Long-term outcomes in young patients with atrioventricular block of unknown aetiology

Late outcomes of congenital and childhood non-immune, isolated atrioventricular block: a French nationwide retrospective cohort study

AIMS

The natural history of congenital or childhood non-immune, isolated atrioventricular block (AVB) is poorly defined. We aimed at clarifying its long-term outcomes.

METHODS AND RESULTS

We retrospectively studied 385 children with isolated, non-immune AVB diagnosed from in utero or up to 18 years of age, at 29 French medical centres, between 1980 and 2022. Patients with structural heart disease, endomyocardial fibrosis, or maternal antibodies were excluded. Atrioventricular block was asymptomatic in 314 (81.6%) and complete in 263 (68.3%) patients at the time of diagnosis. There was progression to complete AVB in 84/122 (68.8%) patients with incomplete AVB over 12 years (7-17). A total of 286/385 patients (74.3%) received a permanent pacemaker, implanted in the first year of life in 39 (14%) and before 10 years of age in 172 (60%) children. The pacing indication was prophylactic in 203 children (71%). Genetic screening was performed in 133/385 patients (34.5%), leading to the identification of a clinically actionable variant in 11 (8.3%) patients. After a median follow-up of 10 years (5-17), no patient died or developed endomyocardial fibrosis or dilated cardiomyopathy.

CONCLUSION

In this large nationwide study, the long-term outcome of congenital or childhood non-immune, isolated AVB was excellent. Most children required pacemaker implantation over time, albeit often as a prophylactic measure.

Associations between cardiac arrhythmias and cardiovascular disease incidence and all-cause mortality: the Kailuan study

AIMS

Cardiac arrhythmia is a rising public health issue. The aim of this study was to determine the associations of atrial fibrillation (AF) and heart block with cardiovascular disease (CVD) incidence and all-cause mortality.

METHODS AND RESULTS

We included 141,362 participants (mean age [49.3], 80.9% men) from the Kailuan study. Arrhythmias were diagnosed through a 12-lead electrocardiograph (ECG). Mortality and CVD events were ascertained through multiple sources, including a municipal social insurance institution, hospital records, death certificates, and regular active follow-ups. During a median follow-up of 12.5 years, 18,301 total deaths and 13,208 cases of CVD were documented. The multivariable-adjusted hazard ratios (HRs) with 95% confidence intervals (CIs) comparing participants with AF to those without arrhythmia were 1.76 (1.61-1.93) for all-cause mortality, 2.11 (1.86-2.39) for CVD, 3.99 (3.33-4.79) for heart failure, and 1.56 (1.30-1.90) for stroke. Further, comparing participants with heart block to those without arrhythmia, the multivariable-adjusted HRs (95% CIs) were 1.31 (1.24-1.38) for all-cause mortality, 1.26 (1.18-1.35) for CVD, 1.40 (1.23-1.59) for heart failure, and 1.25 (1.15-1.37) for stroke. Additionally, there were generally stronger associations for AF and heart block with all-cause mortality and CVD in younger participants compared with their older counterparts (Ps-interaction ≤ 0.02) and a stronger association between AF and CVD in women compared with men (Ps-interaction ≤ 0.006).

CONCLUSION

AF and heart block were associated with a higher risk of subsequent adverse CVD events and mortality. Our findings highlight the importance of strategies for preventing cardiac arrhythmias to reduce the risk of CVD and mortality.

Rare Genetic Variants in Young Adults Requiring Pacemaker Implantation

BACKGROUND

Genetic disease has recently emerged as a cause of cardiac conduction disorders (CCDs), but the diagnostic yield of genetic testing and the contribution of the different genes to CCD is still unsettled.

OBJECTIVES

This study sought to determine the diagnostic yield of genetic testing in young adults with CCD of unknown etiology requiring pacemaker implantation. We also studied the prevalence of rare protein-altering variants across individual genes and functional gene groups.

METHODS

We performed whole exome sequencing in 150 patients with CCD of unknown etiology who had permanent pacemaker implanted at age ≤60 years at 14 Spanish hospitals. Prevalence of rare protein-altering variants in patients with CCD was compared with a reference population of 115,522 individuals from gnomAD database (control subjects).

