Implantable Cardioverter Defibrillator Discharges Research Articles

Exercise and arrhythmic risk in TMEM43 p.S358L arrhythmogenic right ventricular cardiomyopathy

High-level exercise has been associated with a malignant phenotype in desmosomal and genotype-negative forms of arrhythmogenic right ventricular cardiomyopathy (ARVC). This is the first study to examine this issue with ARVC secondary to the TMEM43 p.S358L mutation. The purpose of this study was to evaluate the impact of exercise on arrhythmic risk and cardiac death in TMEM43 p.S358L ARVC. Individuals with the TMEM43 p.S358L mutation enrolled in a prospective registry who had received a primary prevention implantable cardioverter-defibrillator (ICD) were invited to complete the modified Paffenbarger Physical Activity Questionnaire to assess their physical activity in the year before their ICD implantation. Time-to-event analyses using unadjusted and adjusted Cox proportional hazards models evaluated associations between physical activity and first appropriate ICD discharge secondary to malignant ventricular arrhythmia or cardiac death. In 80 subjects with the TMEM43 p.S358L mutation, exercise ≥9.0 metabolic equivalent of task (MET)-hours/day (high level) in the year before ICD implantation was associated with an adjusted 9.1-fold increased hazard of first appropriate ICD discharge (there were no deaths) relative to physical activity <9.0 MET-hours/day (moderate level) (95% confidence interval [CI] 3.3-24.6 MET-hours/day; P < .001). The median age from birth to first appropriate ICD discharge was 58.5 years (95% CI 56.5-60.5 years) vs 35.8 years (95% CI 28.2-43.4 years) (P < .001) in subjects in moderate- and high-level exercise groups, respectively. Exercise ≥9.0 MET-hours/day is associated with an increased risk of malignant ventricular arrhythmias in the TMEM43 p.S358L subtype of ARVC. Extrapolating these data, we suggest molecular testing be offered in early childhood to inform exercise choices reflective of the genotype.

Electrical Storm in Patients with Inappropriate Implantable Cardioverter-Defibrillator Therapy: Current Trends in Clinical Practice between Guidelines and Technology Progress

The term “Electrical Storm” (ES) indicates cardiac electrical instability manifested by several episodes of ventricular tachyarrhythmias within a short time. In the contemporary implantable cardioverter-defibrillator (ICD) era, ES is defined as recurrent (three or more separate episodes) of ICD discharges over 24 hours. Some ESs are due to inappropriate repetitive shock and are potentially lethal for the patient. The most common causes of inappropriate ICD shock include supraventricular tachycardia with high ventricular response and oversening of peaked T waves or R wave, myopotentials or electrical noise. Appropriate diagnosis and treatment are critical in the Emergency Department. To approach these patients systematically, it is important to understand, that there are four causes of shock. Modern ICD incorporate sophisticated tachycardia detection algorithms within their programming designed to minimize devices’ detection mistakes and ICD-related information can also be checked using remote home monitoring systems. However, these opportunities are often not utilized to their full benefit. Thus, careful attention should be paid to the programming of the device. Fine tuning of the detection and differentiation algorithms is critical, and best done by a practitioner who understands the subtle differences among the different manufacturers. The racommendations for those problems should be revised.

Long-term follow-up of implantable cardioverter-defibrillators in children: Indications and outcomes.

