A Modular Communicative Leadless Pacing-Defibrillator System.

BACKGROUND: The subcutaneous implantable cardioverter-defibrillator (ICD) is associated with fewer lead-related complications than a transvenous ICD; however, the subcutaneous ICD cannot provide bradycardia and antitachycardia pacing. Whether a modular pacing-defibrillator system comprising a leadless pacemaker in wireless communication with a subcutaneous ICD to provide antitachycardia and bradycardia pacing is safe remains unknown. METHODS: We conducted a multinational, single-group study that enrolled patients at risk for sudden death from ventricular arrhythmias and followed them for 6 months after implantation of a modular pacemaker-defibrillator system. The safety end point was freedom from leadless pacemaker-related major complications, evaluated against a performance goal of 86%. The two primary performance end points were successful communication between the pacemaker and the ICD (performance goal, 88%) and a pacing threshold of up to 2.0 V at a 0.4-msec pulse width (performance goal, 80%). RESULTS: We enrolled 293 patients, 162 of whom were in the 6-month end-point cohort and 151 of whom completed the 6-month follow-up period. The mean age of the patients was 60 years, 16.7% were women, and the mean (±SD) left ventricular ejection fraction was 33.1±12.6%. The percentage of patients who were free from leadless pacemaker-related major complications was 97.5%, which exceeded the prespecified performance goal. Wireless-device communication was successful in 98.8% of communication tests, which exceeded the prespecified goal. Of 151 patients, 147 (97.4%) had pacing thresholds of 2.0 V or less, which exceeded the prespecified goal. The percentage of episodes of arrhythmia that were successfully terminated by antitachycardia pacing was 61.3%, and there were no episodes for which antitachycardia pacing was not delivered owing to communication failure. Of 162 patients, 8 died (4.9%); none of the deaths were deemed to be related to arrhythmias or the implantation procedure. CONCLUSIONS: The leadless pacemaker in wireless communication with a subcutaneous ICD exceeded performance goals for freedom from major complications related to the leadless pacemaker, for communication between the leadless pacemaker and subcutaneous ICD, and for the percentage of patients with a pacing threshold up to 2.0 V at a 0.4-msec pulse width at 6 months. (Funded by Boston Scientific; MODULAR ATP ClinicalTrials.gov NCT04798768.).

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.

Initial clinical experience of atrial fibrillation ablation guided by a cryoballoon-compatible, magnetic-based circular catheter.

INTRODUCTION: The circular catheter compatible with current cryoballoon system for atrial fibrillation (AF) ablation is exclusively sensed by impedance-based electro-anatomical mapping (EAM) system, limiting the accuracy of maps. We aim to investigate the feasibility and safety of a magnetic-based circular mapping catheter for AF ablation with cryoballoon. METHODS: Nineteen consecutive patients who underwent pulmonary vein isolation (PVI) with cryoballoon for paroxysmal or persistent AF were included. EAMs of left atrium (LA) created by the LASSOSTAR™NAV catheter (Lassostar map) before and after PVI were compared to that generated by a high-density mapping catheter (Pentaray map) from different aspects including structural similarity, PV angle, LA posterior wall (LAPW) and low voltage areas (LVAs), and the amplitude of far field electrograms (FFEs) recorded by catheters. RESULTS: All patients had successful PVI without major complications. With similar mapping time and density, the LA volume calculated from the Pentaray map and Lassostar map were comparable. There were no significant differences in PV angle of all PVs and PW area (16.8 ± 3.2 vs. 17.1 ± 2.8, p = .516) between Pentaray map and Lassostar map. High structural similarity score was observed between two maps (0.783 in RAO/LAO view and 0.791 in PA view). Lassostar map detected lesser but not statistically significant extension of LVA (13.9% vs. 18.3%, p = .07). Amplitude of FFE was larger at the right superior PV on Lassostar map (0.21 ± 0.16 vs. 0.14 ± 0.11 mV, p = .041) compared to that on the Pentaray map. CONCLUSION: In our initial experience, PVI with cryoballoon and magnetic-based circular LASSOSTAR™NAV catheter was safe and effective based on the accurate LA geometry it created.

One-year outcomes of pulmonary vein isolation with a novel cryoballoon: Primary results of the FROZEN AF trial.