RESULTS

Among 39 prioritized genes, patients with CCD had more rare protein-altering variants than control subjects (OR: 2.39; 95% CI: 1.75-3.33). Significant enrichment of rare variants in patients with CCD was observed in all functional gene groups except in the desmosomal genes group. Rare variants in the nuclear envelope genes group exhibited the strongest association with CCD (OR: 6.77; 95% CI: 3.71-13.87). Of note, rare variants in sarcomeric genes were also enriched (OR: 1.73; 95% CI: 1.05-3.10). An actionable genetic variant was detected in 21 patients (14%), with LMNA being the most frequently involved gene (4.6%).

CONCLUSIONS

Unrecognized rare genetic variants increase the risk of CCD in young adults with CCD of unknown etiology. Genetic testing should be performed in patients age ≤60 years with CCD of unknown etiology. The role of genetic variants in sarcomeric genes as a cause of CCD should be further investigated.

Prevalence of atrial fibrillation in ischemic stroke and associated risk factors: A hospital-based study in Indonesia

CONTEXT

The prevalence of ischemic stroke increases each year. One such important factor is the presence of atrial fibrillation (AF), but data regarding this are scarce in Indonesia.

AIMS

This study aimed to understand the prevalence of AF in ischemic stroke and its associated risk factors.

SETTINGS AND DESIGN

A cross-sectional study was conducted from January 2021 to 2023 in Fatima Hospital, through medical records.

SUBJECTS AND METHODS

Subjects were ischemic stroke patients aged ≥18 years. Additional data included demographic characteristics, congestive heart failure (CHF), hypertension, diabetes mellitus, stroke history, vascular disease, AF, dyslipidemia, Glasgow Coma Scale, and anticoagulant usage.

STATISTICAL ANALYSIS USED

Data were analyzed using Chi-square, Fisher, Student's t-test, Mann-Whitney, and logistic regression.

RESULTS

Out of 148 subjects, AF was detected in 16 (10.8%). Among these, 14 (87.5%) had a CHA2DS2-VASc score of ≥2 and were given anticoagulant therapy. A higher proportion of subjects aged over 75 years was observed in the AF group (31.2% vs. 3.8%; P < 0.001). A similar pattern was seen with CHF and dyslipidemia (CHF: 56.3% vs. 8.3%; P < 0.000; dyslipidemia: 93.7% vs. 58.3%; P < 0.005). CHF and dyslipidemia increased the risk of AF by 27-fold (P = 0.001, odds ratio [OR]: 27.400) and 21-fold (P = 0.013, OR: 21.812), respectively.

CONCLUSIONS

These findings underscore the importance of vigilant screening for AF in ischemic stroke, particularly in patients with CHF and dyslipidemia, to guide appropriate anticoagulation therapy and reduce the risk of recurrent stroke. This study was limited by its single-center design and small sample size. A larger, multicenter study is recommended.

Cardiac conduction disorders in young adults: Clinical characteristics and genetic background of an underestimated population

BACKGROUND

Cardiac conduction disorder (CCD) in patients <50 years old is a rare and mostly unknown condition.

OBJECTIVE

We aimed to assess clinical characteristics and genetic background of patients <50 years old with CCD of unknown origin.

METHODS

We retrospectively reviewed a consecutive series of patients with a diagnosis of CCD before the age of 50 years referred to our center between January 2019 and December 2021. Patients underwent complete clinical examination and genetic evaluation.

RESULTS

We enrolled 39 patients with a median age of 40 years (28-47 years) at the onset of symptoms. A cardiac implantable electronic device was implanted in 69% of the patients. In 15 of 39 CCD index patients (38%), we found a total of 13 different gene variations (3 pathogenic, 6 likely pathogenic, and 4 variants of uncertain significance), mostly in 3 genes (SCN5A, TRPM4, and LMNA). In our cohort, genetic testing led to the decision to implant an implantable cardioverter-defibrillator in 2 patients for the increased risk of sudden cardiac death.

CONCLUSION

Patients with the occurrence of CCD before the age of 50 years present with a high rate of pathologic gene variations, mostly in 3 genes (SCN5A, TRPM4, and LMNA). The presence of pathogenic variations may add information about the prognosis and lead to an individualized therapeutic approach.

Frequency of Electrocardiogram-Defined Cardiac Conduction Disorders in a Multi-Institutional Primary Care Cohort

Background

Disorders affecting cardiac conduction are associated with substantial morbidity. Understanding the epidemiology and risk factors for conduction disorders may enable earlier diagnosis and preventive efforts.

Objectives

The purpose of this study was to quantify contemporary frequency and risk factors for electrocardiogram (ECG)-defined cardiac conduction disorders in a large multi-institutional primary care sample.