Validation data of the use of implantable cardioverter-defibrillators (ICD) in the pediatric population is insufficient, with limited follow-up periods. The aim of the study was to report on 17 years of experience with implantable cardioverter-defibrillator (ICD) therapy in children and young adults. This retrospective review included patients below the age of 18 years at the time of ICD implantation between May 2000 and December 2017. For the statistical analysis, the sample was divided into groups by gender and the type of indications for ICD implantation (primary vs secondary prevention). The study group included 20 children (8 female, 12 male) who underwent ICD implantation for primary or secondary prevention of sudden cardiac death (SCD). The average age at the time of the initial procedure was 15.6 years (range: 3.8-17.7 years). Primary electrical disease (PED) was present in 9 patients, cardiomyopathy (CMP) in 9 and 2 others had congenital heart defects (CHDs). The median follow-up time was 6.7 years (range: 0.4-12.5 years). The outcomes of ICD therapy were analyzed. No differences between the sexes were found in terms of treatment strategy effectiveness (p > 0.05). The girls were more often treated as primary prevention (p = 0.009). After implantation, all the patients were on optimal pharmacotherapy. Alltogether there were 126 ICD interventions in 11 patients, including 23 inadequate interventions (IA) in 2 children (18.2%).Three children (15%) died due to electrical storms. In the per-procedure analysis, the overall freedom rate from ICD lead replacement was 90%, 80% and 57% at 1, 5 and 10 years of observation, respectively. Implantable cardioverter-defibrillator implantation indications in children are more heterogeneous in comparison to adult population. In the pediatric population undergoing ICD implantation, the treatment strategy is influenced by gender. The rate of inappropriate ICD discharges (IA) in our group of pediatric patients was low. Rigorous pharmacotherapy and individual ICD programming seemed of paramount importance. Lead malfunctions LF constituted the most prevalent complication observed.

P5975Diminished LV systolic velocity on tissue Doppler imaging is linked to an amplified risk of lethal arrhythmias independently of LV ejection fraction

Abstract Background Life threatening arrhythmias (LTA) can trigger sudden cardiac death, or provoke implantable cardioverter defibrillator (ICD) discharges that escalate morbidity and mortality. Longitudinal myofibrils predominate in the subendocardium which is uniquely sensitive to arrhythmogenic triggers. Objectives To test the hypothesis that mitral annular systolic velocity (S'), a tissue Doppler index of LV long-axis systolic function, might predict lethal arrhythmias irrespective of LVEF. Methods We analysed data from diverse ICD and cardiac resynchronization therapy defibrillator (CRT-D) patients at 2 London centres. Channelopathies were excluded. S' was averaged from medial and lateral mitral annuli velocities. Primary outcome was time to sustained ventricular tachycardia (VT) or fibrillation (VF) needing device therapy. Results In 302 patients (mean age 68 years, LVEF 32%, 77% male, 52% ischemic, 35% primary prevention, and 53% CRT-D), median S' was 5.1 (IQR: 4.0–6.2) cm/s and lower in CRT-D than ICD subjects. After a median follow-up of 15 months, 56 (19%) subjects had LTA and those who did had a lower S' than those who did not (4.6±1.4 cm/s vs. 5.4±1.7 cm/s, P=0.003-Fig A). Each 1cm/s lower S' correlated to a 43% increased risk of LTA (HR: 0.70, 95% CI: 0.57–0.87, P=0.001) independently of age, gender, β-blocker use, centre, ICD use and LVEF. Adding S' to the baseline model improved net reclassification (P=0.02) implying incremental utility (Fig B). An S' ≤5.6cm/s was the best cut-off, conferring a 2.4-fold higher LTA risk than an S'&gt;5.6 cm/s (95% CI: 1.17–4.37, P=0.02–Fig C). Conclusion A lower S' forecasts an enhanced probability of LTA in cardiac device recipients irrespective of LVEF, and could be used to titrate medical, device and ablative therapies to mitigate future arrhythmic risk.

