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Abstract Funding Acknowledgements Type of funding sources: None. Background/Introduction Idiopathic ventricular fibrillation (IVF) is responsible for 5-7% of sudden cardiac arrests in the absence of substrate for ventricular arrhythmia, structural diseases, or primary arrhythmic syndromes. The characteristics, management, and prognosis of these patients are unclear. Purpose To investigate the clinical features, management, and prognosis of IVF in our hospital healthcare system Methods Mayo Database Explorer software was used to identify IVF patients from our hospital electronic medical records between 1990 to 2022 in 5 states. The medical records were manually reviewed. Results A total of 132 patients were initially diagnosed with IVF. During the 9.2±6.8 years mean follow-up, 36 [27.3%] patients were later diagnosed with structural diseases or primary arrhythmic syndromes (dilated cardiomyopathy [41.7%], Long QT syndrome [27.8%], catecholaminergic polymorphic ventricular tachycardia [8.3%], Brugada syndrome [5.6%], mitral valve-related arrhythmia [5.6%], and short QT syndrome [2.8%]). Among the rest of the 96 patients with true IVF (mean age 38.4±15.7 years, male 59.4%, Caucasian 80.2%, hypertension 28.1%, diabetes 8.3%), 91 (94.8%) patients presented with out-of-hospital cardiac arrest and 88 (91.7%) patients had a history of syncope. Early repolarization and fragmented QRS were noted in 32 (33.3%) and 28 (29.1%) patients, respectively. Defibrillators were implanted in 92 (95.8%) patients. Genetic testing was performed in 35 (36.5%) patients, and possible associated mutations were found in 13 (37.1%) patients. An Electrophysiology study was conducted in 55 (57.3%) patients, and ventricular fibrillation was induced in 17 (30.9%) patients. The medical management with antiarrhythmic drugs was selected in 60 (62.5%) patients, and the catheter ablation ± anti-arrhythmic drugs was selected in 36 (37.5%) patients. The recurrence of ventricular fibrillation during 9.2±6.8 years of mean follow-up was significantly higher in the ablation strategy group (p=0.0003) (Figure 1). Conclusions We reported the largest cohort of IVF patients from a single healthcare system. Early repolarization and fragmented QRS were common in IVF. The possible associated mutations were found in one-third of IVF who underwent genetic testing. The ventricular fibrillation recurrences were significantly higher in the catheter ablation strategy group.

Background: Atypical Atrial Flutter (AAFL) prevalence is increasing due to the escalating Atrial Fibrillation (AF) ablations and cardiac surgeries. We wanted to explore the outcome of the AAFL ablation, considering the recent changes in mapping and ablation. Methods: This study was approved by the Institutional Review Board (IRB) of Mayo Clinic hospital. We retrospectively studied 419 patients who had undergone AAFL ablation at Mayo Clinic from January 2017 to June 2022. Thirteen patients declined research authorization, and 19 patients were lost to follow-up during the 90-day blanking period, resulting in a sample size of 387. The median follow-up time for patients was 25.7 months (95% CI 23.7, 32.3). Results: Recurrent symptoms with documentation of atrial arrhythmia Occurred in 226/387 (58.4%) patients, of which 151/226 (66.8%) occurred within the first year. The median time to recurrence was 8.5 months (max 57.8 months). Eleven patients died during the study period, 9 of whom experienced recurrence prior to death. Overall, the median recurrence-free survival (RFS) time was 16.6 months (95% CI 13.2, 20.0) with a 1-year RFS rate of 57.2% (95% CI 52.2, 62.7%). Acute termination occurred 324/387 (83.7%) during the ablation. The 1-year RFS rate was 58.9% (95% CI 53.5%, 64.9%) for patients with acute termination and 49.0% (95% CI 37.9%, 63.4%) for those without acute termination. The rate was not significantly different based on acute termination status (p = 0.11). Conclusions: The one-year RFS rate of 57.2% following AAFL ablation, even though 83.7% achieved acute termination during the procedure, signifies the extent of the underlying substrate abnormalities.

Background: Recognition of the causes of early mortality after atrial fibrillation (AF) catheter ablation is essential for the improvement of patient safety. This study sought to determine the causes of early mortality (≤90 days) after AF ablation. Methods: We performed a retrospective analysis of AF ablation from January 1, 2013, to December 1, 2021 at the Mayo Clinic (Rochester, Phoenix, and Jacksonville). Causes of death were identified through a comprehensive chart review of the electronic health record from within the Mayo Clinic system and outside records when available. Results: A total of 6723 patients were included in the study. The 90-day all-cause mortality rate was 0.22% (n=15). Among all 90-day deaths, majority of the deaths (73.3%) did not have a direct relationship with the procedure. Sudden death was the most common cause of early death (20%), followed by peri-procedural stroke (13%), respiratory failure (13%), atrioesophageal fistula (13%), infection (7%), heart failure (7%), and traumatic brain injury (7%). The 90-day mortality rate directly due to AF ablation procedural complications was 0.06% (n=4). Conclusions: AF ablation procedure has a 90-day mortality of 0.22%, and the most common cause of early mortality was sudden death. The majority (73.3%) of early mortality was not directly associated with a procedural complication, and the mortality rate due to complications associated with the AF ablation procedure was low at 0.06%. Further studies are required to investigate causes and risk factors associated with sudden death in this patient population.