Methods

We quantified prevalence and incidence of conduction disorders among adults receiving longitudinal primary care between 2001 and 2019, each with at least one 12-lead ECG performed prior to the start of follow-up and at least one ECG during follow-up. We defined conduction disorders using curated terms extracted from ECG diagnostic statements by cardiologists. We grouped conduction disorders by inferred anatomic location of abnormal conduction. We tested associations between clinical factors and incident conduction disease using multivariable proportional hazards regression.

Results

We analyzed 189,163 individuals (median age 55 years; 58% female). The overall prevalence of conduction disorders was 27% among men and 15% among women. Among 119,926 individuals (median age 55 years; 51% female), 6,802 developed an incident conduction system abnormality over a median of 10 years (Q1, Q3: 6, 15 years) of follow-up. Incident conduction disorders were more common in men (8.78 events/1,000 person-years) vs women (4.34 events/1,000 person-years, P < 0.05). In multivariable models, clinical factors including older age (HR: 1.25 per 5-year increase [95% CI: 1.24-1.26]) and myocardial infarction (HR: 1.39 [95% CI: 1.26-1.54]) were associated with incident conduction disorders.

Conclusions

Cardiac conduction disorders are common in a primary care population, especially among older individuals with cardiovascular risk factors.

Advanced Atrioventricular Block in Athletes: Prevalence and Role of Anti-Ro/Sjögren Syndrome-Related Antigen A Antibodies

BACKGROUND

Advanced atrioventricular block (AVB), that is, higher than second-degree Mobitz-1, is an abnormal finding in athletes. Despite intensive investigation, in several cases the pathogenesis remains unknown, but frequently pacemaker implantation is still indicated. Increasing evidence points to circulating anti-Ro/Sjögren syndrome-related antigen A (SSA) antibodies cross-reacting with L-type calcium channel and inhibiting the related current as an epidemiologically relevant and potentially reversible cause of isolated AVB in adults. The aim of the study was to determine the prevalence of anti-Ro/SSA-associated advanced AVBs in a large sample of young athletes.

METHODS AND RESULTS

A total of 2536 consecutive athletes aged <40 years without a history of cardiac diseases/interventions were enrolled in a cross-sectional study. Resting and exercise electrocardiography was performed, and those presenting any AVB were further evaluated by 24-hour Holter ECG. Athletes with second-degree AVBs and their mothers underwent anti-Ro/SSA testing. Moreover, purified immunoglobulin G from subjects with anti-Ro/SSA-positive and anti-Ro/SSA-negative advanced AVB were tested on L-type calcium current and L-type-calcium channel expression using tSA201 cells. The global prevalence of advanced AVB in the overall sample was ≈0.1%, but the risk considerably increased (2%) when intensely trained postpubertal male subjects were selectively considered. While none of the athletes with advanced AVB showed heart abnormalities, in 100% of cases anti-Ro/SSA antibodies were detected. Ex vivo experiments showed that immunoglobulin G from anti-Ro/SSA-positive but not -negative subjects with advanced AVB acutely inhibit L-type calcium current and chronically downregulate L-type-calcium channel expression.

CONCLUSIONS

Our study provides evidence that advanced AVB occurs in young athletes, in most cases associated with anti-Ro/SSA antibodies blocking L-type calcium channels. These findings may open new avenues for immunomodulating therapies to reduce the risk of life-threatening events in athletes, avoiding or delaying pacemaker implantation.

High prevalence and distinctive clinical features of LMNA-associated atrioventricular block in young patients

BACKGROUND AND AIMS

Atrioventricular block (AVB) is a degenerative disease and more commonly encountered in elderly patients, but unusual and often of unknown etiology in young patients. This study aimed to investigate the potential contributions of genetic variations to AVB of unknown reasons in young patients.

METHODS

We enrolled 41 patients aged <55 years with high-degree AVB of unknown etiology whose clinical and genetic data were collected.

RESULTS

Genetic variants were identified in 20 (20/41, 48.8%) patients, 11 (11/20, 55%) of whom had LMNA variants including 3 pathogenic (c.961C > T, c.936+1G > T and c.646C > T), 4 likely pathogenic (c.1489-1G > C, c.265C > A, c.1609-2A > G and c.1129C > T) and 3 of uncertain significance (c.1158-3C > G, c.776A > G and c.674G > T). Compared to those without LMNA variants, patients with LMNA variants demonstrated a later age at onset of AVB (41.45 ± 9.89 years vs 32.93 ± 12.07 years, P = .043), had more prevalent family history of cardiac events (81.8% vs 16.7%, P < .000), suffered more frequently atrial (81.8% vs 10.0%, P < .000) and ventricular (72.7% vs 10.0%, P < .000) arrhythmias, and were more significantly associated with enlargement of left atrium (39.91 ± 7.83 mm vs 34.30 ± 7.54 mm, P = .043) and left ventricle (53.27 ± 8.53 mm vs 47.77 ± 6.66 mm, P = .036).

