Utilizing median and maximum QTc values improves prediction of breakthrough cardiac events in pediatric long QT syndrome.

INTRODUCTION: Although prior studies indicate that a QTc > 500 ms on a single baseline 12-lead electrocardiogram (ECG) is associated with significantly increased risk of arrhythmic events in long QT syndrome (LQTS), less is known about the risk of persistent QT prolongation. We sought to determine QTc persistence and its prognostic effect on breakthrough cardiac events (BCEs) among pediatric patients treated for LQTS. METHODS: We performed a retrospective analysis of 433 patients with LQTS evaluated, risk-stratified, and undergoing active guideline-based LQTS treatment between 1999 and 2019. BCEs were defined as arrhythmogenic syncope/seizure, sudden cardiac arrest (SCA), appropriate VF-terminating ICD shock, and sudden cardiac death (SCD). RESULTS: During the median follow-up of 5.5 years (interquartile range [IQR] = 3-9), 32 (7%) patients experienced a total of 129 BCEs. A maximum QTc threshold of 520 ms and median QTc threshold of 490 ms were determined to be strong predictors for BCEs. A landmark analysis controlling for age, sex, genotype, and symptomatic status demonstrated models utilizing both the median QTc and maximum QTc demonstrated the highest discriminatory value (c-statistic = 0.93-0.95). Patients in the high-risk group (median QTc > 490 ms and maximum QTc > 520 ms) had a significantly lower BCE free survival (70%-81%) when compared to patients in both medium-risk (93%-97%) and low-risk (98%-99%) groups. CONCLUSIONS: The risk of BCE among patients treated for LQTS increases not only based upon their maximum QTc, but also their median QTc (persistence of QTc prolongation). Patients with a maximum QTc > 520 ms and median QTc > 490 ms over serial 12-lead ECGs are at the highest risk of BCE while on guideline-directed medical therapy.

Arrhythmic manifestations and outcomes of definite and probable cardiac sarcoidosis.

BACKGROUND: The 2014 Heart Rhythm Society consensus statement defines histological (definite) and clinical (probable) diagnostic categories of cardiac sarcoidosis (CS), but few studies have compared their arrhythmic phenotypes and outcomes. OBJECTIVE: The purpose of this study was to evaluate the electrophysiological/arrhythmic phenotype and outcomes of patients with definite and probable CS. METHODS: We analyzed the arrhythmic/electrophysiological phenotype in a single-center North American cohort of 388 patients (median age 56 years; 39% female, n = 151) diagnosed with definite (n = 58) or probable (n = 330) CS (2000-2022). The primary composite outcome was survival to first ventricular tachycardia/fibrillation (VT/VF) event or sudden cardiac death. Key secondary outcomes were also assessed. RESULTS: At index evaluation, in situ cardiac implantable electronic devices and antiarrhythmic drug use were more common in definite CS. At a median follow-up of 3.1 years, the primary outcome occurred in 22 patients with definite CS (38%) and 127 patients with probable CS (38%) (log-rank, P = .55). In multivariable analysis, only a higher ratio of the 18F-fluorodeoxyglucose maximum standardized uptake value of the myocardium to the maximum standardized uptake value of the blood pool (hazard ratio 1.09; 95% confidence interval 1.03-1.15; P = .003, per 1 unit increase) was associated with the primary outcome. During follow-up, patients with definite CS had a higher burden of device-treated VT/VF events (mean 2.86 events per patient-year vs 1.56 events per patient-year) and a higher rate of progression to heart transplant/left ventricular assist device implantation but no difference in all-cause mortality compared with patients with probable CS. CONCLUSION: Patients with definite and probable CS had similarly high risks of first sustained VT/VF/sudden cardiac death and all-cause mortality, though patients with definite CS had a higher overall arrhythmia burden. Both CS diagnostic groups as defined by the 2014 Heart Rhythm Society criteria require an aggressive approach to prevent arrhythmic complications.

Complexity analysis of electrical activity during endocardial and epicardial biventricular mapping of ventricular fibrillation.

