Direct inhibition of expressed cardiac l- and t-type calcium channels by igg from mothers whose children have congenital heart block

An engineered human cardiac tissue model reveals contributions of systemic lupus erythematosus autoantibodies to myocardial injury

Systemic lupus erythematosus (SLE) is a highly heterogenous autoimmune disease that affects multiple organs, including the heart. The mechanisms by which myocardial injury develops in SLE, however, remain poorly understood. Here we engineered human cardiac tissues and cultured them with IgG fractions containing autoantibodies from SLE patients with and without myocardial involvement. We observed unique binding patterns of IgG from two patient subgroups: (i) patients with severe myocardial inflammation exhibited enhanced binding to apoptotic cells within cardiac tissues subjected to stress, and (ii) patients with systolic dysfunction exhibited enhanced binding to the surfaces of viable cardiomyocytes. Functional assays and RNA sequencing (RNA-seq) revealed that IgGs from patients with systolic dysfunction exerted direct effects on engineered tissues in the absence of immune cells, altering tissue cellular composition, respiration and calcium handling. Autoantibody target characterization by phage immunoprecipitation sequencing (PhIP-seq) confirmed distinctive IgG profiles between patient subgroups. By coupling IgG profiling with cell surface protein analyses, we identified four pathogenic autoantibody candidates that may directly alter the function of cells within the myocardium. Taken together, these observations provide insights into the cellular processes of myocardial injury in SLE that have the potential to improve patient risk stratification and inform the development of novel therapeutic strategies.

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.

Congenital Heart Block

Congenital complete heart block (CCHB) defines atrioventricular conduction abnormalities diagnosed in utero or within the first 27 days of life. Maternal autoimmune disease and congenital heart defects are most commonly responsible. Recent genetic discoveries have highlighted our understanding of the underlying mechanism. Hydroxychloroquine shows promise in preventing autoimmune CCHB. Patients may develop symptomatic bradycardia and cardiomyopathy. The presence of these and other specific findings warrants placement of a permanent pacemaker to relieve symptoms and prevent catastrophic events. The mechanisms, natural history, evaluation, and treatment of patients with or at risk for CCHB are reviewed.

Association of anti-Ro seropositivity with cardiac rhythm and conduction disturbances

AIMS

Anti-Ro/La autoantibodies are especially prevalent in autoimmune diseases but are also relatively frequent in healthy adults. Their arrhythmogenic effect on the immature cardiac conductive system is well established, with substantial evidence demonstrating an increased risk for congenital atrioventricular block in neonates of seropositive mothers. Despite their wide distribution and their arrhythmogenic potential effect, there are no large population studies conducted in seropositive adults. Thus, this is the first large population-based study to examine the association of anti-Ro/La seropositivity with cardiac rhythm and conduction disturbances.

METHODS AND RESULTS

This cross-sectional designed study involved the electronic health records of the largest health maintenance organization in Israel. All subjects that were tested positive for anti-Ro/anti-La antibodies between the years 2002 and 2019 were included and were matched by age, gender, and place of residence, with controls. Rates of different cardiac rhythm and conduction disturbances were compared between groups. Sensitivity analyses were performed using propensity score matching. The study population included 17 231 anti-Ro/La seropositive subjects and 84 368 controls. Anti-Ro seropositive patients had higher rates of conduction disturbances (3.0 vs. 1.7%, P < 0.001) and rhythm disturbances (10.5 vs. 7.0%, P < 0.001). Patients who tested positive for anti-La alone did not demonstrate a significant association with arrhythmias. Multivariate logistic regression analysis, controlling for possible confounders, showed an increased risk for cardiac conduction disturbances [odds ratio (OR) 1.44, 95% confidence interval (CI) 1.25-1.66, P < 0.001], as well as for cardiac rhythm disturbances (OR 1.21, 95% CI 1.11-1.31, P < 0.001) among anti-Ro seropositive patients. However, the association with rhythm disturbances was more robust in certain subgroup analyses.

CONCLUSIONS

Anti-Ro seropositivity is positively associated with adult cardiac conduction disturbances and, to a lesser extent, cardiac rhythm disturbances, regardless of the presence of concurrent autoimmune disease.

Congenital Heart Block

Congenital complete heart block (CCHB) defines atrioventricular conduction abnormalities diagnosed in utero or within the first 27 days of life. Maternal autoimmune disease and congenital heart defects are most commonly responsible. Recent genetic discoveries have highlighted our understanding of the underlying mechanism. Hydroxychloroquine shows promise in preventing autoimmune CCHB. Patients may develop symptomatic bradycardia and cardiomyopathy. The presence of these and other specific findings warrants placement of a permanent pacemaker to relieve symptoms and prevent catastrophic events. The mechanisms, natural history, evaluation, and treatment of patients with or at risk for CCHB are reviewed.