CONCLUSIONS

Our findings provide insights into the genetic etiology of AVB in young patients. LMNA variants are predominant in genotype positive patients and relevant to distinctive phenotypic properties.

Echocardiographic mechanical dyssynchrony predicts long-term mortality in patients with cardiac resynchronisation therapy

Cardiac resynchronisation therapy (CRT) is an established treatment for patients with symptomatic heart failure with reduced left ventricular ejection fraction (LVEF ≤ 35%; HFrEF) and conduction disturbances (QRS duration ≥ 130 ms). The presence of mechanical dyssynchrony (MD) on echocardiography has been hypothesised to be of predictive value in determining indication for CRT. This study investigated the impact of MD (apical rocking [AR] and septal flash [SF]) on long-term survival in CRT recipients. HFrEF patients (n = 425; mean age 63.0 ± 10.6 years, 72.3% male, 60.7% non-ischaemic aetiology) with a guideline-derived indication for CRT underwent device implantation. MD markers were determined at baseline and after a mean follow-up of 11.5 ± 8.0 months; long-term survival was also determined. AR and/or SF were present in 307 (72.2%) participants at baseline. During post-CRT follow-up, AR and/or SF disappeared in 256 (83.4%) patients. Overall mean survival was 95.9 ± 52.9 months, longer in women than in men (109.1 ± 52.4 vs. 90.9 ± 52.4 months; p < 0.001) and in younger (< 60 years) versus older patients (110.6 ± 53.7 vs. 88.6 ± 51.1 months; p < 0.001). Patients with versus without MD markers at baseline generally survived for longer (106.2 ± 52.0 vs. 68.9 ± 45.4 months; p < 0.001), and survival was best in patients with resolved versus persisting MD (111.6 ± 51.2 vs. 79.7 ± 47.6 months p < 0.001). Age and MD at baseline were strong predictors of long-term survival in HFrEF patients undergoing CRT on multivariate analysis. Novel echocardiography MD parameters in HFrEF CRT recipients predicted long-term mediated better outcome, and survival improved further when AR and/or SF disappear after CRT implantation.

Imaging in patients with cardiovascular implantable electronic devices: part 1-imaging before and during device implantation. A clinical consensus statement of the European Association of Cardiovascular Imaging (EACVI) and the European Heart Rhythm Association (EHRA) of the ESC

More than 500 000 cardiovascular implantable electronic devices (CIEDs) are implanted in the European Society of Cardiology countries each year. The role of cardiovascular imaging in patients being considered for CIED is distinctly different from imaging in CIED recipients. In the former group, imaging can help identify specific or potentially reversible causes of heart block, the underlying tissue characteristics associated with malignant arrhythmias, and the mechanical consequences of conduction delays and can also aid challenging lead placements. On the other hand, cardiovascular imaging is required in CIED recipients for standard indications and to assess the response to device implantation, to diagnose immediate and delayed complications after implantation, and to guide device optimization. The present clinical consensus statement (Part 1) from the European Association of Cardiovascular Imaging, in collaboration with the European Heart Rhythm Association, provides comprehensive, up-to-date, and evidence-based guidance to cardiologists, cardiac imagers, and pacing specialists regarding the use of imaging in patients undergoing implantation of conventional pacemakers, cardioverter defibrillators, and resynchronization therapy devices. The document summarizes the existing evidence regarding the use of imaging in patient selection and during the implantation procedure and also underlines gaps in evidence in the field. The role of imaging after CIED implantation is discussed in the second document (Part 2).

A retrospective audit of young adults who received permanent pacemakers at a teaching hospital in the Western Cape, South Africa

Introduction

While most pacemaker implantations occur in older individuals, younger patients also receive pacemakers. In these, degenerative conduction system disease is less likely to be the cause of atrioventricular block (AVB), with other diseases being more common. There is, however, a paucity of data on this group as well as on younger pacemaker recipients that have undergone pacemaker implantation for reasons other than AVB. The aim of this study was to perform an audit of young adult permanent pacemaker recipients.