Analysis of 30 cases of inherited cardiac arrhythmia syndrome in children

Objective: To analyze and summarize the diagnosis and treatment experience of common inherited cardiac arrhythmia syndrome in pediatric patients, and explore the most appropriate therapy. Methods: A retrospective review identified 30 pediatric cases (19 males, 11 females) diagnosed with long QT syndrome (LQTS), Brugada syndrome (BrS), catecholaminergic polymorphic ventricular tachycardia (CPVT), hypertrophic cardiomyopathy (HCM), arrhythmogenc right ventricular cardiomyopathy (ARVC) from January 2008 to December 2018 in the Pediatric Cardiology Department, Guangdong Provincial People's Hospital. Data obtained included the diagnosis, treatment and follow-up outcome. Results: The most common inherited cardiac arrhythmia syndromes were LQTS (n=14) including 1 case with epilepsy, CPVT (n=5), HCM (n=7), ARVC (n=1), and BrS (n=3). Twenty-seven cases were admitted to hospital due to syncope, whereas the remaining 3 cases of BrS had not presented with syncope before admission. The average onset age of inherited arrhythmia was (10.0±3.3) years. Genetic testing was performed on 20 patients. The median follow-up time was 40 months. Among 15 patients who underwent implantable cardioverter defibrillator (ICD) and survived, 2 patients had frequent ICD discharge. One patient underwent radiofrequency ablation, and the other one received left cardiac sympathetic denervation and an increased ICD defibrillation threshold, and the number of ICD discharge was significantly reduced. Among 10 patients who received drug therapy, 4 patients including two patients who discontinued treatment without advices died. Two patients whose parents refused treatment died, 1 case diagnosed with unexplained sudden cerebral death, and the remaining 2 cases without indication for drug therapy survived without any treatment. Conclusions: Mortality rate is high in pediatric patients with inherited cardiac arrhythmia and syncope. The therapeutic effect of drugs are not satisfactory, ICD implantation is the most effective treatment to prevent sudden cardiac death currently, but the postoperative frequent discharge should be brought to the forefront and handled in time.

Pseudo-Electrical Storm in Patients with Implanted Cardioverter Defibrillator

The Electrical Storm indicates cardiac electrical instability manifested by several episodes of ventricular tachyarrhythmias within a short time. Pseudo-ES is defined as recurrent inappropriate implantable cardioverter-defibrillator discharges over 24 hours. Far from being a minor complication, Pseudo-ES is usually physical and psychological harmful and potentially lethal.

Pseudo-Electrical Storm in Patients with Implanted Cardioverter Defibrillator

The Electrical Storm indicates cardiac electrical instability manifested by several episodes of ventricular tachyarrhythmias within a short time. Pseudo-ES is defined as recurrent inappropriate implantable cardioverter-defibrillator discharges over 24 hours. Far from being a minor complication, Pseudo-ES is usually physical and psychological harmful and potentially lethal.

Phantom shocks in implantable cardioverter-defibrillator recipients: impact of education level, anxiety, and depression.

Implantable cardioverter defibrillators (ICDs) are designed to deliver shocks in the event of ventricular arrhythmias. Some ICD recipients experience the sensation of ICD discharge in the absence of an actual discharge (phantom shock, PS). The aim of this study was to evaluate the incidence, predictors, and consequences of PS in ICD recipients. Consecutive ICD recipients were examined during aroutine outpatient follow-up (FU) visit. Subjects completed awritten survey; their level of depression and anxiety was assessed with the hospital anxiety and depression scale (HADS). Quality of life (QOL) was assessed using the Minnesota living with heart failure questionnaire. Of 434 patients invited to the study, 423 (97.5%) ICD recipients agreed to and completed the survey; 349 (83%) had aprimary prevention indication and 339 (80%) ischemic cardiomyopathy. Atotal of 27patients (6.4%) reported aPS during amean FU of 64 ± 44months (5.4% in the primary prevention group and 10.8% in the secondary prevention group; p = 0.11). PS were related to higher education (≥bachelor's degree 41% versus 20%; p = 0.03), and more frequent in patients receiving adequate shocks during FU (34% versus 0.5%; p < 0.001). HADS score levels were higher following PS (15 ± 6 versus 8.8 ± 7.4; p < 0.001). The majority of patients reporting PS felt that the information provided to them prior to ICD placement was insufficient (22.2% versus 5.0%), that they needed psychological support after ICD implantation (26% versus 3%), and considered ICD deactivation in near end-of-life situations (59% versus 29%; p < 0.001 for all). PS occur in 6.4% of all ICD recipients and are related to higher education and to patients that experienced adequate shocks during FU.