BACKGROUND: Ventricular fibrillation (VF) is a lethal cardiac arrhythmia that is a significant cause of sudden cardiac death. Comprehensive studies of spatiotemporal characteristics of VF in situ are difficult to perform with current mapping systems and catheter technology. OBJECTIVE: The goal of this study was to develop a computational approach to characterize VF using a commercially available technology in a large animal model. Prior data suggests that characterization of spatiotemporal organization of electrical activity during VF can be used to provide better mechanistic understanding and potential ablation targets to modify VF and its substrate. We therefore evaluated intracardiac electrograms during biventricular mapping of the endocardium (ENDO) and epicardium (EPI) in acute canine studies. METHODS: To develop thresholds for organized and disorganized activity, a linear discriminant analysis (LDA)-based approach was performed to the known organized and disorganized activities recorded in ex vivo Langendorff-perfused rat and rabbit hearts using optical mapping experiments. Several frequency- and time-domain approaches were used as individual and paired features to identify the optimal thresholds for the LDA approach. Subsequently, VF was sequentially mapped in 4 canine hearts, using the CARTO mapping system with a multipolar mapping catheter in the ENDO left and right ventricles and EPI to capture the progression of VF at 3 discrete post-induction time intervals: VF period 1 (just after induction of VF to 15 min), VF period 2 (15 to 30 min), and VF period 3 (30 to 45 min). The developed LDA model, cycle lengths (CL), and regularity indices (RI) were applied to all recorded intracardiac electrograms to quantify the spatiotemporal organization of VF in canine hearts. RESULTS: We demonstrated the presence of organized activity in the EPI as VF progresses, in contrary to the ENDO, where the activity stays disorganized. The shortest CL always occurred in the ENDO, especially the RV, indicating a faster VF activity. The highest RI was found in the EPI in all hearts for all VF stages, indicating spatiotemporal consistency of RR intervals. CONCLUSION: We identified electrical organization and spatiotemporal differences throughout VF in canine hearts from induction to asystole. Notably, the RV ENDO is characterized by a high level of disorganization and faster VF frequency. In contrast, EPI has a high spatiotemporal organization of VF and consistently long RR intervals.

Novel insights into the substrate involved in maintenance of ventricular fibrillation: results from continuous multipolar mapping in a canine model.

BACKGROUND: While the triggers for ventricular fibrillation (VF) are well-known, the substrate required for its maintenance remains elusive. We have previously demonstrated dynamic spatiotemporal changes across VF from electrical induction of VF to asystole. Those data suggested that VF drivers seemed to reside in the distal RV and LV. However, signals from these areas were not recorded continuously. The aim of this study was to map these regions of significance with stationary basket electrodes from induction to asystole to provide further insights into the critical substrate for VF rhythm sustenance in canines. METHODS: In six healthy canines, three multipolar basket catheters were positioned in the distal right ventricle (RV), RV outflow tract, and distal left ventricle (LV), and remained in place throughout the study. VF was induced via direct current application from an electrophysiologic catheter. Surface and intracardiac electrograms were recorded simultaneously and continuously from baseline, throughout VF, and until asystole, in order to get a complete electrophysiologic analysis of VF. Focused data analysis was also performed via two defined stages of VF: early VF (immediately after induction of VF to 10 min) and late VF (after 10 min up to VF termination and asystole). RESULTS: VF was continuously mapped for a mean duration of 54 ± 9 min (range 42-70 min). Immediately after initiation of VF in the early phase, the distal LV region appeared to drive the maintenance of VF. Towards the terminal stage of VF, the distal RV region appeared to be responsible for VF persistence. In all canines, we noted local termination of VF in the LV, while VF on surface ECG continued; conversely, subsequent spontaneous termination of VF in the RV was associated with termination of VF on surface ECG into a ventricular escape rhythm. Continuous mapping of VF showed trends towards an increase in peak-to-peak ventricular electrogram cycle length (p = 0.06) and a decrease in the ventricular electrogram amplitude (p = 0.06) after 40 min. Once we could no longer discern surface QRS activity, we demonstrated local ventricular myocardial capture in both the RV and LV but could not reinitiate sustained VF despite aggressive ventricular burst pacing. CONCLUSIONS: This study describes the evolution of VF from electrical initiation to spontaneous VF termination without hemodynamic support in healthy canines. These data are hypothesis-generating and suggest that critical substrate for VF maintenance may reside in both the distal RV and LV depending on stage of VF. Further studies are needed to replicate these findings with hemodynamic support and to translate such findings into clinical practice. Ventricular fibrillation maintenance may be dependent on critical structures in the distal RV. ECG: electrocardiogram; LV: left ventricle; RV: right ventricle; RVOT: right ventricular outflow tract; VF: ventricular fibrillation.