INTRODUCTION: Cryoablation therapy for pulmonary vein isolation (PVI) to treat paroxysmal atrial fibrillation (PAF) is well established. A novel 28 mm cryoballoon system designed to operate under low pressure to safely reach a lower nadir temperature and maintain constant balloon size during cooling has not been prospectively studied in a large patient population for safety and efficacy. The FROZEN AF (NCT04133168) trial was an international multicenter, open-label, prospective, single-arm study on the safety and performance of a novel cryoballoon system for treatment of PAF. METHODS AND RESULTS: The study enrolled patients at 44 sites in 10 countries across North America, Europe, and Asia. Subjects were indicated for PVI treatment of PAF and had failed or were intolerant of one or more antiarrhythmic drugs. Procedural outcomes were defined based on the 2017 HRS consensus statement. Follow-up was performed at 7 days, 3, 6, and 12 months. Data are reported as mean ± SD or median (IQR). PVI was performed with a 28 mm cryoballoon in 325 drug refractory PAF patients. Complete PVI was achieved in 95.7% of patients. In cryoablation lesions longer than 60 s, 60.1% of PV isolations required only a single cryoballoon application. Procedure related complications included: phrenic nerve palsy [temporary 4 (1.2%), persistent 0 (0.0%)], cardiac tamponade/perforation 2 (0.6%), and air embolism 1 (0.3%). Freedom from documented atrial arrhythmia recurrence at 12 months was 79.9% (AF 82.7%, AFL 96.5%, AT 98.1%), antiarrhythmic drugs (AAD) were continued or re-initiated in 26.8% of patients after the 3-month blanking period. Additionally, an extension arm enrolled 50 pts for treatment with 28/31 mm variable size cryoballoon. A single temporary PNP occurred in this group, which resolved before discharge. Freedom from documented recurrence at 12 months in these pts was 82.0%. CONCLUSIONS: This novel cryoballoon may facilitate PVI to treat PAF, providing more options to address the variety of anatomies present in patients with PAF. This cryoballoon system proved to be safe and effective for treatment of patients with drug refractory or drug intolerant PAF.

Use of three-dimensional electroanatomic mapping for epicardial access: needle tracking, electrographic characteristics, and clinical application.

AIMS: Pericardiocentesis is usually completed under fluoroscopy. The electroanatomic mapping (EAM) system allows visualizing puncture needle tip (NT) while displaying the electrogram recorded from NT, making it possible to obtain epicardial access (EA) independent of fluoroscopy. This study was designed to establish and validate a technique by which EA is obtained under guidance of three-dimensional (3D) EAM combined with NT electrogram. METHODS AND RESULTS: 3D shell of the heart was generated, and the NT was made trackable in the EAM system. Unipolar NT electrogram was continuously monitored. Penetration into pericardial sac was determined by an increase in NT potential amplitude and an injury current. A long guidewire of which the tip was also visible in the EAM system was advanced to confirm EA. Epicardial access was successfully obtained without complication in 13 pigs and 22 patients. In the animals, NT potential amplitude was 3.2 ± 1.0 mV when it was located in mediastinum, 5.2 ± 1.6 mV when in contact with fibrous pericardium, and 9.8 ± 2.8 mV after penetrating into pericardial sac (all P ≤ 0.001). In human subjects, it measured 1.54 ± 0.40 mV, 3.61 ± 1.08 mV, and 7.15 ± 2.88 mV, respectively (all P < 0.001). Fluoroscopy time decreased in every 4-5 cases (64 ± 15, 23 ± 17, and 0 s for animals 1-4, 5-8, 9-13, respectively, P = 0.01; 44 ± 23, 31 ± 18, 4±7 s for patients 1-7, 8-14, 15-22, respectively, P < 0.001). In five pigs and seven patients, EA was obtained without X-ray exposure. CONCLUSION: By tracking NT in the 3D EAM system and continuously monitoring the NT electrogram, it is feasible and safe to obtain EA with minimum or no fluoroscopic guidance.

Leadless pacemaker implementation at the right atrial appendage apex: An initial preclinical assessment.