What causes sudden death in patients with chronic heart failure and a reduced ejection fraction?

Sudden death characterizes the mode of demise in 30–50% of patients with chronic heart failure and a reduced ejection fraction. Occasionally, these events have an identifiable pathophysiological trigger, e.g. myocardial infarction, catecholamine surges, or electrolyte imbalances, but in most circumstances, there is no acute precipitating mechanism. Instead, adverse left ventricular remodelling and fibrosis creates an exceptionally fragile and highly vulnerable substrate, which can be characterized using the model developed in theoretical physics of ‘self-organizing criticality’. This framework has been applied to describe the genesis of avalanches, nodes of traffic congestion unrelated to an accident, the abrupt system-wide failure of electrical grids, and the initiation of cancer and neurodegenerative diseases. Self-organizing criticality within the ventricular myocardium relies on complex adaptations to progressive stress and stretch, which evolve inevitably to an abrupt end (termed ‘cascading failure’), even though the rate of deterioration of the underlying disease process has not changed. The result is acute circulatory collapse (i.e. sudden death) in the absence of an identifiable triggering event. Cascading failure in a severely remodelled or fibrotic heart can become manifest electrically as a first-time ventricular tachyarrhythmia that is responsive to the shock delivered by an implantable cardioverter-defibrillator (ICD). Alternatively, it may present as an acute mechanical failure, which is manifest as (i) asystole, bradyarrhythmia, or electromechanical dissociation; or (ii) incessant ventricular fibrillation that persists despite repetitive ICD discharges; in both instances, the sudden deaths cannot be prevented by an ICD. This conceptual framework explains why anti-remodelling and antifibrotic interventions (i.e. neurohormonal antagonists and cardiac resynchronization) reduce the risk of sudden death in patients with heart failure in the absence of an ICD and provide incremental benefits in those with an ICD. The adoption of anti-remodelling and antifibrotic treatments may explain why the incidence of sudden death in clinical trials of heart failure has declined dramatically over the past 10–15 years, independent of the use of ICDs.

The prognostic value of biventricular long axis strain using standard cardiovascular magnetic resonance imaging in patients with hypertrophic cardiomyopathy

BackgroundLong axis strain (LAS) is a parameter derived from standard cardiovascular magnetic resonance imaging. However, the prognostic value of biventricular LAS in hypertrophic cardiomyopathy (HCM) is unknown. MethodsPatients with HCM (n = 384) and healthy volunteers (n = 150) were included in the study. Left ventricular (LV)-LAS was defined as the percentage change in the length measured from the epicardial border of the LV apex to the midpoint of a line connecting the mitral annulus at end-systole and end-diastole. Right ventricular (RV)-LAS represented the percentage change of length between epicardial border of the LV apex to the midpoint of a line connecting the tricuspid annulus at end-systole and end-diastole. The primary endpoint was a combination of all-cause death and sudden cardiac death aborted by appropriate implantable cardioverter-defibrillator discharge and cardiopulmonary resuscitation after syncope. The secondary endpoint was a combination of the primary endpoint and hospitalization for congestive heart failure. ResultsTwenty-nine patients (7.6%) achieved the primary endpoint, and the secondary endpoint occurred in 66 (17.2%) patients. In multivariate Cox regression analysis, RV-LAS was an independent prognostic factor for the primary (hazard ratio (HR), 1.13) and secondary (HR, 1.11) endpoints. In the subgroup of patients with a normal RV ejection fraction (EF) (>45.0%, n = 345), impaired RV-LAS was associated with adverse outcomes and might add incremental prognostic value to RVEF and tricuspid annular plane systolic excursion (TAPSE) (p < 0.01). ConclusionsRV-LAS is an independent predictor of adverse prognosis in HCM in addition to RVEF and TAPSE.

