The impact of supraventricular arrhythmias on the outcomes of guideline-compliant implantable cardioverter defibrillator programming.

INTRODUCTION: Several implantable cardioverter defibrillators (ICD) programming strategies are applied to minimize ICD therapy, especially unnecessary therapies from supraventricular arrhythmias (SVA). However, it remains unknown whether these optimal programming recommendations only benefit those with SVAs or have any detrimental effects from delayed therapy on those without SVAs. This study aims to assess the impact of SVA on the outcomes of ICD programming based on 2015 HRS/EHRA/APHRS/SOLAECE expert consensus statement and 2019 focused update on optimal ICD programming and testing guidelines. METHODS: Consecutive patients who underwent ICD insertion for primary prevention were classified into four groups based on SVA status and ICD programming: (1) guideline-concordant group (GC) with SVA, (2) GC without SVA, (3) nonguideline concordant group (NGC) with SVA, and (4) NGC without SVA. Cox proportional hazard models were analyzed for freedom from ICD therapies, shock, and mortality. RESULTS: Seven hundred and seventy-two patients (median age, 64 years) were enrolled. ICD therapies were the most frequent in NGC with SVA (24.0%), followed by NGC without SVA (19.9%), GC without SVA (11.6%), and GC with SVA (8.1%). Guideline concordant programming was associated with 68% ICD therapy reduction (HR 0.32, p = .007) and 67% ICD shock reduction (HR 0.33, p = .030) in SVA patients and 44% ICD therapy reduction in those without SVA (HR 0.56, p = .030). CONCLUSION: Programming ICDs in primary prevention patients based on current guidelines reduces therapy burden without increasing mortality in both SVA and non-SVA patients. A greater magnitude of reduced ICD therapy was found in those with supraventricular arrhythmias.

Containing the Cost of Heart Failure Management: A Focus on Reducing Readmissions.

Heart failure (HF) consumes a large proportion of the total national health care budget. Incidence and prevalence of HF are increasing and may give rise to an unsustainable increase in health care spending. Hospitalizations account for the vast majority of HF-related expenses, and 20% to 25% of patients discharged with a diagnosis of HF are readmitted within 60 days. Thus, efforts to reduce HF readmissions are a reasonable target for reducing overall expenses. It is to be seen if targeting readmission rates will lead to significant cost savings, and more importantly, to improved patient outcomes.

Use of the Wearable Cardioverter Defibrillator in High-Risk Populations.

The United States Food and Drug Administration has approved the wearable cardioverter defibrillator (WCD) for use in patients who are at high risk for sudden cardiac arrest (SCA) and who do not yet have an established indication for an implantation cardioverter defibrillator (ICD) or have contraindications for device implantation for various reasons. The WCD is typically used for primary prevention in (1) high-risk patients with reduced left ventricular ejection fraction (LVEF) ≤35 % after recent acute myocardial infarction (MI) during the 40-day ICD waiting period, (2) before and after coronary artery bypass graft or percutaneous coronary intervention during the 90-day ICD waiting period, (3) after recently diagnosed nonischemic dilated cardiomyopathy (NICM) during the 3- to 9-month medical therapy optimization period, or (4) for those with inherited proarrhythmic conditions such as long QT syndrome or hypertrophic cardiomyopathy. Unlike the automatic external defibrillator, the WCD does not require assistance from bystanders for therapy and conscious patients can delay or avert therapy with the use of response buttons. The WCD exhibits a small risk of inappropriate shock, mostly due to supraventricular tachycardia and/or electrical noise. Multiple non-randomized observational studies have shown high efficacy in detection and appropriate shock therapy for sustained ventricular tachyarrhythmias. This paper discusses the use of the WCD for prevention of SCA in patients with various cardiac substrates.

Assessment of adequate safety margin using single coupling interval-upper limit of vulnerability test.

