Evaluation of microembolic signals on carotid ultrasound during pulmonary vein isolation with high-power short-duration and cryoballoon ablations: When and where do bubble and solid emboli arise?

INTRODUCTION: The underlying risks of asymptomatic embolization during high-power short-duration (HPSD) ablation for atrial fibrillation remain unclear. We aimed to evaluate microembolic signals (MESs) during HPSD ablation with power settings of 50 and 90 W in comparison with those during cryoballoon (CB) ablation using a novel carotid ultrasound-Doppler system that classifies solid and air bubble signals using real-time monitoring. METHODS AND RESULTS: Forty-seven patients underwent HPSD ablation using radiofrequency (RF), and 13 underwent CB ablation. MESs were evaluated using a novel pastable soft ultrasound probe equipped with a carotid ultrasound during pulmonary vein isolation. We compared the detailed MESs and their timing between RF and CB ablations. The number of MESs and solid signals were significantly higher in the RF group than in CB group (209 ± 229 vs. 79 ± 32, p = .047, and 83 ± 89 vs. 28 ± 17, p = .032, respectively). In RF ablation, the number of MESs, solid, and bubble signals per ablation point, or per second, was significantly higher at 90 W than at 50 W ablation. The MESs, solid, and bubble signals were detected more frequently in the bottom and anterior walls of the left pulmonary vein (LPV) ablation. In contrast, many MESs were observed before the first CB application and decreased chronologically as the procedure progressed. Signals were more prevalent during the CB interval rather than during the freezing time. Among the 28 patients, 4 exhibited a high-intensity area on postbrain magnetic resonance imaging (MRI). The MRI-positive group showed a trend of larger signal sizes than did the MRI-negative group. CONCLUSION: The number of MESs was higher in the HPSD RF group than in the CB group, with this risk being more pronounced in the 90 W ablation group. The primary detection site was the anterior wall of the LPV in RF and the first interval in CB ablation.

Refractory atrial tachycardia after transcatheter closure of an atrial septal defect, successfully treated by catheter ablation with transseptal approach via the side of the device.

Atrial tachyarrhythmias occurring after transcatheter atrial septal defect closure are not uncommon; however, those related to device stimulation are rare. Herein, a case involving a 24-year-old female, who developed drug-refractory atrial tachycardia during the early postoperative period, is reported. The results of electroanatomical mapping could eventually be obtained from both atria. They revealed a focal pattern, and the earliest site was located on the left atrial side of the superior atrial septum, between the left and right atrial discs of the device. An ablation catheter was inserted through the side of the device into the left atrial septum, and cauterization successfully achieved recovery of the sinus rhythm without device dislodgement. Learning objective: Atrial tachyarrhythmia related to mechanical stimulation with an atrial septal defect closure device in the early perioperative period is a rare complication. Catheter ablation with transseptal approach through the side of the device might be an option, although careful attention should be paid to the risk for device dislodgement.

Optimal ablation settings of TactiFlex SE laser-cut irrigated-tip catheter: comparison with ThermoCool SmartTouch SurroundFlow porous irrigated-tip catheter.

BACKGROUND: The TactiFlex SE catheter (TFSE, Abbott) with a contact force (CF) sensor and a laser-cut irrigated-tip has recently become available but lacks a lesion quality marker. This study aimed to explore distinctions in lesion characteristics between the TFSE and the ThermoCool SmartTouch SurroundFlow catheter (STSF, Biosense Webster), which utilizes a porous irrigated tip, and to assess the most effective application settings for the TFSE. METHODS: Lesions were generated using varying settings of radiofrequency power (30-50 W), CF (10-20 g), application duration (10-40 s), and catheter orientation (perpendicular or parallel) in an ex vivo porcine model. Comparative analysis between the TFSE and STSF was conducted for lesion characteristics and incidence of steam pops using predictive models in regression analyses. RESULTS: Among 720 applications, the TFSE exhibited a significantly lower incidence of steam pops compared to the STSF (0.6% vs. 36.8%, P < 0.001). Moreover, coefficients of determination (R2) for the TFSE were higher than those for the STSF concerning lesion depth (0.710 vs. 0.541) and volume (0.723 vs. 0.618). The lesion size generated with the TFSE was notably smaller than that with the STSF under identical application settings. Additionally, to achieve a lesion depth ≥ 4.0 mm, the TFSE required an application duration 8-12 s longer than the STSF under similar settings. CONCLUSIONS: The TFSE demonstrated a lower incidence of steam pops and superior predictability in lesion size compared to the STSF. However, the TFSE necessitated a longer application duration than the STSF to achieve an adequate lesion size.

Feasibility and efficacy of real-time ultrasound-guided venous closure with suture-mediated vascular closure device.