Prognostic value of cardiac metaiodobenzylguanidine imaging and QRS duration in implantable cardioverter defibrillator patients with and without heart failure

BackgroundCardiac metaiodobenzylguanidine (MIBG) imaging provides prognostic information in patients with heart failure (HF). Recent studies showed that the highest rate of ventricular tachyarrhythmias (VTs) is seen in HF patients with an intermediate decrease in MIBG uptake, rather than in those with the lowest values. However, prolonged QRS duration (QRSd) has been shown to be associated with VTs in HF patients. This study assessed the prognostic value of the combination of an intermediate decrease in MIBG uptake and prolonged QRSd for predicting VTs in patients with implantable cardioverter defibrillators (ICDs) in relation to the presence of heart failure (HF). Methods and resultsA total of 196 outpatients with ICDs (age: 64 ± 14 years, male: 81%, left ventricular ejection fraction [LVEF]: 49% ± 16%) were prospectively enrolled; 135 had HF (NYHA class: 2.0 ± 0.6). At entry, cardiac MIBG imaging was performed, and QRSd was measured on standard 12‑lead electrocardiography. An intermediate decrease in the heart-to-mediastinum ratio on the delayed planar image (ID-H/M) was defined as 1.40–1.89. During the 3.3 ± 2.2-year follow-up, 59 patients had appropriate ICD discharges (ATx) for VTs. On multivariate Cox analysis, ID-H/M and prolonged QRSd (≥147 ms) were significantly and independently associated with ATx. In both patients with and without HF, ATx were significantly more frequent in patients with ID-H/M and/or prolonged QRSd than in those with neither (with HF: 40% vs. 14%, p = 0.020; without HF: 43% vs. 10%, p = 0.0028). ConclusionsThe combination of ID-H/M and prolonged QRSd provided more prognostic information for predicting VTs in ICD patients, with and without HF.

ICD Therapy in LVAD: Rates and Predictors of Appropriate and Inappropriate Shock

Purpose Ventricular arrhythmias (VA) are common in continuous flow-left ventricular assist devices (CF-LVAD) patients. We investigated the rates of appropriate and inappropriate implantable cardioverter defibrillator (ICD) discharges following CF-LVAD placement without planned ICD reprograming. Methods All patients with CF-LVAD and prior ICD implants from 2008-2018 with pre and post implant follow up data (n=82) were eligible. Appropriate ICD discharge was defined as shock received for VA as reported by an electrophysiologist, whereas shocks received for any other rhythms were considered inappropriate. Results 16 out of 82 patients received an appropriate ICD discharge whereas 6 received an inappropriate shock during follow up (mean 1.51 years). The rates of receiving appropriate shock for VA were 19.5% (0.129 per patient year), and for inappropriate shock were 7.3% (0.064 per patient year). We compared the baseline characteristics of patients who received an appropriate ICD shock to those without any shocks (Table). In a multivariate logistic model, after adjusting for several variables including atrial fibrillation, amiodarone use, NYHA class, and type of cardiomyopathy, only the history of pre-LVAD VA was associated with higher odds of post left ventricular assist device (LVAD) appropriate discharge (p=0.004). There were no baseline characteristics predictive of inappropriate ICD shock. Conclusion Patients with CF-LVAD and ICD have a high burden of appropriate and inappropriate ICD shocks. History of pre-LVAD VA predicted higher chances of appropriate ICD shock post LVAD. Prospective multicenter trials are necessary to investigate optimal ICD programing to safely reduce rates of appropriate and inappropriate therapy.

Leakage current from transvenous and subcutaneous implantable cardioverter defibrillators (ICDs): A risk to the rescuer?