Ventricular nanosecond pulsed electric field delivery using active fixation leads: a proof-of-concept preclinical study.

BACKGROUND: Mid-myocardial ventricular arrhythmias are challenging to treat. Cardiac electroporation via pulsed electric fields (PEFs) offers significant promise. We therefore tested PEF delivery using screw-in pacemaker leads as proof-of-concept. METHODS: In 5 canine models, we applied nanosecond PEF (pulse width 300 ns) across the right ventricular (RV) septum using a single lead bipolar configuration (n = 2) and between two leads (n = 3). We recorded electrograms (EGMs) prior to, immediately post, and 5 min after PEF. Cardiac magnetic resonance imaging (cMRI) and histopathology were performed at 2 weeks and 1 month. RESULTS: Nanosecond PEF induced minimal extracardiac stimulation and frequent ventricular ectopy that terminated post-treatment; no canines died with PEF delivery. With 1 lead, energy delivery ranged from 0.64 to 7.28 J. Transient ST elevations were seen post-PEF. No myocardial delayed enhancement (MDE) was seen on cMRI. No lesions were noted on the RV septum at autopsy. With 2 leads, energy delivery ranged from 56.3 to 144.9 J. Persistent ST elevations and marked EGM amplitude decreases developed post-PEF. MDE was seen along the septum 2 weeks and 1 month post-PEF. There were discrete fibrotic lesions along the septum; pathology revealed dense connective tissue with < 5% residual cardiomyocytes. CONCLUSIONS: Ventricular electroporation is feasible and safe with an active fixation device. Reversible changes were seen with lower energy PEF delivery, whereas durable lesions were created at higher energies. Central illustration: pulsed electric field delivery into ventricular myocardium with active fixation leads.

Leak closure following left atrial appendage exclusion procedures: A multicenter registry.

BACKGROUND: Though infrequent, incomplete left atrial appendage closure (LAAC) may result from residual leaks. Percutaneous closure has been described though data is limited. METHODS: We compiled a registry from four centers of patients undergoing percutaneous closure of residual leaks following LAAC via surgical means or with the Watchman device. Leak severity was classified as none (no leak), mild (1-2 mm), moderate (3-4 mm), or severe (≥5 mm). Procedural and clinical success was defined as the elimination of leak or mild residual leak at the conclusion of the procedure or follow-up, respectively. RESULTS: Of 72 (age 72.2 ± 9.2 years; 67% male) patients, 53 had undergone prior LAAC using the Watchman device and 19 patients surgical LAAC. Mean CHADS2 -VA2 Sc score was 4.0 ± 1.8. The median leak size was 5 mm, range: 2-13). A total of 13 received Amplatzer Vascular Plug-II, 18 received Amplatzer Duct Occluder-II and 40 patients received coils. One underwent closure using a 21 mm-Watchman. Procedural success was 94%. Zero surgical and nine Watchman patients (13%) had a residual leak at procedural-end (five mild, three moderate, and one severe)-only one patient had no reduction in leak size. Overall leak size reduction was 94%. Two (3%) had intraoperative pericardial effusion. There were no device embolizations, device-related thrombi, or procedural deaths. Clinical success was maintained at 94%. Two had cerebrovascular accidents-at 2 days (transient ischemic attack) and 10 months postprocedure. Two had major bleeding outside the 30-day periprocedural window. CONCLUSION: Percutaneous closure of residual leaks following left atrial appendage closure is feasible and associated with good outcomes. The procedural risk appears to be satisfactory.

Regional and Temporal Variation of Ventricular and Conduction Tissue Activity During Ventricular Fibrillation in Canines.

[Figure: see text].

Sinus rhythm heart rate increase after atrial fibrillation ablation is associated with lower risk of arrhythmia recurrence.