OBJECTIVE: This study evaluates the feasibility and efficacy of implanting a leadless pacemaker at the right atrial appendage (RAA) in a preclinical minipig model, aiming to address the limitations of atrial pacing with current leadless devices like the Medtronic Micra, which is typically used for right ventricular implantation. METHODS: Four minipigs, each with a median body weight of 45.8 ± 10.0 kg, underwent placement of the Micra transcatheter pacing system (TPS) via the right femoral vein into the RAA apex. The pacing performance was assessed over 1-week (short-term) and 3-month (long-term) periods. OUTCOMES: The initial findings indicated successful implantation, with satisfactory intrinsic R-wave amplitudes and pacing threshold. In the following period, the sensitivity, threshold, and impedance were stable with time. Notably, upon explanation at 3 months, a deep myocardial penetration by the device was observed, necessitating a redesign for safe long-term use in a growing subject's heart. CONCLUSION: While initial results suggest that RAA apex placement of the Micra TPS is promising for potential inclusion in a dual-chamber pacing system, the issue of myocardial penetration highlights the need for device redesign to ensure safety and effectiveness in long-term applications.

Incidence of cryoballoon expansion dislodgement during pulmonary vein isolation-An underappreciated frequent cause of incomplete isolation.

BACKGROUND: Cryoballoon ablation for atrial fibrillation (AF) requires adequate contact between the pulmonary vein (PV) antrum and cryoballoon. The surge of intraballoon pressure during the initial phase of ablation may change the balloon's shape and compliance, resulting in balloon dislodgement and loss of PV occlusion. Without continuous monitoring, this phenomenon is often undetected but can be associated with incomplete PV isolation (PVI). METHODS: Primary cryoablation of AF was performed in 15 patients. PV occlusion status pre- and post-freezing were analyzed with intracardiac echocardiography (ICE) and dielectric imaging-based occlusion tool (DIOT) to calculate the incidence of expansion dislodgement of cryoballoon. RESULTS: A total of 105 cryoablation applications were performed on 57 veins, including three common ostiums of left pulmonary veins. In the evaluation of PV occlusion, both modalities reported consistent results in 86.7% of the assessments. Despite complete PV occlusion before ablation, peri-balloon leak after initiation of freezing was detected by ICE in 5/22 (22.7%) applications and by DIOT in 8/25 (32%) applications. CONCLUSION: Incidence of expansion dislodgement of the cryoballoon was detected in one-fourth to one-third of cryoablation applications depending on the imaging modality used, which was clinically frequent and significant.

Weight loss and atrial fibrillation: a review.

PURPOSE OF REVIEW: Despite technological advancements in catheter ablation, patients with atrial fibrillation often require multiple ablations, with diminishing returns depending on duration and persistence. Although early ablation is vital, modification of atrial fibrillation disease can be achieved with modification of existing risk factors. Obesity is an important modifiable risk factor, but there does not appear to be a consensus on the best method or goal for weight reduction. RECENT FINDINGS: The relationship between atrial fibrillation and obesity has been acknowledged. This review examines the clinical evidence demonstrating the benefit of weight reduction in the management of atrial fibrillation. In particular, this review compares the different approaches of recent studies. SUMMARY: On the basis of the literature, the authors recommend a structured weight loss programme with dietary and behavioural modifications individualized to each patient and including the implementation of physical activity. Consideration of bariatric surgery is appropriate in certain patients with obesity.

Impact of cryoballoon application abortion due to phrenic nerve injury on reconnection rates: a YETI subgroup analysis.

AIMS: Cryoballoon (CB)-based pulmonary vein isolation (PVI) is an effective treatment for atrial fibrillation (AF). The most frequent complication during CB-based PVI is right-sided phrenic nerve injury (PNI) which is leading to premature abortion of the freeze cycle. Here, we analysed reconnection rates after CB-based PVI and PNI in a large-scale population during repeat procedures. METHODS AND RESULTS: In the YETI registry, a total of 17 356 patients underwent CB-based PVI in 33 centres, and 731 (4.2%) patients experienced PNI. A total of 111/731 (15.2%) patients received a repeat procedure for treatment of recurrent AF. In 94/111 (84.7%) patients data on repeat procedures were available. A total of 89/94 (94.7%) index pulmonary veins (PVs) have been isolated during the initial PVI. During repeat procedures, 22 (24.7%) of initially isolated index PVs showed reconnection. The use of a double stop technique did non influence the PV reconnection rate (P = 0.464). The time to PNI was 140.5 ± 45.1 s in patients with persistent PVI and 133.5 ± 53.8 s in patients with reconnection (P = 0.559). No differences were noted between the two populations in terms of CB temperature at the time of PNI (P = 0.362). The only parameter associated with isolation durability was CB temperature after 30 s of freezing. The PV reconnection did not influence the time to AF recurrence. CONCLUSION: In patients with cryoballon application abortion due to PNI, a high rate of persistent PVI rate was found at repeat procedures. Our data may help to identify the optimal dosing protocol in CB-based PVI procedures. CLINICAL TRIAL REGISTRATION: https://clinicaltrials.gov/ct2/show/NCT03645577?term=YETI&cntry=DE&draw=2&rank=1 ClinicalTrials.gov Identifier: NCT03645577.