BackgroundImplantable cardioverter-defibrillators (ICDs) are a well-established therapy for patients at risk of life-threatening ventricular arrhythmias. With rising implant rates, the risk of a rescuer performing chest compressions during discharge is increasing, leading to concerns over rescuer safety from the resultant leakage current. More recently, subcutaneous ICDs (S-ICD) have been developed, which utilise a higher energy and more superficial electrodes compared with transvenous ICDs (T-ICD), raising safety concerns further. ObjectiveWe measured the current a rescuer would potentially receive from T-ICDs and S-ICDs if they were in contact with the patient at the time of ICD discharge to assess its magnitude in relation to international safety standards. MethodsSurface voltages adjacent to ICD electrodes were measured on patients undergoing defibrillation threshold checks. Rescuer current was then calculated assuming a total rescuer circuit impedance of 1696 Ω. ResultsTwenty-five patients were recruited. Rescuer current from S-ICDs was significantly higher than those from T-ICDs (S-ICD: Median RMS 135 mA range 91 mA–164 mA, T-ICD: Median RMS 31 mA, range 9 mA–75 mA, P < 0.0001). Surface voltages (median RMS) to which the rescuer is likely to be exposed are higher when performing chest compressions from the patient’s left side compared with the right (127 V vs 67 V respectively, 95% CI of difference −34 V to −67 V, P < 0.0001). ConclusionsRescuers performing chest compressions on ICD patients are at risk from leakage current, particularly from S-ICDs. Chest compressions should be performed from the opposite side to the ICD to reduce rescuer risk.

Time-to-first appropriate shock in patients implanted prophylactically with an implantable cardioverter-defibrillator: data from the Survey on Arrhythmic Events in BRUgada Syndrome (SABRUS).

Data on predictors of time-to-first appropriate implantable cardioverter-defibrillator (ICD) therapy in patients with Brugada Syndrome (BrS) and prophylactically implanted ICD's are scarce. SABRUS (Survey on Arrhythmic Events in BRUgada Syndrome) is an international survey on 678 BrS patients who experienced arrhythmic event (AE) including 252 patients in whom AE occurred after prophylactic ICD implantation. Analysis was performed on time-to-first appropriate ICD discharge regarding patients' characteristics. Multivariate logistic regression models were utilized to identify which parameters predicted time to arrhythmia ≤5 years. The median time-to-first appropriate ICD therapy was 24.8 ± 2.8 months. A shorter time was observed in patients from Asian ethnicity (P < 0.05), those with syncope (P = 0.001), and those with Class IIa indication for ICD (P = 0.001). A longer time was associated with a positive family history of sudden cardiac death (P < 0.05). Multivariate Cox regression revealed shorter time-to-ICD therapy in patients with syncope [odds ratio (OR) 1.65, P = 0.001]. In 193 patients (76.6%), therapy was delivered during the first 5 years. Factors associated with this time were syncope (OR 0.36, P = 0.001), spontaneous Type 1 Brugada electrocardiogram (ECG) (OR 0.5, P < 0.05), and Class IIa indication (OR 0.38, P < 0.01) as opposed to Class IIb (OR 2.41, P < 0.01). A near-significant trend for female gender was also noted (OR 0.13, P = 0.052). Two score models for prediction of <5 years to shock were built. First appropriate therapy in BrS patients with prophylactic ICD's occurred during the first 5 years in 76.6% of patients. Syncope and spontaneous Type 1 Brugada ECG correlated with a shorter time to ICD therapy.

Clinically overt infections and markers of inflammation in patients admitted to Emergency Department due to high-energy discharges of implantable cardioverter-defibrillator

Clinically overt infections and markers of inflammation in patients admitted to Emergency Department due to high-energy discharges of implantable cardioverter-defibrillator

Sudden cardiac arrest in patients without overt heart disease: a limited value of next generation sequencing.

