Background: The subcutaneous (S) implantable cardioverter-defibrillator (ICD) is safe and effective for sudden cardiac death prevention. However, patients in previous S-ICD studies had fewer comorbidities, had less left ventricular dysfunction, and received more inappropriate shocks (IAS) than in typical transvenous ICD trials. The UNTOUCHED trial (Understanding Outcomes With the S-ICD in Primary Prevention Patients With Low Ejection Fraction) was designed to evaluate the IAS rate in a more typical, contemporary ICD patient population implanted with the S-ICD using standardized programming and enhanced discrimination algorithms. Methods: Primary prevention patients with left ventricular ejection fraction ≤35% and no pacing indications were included. Generation 2 or 3 S-ICD devices were implanted and programmed with rate-based therapy delivery for rates ≥250 beats per minute and morphology discrimination for rates ≥200 and <250 beats per minute. Patients were followed for 18 months. The primary end point was the IAS-free rate compared with a 91.6% performance goal, derived from the results for the ICD-only patients in the MADIT-RIT study (Multicenter Automatic Defibrillator Implantation Trial-Reduce Inappropriate Therapy). Kaplan-Meier analyses were performed to evaluate event-free rates for IAS, all-cause shock, and complications. Multivariable proportional hazard analysis was performed to determine predictors of end points. Results: S-ICD implant was attempted in 1116 patients, and 1111 patients were included in postimplant follow-up analysis. The cohort had a mean age of 55.8±12.4 years, 25.6% were women, 23.4% were Black, 53.5% had ischemic heart disease, 87.7% had symptomatic heart failure, and the mean left ventricular ejection fraction was 26.4±5.8%. Eighteen-month freedom from IAS was 95.9% (lower confidence limit, 94.8%). Predictors of reduced incidence of IAS were implanting the most recent generation of device, using the 3-incision technique, no history of atrial fibrillation, and ischemic cause. The 18-month all-cause shock-free rate was 90.6% (lower confidence limit, 89.0%), meeting the prespecified performance goal of 85.8%. Conversion success rate for appropriate, discrete episodes was 98.4%. Complication-free rate at 18 months was 92.7%. Conclusions: This study demonstrates high efficacy and safety with contemporary S-ICD devices and programming despite the relatively high incidence of comorbidities in comparison with earlier S-ICD trials. The inappropriate shock rate (3.1% at 1 year) is the lowest reported for the S-ICD and lower than many transvenous ICD studies using contemporary programming to reduce IAS. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT02433379.

Deep brain stimulators (DBS), used in the treatment of Parkinson disease (PD), may interfere with the function of implantable cardioverter-defibrillators (ICD) used for prevention of sudden cardiac death. DBS have been implanted in 150,000 patients worldwide. Few reports of implantation of an ICD in patients with preexisting DBS have reported safe outcomes when the 2 devices are placed away from each other (ie, in the contralateral shoulders or the abdomen and shoulder).1, 2 One report of a subcutaneous ICD (S-ICD) implantation in a patient with a right pectoral DBS demonstrated feasibility without evidence of oversensing or inappropriate shocks.

Aims: Clinical trials have demonstrated the safety and efficacy of the Micra leadless VVI pacemaker; however, longer-Term outcomes in a large, real-world population with a contemporaneous comparison to transvenous VVI pacemakers have not been examined. We compared reinterventions, chronic complications, and all-cause mortality at 2 years between leadless VVI and transvenous VVI implanted patients. Methods and results: The Micra Coverage with Evidence Development study is a continuously enrolling, observational, cohort study of leadless VVI pacemakers in the US Medicare fee-for-service population. Patients implanted with a leadless VVI pacemaker between March 9, 2017, and December 31, 2018, were identified using Medicare claims data linked to manufacturer device registration data (n = 6219). All transvenous VVI patients from facilities with leadless VVI implants during the study period were obtained directly from Medicare claims (n = 10 212). Cox models were used to compare 2-year outcomes between groups. Compared to transvenous VVI, patients with leadless VVI had more end-stage renal disease (12.0% vs. 2.3%) and a higher Charlson comorbidity index (5.1 vs. 4.6). Leadless VVI patients had significantly fewer reinterventions [adjusted hazard ratio (HR) 0.62, 95% confidence interval (CI) 0.45-0.85, P = 0.003] and chronic complications (adjusted HR 0.69, 95% CI 0.60-0.81, P < 0.0001) compared with transvenous VVI patients. Adjusted all-cause mortality at 2 years was not different between the two groups (adjusted HR 0.97, 95% CI 0.91-1.04, P = 0.37). Conclusion: In a real-world study of US Medicare patients, the Micra leadless VVI pacemaker was associated with a 38% lower adjusted rate of reinterventions and a 31% lower adjusted rate of chronic complications compared with transvenous VVI pacing. There was no difference in adjusted all-cause mortality at 2 years.