AbstractBackgroundThe incidence and impact of noise in a subcutaneous implantable cardioverter defibrillator (S‐ICD) after left ventricular assist device (LVAD) implantation is not well established.MethodsWe performed a retrospective study of patients implanted with LVAD and with a pre‐existing S‐ICD between January 2005 and December 2020 at the three Mayo Clinic centers (Minnesota, Arizona, and Florida).ResultsOf the 908 LVAD patients, a pre‐existing S‐ICD was present in 9 patients (mean age 49.1 ± 13.7 years, 66.7% males), 100% with Boston Scientific third‐generation EMBLEM MRI S‐ICD, 11% with HeartMate II (HM II), 44% with HeartMate 3 (HM 3), and 44% with HeartWare (HW) LVAD. The incidence of noise from LVAD‐related electromagnetic interference (EMI) was 33% and was only seen with HM 3 LVAD. Multiple measures attempted to resolve noise, including using alternative S‐ICD sensing vector, adjusting S‐ICD time zone, and increasing LVAD pump speed, were unsuccessful, necessitating S‐ICD device therapies to be turned off permanently.ConclusionsThe incidence of LVAD‐related S‐ICD noise is high in patients with concomitant LVAD and S‐ICD with significant impact on device function. As conservative management failed to resolve the EMI, the S‐ICDs had to be programmed off to avoid inappropriate shocks. This study highlights the importance of awareness of LVAD‐SICD device interference and the need to improve S‐ICD detection algorithms to eliminate noise.

Abstract Introduction Placing a magnet over a Permanent Pacemaker (PPM) or Implanted Cardioverter-Defibrillator (ICD) may cause the device to pace asynchronously or inhibit tachyarrhythmia detection, respectively, potentially preventing delivery of electrical shocks. Manufacturers for masks used with positive airway pressure devices have started using magnets in place of more traditional headgear clips to connect the headgear to mask. Mask manufactures do not list presence of a PPM/ICD as a contraindication to use of a mask with magnet but do recommend keeping the mask some distance away from PPM/ICD. A published case series describes two patients with magnet response events captured during PPM/ICD interrogation that correlated with nightly use of CPAP. The authors were able to replicate the response by placing the mask with magnet directly over the patient’s pulse generate site. Although we advise all patients with implanted device to avoid use of masks with magnets, select patients refuse to stop using mask with magnets regardless of our policy. We, therefore, started offering these patients referral for PPM/ICD interrogation to evaluate for an interaction between mask with magnet and PPM/ICD as next best alternative. Methods We retrospectively reviewed all patients (n=10) referred for routine PPM/ICD interrogation to test whether the mask with magnet interacted with PPM/ICD when mask on face as during normal use (i.e., simulated normal use) or magnetic area of mask placed directly over the PPM/ICD (i.e., direct contact). Results Although no interaction was detected in any patient (n=10) with simulated normal use (0 %), one interaction was documented with direct contact (10 %). Conclusion Although simulated normal use of masks with magnets did not demonstrate any interactions, it is concerning that one patient (10 % of patients) demonstrated an interaction with direct contact of magnetic area of mask over the PPM/ICD. It is not uncommon for patients to remove a mask during the night while sleeping. This preliminary data along with the published case series calls for further research and increased awareness of this potential interaction for both sleep and cardiac health care providers. Support (If Any) None

Introduction: Atrial flutter (AFL) with figure-of-eight reentry (FOER) is effectively terminated by catheter ablation (CA) of the shared isthmus. Case: A 50-year-old man with prior mitral valve (MV) repair presented to our hospital with palpitations for 9 months refractory to metoprolol. ECG showed coarse atrial fibrillation at 61 bpm. Echocardiography showed left ventricular LVEF of 45%. Electrophysiology study revealed AFL (cycle length, TCL 290 msec) with a concentric activation pattern on the coronary sinus (CS) catheter, and a chevron pattern on the Halo catheter placed against the lateral tricuspid annulus (TA). Entrainment map revealed a near equal post-pacing interval and TCL in proximal CS, low lateral right atrium (RA), and CTI. Incomplete line of block was noted in the anterior wall of RA near the superior vena cava (SVC), likely from prior atriotomy scar. Double loop reentry (DLR) was demonstrated with one wavefront (WV) traveling counterclockwise around the TA using the CTI, and the other WV traveling posteriorly around the SVC (Figure). After CTI ablation, TCL changed from 290 msec to 330 msec suggesting blocked CTI. Now, the WV was a single loop around the SVC, confirmed by repeat activation mapping. Linear ablation from anterior TA to the anterior aspect of the SVC terminated the AFL. Differential pacing from either side of the anterior line and the CTI demonstrated a conduction time of > 200 msec and 150 msec in either direction, respectively. Decremental atrial pacing was unable to induce any arrhythmias. Discussion: FOER in this case is suggested by fusion of WVs in the lateral RA. The 2 circuits each had their own conduction gap, in the CTI and anterior RA wall near the SVC, respectively. DLR was proven by entrainment as well as activation mapping. The faster CTI-dependent AFL was entraining the upper loop reentry circuit. Conclusion: Atypical right AFL with DLR mimicking FOER was successfully terminated by CA of CTI and anterior line of ablation from TA to SVC.