PURPOSE: Upper limit of vulnerability (ULV) testing using T-wave scanning shocks at multiple coupling intervals correlates well with defibrillation threshold (DFT), but remains underutilized in clinical practice. We measured DFT and ULV at a single coupling interval (SCI), with the aim to identify adequate safety margin at a coupling interval that correlates best with DFT. METHODS: Consecutive patients undergoing implantable cardioverter defibrillator implantation underwent simultaneous SCI-ULV and DFT assessment. Following a drive train of 400 ms, a T-wave-coupled shock was delivered. To minimize shocks, patients were randomized to programmed shock at 20 ms before peak (Group I), at peak (Group II), or 20 ms after peak (Group III) of T wave. An initial T-wave test shock at 9 J was followed by ±2 J shocks, until SCI-ULV was ascertained. Device rescue shocks were programmed at test shock +2 J and +4 J shocks followed by external rescue shock. RESULTS: There were 200 patients: 66 patients in Group I, 67 patients each in Groups II and III; mean age was 68.9 ± 12.4 years; 75% of patients men, 66% with ischemic heart disease and mean ejection fraction of 27.1 ± 7.1%. Overall, the mean number of ventricular fibrillation induction was 1.39 ± 0.8, mean SCI-ULV energy was 7.97 ± 3.39 J, and mean DFT was 8.68 ± 3.19 J. The correlation between SCI-ULV and DFT improved from Group I to Group III and was best in Group III (r(2) = 0.689). There were no major adverse events. CONCLUSIONS: SCI-ULV measured 20 ms after the peak of the T wave correlates well with DFT for assessment of adequate safety margin.

Meteorological Influence on Atrial Fibrillation and Flutter: A Nationwide Observational Study in South Korea (2010-2022).

Background and rationale The impact of meteorological factors, including atmospheric temperature, humidity, and wind speed, on the incidence of atrial fibrillation and flutter (AF) has been the subject of several studies, but the findings have been inconsistent. Given the complex and multifaceted nature of this relationship, a larger-scale study was necessary to provide sufficient statistical power and elucidate potential associations between them. The aim of this study was, thus, to investigate the potential associations between meteorological factors and the incidence of AF. Methods The South Korean government provides open access to national health insurance and weather data for its citizens; the data was available from January 2010 to July 2022. The national health insurance data includes the monthly number of patients diagnosed with a specific condition, reflecting the incidence and prevalence of the condition. Pearson correlation analyses were performed using the statistical analysis software, SAS® OnDemand for Academics (SAS Institute Inc., Cary, North Carolina, United States), to examine the association between each month's national average climate data and the number of patients diagnosed with AF. Results The number of patients diagnosed with AF in the total population showed a statistically significant correlation only with average wind speed (correlation coefficient (r)=-0.42, 95%CI -0.55 to -0.28, p<0.001) and sunshine duration (r=0.27, 95%CI 0.12 to 0.41, p<0.001). Among females aged 20-24 years, there was a statistically significant association with other variables, including average temperature, precipitation, humidity, and atmospheric pressure (p<0.05). Diurnal temperature variation showed inconsistent associations across different age and sex groups. Conclusion The number of patients diagnosed with AF is negatively correlated with average wind speed and positively correlated with sunshine duration in the general population, particularly among the elderly. There was no significant association between the number of patients diagnosed with AF and average temperature, precipitation, or humidity, except for females aged 20-24 years, who exhibited a significant association with these variables. However, it is important to note that these correlations do not establish causality.

Programming of implantable cardioverter defibrillators for primary prevention: outcomes at centers with high vs. low concordance with guidelines.