Background: Infection is a well-recognized complication of cardiovascular implantable electronic device (CIED) implantation, including the more recently available subcutaneous implantable cardioverter-defibrillator (S-ICD). Although the AHA/ACC/HRS guidelines include recommendations for S-ICD use, currently there are no clinical trial data that address the diagnosis and management of S-ICD infections. Therefore, an expert panel was convened to develop consensus on these topics. Methods: A process mapping methodology was used to achieve a primary goal – the development of consensus on the diagnosis and management of S-ICD infections. Two face-to-face meetings of panel experts were conducted to recommend useful information to clinicians in individual patient management of S-ICD infections. Results: Panel consensus of a stepwise approach in the diagnosis and management was developed to provide guidance in individual patient management. Conclusion: Achieving expert panel consensus by process mapping methodology in S-ICD infection diagnosis and management was attainable, and the results should be helpful in individual patient management.

Background: Head-to-head comparative data for the postoperative care of patients undergoing left atrial ablation procedures are lacking. Objective: We sought to investigate complication and readmission rates between patients undergoing same-day (SD) or next-day (ND) discharges for ablative procedures in the left atrium, primarily atrial fibrillation (AF). Methods: Two electrophysiology centers simultaneously perform left atrial ablations with differing discharge strategies. We identified all patients who underwent left atrial ablation from August 2017 to August 2019 (n = 409) undergoing either SD (n = 210) or ND (n = 199) discharge protocols. We analyzed any clinical events that resulted in procedural abortion, extended hospitalization, or readmission within 72 hours. Results: The primary endpoint of complication and readmission rate was similar between SD and ND discharge (14.3% vs 12.6%, p = 0.665). Rates of complications categorized as major (2.4% vs 3.0%, p = 0. 776) and minor (11.9% vs 9.5%, p = 0.524) were also similar. Multivariable regression modeling revealed no significant correlation between discharge strategy and complication/readmission occurrence (OR 1.565 [0.754 – 3.248], p = 0.23), but a positive association of hypertension and procedure duration (OR 3.428 [1.436 – 8.184], p = 0.006) and (OR 1.01 [1 – 1.019], p = 0.046) respectively. Conclusions: Left atrial ablation complication and readmission rates were similar between SD and ND discharge practices. Hypertension and procedural duration were associated with increased complication rates irrespective of discharge strategy. These data, which represent the first side-by-side comparison of discharge strategy, suggests same-day discharge is safe and feasible for left atrial ablation procedures.

Background: Cancer treatment induced arrhythmia (CTIA) is a well-recognized form of cardiotoxicity associated with chemotherapy. Immune checkpoint inhibitors (ICI) have been associated with important forms of cardiotoxicity, including myocarditis. However, the incidence of CTIA associated with ICI has not been well characterized. Methods: We reviewed all patients treated with ICIs at our institution from Jan. 2010 to Oct. 2015. CTIA was defined as a new diagnosis of clinically relevant arrhythmia within 6 months after ICI initiation. Results: During the study period, 268 patients were treated with immune checkpoint inhibitors, of whom 190 received monotherapy with ipilimumab (n=114), nivolumab (n=52) or pembrolizumab (n=24) and 78 received combination therapy: ipilimumab & nivolumab (n=37), ipilimumab & pembrolizumab (n=39) and nivolumab & pembrolizumab (n=2). Four patients (1.5%) developed CTIA. Of these, 3 patients developed a new diagnosis of atrial fibrillation (AF), one of whom required cardioversion. In 2 cases of new-onset AF, significant provoking factors were present in addition to ICI therapy including thyrotoxicosis in one and metabolic disarray in another. Six patients (2.2%) with a pre-existing diagnosis of paroxysmal AF experienced episodes within 6 months of initiating ICI therapy. None of the arrhythmic events were associated with known or suspected myocarditis. Conclusion: The incidence of arrhythmic complications associated with immune checkpoint inhibitors appears to be very low (~1.5%). Patients with a pre-existing diagnosis of AF may be at-risk of recurrence during ICI treatment and should be monitored accordingly. These data suggest that from an arrhythmia perspective, ICIs appear to be very safe and well-tolerated.

