Introduction: Leadless pacemakers (LPs) have been suggested to have a lower incidence of pacemaker induced cardiomyopathy (PICM) compared with transvenous systems. LPs have also been suggested to cause less frequent and less severe tricuspid valve regurgitation (TVR) when compared to traditional transvenous pacemakers (TVPs). Given limited research in this field, our study aims to better understand the incidence of PICM and TVR in patients with a LP and the factors that affect these incidences. Methods: The study comprised of patients within the National Capital Region Military Health System who received a Medtronic Micra LP from 2017 to 2021 and had a pacing percentage of >20%. Pre-procedural and follow-up echocardiograms were retrospectively assessed to determine the change in left ventricular ejection fraction (LVEF) and the degree of TVR. Given the known impact of the PICM definition on the reported incidence, we assessed rates of PICM using two distinct definitions, 1.) ≥10% decrease in LVEF or 2.) ≥10% decrease in LVEF to an LVEF of <50%. We also assessed the pacemaker implantation location and the change in QRS duration after implantation and pacing. Results: The study included a total of 48 patients. The average age of patients in the study was 77, with 67% males. The most common reason for LP implantation was complete AV block (38%). Pacemaker locations included high (13%), mid (31%), and apical septum (56%). The mean time interval between pacemaker implantation and follow up echocardiogram was 697 days (SD 460). A total of 5 patients (12.5%) met definition 1 for PICM and 3 patients (6.25%) met definition 2. TVR was graded to be more severe than baseline in 37% of patients, unchanged in 32%, and improved in 30%. The average change in QRS duration after pacing was an increase of 46ms with an average QRS duration of 159ms at follow-up. Conclusion: Compared to commonly reported incidences of PICM, LPs appear to have a significantly lower rate of PICM, regardless of the PICM definition used, increase in QRS duration, or implantation location. In this study, LPs did not statistically significantly impact TVR severity.

Introduction. Atrial Fibrillation and Atrial Flutter (AF/AFL), the most common atrial arrhythmias, have never been examined in combat casualties. In this study, we investigated the impact of traumatic injury on AF/AFL among service members with deployment history. Methods. Sampled from the Department of Defense (DoD) Trauma Registry (n=10,000), each injured patient in this retrospective cohort study was matched with a non-injured service member drawn from the Veterans Affairs/DoD Identity Repository. The primary outcome was AF/AFL diagnosis identified using ICD-9-CM and ICD-10-CM codes. Competing risk regressions based on Fine and Gray subdistribution hazards model with were utilized to assess the association between injury and AF/AFL. Results. There were 130 reported AF/AFL cases, 90 of whom were injured and 40 were non-injured. The estimated cumulative incidence rates of AF/AFL for injured was higher compared to non-injured patients (HR = 2.04; 95% CI = 1.44, 2.87). After adjustment demographics and tobacco use, the association did not appreciably decrease (HR = 1.90; 95% CI = 1.23, 2.93). Additional adjustment for obesity, hypertension, diabetes, and vascular disorders, the association between injury and AF/AFL was no longer statistically significant (HR: 1.51; 95% CI = 0.99, 2.52). Conclusion. Higher AF/AFL incidence rate was observed among deployed service members with combat injury compared to servicemembers without injury. The association did not remain significant after adjustment for cardiovascular-related covariates. These findings highlight the need for combat casualties surveillance to further understand the AF/AFL risk within the military population and to elucidate the potential underlying pathophysiologic mechanisms.

A patient presented with torsade de pointes after inhaling tetrafluoroethane, a volatile gas propellant used to clean keyboards. She had a prior hospitalization for cardiac arrest without rhythm documentation after inhaling a similar product. Urine toxicology revealed methamphetamine. We are unaware of previous descriptions of torsade de pointes associated with volatile hydrocarbon inhalation or “huffing.” Although sudden death is associated with “huffing,” an arrhythmic mechanism has not been elucidated. Tetrafluoroethane, however, is chemically similar to chlorophorm (trichloromethane), which blocks the delayed rectifier potassium ion current (Ikr). Thus, we postulate that delayed repolarization with methamphetamine triggering may account for this arrhythmia.