BACKGROUND: While ICD therapy reduction programming strategies are recommended in current multi-society guidelines, concerns remain about a possible trade-off between the benefits of ICD therapy reduction and failure to treat episodes of ventricular arrhythmias. The study is to evaluate the outcomes of primary prevention patients followed in centers with high and low concordance with the 2015 HRS/EHRA/APHRS/SOLAECE expert consensus statement and 2019 focused update on optimal ICD programming and testing guidelines. METHODS: Consecutive patients with primary prevention ICD implantation from two centers between 2014 and 2016 were included. One center was classified as high guideline concordance center (HGC) with 47% (146/310) of patients with initial ICD concordant with the guidelines, and the other center was classified as low guideline concordance center (LGC) with only 1% (2/178) of patients with guideline-concordant initial ICD programming. Cox proportional hazard models were used to assess risk of first ICD therapy (ATP or shock), first ICD shock, and mortality. RESULTS: A total of 488 patients were included (mean age, 66 ± 13 years). During a mean follow-up of 1.9 ± 0.9 years, patients followed at HGC were 63% less likely to receive any ICD therapy (adjusted HR [aHR] 0.37, 95% CI 0.42-0.99). There were no significant differences in the rate of first ICD shock (aHR 0.72, 95% CI 0.34-1.52) or mortality (aHR 1.19, 95% CI, 0.47-3.05). CONCLUSIONS: Compared to primary prevention patients followed at LGC, primary prevention ICD patients followed at HGC received a significantly lower rate of ICD therapy, mainly from ATP reduction, without a difference in mortality during follow-up.

Implantable defibrillators improve survival in end-stage renal disease: results from a multi-center registry.

BACKGROUND: Small retrospective analyses suggest that end-stage renal disease (ESRD) patients do not obtain as much of a survival benefit from an implantable cardioverter-defibrillator (ICD) as non-ESRD patients do. We aimed to assess the survival effect of an ICD in ESRD patients with left ventricular dysfunction. METHODS: Data from two registries identified ESRD patients with an ICD and ESRD patients with left ventricular dysfunction (defined as ejection fraction <0.35). Cox proportional hazards regression was performed, including certain predefined covariates to assess the effect of an ICD on survival. RESULTS: Overall survival in the full cohort was a median of 4.7 years with 20 deaths in the ICD group and 29 deaths in the no-ICD group. The median survival in the ICD group was 8.0 years and 3.1 years in the no-ICD group. Crude analysis showed a better survival in the ICD group as compared to the no-ICD group (p = 0.016). The multivariable analysis confirmed that the ICD group had significantly less all-cause mortality compared to the no-ICD group (HR: 0.40; 95% CI: 0.19, 0.82; p = 0.013). CONCLUSION: An ICD is associated with a higher survival in ESRD patients with left ventricular dysfunction. This result merits further study in a larger cohort of patients.

Characteristics of telemetry interference with pacemakers caused by digital media players.

BACKGROUND: Contemporary implantable heart rhythm devices communicate multiple complex data simultaneously using radiofrequency telemetry. Interference in communication can expose them to the risk of potential corruption, leading to adverse clinical consequences. METHODS & RESULTS: We studied the characteristics of interference with uplink (real time intracardiac electrograms, marker channel, and stored histograms) and downlink (attempt to program a change in the lower rate limit, the pacing mode, and the ventricular lead configuration) data transmission between the wand and the pacemaker caused by digital media players (iPods--Photo and 3G) in 50 patients. We also measured and characterized worst-case magnetic field emissions (MFE) from the wand (

Programming implantable cardioverter-defibrillator in primary prevention: Guideline concordance and outcomes.

BACKGROUND: Inappropriate therapy is a common adverse effect in patients with an implantable cardioverter-defibrillator (ICD) that may be prevented by appropriate programming. OBJECTIVE: The purpose of this study was to assess the outcomes of device programming based on a 2015 HRS/EHRA/APHRS/SOLAECE expert consensus statement and a 2019 focused update on optimal ICD programming and testing. METHODS: Consecutive patients who underwent ICD insertion for primary prevention from 2014-2016 at 3 centers were included in the retrospective analysis. Patients were classified into 2 groups based on the tachycardia programming at the time of implant: guideline concordant group (GC) and non-guideline concordant group (NGC). Kaplan-Meier analysis and Cox proportional hazard models were used to estimate freedom from ICD therapy (antitachycardia pacing or shock), ICD shock, and death. RESULTS: A total of 772 patients were included in the study (mean age 63.3 ± 13.8 years). Of this total, 258 patients (33.4%) were in the GC group and 514 patients (66.6%) were in the NGC group. During mean follow-up of 2.02 ± 0.91 years, guideline concordant programming was associated with a 53% reduction in ICD therapy (P <.01) and 50% reduction in ICD shock (P = .02). There were no significant differences in mortality (6% in GC group vs11% in NGC group; P = .22). CONCLUSION: Only one-third of the studied population had an ICD device programmed in concordance with current guidelines. ICD programming based on the current guidelines was associated with a significantly lower rate of ICD therapy and shock without changes in mortality during intermediate-term follow-up.