INTRODUCTION Unexplained sudden cardiac arrest (SCA), occurs in up to 10% of patients and is often attributed to an inherited arrhythmia syndrome. Family screening and genetic testing may help clarify the cause of unexplained SCA. OBJECTIVES We aimed to assess the usefulness of clinical evaluation and genetic testing in patients after unexplained SCA and in their families. PATIENTS AND METHODS In the years 2014-2017, we studied 44 unrelated patients after unexplained SCA and 96 of their relatives. All patients and relatives underwent comprehensive cardiac evaluation. In 31 patients with SCA, next generation sequencing (NGS) was performed. The Kaplan-Meier survival curve was constructed to compare the event-free survival depending on clinical diagnosis or genotype. An adverse event was defined as an adequate implantable cardioverter-defibrillator discharge. RESULTS Based on the clinical evaluation, diagnosis was established in 39% of probands (long QT syndrome 21%; short QT syndrome 7%; Brugada syndrome 7%; catecholaminergic polymorphic ventricular tachycardia, 2%; and early repolarization syndrome, 2%). Ventricular arrhythmia was identified in the relatives of 19% of probands. In 18 of the 31 probands (54.8%), 23 rare gene variants were identified, of which only 2 were classified as pathogenic. The event-free survival over a median of 4.5 years was similar in patients with or without clinical diagnosis and in carriers and noncarriers of a rare genetic variant. CONCLUSIONS This study shows the significance of an extensive clinical assessment in unexplained SCA victims and their relatives. Routine genetic testing by NGS has low diagnostic and prognostic value.

Myocardial Irritation from a Left Ventricular Assist Device Resulting in Refractory Ventricular Tachycardia

BackgroundDue to an increasing prevalence of heart failure but a steady rate of heart transplantation, the number of left ventricular assist devices (LVADs) implanted is growing. These patients present to emergency departments (EDs) with a variety of complications from their implanted device as well as their baseline cardiomyopathy. One-third of patients will present with a dysrhythmia, the most common of which is ventricular tachycardia. Case ReportA 77-year-old man with nonischemic cardiomyopathy and HeartMate II LVAD presented with sustained ventricular tachycardia and 43 automatic implantable cardioverter-defibrillator (AICD) discharges. Due to left ventricular remodeling, ongoing diuresis, and positioning of his LVAD inflow cannula against his interventricular septum, a likely dysrhythmogenic foci, he quickly decompensated with sedation while in the ED. Why Should an Emergency Physician Be Aware of This?Refractory ventricular tachycardia is a common dysrhythmia for LVAD patients and may lead to full cardiopulmonary arrest. Common strategies such as chest compressions are used only in limited scenarios, but medical management is possible. This should focus on resolution of the dysrhythmia and identification of the etiology, including possible mechanical compromise.

Transvenous and non-transvenous implantable cardioverter-defibrillators in children, adolescents, and adults with congenital heart disease: who is at risk for appropriate and inappropriate shocks?

Non-transvenous implantable cardioverter-defibrillators (ICDs) as used in small patients and in patients with congenital heart disease (CHD) have not been compared with transvenous systems with respect to safety and efficacy yet. Aim of the present study was to describe the prevalence of and to identify contributing factors for appropriate and inappropriate ICD discharges in patients with non-transvenous and transvenous ICD. Single centre analysis of all paediatric and CHD patients who had received an ICD since 1995. One hundred and ninety-five patients were included. A transvenous system had been implanted in 153 (78%) subjects, the remaining 42 (22%) individuals received an extracardiac (EC)-ICD system. During mean follow-up of 4.5 years appropriate ICD shocks were noted in 32 (16%) individuals, whereas inappropriate shocks occurred in 22 (11%) patients. Appropriate shocks were more frequent in patients with an EC-ICD than in individuals with transvenous systems (29% vs. 13%, P = 0.02). Rapidly conducted atrial tachycardia (AT) was the most common reason for inappropriate shocks (76%). Rate of inappropriate shocks was not different between EC and transvenous systems (12% vs. 11%, P = 0.26). Lead failure was more prevalent in subjects with an EC-ICD (29% vs. 7%, P = 0.001). Individuals with EC-ICD systems were particularly prone to experience appropriate shocks. As rapidly conducted AT was the most common reason for inappropriate ICD shocks, rigorous treatment of these arrhythmias and proper ICD programming are mandatory. Though lead failure was of concern in EC-ICD patients, EC-ICD systems were not inferior with respect to inappropriate shocks.