BACKGROUND: Venous vascular access complications are usually nonfatal but are the most common complications after transvenous catheter intervention. Vascular closure devices (VCDs) have recently become available for venous closure. OBJECTIVE: This study aimed to evaluate the feasibility and efficacy of real-time ultrasound-guided venous closure with suture-mediated VCDs in patients who underwent catheter ablation. METHODS: This single-center observational study enrolled 226 consecutive patients who underwent elective catheter ablation with femoral venipuncture. For hemostasis, vessel closure by VCD was performed with real-time ultrasound guidance after 2022 (n = 123) and without ultrasound guidance in 2021 (n = 103). The occurrence of venous access site-related complications (major, minor, or other) was compared. RESULTS: The rate of device failure was significantly lower in patients with ultrasound guidance than in those without (1.6% vs 6.3%; P = .048). The occurrence of all venous access site-related complications was significantly lower in patients with ultrasound guidance than in those without (4.9% vs 18.4%; P = .001). Time to ambulation was shorter in patients with ultrasound guidance than in those without (2.0 ± 0.1 hours vs 2.2 ± 0.6 hours; P < .001). CONCLUSION: Real-time ultrasound guidance can reduce device failure, access site-related complications, and time to ambulation in performing venous closure with a VCD.

Comparison of novel intrinsic versus conventional antitachycardia pacing for ventricular tachycardia among implantable cardioverter-defibrillator recipients.

INTRODUCTION: Intrinsic antitachycardia pacing (iATP) is a novel automated antitachycardia pacing (ATP) that provides individual treatment to terminate ventricular tachycardia (VT). However, the clinical efficacy of iATP in comparison with conventional ATP is unknown. We aim to compare the termination rate of VT between iATP and conventional ATP in patients with implantable cardioverter-defibrillators using a unique setting of different sequential orders of both ATP algorisms. METHODS: Patients with the iATP algorithm were assigned to iATP-first and conventional ATP-first groups sequentially. In the iATP-first group, a maximum of seven iATP sequences were delivered, followed by conventional burst and ramp pacing. In contrast, in the conventional ATP-first group, two bursts and ramp pacing were initially programmed, followed by iATP sequences. We compared the success rates of VT termination in the first and secondary programmed ATP zones between the two groups. RESULTS: Fifty-eight and 56 patients were enrolled in the iATP-first and conventional ATP-first groups, and 67 and 44 VTs were analyzed in each group, respectively. At the first single ATP therapy, success rates were 64% and 70% in the iATP and conventional groups, respectively. At the end of the first iATP treatment zone, the success rate increased from 64% to 85%. Moreover, secondary iATP therapy following the failure of conventional ATPs increased the success rate from 80% to 93%. There was a significant benefit of alternative iATP for VT termination compared to secondary conventional ATP (100% vs. 33%, p = .028). CONCLUSIONS: iATP may be beneficial as a secondary therapy after failure of conventional ATP to terminate VT.

Mechanisms of torsades de pointes: an update.

Torsades de Pointes (TdP) refers to a polymorphic ventricular tachycardia (VT) with undulating QRS axis that occurs in long QT syndrome (LQTS), although the term has been used to describe polymorphic ventricular tachyarrhythmias in which QT intervals are not prolonged, such as short-coupled variant of TdP currently known as short-coupled ventricular fibrillation (VF) and Brugada syndrome. Extensive works on LQTS-related TdP over more than 50 years since it was first recognized by Dessertennes who coined the French term meaning "twisting of the points", have led to current understanding of the electrophysiological mechanism that TdP is initiated by triggered activity due to early afterdepolarization (EAD) and maintained by reentry within a substrate of inhomogeneous repolarization. While a recently emerging notion that steep voltage gradients rather than EADs are crucial to generate premature ventricular contractions provides additions to the initiation mode, the research to elucidate the maintenance mechanism hasn't made much progress. The reentrant activity that produces the specific form of VT is not well characterized. We have conducted optical mapping in a rabbit model of electrical storm by electrical remodeling (QT prolongation) due to chronic complete atrioventricular block and demonstrated that a tissue-island with prolonged refractoriness due to enhanced late Na+ current (INa-L) contributes to the generation of drifting rotors in a unique manner, which may explain the ECG characteristic of TdP. Moreover, we have proposed that the neural Na+ channel NaV1.8-mediated INa-L may be a new player to form the substrate for TdP. Here we discuss TdP mechanisms by comparing the findings in electrical storm rabbits with recently published studies by others in simulation models and human and animal models of LQTS.

Clinical outcomes and predictors of delayed echocardiographic response to cardiac resynchronization therapy.