BACKGROUND: Pulmonary vein isolation (PVI) with autonomic modulation may be more successful than PVI alone for atrial fibrillation (AF) ablation and may be signaled by changes in sinus rhythm heart rate (HR) post ablation. We sought to determine if a change in sinus rhythm HR predicted AF recurrence post PVI. METHODS: Patients who underwent AF ablation from 2000 to 2011 were included if sinus rhythm was noted on ECG within 90 days pre and 7 days post ablation. Basic ECG interval and HR changes were analyzed and outcomes determined. RESULTS: A total of 1152 patients were identified (74.3% male, mean age 57 ± 11 years). Mean AF duration was 5.2 ± 5.3 years. Paroxysmal AF was noted in 712 (61.8%) of the patients. Mean EF was 61% ± 6%. Sinus rhythm HR was 61 ± 11 pre-ablation and 76 ± 13 bpm post-ablation (27% ± 24% increase, p < .001). The ability of relative HR change post-ablation to predict AF recurrence was borderline (hazard ratio 0.65 [0.41-1.01], p = .067). With patients separated into quartiles based on the relative HR change, the upper quartile with the largest relative increase in HR had a significantly lower rate of AF recurrence compared to the lowest quartile following multi variable modeling (p = .038). There were significant changes in PR (171 ± 28 to 167 ± 30 ms) and QTc (424 ± 25 to 434 ± 29 ms) intervals (both p < .001) but these were not predictive of outcome. CONCLUSION: Relative changes in HR post AF ablation correlates with AF recurrence. Further prospective studies are needed to confirm this relationship.

Intentional nontherapy in long QT syndrome.

BACKGROUND: International guidelines advise universal beta-blocker therapy as either a class I (symptomatic or QTc ≥470 ms) or class II (asymptomatic and QTc <470 ms) recommendation for treatment of long QT syndrome (LQTS). OBJECTIVE: The purpose of this study was to evaluate the outcomes of a highly selected cohort of patients with LQTS managed with an observation-only (intentional nontreatment) strategy. METHODS: The cohort was derived from a comprehensive retrospective registry of patients with LQTS. Clinical phenotype and genotype data were collected via review of electronic health records. RESULTS: Among 661 patients with LQTS, 55 (8.3%) asymptomatic patients (53% female; 16 age <18 years) were managed with intentional nontherapy. Only preventative measures were advised. Mean age at diagnosis was 37.8 ± 21.2 years. Mean QTc was 448 ± 30 ms. None of the patients experienced an LQTS-triggered cardiac event over mean follow-up of 7.5 ± 4.3 years. Compared to the larger treated cohort, this intentionally untreated cohort was less symptomatic, was older at diagnosis, and had lower resting QTc values (P <.0001). CONCLUSION: After careful clinical evaluation, risk assessment, and institution of precautionary measures, an observation-only strategy may be considered in a highly selected group of LQTS patients with a clinical profile that includes asymptomatic status, older age at diagnosis, and QTc <470 ms, with excellent outcomes and better quality of life than LQTS patients treated with beta-blocker. LQTS patients with this low-risk profile should not receive a prophylactic implantable cardioverter-defibrillator.

Three-Dimensional Printed Biopatches With Conductive Ink Facilitate Cardiac Conduction When Applied to Disrupted Myocardium.

BACKGROUND: Reentrant ventricular arrhythmias are a major cause of sudden death in patients with structural heart disease. Current treatments focus on electrically homogenizing regions of scar contributing to ventricular arrhythmia with ablation or altering conductive properties using antiarrhythmic drugs. The high conductivity of carbon nanotubes may allow restoration of conduction in regions where impaired electrical conduction results in functional abnormalities. We propose a new concept for arrhythmia treatment using a stretchable, flexible biopatch with conductive properties to attempt to restore conduction across regions in which activation is disrupted. METHODS: Carbon nanotube patches composed of nanofibrillated cellulose/single-walled carbon nanotube ink 3-dimensionally printed in conductive patterns onto bacterial nanocellulose were developed and evaluated for conductivity, flexibility, and mechanical properties. The patches were applied on 6 canines to epicardium before and after surgical disruption. Electroanatomic mapping was performed on normal epicardium, then repeated over surgically disrupted epicardium, and then finally with the patch applied passively. RESULTS: We developed a 3-dimensional printable carbon nanotube ink complexed on bacterial nanocellulose that was (1) expressable through 3-dimensional printer nozzles, (2) electrically conductive, (3) flexible, and (4) stretchable. Six canines underwent thoracotomy, and, during epicardial ventricular pacing, mapping was performed. We demonstrated disruption of conduction after surgical incision in all 6 canines based on activation mapping. The patch resulted in restored conduction based on mapping and assessment of conduction direction and velocities in all canines. CONCLUSIONS: We have demonstrated 3-dimensional custom-printed electrically conductive carbon nanotube patches can be surgically manipulated to improve cardiac conduction when passively applied to surgically disrupted epicardial myocardium in canines.