Atrial fibrillation: a historical perspective.

Atrial fibrillation (AF) undoubtedly has become one of the most well studied arrhythmias today in terms of pathophysiology and diagnostic and therapeutic (interventional) electrophysiology. Although it lends itself to an apparently easy diagnosis on a surface ECG, myriad electromechanical mechanisms underlie its origin. An era of technology has been reached that makes AF not only "treatable" but also potentially "curable." This article aims at walking through the historical corridors and maze that have led to the present-day understanding of this most common yet complex arrhythmia.

Electromagnetic interference in an implantable loop recorder caused by a portable digital media player.

The implantable loop recorder has been shown to be a cost-effective tool for diagnosis of intermittent cardiovascular symptoms such as syncope and palpitations. Electromagnetic interference in these recorders may be caused by commonly encountered electronic devices such as antitheft electronic surveillance systems and magnetic resonance imaging cameras. In this report, we describe interference in two patients with implantable loop recorders from a portable digital media player.

Amiodarone-induced Hyponatremia: A Case Report and a Review of the Literature.

Amiodarone is a widely used medication for controlling various types of cardiac arrhythmias. Nonetheless, it carries several known adverse effects that may preclude its use or necessitate discontinuation. Hyponatremia resulting from amiodarone is rarely reported, and its incidence is unknown. We present a case of severe hyponatremia secondary to amiodarone therapy and a review of the literature.

National experience with long-term use of the wearable cardioverter defibrillator in patients with cardiomyopathy.

PURPOSE: The wearable cardioverter defibrillator (WCD) is generally used for short periods of sudden cardiac death (SCD) risk; circumstances may occasionally result in prolonged use (over 1 year). The aim of this study was to determine the benefits and risks of prolonged use in patients with systolic heart failure (HF). METHODS: ZOLL's post-market US database included adult patients (≥18 years) with ischemic and/or non-ischemic cardiomyopathy (ICM, NICM) and at least 1 year of use. Cox-regression was used to identify factors associated with survival with WCD use, and reasons for stopping use were entered as time-dependent factors. RESULTS: Among 220 patients, age (mean ± SD) 55.4 ± 14.8 years, WCD use 451.4 ± 289.9 days, and 67.3 % were male and their left ventricle ejection fraction (EF) averaged 20.9 ± 7.2 %. Eighty-nine (40.5 %) were continuing WCD use at the last follow-up. Thirty-six (16.4 %) and 56 (25.5 %) patients discontinued WCD use because of EF recovery and implantable cardioverter (ICD) implantation, respectively. Nine patients (4.1 %) received appropriate shock therapy for 13 episodes of sustained ventricular tachyarrhythmia with 12 (92.3 %) successful shocks. One patient died of refractory ventricular fibrillation. One patient died from sinus bradycardia transitioning to asystole. Eight patients (3.6 %) had nine episodes of non-fatal inappropriate shocks. CONCLUSIONS: Long-term use of the WCD is safe and effective. Recovery of EF was seen in significant number of patients even after 1 year of WCD use.

Unusual complications of coronary artery bypass graft surgery.

Complications after coronary artery bypass grafting are myriad and are to a certain extent operator dependent. The investigators report 2 unusual cases of inadvertent aortocoronary fistula after coronary artery bypass grafting that escaped routine detection. In conclusion, the development of heart failure led to the detection of this rare complication.

Recurrent syncope following radiation therapy.

This case report describes a 51-year-old man who presented with syncope. His electrocardiogram showed an abnormally long pause and the electrophysiology study revealed a prolonged H-V interval. This was attributed to the radiation therapy he received to the chest. He was successfully treated with implantation of a permanent pacemaker. This case highlights this rare complication of radiation-induced conduction system disease and management of this potentially life-threatening condition.