Anti-Ro/SSA Antibodies and the Autoimmune Long-QT Syndrome

Autoimmunity is increasingly recognized as a novel pathogenic mechanism for cardiac arrhythmias. Several arrhythmogenic autoantibodies have been identified, cross-reacting with different types of surface proteins critically involved in the cardiomyocyte electrophysiology, primarily ion channels (autoimmune cardiac channelopathies). Specifically, some of these autoantibodies can prolong the action potential duration leading to acquired long-QT syndrome (LQTS), a condition known to increase the risk of life-threatening ventricular arrhythmias, particularly Torsades de Pointes (TdP). The most investigated form of autoimmune LQTS is associated with the presence of circulating anti-Ro/SSA-antibodies, frequently found in patients with autoimmune diseases (AD), but also in a significant proportion of apparently healthy subjects of the general population. Accumulating evidence indicates that anti-Ro/SSA-antibodies can markedly delay the ventricular repolarization via a direct inhibitory cross-reaction with the extracellular pore region of the human-ether-a-go-go-related (hERG) potassium channel, resulting in a higher propensity for anti-Ro/SSA-positive subjects to develop LQTS and ventricular arrhythmias/TdP. Recent population data demonstrate that the risk of LQTS in subjects with circulating anti-Ro/SSA antibodies is significantly increased independent of a history of overt AD, intriguingly suggesting that these autoantibodies may silently contribute to a number of cases of ventricular arrhythmias and cardiac arrest in the general population. In this review, we highlight the current knowledge in this topic providing complementary basic, clinical and population health perspectives.

TRIM21/Ro52 - Roles in Innate Immunity and Autoimmune Disease

TRIM21 (Ro52/SSA1) is an E3 ubiquitin ligase with key roles in immune host defence, signal transduction, and possibly cell cycle regulation. It is also an autoantibody target in Sjögren's syndrome, systemic lupus erythematosus, and other rheumatic autoimmune diseases. Here, we summarise the structure and function of this enzyme, its roles in innate immunity, adaptive immunity and cellular homeostasis, the pathogenesis of autoimmunity against TRIM21, and the potential impacts of autoantibodies to this intracellular protein.

An Overview of Neonatal Lupus with Anti-Ro Characteristics

Neonatal lupus erythematosus (NLE) is a syndrome of clinical symptoms observed in neonates born to mothers with antibodies to soluble antigens of the cell nucleus. The main factors contributing to the pathogenesis of this disease are anti-Sjögren Syndrome A (anti-SS-A) antibodies, known as anti-Ro, and anti-Sjögren Syndrome B (anti-SS-B) antibodies, known as anti-La. Recent publications have also shown the significant role of anti-ribonucleoprotein antibodies (anti-RNP). Seropositive mothers may have a diagnosed rheumatic disease or they can be asymptomatic without diagnosis at the time of childbirth. These antibodies, after crossing the placenta, may trigger a cascade of inflammatory reactions. The symptoms of NLE can be divided into reversible symptoms, which concern skin, hematological, and hepatological changes, but 2% of children develop irreversible symptoms, which include disturbances of the cardiac stimulatory and conduction system. Preconceptive care and pharmacological prophylaxis of NLE in the case of mothers from the risk group are important, as well as the monitoring of the clinical condition of the mother and fetus throughout pregnancy and the neonatal period. The aim of this manuscript is to summarize the previous literature and current state of knowledge about neonatal lupus and to discuss the role of anti-Ro in the inflammatory process.

Congenital Heart Disease: An Immunological Perspective

Congenital heart disease (CHD) poses a significant global health and economic burden-despite advances in treating CHD reducing the mortality risk, globally CHD accounts for approximately 300,000 deaths yearly. Children with CHD experience both acute and chronic cardiac complications, and though treatment options have improved, some remain extremely invasive. A challenge in addressing these morbidity and mortality risks is that little is known regarding the cause of many CHDs and current evidence suggests a multifactorial etiology. Some studies implicate an immune contribution to CHD development; however, the role of the immune system is not well-understood. Defining the role of the immune and inflammatory responses in CHD therefore holds promise in elucidating mechanisms underlying these disorders and improving upon current diagnostic and treatment options. In this review, we address the current knowledge coinciding CHDs with immune and inflammatory associations, emphasizing conditions where this understanding would provide clinical benefit, and challenges in studying these mechanisms.

Arrhythmias and Conduction Disturbances in Autoimmune Rheumatic Disorders

Rhythm and conduction disturbances and sudden cardiac death are important manifestations of cardiac involvement in autoimmune rheumatic diseases (ARD), which have a serious impact on morbidity and mortality. While the underlying arrhythmogenic mechanisms are multifactorial, myocardial fibrosis plays a pivotal role. It accounts for a substantial portion of cardiac mortality and may manifest as atrial and ventricular arrhythmias, conduction system abnormalities, biventricular cardiac failure or sudden death. In patients with ARD, myocardial fibrosis is considered to be the hallmark of cardiac involvement as a result of inflammatory process or to coronary artery occlusive disease. Myocardial fibrosis constitutes the pathological substrates for reentrant circuits. The presence of supraventricular extra systoles, tachyarrhythmias, ventricular activity and conduction disturbances are not uncommon in patients with ARDs, more often in systemic lupus erythematosus, systemic sclerosis, rheumatoid arthritis, inflammatory muscle disorders and anti-neutrophil cytoplasm antibody-associated vasculitis. In this review, the type, the relative prevalence and the underlying mechanisms of rhythm and conduction disturbances in the emerging field of cardiorheumatology are provided.