Potentially modifiable factors of dofetilide-associated risk of torsades de pointes among hospitalized patients with atrial fibrillation.

PURPOSE: There is a significant variation in the clinical approach of initiation and dose adjustment of dofetilide in atrial fibrillation (AF). Excessive QT prolongation could predispose patients to torsades de pointes (TdP), which can be fatal. METHODS: We performed a retrospective case-control study at Mayo Clinic Rochester (January 1, 2003 to December 31, 2016). "TdP risk" cases were defined as patients on dofetilide therapy for AF with subsequent TdP or excessive QTc prolongation requiring dose reduction or discontinuation (N = 31). A control group was matched 1:1 with cases by age, gender, year of admission, and dofetilide dose (N = 31). RESULTS: Using multivariate regression analysis, independent predictors of TdP risk included baseline QTc exceeding recommendations (adjusted odd ratio [AOR] 4.57; P = 0.023); underlying AF with rapid ventricular rate (AOR 16.95; P = 0.004); and diuretic therapy for acute heart failure (AOR 8.42; P = 0.007). Poor inter-observer agreement was identified among QT interval measurement in patients with AF and rapid ventricular rate compared to those in rate controlled AF or sinus rhythm. TdP risk cases receiving diuretics for acute heart failure had a significant decline in creatinine clearance than controls, although serum electrolytes and replacement did not differ among the two groups. CONCLUSIONS: Excessive QTc prolongation and AF with rapid ventricular rate at time of dofetilide initiation (likely due to difficulty in measuring QT intervals), and diuretic therapy for acute heart failure were independent factors for dofetilide-related TdP risk. Based on these data, possible preventive strategies could be adapted for safety protocols among hospitalized patients.

Right Heart Failure in a Cardiac Allograft Following Remote Transvenous Lead Extraction.

A heart transplant recipient presented with right heart failure. He had a history of implantable cardioverter-defibrillator implantation and extraction before undergoing heart transplantation 4 years earlier. A large fistula was found between the left subclavian artery and vein. Following successful percutaneous fistula closure, symptoms and right ventricular function improved. (Level of Difficulty: Advanced.).

Intramural conduction system gradients and electrogram regularity during ventricular fibrillation.

INTRODUCTION: The His-Purkinje system has been shown to harbor triggers for ventricular fibrillation (VF) initiation. However, the substrate responsible for VF maintenance remains elusive. We hypothesized that standard, electrode-based, point-to-point mapping would yield meaningful insight into site-specific patterns and organization which may shed light on the critical substrate for maintenance of VF. METHODS: VF was induced under general anesthesia by direct current (DC) application to the right ventricle in 7 acute canines. A standard EPT Blazer mapping catheter (Boston Scientific, Natuck, MA) was used for mapping in conjunction with a Prucka recording system. We collected 30 consecutive electrograms at 24 distinct sites, confirmed by fluoroscopy and intracardiac echo. These sites included both endocardial and epicardial locations throughout the ventricles and conduction system. RESULTS: A total of 5040 individual data points were collected in 7 separate canine studies. During VF mapping, a transmural disparity was found between the epicardium (average cycle length [CL] of 1136 m s) and the endocardium (average CL of 123 m s) with a p value of <0.01. An additional, intramural gradient was found when comparing the proximal, insulated conduction system to the distal, non-insulated conduction system (average CL 218 versus 111 m s [p = 0.03]). CONCLUSION: Our data are supportive of a novel observation of intramural difference between insulated and non-insulated regions of the His-Purkinje network in canines. In addition, certain areas exhibited periods of regular electrogram characteristics; this was despite the heart remaining in terminal VF. These early canine data merit further study to investigate if specific ablation of the distal conduction system can perturb or extinguish VF.

