Circadian Rhythm of Appropriate Implantable Cardioverter Defibrillator Discharges in Patients with Hypertrophic Cardiomyopathy

Effect of beta-blockers and exercise restriction on the prevention of sudden cardiac death in pediatric hypertrophic cardiomyopathy

BACKGROUND

Risk assessment tools and effective prevention strategies for sudden cardiac death (SCD) in pediatric patients with hypertrophic cardiomyopathy (HCM) have not been established. This study aimed to evaluate the efficacy of beta-blockers and exercise restriction for SCD prevention in this population.

METHODS

We retrospectively reviewed the medical records of patients aged <18 years who were diagnosed with HCM at our center between January 1996 and December 2021. SCD and aborted SCD were defined as SCD equivalents. We divided patients based on whether they were prescribed beta-blockers or exercise restriction and compared the outcomes among the groups. The primary outcome was the overall survival (OS), and the secondary outcome was the cumulative SCD equivalent rate. Outcomes were analyzed using Kaplan-Meier curves and Cox proportional hazard analysis. We also compared patients according to the occurrence of SCD equivalents to identify SCD risk predictors.

RESULTS

Among the 43 included patients [mean age, 7.7 (1.6-12.1) years; 23 male individuals], SCD equivalents occurred in 13 patients over 11.2 (4.5-15.6) years of follow-up, among whom 12 were resuscitated and 1 died. The OS rate was significantly higher in the beta-blocker and exercise restriction groups than in the non-beta-blocker and non-exercise restriction groups (81.3 % vs. 19.1 %, p < 0.01 and 57.4 % vs. 12.7 %, p < 0.01, respectively). Among the 13 patients with SCD equivalents, 5 had 9 recurrent SCD equivalents. A significant difference was observed between the SCD equivalent and non-SCD equivalent groups in the history of suspected arrhythmogenic syncope (p < 0.01) in the univariable but not in the multivariable analysis.

CONCLUSIONS

Beta-blockers and exercise restriction may decrease the risk of SCD in pediatric patients with HCM and should be considered for SCD prevention in this population, particularly because predicting SCD in these patients remains challenging.

Circadian and Seasonal Pattern of Arrhythmic Events in Arrhythmogenic Cardiomyopathy Patients

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited cardiac disease associated with an increased risk of life-threatening arrhythmias. The aim of the present study was to evaluate the association of ventricular arrhythmias (VA) with circadian and seasonal variation in ARVC. One hundred two ARVC patients with an implantable cardioverter defibrillator (ICD) were enrolled in the study. Arrhythmic events included (a) any initial ventricular tachycardia (VT) or fibrillation (VF) prompting ICD implantation, (b) any VT or non-sustained VT (NSVT) recorded by the ICD, and (c) appropriate ICD shocks/therapy. Differences in the annual incidence of events across seasons (winter, spring, summer, autumn) and period of the day (night, morning, afternoon, evening) were assessed both for all cardiac events and major arrhythmic events. In total, 67 events prior to implantation and 263 ICD events were recorded. These included 135 major (58 ICD therapies, 57 self-terminating VT, 20 sustained VT) and 148 minor (NSVT) events. A significant increase in the frequency of events was observed in the afternoon versus in the nights and mornings (p = 0.016). The lowest number of events was registered in the summer, with a peak in the winter (p < 0.001). Results were also confirmed when excluding NSVT. Arrhythmic events in ARVC follow a seasonal variation and a circadian rhythm. They are more prevalent in the late afternoon, the most active period of the day, and in the winter, supporting the role of physical activity and inflammation as triggers of events.

Arrhythmia in chronic hemodialysis as a function of predialysis electrolytes and interdialytic interval

INTRODUCTION

People with end-stage renal disease on hemodialysis are at increased risk for death due to arrhythmia associated with the prolonged interdialytic interval that typically spans the weekend, with bradycardia being the arrhythmia most closely associated with sudden death. In this prospective observational study we assessed whether predialysis fluid and electrolytes values including hyperkalemia are risk factors for the arrhythmias associated with the prolonged interdialytic interval.

METHODS

Sixty patients on hemodialysis with a history of hyperkalemia underwent cardiac monitoring for 1 week. Arrhythmia frequency, average QTc interval, and average root mean square of successive differences (rMSSD) per 4-h period were reported. Predialysis electrolytes and electrocardiograms were collected prior to pre- and post-weekend dialysis sessions. Clinical variables were assessed for correlation with arrhythmias.