Risk factors of sudden cardiac death in hypertrophic cardiomyopathy.

PURPOSE OF REVIEW: Hypertrophic cardiomyopathy (HCM) is one of the leading causes of sudden cardiac death (SCD) in younger people and athletes. It is crucial to identify the risk factors for SCD in individuals with HCM. This review, based on recent systematic literature studies, will focus on the risk factors for SCD in patients with HCM. RECENT FINDINGS: An increasing number of studies have further explored the risk factors for SCD in patients with HCM, and new risk markers have emerged accordingly. In addition, more accurate SCD risk estimation and stratification methods have been proposed and continuously improved. SUMMARY: The identification of independent risk factors for HCM-related SCD would likely contribute to risk stratification. However, it is difficult to predict SCD with absolute certainty, as the annual incidence of SCD in adult patients with HCM is approximately 1%. The review discusses the established risk factors, such as a family history of SCD, unexplained syncope and some new risk factors. Taken together, the findings of this review demonstrate that there is a need for further research on individual risk factors and that SCD risk stratification in HCM patients remains a clinical challenge.

Exclusion of left atrial appendage: effects beyond thromboembolic prevention.

PURPOSE OF REVIEW: This review aims to summarize the nonthromboembolic prevention effects of left atrial appendage exclusion (LAAE). RECENT FINDINGS: Left atrial appendage (LAA) secretes multiple hormones; regulates blood volume and pressure; and generates trigger activities. Exclusion of the LAA by different techniques may lead to downstream effects including changes in blood pressure and cardiac performance, improvement of outcome of atrial fibrillation (AF) ablation, and alteration of metabolism. SUMMARY: LAAE procedures not only prevent thromboembolic events in patients with AF, but rather may bring additional benefits or side-effect to patients undergoing LAAE.

A tale of two balloons: technical and procedural difference between cryoballoon systems.

PURPOSE OF REVIEW: The cryoballoon catheter has been an option for the treatment of atrial fibrillation for over a decade. The most widely used device is the Medtronic Arctic Advance cryoballoon catheter. Recently, Boston Scientific has released the POLARx cryoballoon catheter. Here we review the major changes in the catheter system's design and its implications for procedural practice. RECENT FINDINGS: The POLARx cryoballoon catheter has been approved for use in Europe. Some studies have been published detailing the first clinical experiences in vivo with this newest technology. SUMMARY: The changes to the POLARx cryoballoon catheter, particularly its ability to maintain balloon size and pressure, will improve occlusion and theoretically improve procedural outcomes.

A second cryoballoon system-New and improved?

Generations of cryoballoon transformed the atrial fibrillation ablation landscape. New advancements continue to make cryoballoon more successful and safer treatment. A new cryoballoon PolaRx from Boston Scientific has unique features compared to that of the Medtronic Arctic Front Advance system. Comparison of the two available cryoballoons will require ongoing larger trial and clinical experience.

Focal cryoablation of atrioventricular node reentrant tachycardia: a review and comparison of data.

PURPOSE OF REVIEW: Atrioventricular node reentrant tachycardia (AVNRT) is the most common mechanism of supraventricular tachycardia. Radiofrequency ablation has been the most prevalent method for slow pathway ablation but carries risk of atrioventricular node injury. Focal cryoablation has been utilized as an alternative ablation modality; however, there has been concern about decreased efficacy, resulting in a higher rate of recurrence postablation. We also report outcomes from two international centers using an 8-mm cryocatheter and complete a thorough comparison of existing data on ablation of AVNRT. RECENT FINDINGS: Previous reviews included studies from 2006 onward. These studies included use of the 4 mm focal cryocatheter, which has largely been abandoned in current adult practice. We will cite more contemporary studies within the past 10 years, which also includes use of the 6 and 8 mm cryocatheter. SUMMARY: The use of focal cryoablation allows for reversible injury during AVNRT ablation, providing safety from permanent atrioventricular node injury. With the appropriate ablation endpoints, 8 mm focal cryoablation is more effective for permanent lesion formation, leading to lower recurrences.

Cryoballoon ablation for extrapulmonary vein targets.