Prenatal Management Strategy for Immune-Associated Congenital Heart Block in Fetuses

Fetal congenital heart block (CHB) is the most commonly observed type of fetal bradycardia, and is potentially life-threatening. More than 50% of cases of bradycardia are associated with maternal autoimmunity, and these are collectively termed immune-associated bradycardia. Several methods have been used to achieve reliable prenatal diagnoses of CHB. Emerging data and opinions on pathogenesis, prenatal diagnosis, fetal intervention, and the prognosis of fetal immune-associated CHB provide clues for generating a practical protocol for clinical management. The prognosis of fetal immune-associated bradycardia is based on the severity of heart blocks. Morbidity and mortality can occur in severe cases, thus hieratical management is essential in such cases. In this review, we mainly focus on optimal strategies pertaining to autoimmune antibodies related to CHB, although the approaches for managing autoimmune-mediated CHB are still controversial, particularly with regard to whether fetuses benefit from transplacental medication administration. To date there is still no accessible clinical strategy for autoimmune-mediated CHB. This review first discusses integrated prenatal management strategies for the condition. It then provides some advice for clinicians involved in management of fetal cardiovascular disorder.

Risk of QTc Interval Prolongation Associated With Circulating Anti-Ro/SSA Antibodies Among US Veterans: An Observational Cohort Study

Background

Anti‐Sjögren's syndrome‐related antigen A‐antibodies (anti‐Ro/SSA‐antibodies) are responsible for a novel form of acquired long‐QT syndrome, owing to autoimmune‐mediated inhibition of cardiac human ether‐a‐go‐go‐related gene‐potassium channels. However, current evidence derives only from basic mechanistic studies and relatively small sample‐size clinical investigations. Hence, the aim of our study is to estimate the risk of QTc prolongation associated with the presence of anti‐Ro/SSA‐antibodies in a large population of unselected subjects.

Methods and Results

This is a retrospective observational cohort study using the Veterans Affairs Informatics and Computing Infrastructure. Participants were veterans who were tested for anti‐Ro/SSA status and had an ECG. Descriptive statistics and univariate and multivariate logistic regression analyses were performed to identify risk factors for heart rate‐corrected QT interval (QTc) prolongation. The study population consisted of 7339 subjects (61.4±12.2 years), 612 of whom were anti‐Ro/SSA‐positive (8.3%). Subjects who were anti‐Ro/SSA‐positive showed an increased prevalence of QTc prolongation, in the presence of other concomitant risk factors (crude odds ratios [OR], 1.67 [1.26–2.21] for QTc >470/480 ms; 2.32 [1.54–3.49] for QTc >490 ms; 2.77 [1.66–4.60] for QTc >500 ms), independent of a connective tissue disease history. Adjustments for age, sex, electrolytes, cardiovascular risk factors/diseases, and medications gradually attenuated QTc prolongation estimates, particularly when QT‐prolonging drugs were added to the model. Nevertheless, stepwise‐fully adjusted OR for the higher cutoffs remained significantly increased in anti‐Ro/SSA‐positive subjects, particularly for QTc >500 ms (2.27 [1.34–3.87]).

Conclusions

Anti‐Ro/SSA‐antibody positivity was independently associated with an increased risk of marked QTc prolongation in a large cohort of US veterans. Our data suggest that within the general population individuals who are anti‐Ro/SSA‐positive may represent a subgroup of patients particularly predisposed to ventricular arrhythmias/sudden cardiac death.

A Broader Perspective on Anti-Ro Antibodies and Their Fetal Consequences-A Case Report and Literature Review

The presence of maternal Anti-Ro/Anti-La antibodies causes a passively acquired autoimmunity that may be associated with serious fetal complications. The classic example is the autoimmune-mediated congenital heart block (CHB) which is due in most cases to the transplacental passage of Anti-Ro/Anti-La antibodies. The exact mechanisms through which these pathologic events arise are linked to disturbances in calcium channels function, impairment of calcium homeostasis and ultimately apoptosis, inflammation and fibrosis. CHB still represents a challenging diagnosis and a source of debate regarding the best management. As the third-degree block is usually irreversible, the best strategy is risk awareness and prevention. Although CHB is a rare occurrence, it affects one in 20,000 live births, with a high overall mortality rate (up to 20%, with 70% of in utero deaths). There is also concern over the lifelong consequences, as most babies need a pacemaker. This review aims to offer, apart from the data needed for a better understanding of the issue at hand, a broader perspective of the specialists directly involved in managing this pathology: the rheumatologist, the maternal-fetal specialist and the cardiologist. To better illustrate the theoretical facts presented, we also include a representative clinical case.

