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.).

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.

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.

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.

Impact of Cryoballoon Ablation on Electrophysiology Lab Efficiency During the Treatment of Patients With Persistent Atrial Fibrillation: A Subanalysis of the STOP Persistent AF Study.

BACKGROUND: The volume of atrial fibrillation (AF) catheter ablation procedures has increased to address the growing patient population with AF; however, the impact of cryoballoon ablation on electrophysiology (EP) lab throughput is under-studied when treating patients with persistent AF (PsAF). OBJECTIVE: To assess EP lab utilization associated with cryoballoon ablation for the treatment of patients with PsAF and to evaluate mechanisms that optimize hospital resources. METHODS: Procedural data derived from the STOP Persistent AF trial were input into a discrete event simulation to assess EP lab utilization during AF ablation procedures. Patient and physician delays and lab occupancy times were modeled in a nominal and efficient EP lab setting over 1000 days. Accounting for variation in procedural times, we evaluated the number of days in which preplanned pulmonary vein isolation (PVI) cases resulted in overtime or excess time for non-ablation EP cases within a given lab day. A sensitivity analysis determined the parameters that most strongly influenced EP lab throughput. RESULTS: Lab occupancy times for the Nominal Use (NU) case included 165 procedures, and the High-Efficiency Use (HEU) case was derived from 69 procedures conducted at sites with faster procedure times than average. The HEU case had shorter lab occupancy times than the NU case (158 ± 32 minutes vs 188 ± 51 minutes, respectively). In the NU case, a total of 2000 procedures were conducted, with 28 lab days (2.8%) extending into overtime and 900 lab days (90%) exhibiting excess time for a non-ablation EP case. In the HEU case, a total of 3000 procedures were conducted, with 87 lab days (8.7%) extending into overtime and 635 lab days (63.5%) exhibiting excess time for a non-ablation EP case. The model was most sensitive to lab occupancy duration and the time of day that overtime started. CONCLUSIONS: Cryoballoon ablation for the treatment of patients with PsAF confers EP lab efficiencies that can support 3 PVI cases in a lab day.

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.

Cryoballoon ablation of pulmonary veins for persistent atrial fibrillation: Results from the multicenter STOP Persistent AF trial.

BACKGROUND: Pulmonary vein isolation (PVI) is the cornerstone of catheter ablation to treat patients with symptomatic drug-refractory atrial fibrillation (AF). OBJECTIVE: The purpose of this study was to assess the safety and efficacy of PVI using the cryoballoon catheter to treat patients with persistent AF. METHODS: STOP Persistent AF (ClinicalTrials.gov Identifier: NCT03012841) was a prospective, multicenter, single-arm, Food and Drug Administration-regulated trial designed to evaluate the safety and efficacy of PVI-only cryoballoon ablation for drug-refractory persistent AF (continuous episodes <6 months). The primary efficacy endpoint was 12-month freedom from ≥30 seconds of AF, atrial flutter (AFL), or atrial tachycardia (AT) after a 90-day blanking period. The prespecified performance goals were set at >40% and <13% for the primary efficacy and safety endpoints, respectively. Secondary endpoints assessed quality of life using the AFEQT (Atrial Fibrillation Effect on Quality of Life) and SF (Short Form)-12 questionnaires. RESULTS: Of 186 total enrollments, 165 subjects (70% male; age 65 ± 9 years; left atrial diameter 4.2 ± 0.6 cm; body mass index 31 ± 6) were treated at 25 sites in the United States, Canada, and Japan. Total procedural, left atrial dwell, and fluoroscopy times were 121 ± 46 minutes, 102 ± 41 minutes, and 19 ± 16 minutes, respectively. At 12 months, the primary efficacy endpoint was 54.8% (95% confidence [CI] 46.7%-62.1%) freedom from AF, AFL, or AT. There was 1 primary safety event, translating to a rate of 0.6% (95% CI 0.1%-4.4%). AFEQT and SF-12 assessments demonstrated significant improvements from baseline to 12 months postablation (P <.001). CONCLUSION: The STOP Persistent AF trial demonstrated cryoballoon ablation to be safe and effective in treating patients with drug-refractory persistent AF characterized by continuous AF episodes <6 months.

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.

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.

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.

Novel usage of the cryoballoon catheter to achieve large area atrial substrate modification in persistent and long-standing persistent atrial fibrillation.

BACKGROUND: The cryoballoon catheter has proven to be both safe and effective when used for pulmonary vein (PV) isolation in patients with paroxysmal atrial fibrillation (AF). More recently, the cryoballoon catheter has demonstrated the ability to create durable, transmural, and large areas of PV ablation. However, persistent and long-standing persistent AF can require additional cardiac substrate modification(s) before a patient is returned to normal sinus rhythm. Yet, no study has reported the techniques necessary to achieve extra-PV lesion sets using the cryoballoon catheter. METHODS: Cryoballoon ablation was completed in 225 patients with varying degrees of AF disease. In several cases, the balloon was used for more than PV isolation. This study examines the 11 anatomical cardiac locations where extra-PV lesion sets were utilized. RESULTS: This study demonstrates that these extra-PV ablations can be done safely with the balloon catheter (3.6 % total complication rate). The 12-month efficacy (freedom from all atrial arrhythmia) using these techniques was 88 % in 88 patients with paroxysmal AF, 71 % in 75 patients with persistent AF, and 55 % in 62 patients with long-standing persistent AF. While using this protocol, mean procedure time was 2.2 ± 0.6 h, and average fluoroscopy time was 4.2 ± 2.2 min. CONCLUSIONS: The cryoballoon catheter can be used to make effective and safe extra-PV lesions. However, these techniques will need to be validated in more multi-center studies with review of complication rates and long-term freedom from AF.