Impacts of Acute Changes in Air Pollution on Discharges from Implantable Cardioverter Defibrillators in Ontario, Canada

Background: Acute changes in pollution have been associated with cardiac morbidity and mortality. Air pollution might impact cardiac morbidity and mortality through precipitation of cardiac arrhythmia in susceptible individuals. Despite gradual improvement in air quality over the past decades in North America, the links between days of higher pollution and cardiovascular morbidity and mortality still exist. This suggests that further research, at lower levels of ambient air pollution is warranted. The objective of this study is to examine the influence of acute changes in air pollution in Ontario, Canada on the frequency of discharges from implantable cardioverter defibrillators (ICDs) in response to cardiac arrhythmias.Methods: Using a case-crossover design, we compared ambient air pollution concentrations on the day of an ICD discharge to other days in the same month and year in 10320 patients with ICDs. We adjusted for weather, lagged the data from 0 to 3 days, and stratified the results by several patient-related characteristics.Results: Median (interquartile range) for SO2, NO2, ozone and PM2.5, were 1.0 ppb (0.4, 2.1), 10.0 ppb (6.0, 15.3), 26.0 ppb (19.4, 33.0) and 6.6 µg/m3 (4.3,10.6) respectively. Odds ratios (95%CI) for an ICD discharge associated with an IQR increase in pollutant were 1.0 (0.91, 1.0) for SO2, 1.0 (0.9, 1.1) for NO2, 1.0 (0.9,1.1) for ozone, and 1.0 (0.9, 1.1) for PM2.5.Conclusion: Small day to day changes in air pollution at the relatively low levels seen in our study did not appear to be a risk factor for cardiac arrhythmias in patients with ICDs.

Assessment of baroreflex sensitivity has no prognostic value in contemporary, optimally managed patients with mild-to-moderate heart failure with reduced ejection fraction: a retrospective analysis of 5-year survival.

We evaluated the prognostic value of cardiac baroreflex sensitivity (BRS) in contemporary, optimally treated patients with mild-to-moderate heart failure with reduced ejection fraction (HFrEF). Data from 97 patients with HFrEF (left ventricular ejection fraction 32 ± 6%, all receiving angiotensin-converting enzyme inhibitor/angiotensin receptor blocker and beta-blocker, 85% receiving aldosterone antagonist) were analysed retrospectively. All patients underwent standard clinical assessment, cardiopulmonary exercise testing and BRS evaluation with three methods: the phenylephrine (BRS-Phe), the sequence (BRS-Seq) and the controlled breathing (BRS-CtrBr) method. Data on 5-year all-cause mortality and appropriate and documented implantable cardioverter-defibrillator (ICD) discharges were collected. During a mean follow-up of 53 ± 15 months, the composite endpoint of all-cause death and appropriate and documented ICD discharge occurred in 31 (32%) patients. BRS measures assessed using all three methods were not related to survival in univariate Cox proportional hazards analyses (all P >0.25). There were also no differences in survival between low vs. preserved BRS groups, irrespective of the method used for BRS assessment (all P ≥0.15). BRS-Phe correlated with several clinically important variables (including left ventricular ejection fraction: rS = 0.27, and peak oxygen consumption: rS = 0.32, both P < 0.05), while clinical associations of BRS-Seq and BRS-CtrBr were sparse. Assessment of cardiac BRS provides no prognostic information in the contemporary mild-to-moderate HFrEF population receiving optimal management.