Complete heart block in lupus

Conduction abnormalities are uncommon in adult patients with lupus. We present a young woman with recurrent syncope caused by third-degree atrio-ventricular block as the initial manifestation of lupus and review 31 additional cases of systemic lupus erythematosus patients that have been described previously with complete heart block. Heart blocks occurred almost exclusively in females. The median age was 37 years. In 24 cases heart blocks were diagnosed in patients with established lupus. In only five patients, including the patient presented here, heart blocks were diagnosed before the lupus diagnosis. Syncope was the most common presenting symptom of heart block. Electrocardiographic findings prior to heart block episodes were reported in 17 cases: eight had normal findings, but nine had already variant forms of atrioventricular or intraventricular conduction defects. Anti-nuclear antibody tests were reported in 25 cases and were all positive. Anti-DNA antibodies were also common and were positive in 16 of 19 cases (84%). Anti-La and anti-Ro antibodies were less common (13% and 35%, respectively). Three patients died, all prior to 1975. Heart block resolved in 10 cases. Follow-up was reported in four of these cases and heart block recurred in three of them. A permanent pacemaker was the eventual treatment in 22 cases. The etiology of lupus-associated complete heart block is not clear. It is probably variable, possibly related to effects of autoantibodies reacting with the conduction system, myocardial disease and adverse effects of antimalarials. Insertion of a permanent pacemaker seems to be the preferable method of treatment.

Autoimmune-mediated congenital heart block

Autoimmune-mediated congenital heart block (CHB) is a severe manifestation of neonatal lupus in which conduction tissues of the fetal heart are damaged. This occurs due to passive transference of maternal anti-SSA/Ro and anti-SSB/La autoantibodies and subsequent inflammation and fibrosis of the atrioventricular (AV) node. Notably, the disease manifests after the fetal heart has structurally developed, ruling out other anatomical abnormalities that could otherwise contribute to the block of conduction. Complete AV block is irreversible and the most common manifestation of CHB, although other cardiac complications such as endocardial fibroelastosis (EFE), dilated cardiomyopathy, and valvular insufficiency have been observed. In this review, we detail the classification, prevalence, pathogenesis, and clinical management recommendations for autoimmune CHB.

Autoimmune Calcium Channelopathies and Cardiac Electrical Abnormalities

Patients with autoimmune diseases are at increased risk for developing cardiovascular diseases, and abnormal electrocardiographic findings are common. Voltage-gated calcium channels play a major role in the cardiovascular system and regulate cardiac excitability and contractility. Particularly, by virtue of their localization and expression in the heart, calcium channels modulate pace making at the sinus node, conduction at the atrioventricular node and cardiac repolarization in the working myocardium. Consequently, emerging evidence suggests that calcium channels are targets to autoantibodies in autoimmune diseases. Autoimmune-associated cardiac calcium channelopathies have been recognized in both sinus node dysfunction atrioventricular block in patients positive for anti-Ro/La antibodies, and ventricular arrhythmias in patients with dilated cardiomyopathy. In this review, we discuss mechanisms of autoimmune-associated calcium channelopathies and their relationship with the development of cardiac electrical abnormalities.

Anti-Ro antibodies and complete heart block in adults with Sjögren's syndrome

There are emerging case reports worldwide of complete heart block in adults who test positive for anti-Ro antibodies and the underlying primary Sjögren's syndrome (pSS). The association between fetal/congenital cardiac abnormalities and transplacental transfer of anti-Ro antibodies is well established; there is, however, an ongoing debate about the underlying mechanism of activity of these antibodies in the cardiac tissue. In the past, maternal cardiac tissue was believed to be resistant to these pathogenic effects. This case highlights the need to change our understanding of how these antibodies cause adverse arrhythmogenic cardiac effects in adults. We present the case of a 44-year-old female with pSS and positive anti-Ro autoantibodies, who was diagnosed with autoimmune-induced complete heart block after presenting with dizziness and palpitations. She required insertion of a permanent cardiac pacemaker and has made a full recovery. Although the arrhythmogenic effects are rare, it may be that cardiac conduction in adults is not as resistant to anti-Ro antibodies as proposed.

Role of cardiac pacing in congenital complete heart block

INTRODUCTION

Congenital complete heart block affects 1/15,000 live-born infants, predominantly due to atrioventricular nodal injury from maternal antibodies of mothers with systemic lupus erythermatosus or Sjogren's syndrome. The majority of these children will need a pacemaker implanted prior to becoming young adults. This article will review the various patient and technical factors that influence the type of pacemaker implanted, and the current literature on optimal pacing practices. Areas covered: A literature search was performed using PubMed, Embase and Web of Science. Data regarding epicardial versus transvenous implants, pacing-induced ventricular dysfunction, alternative pacing strategies (including biventricular pacing, left ventricular pacing, and His bundle pacing), and complications with pacemakers in the pediatric population were reviewed. Expert commentary: There are numerous pacing strategies available to children with congenital complete heart block. The risks and benefits of the initial implant should be weighed against the long-term issues inherent with a life-time of pacing.