INTRODUCTION: The clinical outcomes and mechanisms of delayed responses to cardiac resynchronization therapy (CRT) remain unclear. We aimed to investigate the differences in outcomes and gain insight into the mechanisms of early and delayed responses to CRT. METHODS: This retrospective study included 110 patients who underwent CRT implantation. Positive response to CRT was defined as ≥15% reduction of left ventricular (LV) end-systolic volume on echocardiography at 1 year (early phase) and 3 years (delayed phase) after implantation. The latest mechanical activation site (LMAS) of the LV was identified using two-dimensional speckle-tracking radial strain analysis. RESULTS: Seventy-eight (71%) patients exhibited an early response 1 year after CRT implantation. Of 32 non-responders in the early phase, 12 (38%) demonstrated a delayed response, and 20 (62%) were classified as non-responders after 3 years. During the follow-up time of 10.3 ± 0.5 years, the delayed and early responders had a similar prognosis of mortality and heart failure (HF) hospitalization. In contrast, non-responders had a worse prognosis. Multivariate analysis revealed that a longer duration (months) between initial HF hospitalization and CRT (odds ratio [OR]: 1.126; 95% confidence interval [CI]: 1.036-1.222; p = .005), non-exact concordance of LV lead location with LMAS (OR: 32.744; 95% CI: 1.101-973.518; p = .044), and pre-QRS duration (OR: 0.901; 95% CI: 0.827-0.981; p = .016) were independent predictors of delayed response to CRT compared with early response. CONCLUSION: The prognoses were similar regardless of the response time after CRT. A longer history of HF, suboptimal LV lead position, and shorter pre-QRS duration were related to delayed response than early response.

Triggers of Ventricular Fibrillation in Patients With Inferolateral J-Wave Syndrome.

BACKGROUND: There are few data on ventricular fibrillation (VF) initiation in patients with inferolateral J waves. OBJECTIVES: This multicenter study investigated the characteristics of triggers initiating spontaneous VF in inferolateral J-wave syndrome. METHODS: A total of 31 patients (age 37 ± 14 years, 24 male) with spontaneous VF episodes associated with inferolateral J waves were evaluated to determine the origin and characteristics of triggers. The J-wave pattern was recorded in inferior leads in 11 patients, lateral leads in 3, and inferolateral leads in 17. RESULTS: The VF triggers (n = 37) exhibited varying QRS durations (176 ± 21 milliseconds, range 119-219 milliseconds) and coupling intervals (339 ± 46 milliseconds, range 250-508 milliseconds) with a right (70%) or left (30%) bundle branch block (BBB) pattern. Trigger patterns were associated with J-wave location: left BBB triggers with inferior J waves and right BBB triggers with lateral J waves. Electrophysiologic study was performed for 22 VF triggers in 19 patients. They originated from the left or right Purkinje system in 6 and from the ventricular myocardium in 10 and were undetermined in 6. Purkinje vs myocardial triggers showed distinct electrocardiographic characteristics in coupling interval and QRS-complex duration and morphology. Abnormal epicardial substrate associated with fragmented electrograms was identified in 9 patients, with triggers originating from the same region in 7 patients. Catheter ablation resulted in VF suppression in 15 patients (79%). CONCLUSIONS: VF initiation in inferolateral J-wave syndrome is associated with significant individual heterogeneity in trigger characteristics. Myocardial triggers have electrocardiographic features distinct from Purkinje triggers, and their origin often colocalizes with an abnormal epicardial substrate.

Distributions and number of drivers on real-time phase mapping associated with successful atrial fibrillation termination during catheter ablation for non-paroxysmal atrial fibrillation.

BACKGROUND: Real-time phase mapping (ExTRa™) is useful in determining the strategy of catheter ablation for non-paroxysmal atrial fibrillation (AF). This study aimed to investigate the features of drivers of AF associated with its termination during ablation. METHODS: Thirty-six patients who underwent catheter ablation for non-paroxysmal AF using online real-time phase mapping (ExTRa™) were enrolled. A significant AF driver was defined as an area with a non-passively activated ratio of ≥ 50% on mapping analysis in the left atrium (LA). All drivers were simultaneously evaluated using a low-voltage area, complex fractionated atrial electrogram (CFAE), and rotational activity by unipolar electrogram analysis. The electrical characteristics of drivers were compared between patients with and without AF termination during the procedure. RESULTS: Twelve patients achieved AF termination during the procedure. The total number of drivers detected on the mapping was significantly lower (4.4 ± 1.6 vs. 7.4 ± 3.8, p = 0.007), and the drivers were more concentrated in limited LA regions (2.8 ± 0.9 vs. 3.9 ± 1.4, p = 0.009) in the termination group than in the non-termination group. The presence of drivers 2-6 with limited (≤ 3) LA regions showed a tenfold increase in the likelihood of AF termination, with 83% specificity and 67% sensitivity. Among 231 AF drivers, the drivers related to termination exhibited a greater overlap of CFAE (56.8 ± 34.1% vs. 39.5 ± 30.4%, p = 0.004) than the non-related drivers. The termination group showed a trend toward a lower recurrence rate after ablation (p = 0.163). CONCLUSIONS: Rotors responsible for AF maintenance may be characterized in cases with concentrated regions and fewer drivers on mapping.