Reduction of Iatrogenic Atrial Septal Defects with an Anterior and Inferior Transseptal Puncture Site when Operating the Cryoballoon Ablation Catheter.

The cryoballoon catheter ablates atrial fibrillation (AF) triggers in the left atrium (LA) and pulmonary veins (PVs) via transseptal access. The typical transseptal puncture site is the fossa ovalis (FO) - the atrial septum's thinnest section. A potentially beneficial transseptal site, for the cryoballoon, is near the inferior limbus (IL). This study examines an alternative transseptal site near the IL, which may decrease the frequency of acute iatrogenic atrial septal defect (IASD). Also, the study evaluates the acute pulmonary vein isolation (PVI) success rate utilizing the IL location. 200 patients were evaluated by retrospective chart review for acute PVI success rate with an IL transseptal site. An additional 128 IL transseptal patients were compared to 45 FO transseptal patients by performing Doppler intracardiac echocardiography (ICE) post-ablation to assess transseptal flow after removal of the transseptal sheath. After sheath removal and by Doppler ICE imaging, 42 of 128 (33%) IL transseptal patients demonstrated acute transseptal flow, while 45 of 45 (100%) FO transseptal puncture patients had acute transseptal flow. The difference in acute transseptal flow detection between FO and IL sites was statistically significant (P <0.0001). Furthermore, 186 of 200 patients (with an IL transseptal puncture) did not need additional ablation(s) and had achieved an acute PVI by a "cryoballoon only" technique. An IL transseptal puncture site for cryoballoon AF ablations is an effective location to mediate PVI at all four PVs. Additionally, an IL transseptal location can lower the incidence of acute transseptal flow by Doppler ICE when compared to the FO. Potentially, the IL transseptal site may reduce later IASD complications post-cryoballoon procedures.

Unusually high association of hypertrophic cardiomyopathy and complex heart defects in children with fasciculoventricular pathways.

INTRODUCTION: Fasciculoventricular pathways (FVPs) are rare causes of preexcitation that do not mediate tachycardias. We report a two-center experience of pediatric patients with FVP and an unexpectedly high association of complex congenital heart defects (CHDs), chromosomal anomalies, and hypertrophic cardiomyopathy. METHODS: A retrospective review of the electrophysiology database at two institutions was performed to identify patients with FVP from January 2000 to January 2011. Medical records of these patients were reviewed for clinical history and course, presence of comorbidities, and details of intracardiac electrophysiology (EP) study. RESULTS: A total of 17 patients were identified. The primary indication for EP study was a preexcitation pattern on electrocardiogram. The majority of patients, 12/17 (71%), were found to have associated cardiac and genetic anomalies. Hypertrophic cardiomyopathy was found in 5/17 (29%) patients, with genetic testing in two patients demonstrating the lysosomal-associated membrane protein 2 mutation (Danon syndrome). Underlying complex CHDs were present in 3/17 (18%) patients. One patient (6%) was status post (s/p) cardiac transplant, one patient had hypertension, and another had Trisomy 21. Other electrophysiologic substrates mediating tachycardia were found in 3/17 (18%) patients. Only 5/17 patients (29%) were otherwise healthy with structurally normal hearts. CONCLUSIONS: In this largest reported series of FVP in children, there is an unusually high association of FVP with complex CHDs, chromosomal anomalies, and hypertrophic cardiomyopathy. Any patient with such disorders and manifest preexcitation should be evaluated with a high index of suspicion for a FVP.

Creating continuous linear lesions in the atria: a comparison of the multipolar ablation technique versus the conventional drag-and-burn.

INTRODUCTION: Catheter-based treatment of atrial fibrillation (AF) requires the isolation of the triggering foci as well as modification of the atria with substrate that sustains AF. The creation of linear lesions in the left atrium with standard radiofrequency ablative methods requires long procedural times with unpredictable results. METHODS: The simultaneous delivery of phase-shifted radiofrequency energy from a multipolar catheter was compared to the conventional drag-and-burn technique for creating linear lesions in 10 dogs. Four atrial sites were targeted under intracardiac ultrasound and fluoroscopic guidance in each of 10 dogs. The conventional drag-and-burn technique or the multipolar phase-shifted ablation catheter was randomly applied for 60 seconds and compared. RESULTS: Creating linear lesions using the simultaneous multipolar phase-shifted ablation catheter was on average 11.0 minutes faster (33.6 minutes vs 44.6 minutes, P < 0.01) than the drag-and-burn method. The fraction of the lesion length achieved using phase-shifted ablation compared to that intended was 23% greater (76% vs 53%, P < 0.01), and has less discontinuities (0.1 compared to 0.8 discontinuities/line, P < 0.003). There was no significant difference in either the lesion transmurality, or fluoroscopy times. CONCLUSION: The simultaneous delivery of phase-shifted, radiofrequency energy using a multipolar catheter is more effective and efficient in producing linear lesions than the traditional drag-and-burn technique. Using the multipolar ablative method to create linear lesions may be a useful technique in the treatment of patients with substrate-mediated atrial fibrillation.