FINDINGS

Predialysis hyperkalemia occurred in 29 subjects and was more common at the post-weekend dialysis session. Bradycardia occurred in 11 subjects and increased before and during the post-weekend dialysis session, but was not correlated with any electrolyte or clinical parameter. Ventricular ectopy occurred in 50 subjects with diurnal variation unrelated to dialysis. Pre-dialysis prolonged QTc was common and not affected by interdialytic interval. Average QTc increased and rMSSD decreased during dialysis sessions and were not correlated with clinical parameters.

DISCUSSION

The results confirm that arrhythmias are prevalent in dialysis subjects with bradycardia particularly associated with the longer interdialytic interval; EKG markers of arrhythmia risk are increased during dialysis independent of interdialytic interval. Larger sample size and/or longer recording may be necessary to identify the clinical parameters responsible.

Evolution of risk stratification and sudden death prevention in hypertrophic cardiomyopathy: Twenty years with the implantable cardioverter-defibrillator

Hypertrophic cardiomyopathy (HCM) is a relatively common inherited myocardial disorder, once regarded as largely untreatable with ominous prognosis and most visibly as a common cause of sudden death (SD) in the young. Over the last several years, HCM has been transformed into a contemporary treatable disease with management options that significantly alter clinical course. With the use of implantable cardioverter-defibrillators (ICDs) in the HCM patient population, a new paradigm has emerged, with primary prevention device therapy reliably terminating potentially lethal ventricular tachyarrhythmias (3%-4% per year) and being largely responsible for a >10-fold decrease in disease-related mortality (to 0.5% per year), independent of age. An evidenced-based and guideline directed clinical risk stratification algorithm has evolved, including variables identified with cardiac magnetic resonance. One or more risk markers judged major and relevant within a patient's clinical profile can be considered sufficient to recommend a primary prevention implant (associated with a measure of physician judgment and shared decision-making). ICD decisions using the prospective individual risk marker strategy have been associated with 95% sensitivity for identifying patients who subsequently experienced appropriate ICD therapy, (albeit often delayed substantially for >5 or >10 years after implant), but without heart failure deterioration or HCM death following device intervention. A rigid mathematically derived statistical risk model proposed by the European Society of Cardiology is associated with low sensitivity (ie, 33%) for predicting SD events. Introduction of prophylactically inserted ICDs to HCM 20 years ago has significantly altered the clinical course and landscape of this disease. SD prevention has reduced HCM mortality significantly, making preservation of life and the potential for normal longevity a reality for most patients.

Enhanced American College of Cardiology/American Heart Association Strategy for Prevention of Sudden Cardiac Death in High-Risk Patients With Hypertrophic Cardiomyopathy

Importance

Strategies for reliable selection of high-risk patients with hypertrophic cardiomyopathy (HCM) for prevention of sudden cardiac death (SCD) with implantable cardioverter/defibrillators (ICDs) are incompletely resolved.

Objective

To assess the reliability of SCD prediction methods leading to prophylactic ICD recommendations to reduce the number of SCDs occurring in patients with HCM.

Design, Setting, and Participants

In this observational longitudinal study, 2094 predominantly adult patients with HCM consecutively evaluated over 17 years in a large HCM clinical center were studied. All patients underwent prospective ICD decision making relying on individual major risk markers derived from the HCM literature and an enhanced American College of Cardiology/American Heart Association (ACC/AHA) guidelines-based risk factor algorithm with complete clinical outcome follow-up. Data were collected from June 2017 to February 2018, and data were analyzed from February to July 2018.

Main Outcomes and Measures

Arrhythmic SCD or appropriate ICD intervention for ventricular tachycardia or ventricular fibrillation.

Results

Of the 2094 study patients, 1313 (62.7%) were male, and the mean (SD) age was 51 (17) years. Of 527 patients with primary prevention ICDs implanted based on 1 or more major risk markers, 82 (15.6%) experienced device therapy-terminated ventricular tachycardia or ventricular fibrillation episodes, which exceeded the 5 HCM-related SCDs occurring among 1567 patients without ICDs (0.3%), including 2 who declined device therapy, by 49-fold (95% CI, 20-119; P = .001). Cumulative 5-year probability of an appropriate ICD intervention was 10.5% (95% CI, 8.0-13.5). The enhanced ACC/AHA clinical risk factor strategy was highly sensitive for predicting SCD events (range, 87%-95%) but less specific for identifying patients without SCD events (78%). The C statistic calculated for enhanced ACC/AHA guidelines was 0.81 (95% CI, 0.77-0.85), demonstrating good discrimination between patients who did or did not experience an SCD event. Compared with enhanced ACC/AHA risk factors, the European Society of Cardiology risk score retrospectively applied to the study patients was much less sensitive than the ACC/AHA criteria (34% [95% CI, 22-44] vs 95% [95% CI, 89-99]), consistent with recognizing fewer high-risk patients.