Background: The feasibility and outcomes of concomitant atrioventricular node ablation (AVNA) and leadless pacemaker implant are not well studied. We report outcomes in patients undergoing Micra implant with concomitant AVNA. Methods: Patients undergoing AVNA at the time of Micra implant from the Micra Transcatheter Pacing (IDE) Study, Continued Access (CA) study, and Post-Approval Registry (PAR) were included in the analysis and compared to Micra patients without AVNA. Baseline characteristics, acute and follow-up outcomes, and electrical performance were compared between patients with and without AVNA during the follow-up period. Results: A total of 192 patients (mean age 77.4 ± 8.9 years, 72% female) underwent AVNA at the time of Micra implant and were followed for 20.4 ± 15.6 months. AVNA patients were older, more frequently female, and tended to have more co-morbid conditions compared with non-AVNA patients (N = 2616). Implant was successful in 191 of 192 patients (99.5%). The mean pacing threshold at implant was 0.58 ± 0.35 V and remained stable during follow-up. Major complications within 30 days occurred more frequently in AVNA patients than non-AVNA patients (7.3% vs. 2.0%, p <.001). The risk of major complications through 36-months was higher in AVNA patients (hazard ratio: 3.81, 95% confidence interval: 2.33–6.23, p <.001). Intermittent loss of capture occurred in three AVNA patients (1.6%), all were within 30 days of implant and required system revision. There were no device macrodislodgements or unexpected device malfunctions. Conclusion: Concomitant AVN ablation and leadless pacemaker implant is feasible. Pacing thresholds are stable over time. However, patient comorbidities and the risk of major complications are higher in patients undergoing AVNA.

Micra leadless pacemaker has progressed from a single chamber pacemaker that can deliver VVIR pacing to a pacing device that can provide atrio‐ventricular (AV) synchrony via a unique pacing algorithm that relies on identifying mechanical atrial contraction. This novel algorithm has its own limitations and intricacies. In this paper, we review this algorithm, suggest steps for troubleshooting and programming these devices and provide clinical examples of Micra AV cases that required changes in programming for adequate tracking of atrial activity.

Background: QRSduration (QRSd) is associated with higher mortality and morbidity in patients with left ventricular (LV) dysfunction. The association between QRSd and atrial fibrillation (AF) has not been studied in this patient population. Objectives: To investigate the association between QRSd and AF in patients with LV dysfunction. Methods: Data were obtained from the National Registry to Advance Heart Health (ADVANCENT) registry, a prospective multicenter registry of patients with left ventricular ejection fraction (LVEF) ≤40%. A total of 25 268 patients from106 centers in the United States, were enrolled between June 2003 and November 2004. Demographic and clinical characteristics of patientswere collected from interviews and medical records. Results: Mean age was 66.3 ± 13 years, 71.5% were males, and 81.9% were white. A total of 14 452 (57.8%) patients had a QRSd <120 ms, 5304 (21.2%) had a QRSd between 120 and 150 ms, and 5269 (21%) had a QRSd >150 ms. Atrial fibrillation occurred in 20.9%, 27.5%, and 35.5% of patients in the QRS groups, respectively (P < 0.0001). After adjusting for potential AF risk factors (age, gender, race, body mass index, hypertension, diabetes, renal failure, cancer, lung disease, New York Heart Association [NYHA] class, ejection fraction, etiology of cardiomyopathy) and the use of angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, β-blockers, and lipid lowering drugs, QRS duration remained independently associated with AF (odds ratio: 1.20, 95% confidence interval: 1.14-1.25). Conclusion: In this large cohort of patients, QRSd was strongly associated with AF and thereforemay predict the occurrence of this arrhythmia in patients with LV dysfunction. This association persisted after adjusting for disease severity, comorbid conditions, and the use of medications known to be protective against AF.

As the global burden of cardiovascular disease continues to increase worldwide, nurturing the development of early-career cardiologists interested in global health is essential to create a cadre of providers with the skill set to prevent and treat cardiovascular diseases in international settings. As such, interest in global health has increased among cardiology trainees and early-career cardiologists over the past decade. International clinical and research experiences abroad present an additional opportunity for growth and development beyond traditional cardiovascular training. We describe the American College of Cardiology International Cardiovascular Exchange Database, a new resource for cardiologists interested in pursuing short-term clinical exchange opportunities abroad, and report some of the benefits and challenges of global health cardiovascular training in both resource-limited and resource-abundant settings.