Method

This was a retrospective record review, conducted in the Division of Cardiology at Tygerberg Hospital, Cape Town, South Africa. We included 169 adult patients between the ages of 18 and 60, who received permanent pacemakers between 2010 and 2020. A subgroup analysis of patients 55 years and younger was also performed.

Results

Third degree AVB was the most common indication for pacemaker implantation (n = 115; 68%), followed by high degree AVB (n = 23; 13.6%) and sick sinus syndrome (SSS; n = 14; 8.3%). A specific underlying cause for conduction system abnormalities was found in only 25.4% of patients (n = 43), with most of them being 55 years or younger (n = 32; 30.8% of patients ≤ 55 years). Specific causes that were identified included prosthetic valve implantation and/or valve repair (n = 14; 8.3%), myocardial infarction (n = 6; 3.6%), cardiac sarcoidosis (n = 5; 3.0%), coronary artery bypass grafting (n = 3; 1.8%), cardiomyopathy (n = 2; 1.2%), muscular dystrophy (n = 2; 1.2%), congenital heart disease (ventricular septal defect; atrioventricular septal defect; Tetralogy of Fallot; bicuspid aortic valve; n = 6; 3.6%), acute myocarditis (n = 1; 0.6%), atrial myxoma removal (n = 1; 0.6%), planned AV node ablation (n = 2; 1.2%), and following a previous stab in the chest (n = 1; 0.6%).

Conclusion

Given that the mean age of our study population was high, the low number of identified underlying causes in the whole cohort (≤60 years) may reflect some AVB due to age related degeneration of the conductions system in the patients 56 to 60 years age, but also raises the possibility that these patients may be less likely to be extensively investigated for an underlying cause than those ≤55 years, where diseases such as sarcoidosis were more readily confirmed. As access to advanced diagnostic tools improves, the percentage of young pacemaker recipients with an underlying cause identified may increase.

Shared Decision Making and Cardioneuroablation Allow Discontinuation of Permanent Pacing in Patients with Vagally Mediated Bradycardia

BACKGROUND

Safe discontinuation of pacemaker therapy for vagally mediated bradycardia is a dilemma. The aim of the study was to present the outcomes of a proposed diagnostic and therapeutic process aimed at discontinuing or not restoring pacemaker therapy (PPM) in patients with vagally mediated bradycardia.

METHODS

The study group consisted of two subgroups of patients with suspected vagally mediated bradycardia who were considered to have PPM discontinued or not to restore their PPM if cardioneuroablation (CNA) would successfully treat their bradycardia. A group of 3 patients had just their pacemaker explanted but reimplantation was suggested, and 17 patients had preexisting pacemakers implanted. An invasive electrophysiology study was performed. If EPS was negative, extracardiac vagal nerve stimulation (ECVS) was performed. Then, patients with positive ECVS received CNA. Patients with an implanted pacemaker had it programmed to pace at the lowest possible rate. After the observational period and control EPS including ECVS, redo-CNA was performed if pauses were induced. The decision to explant the pacemaker was obtained based on shared decision making (SDM).

RESULTS

After initial clinical and electrophysiological evaluation, 17 patients were deemed eligible for CNA (which was then performed). During the observational period after the initial CNA, all 17 patients were clinically asymptomatic. The subsequent invasive evaluation with ECVS resulted in pause induction in seven (41%) patients, and these patients underwent redo-CNA. Then, SDM resulted in the discontinuation of pacemaker therapy or a decision to not perform pacemaker reimplantation in all the patients after CAN. The pacemaker was explanted in 12 patients post-CNA, while in 2 patients explantation was postponed. During a median follow-up of 18 (IQR: 8-22) months, recurrent syncope did not occur in the CNA recipients.

CONCLUSIONS

Pacemaker therapy in patients with vagally mediated bradycardia could be discontinued safely after CNA.

Etiology Distribution, Clinical Characteristics, and Suboptimal Pacing Outcome of Atrioventricular Block in Young Patients

Background

The causes of atrioventricular block (AVB) are different and diverse young patients, as compared to the old. However, little is known about the etiology distribution and clinical characteristics of AVB in the young group.

Methods

We retrospectively analyzed clinical information for AVB patients under 50 years of age. We summarized clinical phenotypes for patients with undetermined AVB etiology, according to AVB type and cardiac-structural change, whereas those who received pacing therapy were followed up for suspected heart failure events (HFEs).