Conclusions and Relevance

A systematic enhanced ACC/AHA guideline and practice-based risk factor strategy prospectively predicted SCD events in nearly all at-risk patients with HCM, resulting in prophylactically implanted ICDs that prevented many catastrophic arrhythmic events in this at-risk population.

Paradigm of Sudden Death Prevention in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a worldwide genetic heart disease and a common cause of sudden death in the young. Penetration of the implantable cardioverter-defibrillator (ICD) into this patient population over the past 20 years has made accurate selection of patients for primary prevention ICDs a priority. Consequently, a new paradigm has emerged in the management of this complex disease with ICD therapy responsible for a substantial decrease in overall HCM-related mortality (to 0.5%/y) and independent of patient age. Selection of candidates for ICDs has matured substantially with the formulation of an enhanced risk stratification algorithm. One or more contemporary risk markers judged major within a given patient’s clinical profile, in association with physician judgment and shared decision-making, is sufficient to consider a primary prevention ICD implant. An enhanced American College of Cardiology/American Heart Association risk factor model (including new contrast-magnetic resonance–based markers, such as left ventricular apical aneurysm) used prospectively to make ICD decisions proved to be 95% sensitive for identifying patients who would experience ≥1 appropriate device therapies terminating ventricular tachycardia/fibrillation. The number of HCM patients required to treat with ICDs to save 1 patient with abolition of lethal ventricular tachyarrhythmias was 6:1, similar to randomized defibrillator trials in other cardiomyopathies. In contrast to patients with ischemic heart disease, after ICD shock HCM patients rarely experience transformation to heart failure deterioration or sudden arrhythmic death. The mathematically derived risk score model proposed by the European Society of Cardiology was inferior for identifying high-risk patients susceptible to arrhythmic sudden death with a sensitivity of only 33%, leaving many patients exposed to the possibility of sudden death without ICDs. In conclusion, introduction of the ICD associated with a matured risk stratification algorithm has altered management strategy and clinical course of many HCM patients, making the likelihood of sudden death prevention a reality and fulfilling the aspiration of preservation of life and reduced mortality for this vulnerable patient population.

Prevention of sudden death in hypertrophic cardiomyopathy: bridging the gaps in knowledge

Sudden cardiac death (SCD) is the most devastating complication of hypertrophic cardiomyopathy (HCM). Although the annual rate of SCD in the general HCM population is <1% per year according to contemporary series, there is still a small subset of patients who are at increased risk of SCD. The greatest challenge in the management of HCM is identifying those at increased risk as an implantable cardioverter defibrillator is a potentially life-saving therapy. In this review, we sought to summarize the available data on SCD in HCM and provide a clinical perspective on the current differing and somewhat conflicting European and American recommendations on risk stratification, with balanced guidance with regards to rational clinical decision making. Additionally, we sought to learn more on the actual implementation of the guidelines by HCM experts worldwide.

Circadian Variation of Ventricular Arrhythmias in Catecholaminergic Polymorphic Ventricular Tachycardia

OBJECTIVES

The aim of this paper was to investigate whether ventricular arrhythmias in children with catecholaminergic polymorphic ventricular tachycardia (CPVT) show circadian patterns.

BACKGROUND

Circadian arrhythmic patterns have been established in long QT, Brugada, and early repolarization, but have not been investigated in CPVT.

METHODS

This is a multicenter, retrospective review of pediatric CPVT patients, age <21 years at diagnosis. Timing of ventricular tachycardia (VT ≥3 beats) was assessed during 24-h continuous monitoring (Holter, implantable loop recorder, implantable cardioverter defibrillator) and by eliminating sleep hours, in addition to sporadic exercise stress tests. Morning was defined as 6:00 am to 11:59 am, afternoon 12:00 pm to 5:59 pm, and evening 6:00 pm to 11:59 pm. Distribution of VT events was compared by time of day, day of week, age, and sex.