Autoimmune channelopathies as a novel mechanism in cardiac arrhythmias

Cardiac arrhythmias confer a considerable burden of morbidity and mortality in industrialized countries. Although coronary artery disease and heart failure are the prevalent causes of cardiac arrest, in 5-15% of patients, structural abnormalities at autopsy are absent. In a proportion of these patients, mutations in genes encoding cardiac ion channels are documented (inherited channelopathies), but, to date, the molecular autopsy is negative in nearly 70% of patients. Emerging evidence indicates that autoimmunity is involved in the pathogenesis of cardiac arrhythmias. In particular, several arrhythmogenic autoantibodies targeting specific calcium, potassium, or sodium channels in the heart have been identified. Experimental and clinical studies demonstrate that these autoantibodies can promote conduction disturbances and life-threatening tachyarrhythmias by inducing substantial electrophysiological changes. In this Review, we propose the term 'autoimmune cardiac channelopathies' to define this novel pathogenic mechanism of cardiac arrhythmias, which could be more frequent and clinically relevant than previously appreciated. Indeed, pathogenic autoantibodies against ion channels are detectable not only in patients with manifest autoimmune disease, but also in apparently healthy individuals, which suggests a causal role in some cases of unexplained arrhythmias and cardiac arrest. Considering this possibility and performing specific testing in patients with 'idiopathic' rhythm disturbances could create novel treatment opportunities.

Genetic Determinants of Hereditary Bradyarrhythmias: A Contemporary Review of a Diverse Group of Disorders

Bradyarrhythmia is a common clinical presentation. Although the majority of cases are acquired, genetic screening of families with bradyarrhythmia has led to the discovery of a growing number of causative hereditary mutations. These mutations can interfere with any of the steps required for the occurrence of each cardiac cycle, including generation of an action potential in the sinoatrial node, successful exit of the action potential from the node, propagation of the action potential throughout the atria until the depolarization waves reach the atrioventricular node, and finally transmission of the action potential to the ventricles through the His-Purkinje system. As expected, channelopathies are the predominant culprit for hereditary bradyarrhythmias, because they play a crucial role in action potential generation and propagation. Interestingly, there are an increasing number of genes that encode for various regulatory or structural cellular components that have been linked to hereditary bradyarrhythmias. Furthermore, population-based genetic screening has revealed that age-related conduction defects may in fact be caused by genetic predispositions rather than the simple process of aging. With recent advances in genetic testing and the creation of animal models, not only have we discovered new culprit genes but it has also has become evident that there are still significant gaps in our knowledge of cardiac pathophysiology. In this review, we discuss the clinical presentations of known hereditary bradyarrhythmias and their associated conditions in addition to detailing our current molecular understanding of the mechanisms by which they are manifested.

Immune-Mediated Heart Disease

The heart involvement in systemic autoimmune diseases represents a growing burden for patients and health systems. Cardiac function can be impaired as a consequence of systemic conditions and manifests with threatening clinical pictures or chronic myocardial damage. Direct injuries are mediated by the presence of inflammatory infiltrate which, even though unusual, is one of the most danger manifestations requiring prompt recognition and treatment. On the other hand, a not well-managed inflammatory status leads to accelerated atherosclerosis that precipitates ischemic disease. All cardiac structures may be damaged with different grades of intensity; moreover, lesions can appear simultaneously or more frequently at a short distance from each other leading to the onset of varied clinical pictures. The pathogenesis of heart damages in systemic autoimmune conditions is not yet completely understood for the great part of situations, even if several mechanisms have been investigated. The principal biochemical circuits refer to the damaging role of autoantibodies on cardiac tissues and the precipitation of immune complexes on endocardium. These events are finally responsible of inflammatory infiltration which leads to subsequent worsening of the previous damage. For these reasons, it appears of paramount importance a regular and deepened cardiovascular assessment to prevent a progressive evolution toward heart failure in patient affected by autoimmune diseases.

Induction of autoimmune response to the extracellular loop of the HERG channel pore induces QTc prolongation in guinea-pigs

KEY POINTS

Channelopathies of autoimmune origin are novel and are associated with corrected QT (QTc) prolongation and complex ventricular arrhythmias. We have recently demonstrated that anti-SSA/Ro antibodies from patients with autoimmune diseases and with QTc prolongation on the ECG target the human ether-à-go-go-related gene (HERG) K⁺ channel by inhibiting the corresponding current, I_Kr , at the pore region. Immunization of guinea-pigs with a peptide (E-pore peptide) corresponding to the extracellular loop region connecting the S5 and S6 segments of the HERG channel induces high titres of antibodies that inhibit I_Kr , lengthen the action potential and cause QTc prolongation on the surface ECG. In addition, anti-SSA/Ro-positive sera from patients with connective tissue diseases showed high reactivity to the E-pore peptide. The translational impact is the development of a peptide-based approach for the diagnosis and treatment of autoimmune-associated long QT syndrome.