PURPOSE OF REVIEW: Cryoballoon catheter can create large and contiguous lesions with stable contact during ablation. It has proven to be well tolerated and effective in pulmonary vein isolation. But atrial arrhythmias, including atrial fibrillation, atrial tachycardia, and atrial flutter (AFL), also relate to many extrapulmonary vein targets. It is necessary to understand the current evidence for the use of cryoballoon ablation for targets outside of pulmonary veins. RECENT FINDINGS: Studies have shown that the cryoballoon ablation can be used in extrapulmonary vein area, including left atrium roof, left atrial appendages, posterior left atrial wall, mitral isthmus, and right atrial appendage. The results indicate cryoballoon ablation is an effective and well-tolerated treatment option for the atrial arrhythmias in these locations outside of pulmonary vein when clinical necessary. SUMMARY: The cryoballoon ablation can safely and effectively perform contiguous linear lesions, structure isolations, and local ablation for targets outside of the pulmonary veins.

Approach and strategy for repeat catheter ablation of recurrent atrial fibrillation.

Patients with atrial fibrillation often undergo repeat catheter ablation for the recurrence of tachyarrhythmia. If the pulmonary veins were isolated in prior procedure, the operator should focus on substrate homogenization with identification and ablation of only arrhythmogenic areas.

Radiofrequency versus cryoballoon ablation for atrial fibrillation: an argument for a 'cryo-first' approach.

PURPOSE OF REVIEW: Radiofrequency and cryoballoon ablation are the two most common modalities for catheter ablation of atrial fibrillation. Radiofrequency, being more prevalent and having existed for a longer period, is often utilized for patients' first ablations, despite the efficiency and efficacy of the cryoballoon tool. Here we examine the advantages of the cryoballoon for its use in first-time ablation of atrial fibrillation. RECENT FINDINGS: The FIRE & ICE trial is established as conclusive evidence of the noninferiority of cryoballoon ablation to radiofrequency ablation in terms of efficacy. Since the study, cryoballoon has evolved in both form and technique, suggesting need for repeat consideration of the advantages of cryoablation over radiofrequency ablation. The second-generation cryoballoon has led to greater efficiency in achieving permanent pulmonary vein isolation, reducing complications, and reducing procedure times. SUMMARY: There are advantages to the use of cryoballoon which could increase success of first-time ablations, delaying need for repeat procedure and lowering overall burden on patients and the healthcare system. Cryoballoon ablation should be considered for first-time ablation in patients with paroxysmal or persistent atrial fibrillation.

Successful cryoablation of left ventricular summit premature ventricular contractions via the coronary sinus.

The left ventricular summit (LVS) is a challenging location for catheter-based percutaneous ablation due to its anatomical location. There have been case reports of cryoablations performed in this region, but the technique may be underutilized when radiofrequency ablation fails. A 45-year-old male was found to have 25 000 premature ventricular contractions (PVCs) a day despite previous ablation and a reduced ejection fraction of 40% despite medical therapy. Coronary sinus epicardial mapping revealed the coronary sinus distal region generated activations earlier than the QRS onset by 28 ms. Two separate, 4-minute cryoablations were delivered that suppressed the PVCs within 5 seconds. Alternate energy modalities such as cryo may offer a safer and more viable approach for ablation of LVS in select patients.

Comparing radiofrequency and cryoballoon technology for the ablation of atrial fibrillation.

PURPOSE OF REVIEW: With the growing popularity of the cryoballoon tool for catheter ablation of atrial fibrillation, there has been discussion of whether cryothermal energy is just as or more effective than traditional radiofrequency. This review will compare both thermal energies for the treatment of atrial fibrillation. RECENT FINDINGS: Although the FIRE and ICE trial established that cryoballoon technology is noninferior to radiofrequency ablation for the treatment of atrial fibrillation, both thermal technologies have undergone advancement. This review intends to explore recent changes in technology and catheter ablation technique to improve outcomes for patients with atrial fibrillation. SUMMARY: Catheter ablation is standard treatment for patients with atrial fibrillation, which primarily focuses on electrical isolation of the pulmonary veins. Radiofrequency is the most common approach at present times; however, over time, new technology has developed. Most successful among these is the cryoballoon tool. Although the FIRE and ICE trial indicated radiofrequency and cryothermal energy to be approximately equal in efficacy and safety, there are advantages and disadvantages to both. This review seeks to address the value of each tool, as well as further development needed to better address atrial fibrillation while improving procedural safety.