Elevated liver fibrosis-4 index predicts recurrence after catheter ablation for atrial fibrillation in patients with heart failure.

BACKGROUND: The fibrosis-4 (FIB-4) index is a noninvasive scoring system that is used to assess the progression of liver fibrosis. This study aimed to assess whether the FIB-4 index is associated with recurrent atrial fibrillation (AF) after catheter ablation in patients with and without heart failure (HF). METHODS: We included 1,184 patients who underwent initial AF catheter ablation between 2016 and 2021. The patients were classified into low-risk (< 1.3), intermediate-risk (1.3-2.67), and high-risk (> 2.67) groups based on their FIB-4 indices at baseline. The patients were divided into HF (n = 552) and non-HF groups (n = 632); the HF group was further divided into paroxysmal AF (PAF) and non-PAF groups. AF recurrence after catheter ablation was then compared among the groups. RESULTS: In the non-HF group, no significant differences in recurrence after ablation were observed between the low-(n = 219), intermediate-(n = 364), and high-risk (n = 49) groups. In contrast, in the HF group, the intermediate-(n = 341) and high-risk (n = 112) groups had significantly higher recurrence rates than the low-risk group (n = 99) (log-rank test, p = 0.005). This association remained significant after multivariate analysis (hazard ratio [HR]:1.374; p = 0.027). The FIB-4 index increased incrementally as the brain natriuretic peptide levels and severity of tricuspid regurgitation increased. The FIB-4 index was an independent predictor of recurrence in the non-PAF HF group (HR:1.498; p = 0.007) but not in the PAF group. CONCLUSIONS: The FIB-4 index may be a useful predictor of AF recurrence after catheter ablation in patients with HF, particularly in those with non-PAF.

Association Between Catheter Ablation for Nonparoxysmal Atrial Fibrillation and Functional Mitral Regurgitation in Patients With Heart Failure With Preserved Ejection Fraction.

Functional mitral regurgitation (FMR) often coexists with atrial fibrillation (AF) and may have a causal relation with AF persistence and exacerbation of heart failure (HF). The purpose of this study was to investigate the impact of FMR on AF catheter ablation (AFCA) outcomes and improvement in FMR after AFCA in patients with HF with preserved ejection fraction (HFpEF) and nonparoxysmal AF. Excluding patients with primary valve disease or post-mitral valve repair, 280 patients with HFpEF who underwent CA for nonparoxysmal AF were retrospectively included. All patients completed 1-year follow-up and were assessed for FMR, AF recurrence and HF parameters, including echocardiography. At baseline, FMR was present in 153 (54.6%) patients (mild, n = 112; moderate, n = 40; severe, n = 1), and these were decreased to 70 (25%) significantly 1 year after AFCA (mild, n = 64; moderate, n = 6), 119 patients (78%) had improvement in MR (a decrease of ≥1 level in the severity from baseline to 1 year on echocardiography). Overall, 274 patients (97.9%) had sinus rhythm at the 1-year examination, and recurrent AF-free survival did not differ in patients with and without MR improvement (83.2% vs 82.4%, p = 0.908). However, the MR improvement group had a significantly lower cardiothoracic ratio, left atrial diameter, E/e', and B-type natriuretic peptide levels after 1 year than those in the MR nonimprovement group. In conclusion, the majority of the HFpEF patients with nonparoxysmal AF had improvement of FMR after AFCA with the high maintenance of sinus rhythm, leading to a virtuous cycle of cardiac function.

Lethal ventricular arrhythmia due to entrectinib-induced Brugada syndrome: a case report and literature review.

Entrectinib, a multikinase inhibitor of ROS1 and tropomyosin receptor kinases, is recommended to treat ROS1-positive metastatic non-small cell lung cancer (NSCLC). In a previous study, entrectinib-related cardiotoxicity occurred in 2% of patients; however, lethal arrhythmias remain understudied. We encountered a case of fatal arrhythmia due to drug-induced Brugada syndrome caused by entrectinib. An 81-year-old Japanese male with lung adenocarcinoma harboring ROS1-fusion gene was treated with entrectinib. The patient developed lethal arrhythmias three days after drug initiation, including ventricular tachycardia with Brugada-like electrocardiogram changes. Echocardiography and coronary angiography revealed no evidence of acute coronary syndrome or myocarditis. Following the termination of entrectinib, the electrocardiogram abnormality improved within 12 days. Hence, paying special attention to and monitoring electrocardiogram changes is necessary. In addition, it is also necessary to consider early therapeutic interventions and discontinuation of the drug in cases of drug-induced Brugada syndrome.