Results

AVB etiology was identified in only 289 (61.4%) patients, while 38.6% still have undertermined etiology for AVB. Non-ischemic cardiomyopathy (16.6%) and complication of cardiac surgery (13.4%) were the top two etiologies. In addition, four distinct phenotypes were identified in AVB patients with undetermined etiology, of which the severe phenotype (both borderline/elevated left ventricular diameter or abnormal left ventricular ejection fraction and advanced AVB) accounted for 17%. Notably, 80.7% of patients with severe phenotype received pacing therapy. Based on a median follow-up time of 17.5 months, we found the occurrence of 16 suspected HFEs in 110 pacemaker receivers (12 were lost to follow up). Notably, the severe phenotype was associated with a higher risk of heart failure (HF) symptoms.

Conclusions

AVB etiology in young patients under 50 years of age is complex and underdiagnosed. In patients with undetermined etiology, severe phenotype featuring advanced AVB and abnormal Left ventricle (LV) structure/function is associated with a higher rate of HF symptoms even after pacing therapy.

Anti-Ro/SSA Antibodies Blocking Calcium Channels as a Potentially Reversible Cause of Atrioventricular Block in Adults

BACKGROUND

In ∼50% of severe atrioventricular blocks (AVBs) occurring in adults <50 years, the underlying etiology remains unknown. Preliminary evidence from case reports suggests that autoimmunity, specifically the presence of circulating anti-Ro/SSA antibodies in the patient (acquired form), in the patient's mother (late-progressive congenital form), or in both (mixed form), could be involved in a fraction of idiopathic AVBs in adults by possibly targeting the L-type calcium channel (Cav1.2) and inhibiting the related current (ICaL).

OBJECTIVES

The purpose of this study was to evaluate whether anti-Ro/SSA antibodies are causally implicated in the development of isolated AVBs in adults.

METHODS

Thirty-four consecutive patients with isolated AVB of unknown origin and 17 available mothers were prospectively enrolled in a cross-sectional study. Anti-Ro/SSA antibodies were assessed by fluoroenzyme-immunoassay, immuno-Western blotting, and line-blot immunoassay. Purified immunoglobulin-G (IgG) from anti-Ro/SSA-positive and anti-Ro/SSA-negative subjects were tested on ICaL and Cav1.2 expression using tSA201 and HEK293 cells, respectively. Moreover, in 13 AVB patients, the impact of a short course of steroid therapy on AV conduction was evaluated.

RESULTS

Anti-Ro/SSA antibodies, particularly anti-Ro/SSA-52kD, were found in 53% of AVB-patients and/or in their mothers, most commonly an acquired or mixed form (two-thirds of cases) without history of autoimmune diseases. Purified IgG from anti-Ro/SSA-positive but not anti-Ro/SSA-negative AVB patients acutely inhibited ICaL and chronically down-regulated Cav1.2 expression. Moreover, anti-Ro/SSA-positive sera showed high reactivity with peptides corresponding to the Cav1.2 channel pore-forming region. Finally, steroid therapy rapidly improved AV conduction in AVB-patients with circulating anti-Ro/SSA antibodies but not in those without.

CONCLUSIONS

Our study points to anti-Ro/SSA antibodies as a novel, epidemiologically relevant and potentially reversible cause of isolated AVB in adults, via an autoimmune-mediated functional interference with the L-type calcium channels. These findings have significant impact on antiarrhythmic therapies by avoiding or delaying pacemaker implantation.

Genetic Abnormalities of the Sinoatrial Node and Atrioventricular Conduction

The peculiar electrophysiological properties of the sinoatrial node and the cardiac conduction system are key components of the normal physiology of cardiac impulse generation and propagation. Multiple genes and transcription factors and metabolic proteins are involved in their development and regulation. In this review, we have summarized the genetic underlying causes, key clinical findings, and the latest available clinical evidence. We will discuss clinical diagnosis and management of the genetic conditions associated with conduction disorders that are more prevalent in clinical practice, for this reason, very rare genetic diseases presenting sinus node or cardiac conduction system abnormalities are not discussed.

Role of genetic testing in young patients with idiopathic atrioventricular conduction disease

AIMS

To investigate the role of genetic testing in patients with idiopathic atrioventricular conduction disease requiring pacemaker (PM) implantation before the age of 50 years.