ABSTRACT

We recently demonstrated that anti-SSA/52 kDa Ro antibodies (Abs) from patients with autoimmune diseases and corrected QT (QTc) prolongation directly target and inhibit the human ether-à-go-go-related gene (HERG) K⁺ channel at the extracellular pore (E-pore) region, where homology with SSA/52 kDa Ro antigen was demonstrated. We tested the hypothesis that immunization of guinea-pigs with a peptide corresponding to the E-pore region (E-pore peptide) will generate pathogenic inhibitory Abs and cause QTc prolongation. Guinea-pigs were immunized with a 31-amino-acid peptide corresponding to the E-pore region of HERG. On days 10-62 after immunization, ECGs were recorded and blood was sampled for the detection of E-pore peptide Abs. Serum samples from patients with autoimmune diseases were evaluated for reactivity to E-pore peptide by enzyme-linked immunosorbent assay (ELISA), and histology was performed on hearts using Masson's Trichrome. Inhibition of the HERG channel was assessed by electrophysiology and by computational modelling of the human ventricular action potential. The ELISA results revealed the presence of high titres of E-pore peptide Abs and significant QTc prolongation after immunization. High reactivity to E-pore peptide was found using anti-SSA/Ro Ab-positive sera from patients with QTc prolongation. Histological data showed no evidence of fibrosis in immunized hearts. Simulations of simultaneous inhibition of repolarizing currents by anti-SSA/Ro Ab-positive sera showed the predominance of the HERG channel in controlling action potential duration and the QT interval. These results are the first to demonstrate that inhibitory Abs to the HERG E-pore region induce QTc prolongation in immunized guinea-pigs by targeting the HERG channel independently from fibrosis. The reactivity of anti-SSA/Ro Ab-positive sera from patients with connective tissue diseases with the E-pore peptide opens novel pharmacotherapeutic avenues in the diagnosis and management of autoimmune-associated QTc prolongation.

Variants of Transient Receptor Potential Melastatin Member 4 in Childhood Atrioventricular Block

Background

Transient receptor potential melastatin member 4 (TRPM4) is a nonselective cation channel. TRPM4 mutations have been linked to cardiac conduction disease and Brugada syndrome. The mechanisms underlying TRPM4‐dependent conduction slowing are not fully understood. The aim of this study was to characterize TRPM4 genetic variants found in patients with congenital or childhood atrioventricular block.

Methods and Results

Ninety‐one patients with congenital or childhood atrioventricular block were screened for candidate genes. Five rare TRPM4 genetic variants were identified and investigated. The variants were expressed heterologously in HEK293 cells. Two of the variants, A432T and A432T/G582S, showed decreased expression of the protein at the cell membrane; inversely, the G582S variant showed increased expression. Further functional characterization of these variants using whole‐cell patch‐clamp configuration showed a loss of function and a gain of function, respectively. We hypothesized that the observed decrease in expression was caused by a folding and trafficking defect. This was supported by the observation that incubation of these variants at lower temperature partially rescued their expression and function. Previous studies have suggested that altered SUMOylation of TRPM4 may cause a gain of function; however, we did not find any evidence that supports SUMOylation as being directly involved for the gain‐of‐function variant.

Conclusions

This study underpins the role of TRPM4 in the cardiac conduction system. The loss‐of‐function variants A432T/G582S found in 2 unrelated patients with atrioventricular block are most likely caused by misfolding‐dependent altered trafficking. The ability to rescue this variant with lower temperature may provide a novel use of pharmacological chaperones in treatment strategies.

Potassium Channel Block and Novel Autoimmune-Associated Long QT Syndrome

This article reviews advances in the pathogenesis of anti-SSA/Ro antibody-induced corrected QT (QTc) prolongation in patients with autoimmune diseases; particularly connective tissue disease (CTD). Evidence shows that anti-SSA/Ro antibody-positive patients with CTD show QTc prolongation and complex ventricular arrhythmias. Molecular and functional data provide evidence that the human ether-a-go-go-related gene potassium channel conducting the rapidly activating delayed rectifier potassium current is directly inhibited by anti-SSA/Ro antibodies, resulting in action potential duration prolongation leading to QT interval lengthening. Routine electrocardiogram screening in anti-SSA/Ro antibody-positive patients and counseling for patients with other QTc prolonging risk factors is recommended.

Understanding autoimmunity: The ion channel perspective

Ion channels are integral membrane proteins that orchestrate the passage of ions across the cell membrane and thus regulate various key physiological processes of the living system. The stringently regulated expression and function of these channels hold a pivotal role in the development and execution of various cellular functions. Malfunction of these channels results in debilitating diseases collectively termed channelopathies. In this review, we highlight the role of these proteins in the immune system with special emphasis on the development of autoimmunity. The role of ion channels in various autoimmune diseases is also listed out. This comprehensive review summarizes the ion channels that could be used as molecular targets in the development of new therapeutics against autoimmune disorders.