Right Ventricular Dysfunction and Long-Term Risk of Sudden Cardiac Death in Patients With and Without Severe Left Ventricular Dysfunction.

BACKGROUND: Right ventricular systolic dysfunction (RVD) often coexists with various cardiopulmonary diseases. However, the association between RVD and risk of sudden cardiac death (SCD) has not been well studied. This study examined the risk of SCD associated with RVD in patients with heterogeneous underlying cardiac diseases. METHODS: The Mayo Clinic cardiac care unit database included 5463 consecutive patients with complete echocardiographic evaluation to assess right ventricular systolic function and RVD severity. Prospective surveillance follow-up was obtained for all patients. SCD was adjudicated when a malignant ventricular arrhythmia was documented as the primary rhythm leading to death. RESULTS: The prevalence of mild RVD and moderate-severe RVD was 14.9% and 17.1%, respectively. Patients with RVD were more likely to have a history of congestive heart failure, cardiac arrest, pulmonary disease, and lower baseline left ventricular ejection fraction compared with those with normal right ventricular systolic function. During a median follow-up of 14 months, the incidence of SCD was highest in patients with moderate-severe RVD (7.4% versus 4.4% in mild RVD versus 1.6% in normal right ventricular function; P<0.001). After adjustment for baseline characteristics, mild RVD (adjusted hazard ratio, 1.57; P=0.046) and moderate-severe RVD (adjusted hazard ratio, 1.91; P=0.006) were independently associated with an increased risk of SCD. Moderate-severe RVD remained an independent predictor of SCD for patients with left ventricular ejection fraction >35% without or with preexisting implantable cardioverter-defibrillator (adjusted hazard ratio, 4.12; P=0.003 and adjusted hazard ratio, 5.04; P<0.001, respectively). CONCLUSIONS: Presence of RVD in patients with a history of preexisting cardiac disease is an independent predictor of SCD irrespective of left ventricular ejection fraction.

QT Prolongation, Torsades de Pointes, and Psychotropic Medications: A 5-Year Update.

BACKGROUND: Some psychotropic medications have been associated with prolongation of the QT interval and QT prolongation, especially in those with medical illness, and are linked to lethal ventricular arrhythmias, such as Torsades de Pointes (TdP). In 2013, we published a review of QT prolongation, TdP, and psychotropic medications. OBJECTIVE: We provide an update over the past 5 years on the specific concerns most relevant to clinicians who see medically ill patients. METHODS: In this nonsystematic review, we aimed to carefully and intensively identify new articles by utilizing a structured PubMed search from 2012-present. RESULTS: QT prolongation remains an imperfect, though well-established marker of risk for TdP. Among antidepressant medications, citalopram does appear to prolong the QT interval more than other selective serotonin reuptake inhibitors, though the clinical significance of this prolongation remains unclear. Escitalopram appears to prolong the QT interval to a lesser extent. Haloperidol carries a risk for QT prolongation, but the assertion that intravenous haloperidol is inherently riskier may be confounded by its primary use in medically ill populations. Among atypical antipsychotic agents, ziprasidone-and possibly iloperidone-is associated with the greatest QT prolongation, whereas aripiprazole appears safest from this standpoint. CONCLUSIONS: The evidence for clinically meaningful QT prolongation with most classes of psychiatric agents remains minimal. The most important risk-reducing intervention clinicians can make is undertaking a careful analysis of other QT risk factors when prescribing psychiatric medications.

Association of Serum Magnesium on Mortality in Patients Admitted to the Intensive Cardiac Care Unit.

BACKGROUND: Although electrolyte disturbances may affect cardiac action potential, little is known about the association between serum magnesium and corrected QT (QTc) interval as well as clinical outcomes. METHODS: A consecutive 8498 patients admitted to the Mayo Clinic Hospital-Rochester cardiac care unit (CCU) from January 1, 2004 through December 31, 2013 with 2 or more documented serum magnesium levels, were studied to test the hypothesis that serum magnesium levels are associated with in-hospital mortality, sudden cardiac death, and QTc interval. RESULTS: Patients were 67 ± 15 years; 62.2% were male. The primary diagnoses for CCU admissions were acute myocardial infarction (50.7%) and acute decompensated heart failure (42.5%), respectively. Patients with higher magnesium levels were older, more likely male, and had lower glomerular filtration rates. After multivariate analyses adjusted for clinical characteristics including kidney disease and serum potassium, admission serum magnesium levels were not associated with QTc interval or sudden cardiac death. However, the admission magnesium levels ≥2.4 mg/dL were independently associated with an increase in mortality when compared with the reference level (2.0 to <2.2 mg/dL), having an adjusted odds ratio of 1.80 and a 95% confidence interval of 1.25-2.59. The sensitivity analysis examining the association between postadmission magnesium and analysis that excluded patients with kidney failure and those with abnormal serum potassium yielded similar results. CONCLUSION: This retrospective study unexpectedly observed no association between serum magnesium levels and QTc interval or sudden cardiac death. However, serum magnesium ≥2.4 mg/dL was an independent predictor of increased hospital morality among CCU patients.

