75). CONCLUSIONS: DNRA produces larger lesions than SA without increasing the risk of steam-pops. DRA produces the largest lesions among the three groups, but with an increased risk of steam-pops. Even with steam-pops, lesions do not become deeper in vHPSD ablation.

Retrograde fast pathway cryoablation inside the coronary sinus for slow-fast atrioventricular nodal reentrant tachycardia in a patient with persistent left superior vena cava.

INTRODUCTION: Persistent left superior vena cava (PLSVC) is accompanied by enlarged coronary sinus (CS) and deformation of the triangle of Koch. This makes anatomical evaluation of the atrioventricular (AV) nodal pathways difficult. METHODS: We attempted cryoablation of retrograde fast pathway located in the enlarged CS roof of PLSVC for slow-fast AV nodal reentrant tachycardia (AVNRT) induced by inadvertent antegrade fast pathway elimination during ablation of left atrial tachycardia. RESULTS: Slow-fast AVNRT was successfully eliminated without AV block progression. CONCLUSIONS: This is the first case of successful retrograde fast pathway ablation of the CS ostial roof for slow-fast AVNRT with PLSVC.

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

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

Impact of filter configurations on bipolar EGMs: An optimal filter setting for identifying VT substrates.

BACKGROUND: The impact of filtering on bipolar electrograms (EGMs) has not been systematically examined. We tried to clarify the optimal filter configuration for ventricular tachycardia (VT) ablation. METHODS: Fifteen patients with VT were included. Eight different filter configurations were prospectively created for the distal bipoles of the ablation catheter: 1.0-250, 10-250, 100-250, 30-50, 30-100, 30-250, 30-500, and 30-1000 Hz. Pre-ablation stable EGMs with good contact (contact force > 10 g) were analyzed. Baseline fluctuation, baseline noise, bipolar peak-to-peak voltage, and presence of local abnormal ventricular activity (LAVA) were compared between different filter configurations. RESULTS: In total, 2276 EGMs with multiple bipolar configurations in 246 sites in scar and border areas were analyzed. Baseline fluctuation was only observed in the high-pass filter of (HPF) ≤ 10 Hz (p < .001). Noise level was lowest at 30-50 Hz (0.018 [0.012-0.029] mV), increased as the low-pass filter (LPF) extended, and was highest at 30-1000 Hz (0.047 [0.041-0.061] mV) (p < .001). Conversely, the HPF did not affect the noise level at ≤30 Hz. As the HPF extended to 100 Hz, bipolar voltages significantly decreased (p < .001), but were not affected when the LPF was extended to ≥100 Hz. LAVAs were most frequently detected at 30-250 Hz (207/246; 84.2%) and 30-500 Hz (208/246; 84.6%), followed by 30-1000 Hz (205/246; 83.3%), but frequently missed at LPF ≤ 100 Hz or HPF ≤ 10 Hz (p < .001). A 50-Hz notch-filter reduced the bipolar voltage by 43.9% and LAVA-detection by 34.5% (p < .0001). CONCLUSION: Bipolar EGMs are strongly affected by filter settings in scar/border areas. In all, 30-250 or 30-500 Hz may be the best configuration, minimizing the baseline fluctuation, baseline noise, and detecting LAVAs. Not applying the 50-Hz notch filter may be beneficial to avoid missing VT substrate.

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

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

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

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

Genetic risk score of cerebral infarction in atrial fibrillation genome-wide association study.

INTRODUCTION: Stroke is a leading cause of death and the primary cause of adult-acquired disability. Patients with cardiogenic embolic stroke also have higher mortality and recurrence rates than patients with other stroke subtypes. Atrial fibrillation (AF) is a major risk factor for cerebral infarction (CI). The large-scale study identified 32 loci in the MEGASTROKE study. However, few studies have attempted to identify novel stroke risk variants in patients with a history of AF. Our overall aim was to identify novel CI risk variants in AF cases and explore whether their associations with the CI risk were affected by the CHADS2 and CHA2DS2-VASc scores. METHODS: We performed association study with CI using 8181 AF cases in previous genome-wide association study (GWAS) and imputation data without controls. We classified AF cases into those with or without past history of CI, and the genetic associations with the CI risk were examined. RESULTS: GWAS identified eight associated loci. The generated genetic risk score (GRS) for the eight loci was significantly associated with CI in patients with AF (1.46 × 10-8 ). We estimated bivariate logistic regression model which contained GRS and CHADS2 score (GRS: p-Value = 7.41 × 10-9 , CHADS2 score: p-Value <2.0 × 10-16 ) or CHA2DS2-VASc scores (GRS: p-Value = 2.52 × 10-10 , CHA2DS2-VASc score: p-Value <2.0 × 10-16 ). CONCLUSION: We identified eight genetic variants that were potentially associated with the risk of CI of AF cases and the significant GRS, whose associations were independent of the CHADS2 or CHA2DS2-VASc score.

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

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