METHODS AND RESULTS

All consecutive PM implantations in Southern Switzerland between 2010 and 2019 were evaluated. Inclusion criteria were: (i) age at the time of PM implantation: < 50 years; (ii) atrioventricular block (AVB) of unknown aetiology. Study population was investigated by ajmaline challenge and echocardiographic assessment over time. Genetic testing was performed using next-generation sequencing panel, containing 174 genes associated to inherited cardiac diseases, and Sanger sequencing confirmation of suspected variants with clinical implication. Of 2510 patients who underwent PM implantation, 15 (0.6%) were young adults (median age: 44 years, male predominance) presenting with advanced AVB of unknown origin. The average incidence of idiopathic AVB computed over the 2010-2019 time window was 0.7 per 100 000 persons per year (95% CI 0.4-1.2). Most of patients (67%) presented with specific genetic findings (pathogenic variant) or variants of uncertain significance (VUS). A pathogenic variant of PKP2 gene was found in one patient (6.7%) with no overt structural cardiac abnormalities. A VUS of TRPM4, MYBPC3, SCN5A, KCNE1, LMNA, GJA5 genes was found in other nine cases (60%). Of these, three unrelated patients (20%) presented the same heterozygous missense variant c.2531G > A p.(Gly844Asp) in TRPM4 gene. Diagnostic re-assessment over time led to a diagnosis of Brugada syndrome and long-QT syndrome in two patients (13%). No cardiac events occurred during a median follow-up of 72 months.

CONCLUSION

Idiopathic AVB in adults younger than 50 years is a very rare condition with an incidence of 0.7 per 100 000 persons/year. Systematic investigations, including genetic testing and ajmaline challenge, can lead to the achievement of a specific diagnosis in up to 20% of patients. Heterozygous missense variant c.2531G > A p.(Gly844Asp) in TRPM4 gene was found in an additional 20% of unrelated patients, suggesting possible association of the variant with the disease.

Long term clinical outcomes in patients requiring cardiac pacing due to congenital complete heart block

Background

Isolated congenital complete heart block (CCHB) is rare cardiac condition associated with maternal Anti-Rho antibodies. It is managed with permanent pacemaker insertion. We sought to determine the long-term outcomes of individuals with CCHB who had undergone pacemaker insertion.

Methods

A database search was performed at a UK tertiary cardiac referral centre. The online medical records of patients with CCHB were analysed for pacing requirements and complications, echocardiographic data, and clinical status.

Results

A total of 72 patients (female n = 46) were identified, 20% of whom were autoantibody positive. Mean age of initial implantation was 15.5 years (SD 12.7) with mean follow up of 21 years (SD 8.3). 88% of patients were NYHA class I at censure of data. Major adverse cardiac events (MACE) were observed in 2 patients with 0% mortality throughout the follow up period. 16 patients (22.2%) developed cardiomyopathy, of which 15 had CRT devices inserted.Five patients had device related infections and 7 required system extractions. Mean left ventricular ejection fraction on most recent echocardiogram was 53.7% (SD 8.40) with no significant change compared with their historic scan. Mild tricuspid regurgitation was the most frequently observed valvular pathology, identified in 28% of patients. Only 2 patients (2.7%) had severe valve incompetence but neither required surgical intervention.

Conclusion

Long-term outcomes for patients with congenital complete heart block who undergo pacemaker insertion are highly favourable. Despite high pacing requirements over an extended period, the incidence of MACE and pacing related complications is low. Cardiac function and valvular competence are largely preserved but dilated cardiomyopathy remains a late concern in a minority; ongoing clinical surveillance is paramount in this population.

Causes of Heart Block in Young and Middle-Aged South Africans

BACKGROUND

There is a paucity of data regarding the aetiology of atrioventricular heart block (AVB) in young and middle-aged patients, particularly from low- and middle-income countries.

OBJECTIVE

To determine the aetiology of AVB in patients ≤ 55 years treated with transvenous pacemakers in a low- or middle-income country.

METHODS

We performed a retrospective review of all patients who received a transvenous pacemaker for newly diagnosed AVB from 01/01/2013 to 31/12/2020 at Groote Schuur Hospital, Cape Town, South Africa.