Trends in percutaneous pericardial access during catheter ablation of ventricular arrhythmias: a single-center experience.

PURPOSE: Percutaneous pericardial access (EpiAcc) assists ventricular tachycardia/premature ventricular complex (VT/PVC) ablation by permitting epicardial mapping and ablation outside the vicinity of the coronary venous system. We sought to determine whether expanding indications and growing operator experience have led to increased rates of EpiAcc. METHODS: We reviewed the frequency of EpiAcc procedures performed during VT/PVC ablation between 2007 and 2014 to identify temporal trends in the procedure. RESULTS: There were 758 patients undergoing 880 VT/PVC ablation procedures (average 95 patients per year; 110 procedures per year) during the study period. EpiAcc for ablation was utilized in 170 patients (181 procedures). The average age at the time of EpiAcc was 55 ± 16 years and 129 (76.0 %) patients were male. The rate of EpiAcc was 22.9 % in males and 15.4 % in females (P = 0.008). The absolute number of EpiAcc procedures increased from 2007 (6 procedures) to 2014 (27 procedures). Similarly, the proportion of patients undergoing EpiAcc increased from 8.6 % of procedures in 2007 to 24.5 % in 2014 (P < 0.0001). While EpiAcc use became more frequent, the rate of epicardial ablation among those who underwent EpiAcc remained stable (approximately 70 %). CONCLUSIONS: Percutaneous pericardial access has been used with increasing frequency as part of VT/PVC ablations without an increase in the rate of epicardial ablation. This growing utilization may lay the foundation for novel epicardial strategies as new technologies emerge. The frequency of percutaneous pericardial access in VT/PVC ablation appears to be greater in males, reasons for which are undefined.

Ischemic Stroke or Systemic Embolism After Transseptal Ablation of Arrhythmias in Patients With Cardiac Implantable Electronic Devices.

BACKGROUND: Incidental mobile thrombi are commonly found on endovascular leads of cardiac implantable electronic devices (CIEDs). Transseptal puncture for catheter ablation of arrhythmia poses a risk for paradoxical embolism. We examined risk of ischemic stroke, transient ischemic attack (TIA), or systemic embolism after transseptal ablation in patients with and without CIEDs. METHODS AND RESULTS: Using a national administrative claims database, 31 720 patients who underwent a transseptal catheter ablation between January 2004 and September 2014 were identified. Two propensity-matched cohorts were created by matching demographic variables, administrative variables, Charlson Comorbidity Index, CHA2DS2-Vasc score, and year and indication for ablation (5533 and 11 300 patients with and without CIEDs). Incidence rates and Cox proportional hazards models were used to estimate risk of ischemic stroke, TIA, or systemic embolism for patients with and without CIEDs. Impact of oral anticoagulation (OAC) use on the endpoint was examined. Over a mean follow-up of 2.1 years, the incidence of the combined endpoint was 1.9 per 100 person-years in patients with CIEDs and 1.5 per 100 person-years in patients without CIEDs (P=0.03). Among patients not on OAC, presence of a cardiac device was associated with an increased risk (hazard ratio [HR], 1.71 [1.24-2.35]; P<0.01), whereas there was no association noted among patients treated with OAC (HR, 0.98 [0.75-1.28]). CONCLUSION: CIEDs are associated with an increased risk of stroke, TIA, or systemic embolism after transseptal ablation, but this risk is attenuated with postablation OAC use. Role of anticoagulation post-transseptal ablation in patients with CIED warrants further investigation.