RESULTS

Eighty patients (53% male), 61% with an ICD, experienced 423 VT events during a median follow-up time of 6 years (interquartile range: 2 to 10 years). When compared to morning hours, VT was more likely to occur in the afternoon (odds ratio [OR]: 2.54; 95% confidence interval [CI]: 1.69 to 3.83) or evening hours (OR: 2.91; 95% CI: 1.82 to 4.67). The predominance of afternoon/evening events persisted regardless of age, gender, or day of the week. Among 50 patients who underwent exercise stress tests, VT was significantly more likely to occur in the afternoon (OR: 3.00; 95% CI: 1.39 to 6.48).

CONCLUSIONS

In pediatric CPVT patients, ventricular arrhythmias are more likely to occur in the afternoon and evening hours. Because children's activity levels peak in both the morning and afternoon, the lack of arrhythmias in the morning hours raises questions whether factors other than adrenergic stimulation influence arrhythmia induction in pediatric patients with CPVT.

Contemporary strategies for risk stratification and prevention of sudden death with the implantable defibrillator in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is regarded as the most common nontraumatic cause of sudden death (SD) in young people (including trained athletes). Introduction of implantable cardioverter-defibrillators (ICD) to HCM 15 years ago represented a new paradigm for clinical practice and probably the most significant advance in management of this disease. ICDs offer protection against SD by terminating potentially lethal ventricular tachyarrhythmias (11%/year secondary and 4%/year primary prevention), although implant decisions are weighed against the possibility of device-related complications (5%/year). ICDs have altered the natural history of HCM, creating the opportunity for extended or normal longevity for many patients. However, assessing SD risk and targeting appropriate candidates for prophylactic device therapy can be compounded by unpredictability of the underlying arrhythmogenic substrate, evident by delays ≥10 years between implant and first ICD intervention. Multiple or a single strong risk marker within the clinical profile of an individual HCM patient can justify consideration for a primary-prevention ICD when combined with physician judgment and shared decision making. The role of the mathematical SD risk score proposed by the European Society of Cardiology to identify patients who benefit from ICD therapy is incompletely resolved. Contemporary treatment interventions and advanced risk stratification using ≥1 conventional markers have served the HCM patient population well, with reduced disease-related mortality rates across all age groups to <1%/year, due largely to the penetration of ICDs into HCM practice. Prevention of SD has now become an integral, albeit challenging, component of HCM management, contributing importantly to its emergence as a contemporary treatable cardiac disease.

Hypertrophic cardiomyopathy and sudden cardiac death

Hypertrophic cardiomyopathy (HCM) is a common genetic cardiovascular disease that affects the left ventricle. HCM can appear at any age, with the majority of the patients remaining clinically stable. When patients complain of symptoms, these include: dyspnea, dizziness, syncope and angina. HCM can lead to sudden cardiac death (SCD), mainly due to ventricular tachyarrhythmia or ventricular tachycardia. High-risk patients benefit from implantable cardioverter-defibrillators. Left ventricular outflow tract obstruction is not a rare feature in HCM, especially in symptomatic patients, and procedures that abolish that obstruction provide positive and consistent results that can improve long-term survival. HCM is the most common cause of sudden death in young competitive athletes and preparticipation screening programs have to be implemented to avoid these tragic fatalities. The structure of these programs is a matter of large debate. Worldwide registries are necessary to identify the full extent of HCM-related SCD.

Sudden death in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is regarded as the most common cause of sudden cardiac death in young people (including trained athletes). However, assessing sudden death (SD) risk and identifying the most appropriate candidates for prophylactic device therapy is a complex process compounded by the unpredictability of the underlying arrhythmogenic substrate, absence of a single dominant and quantitative risk maker for this heterogeneous disease, and also the difficulty encountered in assembling sufficiently powered prospective and randomized trials in large patient populations. Patients with multiple risk factors and most young patients with one strong and unequivocal risk marker can be considered candidates for primary prevention defibrillators. Despite certain limitations, the current risk factor algorithm (when combined with a measure of individual physician judgment) has proved to be an effective strategy for targeting high-risk status. This approach has served the HCM patient population well, as evidenced by the significant appropriate defibrillator intervention rates, although a very small proportion of patients without conventional risk factors may also be at risk for SD. Indeed, the introduction of implantable defibrillators to the HCM patient population represents a new paradigm for clinical practice, offering the only proven protection against SD by virtue of effectively terminating ventricular tachycardia/fibrillation. In the process, implantable defibrillators have altered the natural history of HCM, potentially providing the opportunity of normal or near-normal longevity for many patients. Prevention of SD is now an integral, albeit challenging, component of HCM management.