RESULTS

One thousand one hundred one (1101) consecutive patients received a permanent transvenous pacemaker for AVB. One hundred thirty-six patients (12.4%) were ≤ 55 years. The study patients' mean (standard deviation) age was 41 (11) years, and 48.5% were female. Third-degree AV block was diagnosed in 73.5%, 2:1 AV block in 8.1%, and Mobitz Ι second degree AV block in 5.9%. The aetiology of AVB could be determined in 97/136 (71.3%) patients. Forty-three of 136 (31.6%) patients were post-surgical, and 16/136 (11.8%) patients had developed AVB from an acute myocardial infarction. Cardiac Magnetic Resonance (CMR) imaging was performed in 26 patients: cardiac sarcoidosis was diagnosed in 7/26 patients. No pathology could be identified in 10/26 patients who had CMR. The aetiology of AVB remained unknown in 39/136 patients (28.7%).

CONCLUSION

Prior valve surgery is the leading cause of AVB treated with a transvenous pacemaker in patients ≤ 55 years in this South African referral unit. Cardiac magnetic resonance imaging identified disease processes that require further management in many cases.

Diagnostic Yield of Genetic Testing in Young Patients With Atrioventricular Block of Unknown Cause

Background

The cause of atrioventricular block (AVB) remains unknown in approximately half of young patients with the diagnosis. Although variants in several genes associated with cardiac conduction diseases have been identified, the contribution of genetic variants in younger patients with AVB is unknown.

Methods and Results

Using the Danish Pacemaker and Implantable Cardioverter Defibrillator (ICD) Registry, we identified all patients younger than 50 years receiving a pacemaker because of AVB in Denmark in the period from January 1, 1996 to December 31, 2015. From medical records, we identified patients with unknown cause of AVB at time of pacemaker implantation. These patients were invited to a genetic screening using a panel of 102 genes associated with inherited cardiac diseases. We identified 471 living patients with AVB of unknown cause, of whom 226 (48%) accepted participation. Median age at the time of pacemaker implantation was 39 years (interquartile range, 32–45 years), and 123 (54%) were men. We found pathogenic or likely pathogenic variants in genes associated with or possibly associated with AVB in 12 patients (5%). Most variants were found in the LMNA gene (n=5). LMNA variant carriers all had a family history of either AVB and/or sudden cardiac death.

Conclusions

In young patients with AVB of unknown cause, we found a possible genetic cause in 1 out of 20 participating patients. Variants in the LMNA gene were most common and associated with a family history of AVB and/or sudden cardiac death, suggesting that genetic testing should be a part of the diagnostic workup in these patients to stratify risk and screen family members.

Familial risk of atrioventricular block in first-degree relatives

Objective

Rare cases of genetically inherited atrioventricular block (AVB) have been reported; however, the heredity of AVB remains unknown. We aimed to assess the heredity of AVB.

Design, setting and participants

Using data from the Danish Civil Registration Registry, we established a nationwide cohort of individuals with parental links. Data were merged with information from the Danish Pacemaker and Implantable Cardioverter Defibrillator Registry, containing information on all pacemaker implantations performed in Denmark during the study period, to identify patients who received a first-time pacemaker because of AVB.

Results

A total of 4 648 204 individuals had parental links and a total of 26 880 consecutive patients received a first-time pacemaker due to AVB. Overall, the adjusted rate ratio (RR) of pacemaker implantation due to AVB was 2.1 (95% CI 1.8 to 2.5) if a father, mother or sibling had AVB compared with the risk in the general population. The adjusted RR was 2.2 (1.7–2.9) for offspring of mothers with AVB, 1.9 (1.5–2.4) for offspring of fathers with AVB and 3.5 (2.3–5.4) for siblings to a patient with AVB. The risk increased inversely proportionally with the age of the index case at the time of pacemaker implantation. The corresponding adjusted RRs were 15.8 (4.8–52.3) and 10.0 (3.3–30.4) if a mother or father, respectively, had a pacemaker implantation before 50 years.

Conclusion and relevance

First-degree relatives to a patient with AVB carry an increased risk of AVB with the risk being strongly inversely associated with the age of the index case at pacemaker implantation. These findings indicate a genetic component in the development of AVB in families with an early-onset disease.

Genetic Abnormalities of the Sinoatrial Node and Atrioventricular Conduction

The peculiar electrophysiological properties of the sinoatrial node and the cardiac conduction system are key components of the normal physiology of cardiac impulse generation and propagation. Multiple genes and transcription factors and metabolic proteins are involved in their development and regulation. In this review, we have summarized the genetic underlying causes, key clinical findings, and the latest available clinical evidence. We will discuss clinical diagnosis and management of the genetic conditions associated with conduction disorders that are more prevalent in clinical practice, for this reason, very rare genetic diseases presenting sinus node or cardiac conduction system abnormalities are not discussed.