Purpose of review Atrial flutter (AFL) is the second most prevalent arrhythmia after atrial fibrillation (AF). It is a macro-reentrant tachycardia that is either cavotricuspid isthmus dependent (typical) or independent (atypical). This review aims at highlighting mechanism, diagnosis and treatment of atypical AFL and the recent developments in electroanatomic mapping. Recent findings Incidence of left AFL is at an exponential rise presently with increase in AF ablation rates. The mechanism of left AFL is most often peri-mitral, roof-dependent or within pulmonary veins in preablated, in contrast to posterior or anterior wall low voltage areas in ablation naïve patients. Linear lesions, compared to pulmonary vein isolation alone, have higher incidence of atypical right or left AFL. Catheter ablation for atypical AFL is associated with lower rates of thromboembolic events, transfusions, and length of stay compared to typical AFL. Summary Advances in mapping have allowed rapid simultaneous acquisition of automatically annotated points in the atria and identification of details of macro-reentrant circuits, including zones of conduction block, scar, and slow conduction.

AbstractBackgroundMany advanced heart failure patients have both a left ventricular assist device (LVAD) and an implantable cardioverter‐defibrillator (ICD). This study examines incidence, clinical impact, and management of LVAD‐related EMI.MethodsWe performed a three‐center retrospective analysis of transvenous ICD implanted patients with LVAD implanted between January 1, 2005 and December 31, 2020. The primary outcome was EMI after LVAD implantation, categorized as LVAD‐related noise or telemetry interference.ResultsThe rate of LVAD‐related EMI among the 737 patients (mean age 58.6 ± 12.8 years) studied was 5.0%. Telemetry interference (1.5%) compromised ICD interrogation in all patients. This was resolved successfully with use of a metal shield, encased wand, radiofrequency tower, different ICD programmer or by increasing distance between ICD programmer and LVAD (n = 6). ICD replacement was required to reestablish successful communication in three patients. LVAD‐related noise (3.5%) led to oversensing (n = 4), inappropriate mode switches (n = 4), noise reversion (n = 3), inhibition of pacing (n = 2), inappropriate detection as atrial fibrillation (AF) (n = 2) and inappropriate detection as ventricular tachycardia (VT) and/or ventricular fibrillation (VF) (n = 2). This noise interference persisted (n = 3), resolved spontaneously (n = 16), resolved with programming change (n = 6) or required lead revision (n = 1).ConclusionsEMI from LVAD impacts ICD function, although, the incidence rate is low. Physicians implanting both, LVAD in patients with ICD (more common) or ICD in patients with LVAD, should be aware of possible interferences. Telemetry failure not resolved by metal shielding was overcome by ICD generator replacement to a different manufacturer. In most cases, LVAD‐related noise resolves spontaneously.

Introduction: Drug challenge testing is performed to unmask Type-1 Brugada pattern. The safety and prevalence of its complications during the test are unclear. We aimed to assess the relation of complications in patients with positive and negative results by a systematic review and meta-analysis. Hypothesis: The prevalence of arrhythmic complications is higher in patients with positive drug challenge testing. Methods: We comprehensively searched the databases of MEDLINE and EMBASE from inception to June 2020. Included studies were cohort studies that reported ventricular arrhythmia that required interventions (VAI) (sustained ventricular tachycardia [VT], polymorphic VT, ventricular fibrillation, appropriate implantable cardioverter defibrillator [ICD] shock, or sudden cardiac arrest) and ventricular arrhythmias that did not required interventions (VANI) (premature ventricular complexes and non-sustained VT) during drug challenge testing. Data were combined using the random-effects model. Results: Thirteen studies involving 2,688 patients (62.7% positive) were included. The overall prevalence of VAI and VANI were 3.7% (95% confidence interval [CI]: 1.8-5.7) and 0.5% (95% CI: 0.1-0.9), respectively. VAI were more common in positive when compared to negative test result patients (1.5% [95% CI: 0.6-2.4] and 0%, respectively) but the prevalence of VANI were similar (2.7% [95% CI: 0.8-4.6] and 2.6% [95% CI: 0.8-4.6], respectively). VAI in positive result patients were more common with flecainide followed by pilsicainide and ajmaline (2.4% [95% CI: -4.3 to 9.2], 2.2% [95% CI: 0.5-4.0], and 1.5% [95% CI: 0.6 to 2.4], respectively). Most of patients with VAI during drug challenge testing underwent ICD implantation (94%). VAI during drug challenge testing in positive result patients carries an increased risk of VAI during 8.6 ± 4.9 years follow-up (odds ratio 3.73, 95% CI: 1.77-7.86, p=0.001). Conclusions: VAI were more common in patients with positive drug challenge testing, more often occurring with positive flecainide challenge, and carries an increased risk of VAI over long-term follow-up in patients with positive drug challenge testing.