Evaluation and management of bradycardia in neonates and children

Heart rate is commonly used in pediatric early warning scores. Age-related changes in the anatomy and physiology of infants and children produce normal ranges for electrocardiogram features that differ from adults and vary with age. Bradycardia is defined as a heart rate below the lowest normal value for age. Pediatric bradycardia most commonly manifests as sinus bradycardia, junctional bradycardia, or atrioventricular block. As a result of several different etiologies, it may occur in an entirely structurally normal heart or in association with concomitant congenital heart disease. Genetic variants in multiple genes have been described to date in the pathogenesis of inherited sinus node dysfunction or progressive cardiac conduction disorders. Management and eventual prognosis of bradycardia in the young are entirely dependent upon the underlying cause. Reasons to intervene for bradycardia are the association of related symptoms and/or the downstream risk of heart failure or pause-dependent tachyarrhythmia. The simplest aspect of severe bradycardia management is reflected in the Pediatric and Advanced Life Support (PALS) guidelines.

CONCLUSION

Early diagnosis and appropriate management are critical in many cases in order to prevent sudden death, and this review critically assesses our current practice for evaluation and management of bradycardia in neonates and children.

WHAT IS KNOWN

Bradycardia is defined as a heart rate below the lowest normal value for age. Age related changes in the anatomy and physiology of infants and children produce normal ranges for electrocardiogram features that differ from adults and vary with age. Pediatric bradycardia most commonly manifests as sinus bradycardia, junctional bradycardia, or atrioventricular block.

WHAT IS NEW

Management and eventual prognosis of bradycardia in the young are entirely dependent upon the underlying cause. Bradycardia may occur in a structurally normal heart or in association with congenital heart disease. Genetic variants in multiple genes have been described. Reasons to intervene for bradycardia are the association of related symptoms and/or the downstream risk of heart failure or pause-dependent tachyarrhythmia. Early diagnosis and appropriate management are critical in order to prevent sudden death.

Cardiac arrhythmias as the initial manifestation of adult primary Sjögren's syndrome: a case report and literature review

Two middle-aged female patients presenting with heart palpitation and electrocardiogram revealed complex cardiac arrhythmias. A review of systems was positive for dry mouth and transient arthralgia, while laboratory and instrumental tests enabled us to make the diagnosis of primary Sjögren's syndrome (pSS). Cardiac electrophysiology revealed atrioventricular node dysfunction and impaired intraventricular conduction. Prednisone therapy induced a significant improvement in symptoms and electrocardiographic readings. The diagnosis of pSS should be considered in a patient presenting with complex cardiac arrhythmias.

Electrocardiographic findings in systemic lupus erythematosus: data from an international inception cohort

OBJECTIVE

To estimate the early prevalence of various electrocardiographic (EKG) abnormalities in patients with systemic lupus erythematosus (SLE) and to evaluate possible associations between repolarization changes (increased corrected QT [QTc] and QT dispersion [QTd]) and clinical and laboratory variables, including the anti-Ro/SSA level and specificity (52 or 60 kd).

METHODS

We studied adult SLE patients from 19 centers participating in the Systemic Lupus International Collaborating Clinics (SLICC) Inception Registry. Demographics, disease activity (Systemic Lupus Erythematosus Disease Activity Index 2000 [SLEDAI-2K]), disease damage (SLICC/American College of Rheumatology Damage Index [SDI]), and laboratory data from the baseline or first followup visit were assessed. Multivariate logistic and linear regression models were used to asses for any cross-sectional associations between anti-Ro/SSA and EKG repolarization abnormalities.

RESULTS

For the 779 patients included, mean ± SD age was 35.2 ± 13.8 years, 88.4% were women, and mean ± SD disease duration was 10.5 ± 14.5 months. Mean ± SD SLEDAI-2K score was 5.4 ± 5.6 and mean ± SD SDI score was 0.5 ± 1.0. EKG abnormalities were frequent and included nonspecific ST-T changes (30.9%), possible left ventricular hypertrophy (5.4%), and supraventricular arrhythmias (1.3%). A QTc ≥440 msec was found in 15.3%, while a QTc ≥460 msec was found in 5.3%. Mean ± SD QTd was 34.2 ± 14.7 msec and QTd ≥40 msec was frequent (38.1%). Neither the specificity nor the level of anti-Ro/SSA was associated with QTc duration or QTd, although confidence intervals were wide. Total SDI was significantly associated with a QTc interval exceeding 440 msec (odds ratio 1.38 [95% confidence interval 1.06, 1.79]).

CONCLUSION

A substantial proportion of patients with recent-onset SLE exhibited repolarization abnormalities, although severe abnormalities were rare.

Molecular mechanisms of congenital heart block

Autoantibody-associated congenital heart block (CHB) is a passively acquired autoimmune condition associated with maternal anti-Ro/SSA antibodies and primarily affecting electric signal conduction at the atrioventricular node in the fetal heart. CHB occurs in 1-2% of anti-Ro/SSA antibody-positive pregancies and has a recurrence rate of 12-20% in a subsequent pregnancy. Despite the long-recognized association between maternal anti-Ro/SSA autoantibodies and CHB, the molecular mechanisms underlying CHB pathogenesis are not fully understood, but several targets for the maternal autoantibodies in the fetal heart have been suggested. Recent studies also indicate that fetal susceptibility genes determine whether an autoantibody-exposed fetus will develop CHB or not, and begin to identify such genes. In this article, we review the different lines of investigation undertaken to elucidate the molecular pathways involved in CHB development and reflect on the hypotheses put forward to explain CHB pathogenesis as well as on the questions left unanswered and that should guide future studies.

Congenital heart block maternal sera autoantibodies target an extracellular epitope on the α1G T-type calcium channel in human fetal hearts

BACKGROUND

Congenital heart block (CHB) is a transplacentally acquired autoimmune disease associated with anti-Ro/SSA and anti-La/SSB maternal autoantibodies and is characterized primarily by atrioventricular (AV) block of the fetal heart. This study aims to investigate whether the T-type calcium channel subunit α1G may be a fetal target of maternal sera autoantibodies in CHB.

METHODOLOGY/PRINCIPAL FINDINGS

We demonstrate differential mRNA expression of the T-type calcium channel CACNA1G (α1G gene) in the AV junction of human fetal hearts compared to the apex (18-22.6 weeks gestation). Using human fetal hearts (20-22 wks gestation), our immunoprecipitation (IP), Western blot analysis and immunofluorescence (IF) staining results, taken together, demonstrate accessibility of the α1G epitope on the surfaces of cardiomyocytes as well as reactivity of maternal serum from CHB affected pregnancies to the α1G protein. By ELISA we demonstrated maternal sera reactivity to α1G was significantly higher in CHB maternal sera compared to controls, and reactivity was epitope mapped to a peptide designated as p305 (corresponding to aa305-319 of the extracellular loop linking transmembrane segments S5-S6 in α1G repeat I). Maternal sera from CHB affected pregnancies also reacted more weakly to the homologous region (7/15 amino acids conserved) of the α1H channel. Electrophysiology experiments with single-cell patch-clamp also demonstrated effects of CHB maternal sera on T-type current in mouse sinoatrial node (SAN) cells.

CONCLUSIONS/SIGNIFICANCE

Taken together, these results indicate that CHB maternal sera antibodies readily target an extracellular epitope of α1G T-type calcium channels in human fetal cardiomyocytes. CHB maternal sera also show reactivity for α1H suggesting that autoantibodies can target multiple fetal targets.

Congenital heart block: evidence for a pathogenic role of maternal autoantibodies

During pregnancy in autoimmune conditions, maternal autoantibodies are transported across the placenta and may affect the developing fetus. Congenital heart block (CHB) is known to associate with the presence of anti-Ro/SSA and anti-La/SSB antibodies in the mother and is characterized by a block in signal conduction at the atrioventricular (AV) node. The mortality rate of affected infants is 15% to 30%, and most live-born children require lifelong pacemaker implantation. Despite a well-recognized association with maternal anti-Ro/La antibodies, CHB develops in only 1% to 2% of anti-Ro-positive pregnancies, indicating that other factors are important for establishment of the block. The molecular mechanisms leading to complete AV block are still unclear, and the existing hypotheses fail to explain all aspects of CHB in one comprehensive model. In this review, we discuss the different specificities of maternal autoantibodies that have been implicated in CHB as well as the molecular mechanisms that have been suggested to operate, focusing on the evidence supporting a direct pathogenic role of maternal antibodies. Autoantibodies targeting the 52-kDa component of the Ro antigen remain the antibodies most closely associated with CHB. In vitro experiments and animal models of CHB also point to a major role for anti-Ro52 antibodies in CHB pathogenesis and suggest that these antibodies may directly affect calcium regulation in the fetal heart, leading to disturbances in signal conduction or electrogenesis or both. In addition, maternal antibody deposits are found in the heart of fetuses dying of CHB and are thought to contribute to an inflammatory reaction that eventually induces fibrosis and calcification of the AV node, leading to a complete block. Considering that CHB has a recurrence rate of 12% to 20% despite persisting maternal autoantibodies, it has long been clear that maternal autoantibodies are not sufficient for the establishment of a complete CHB, and efforts have been made to identify additional risk factors for this disorder. Therefore, recent studies looking at the influence of genetic and environmental factors will also be discussed.

Cardiac manifestations of neonatal lupus: a review of autoantibody-associated congenital heart block and its impact in an adult population

Within the last decade the prevalence of adult patients living with congenital heart disease equals that seen in children. This expanding population poses a challenge to clinical cardiologists who will be caring for patients with the clinical manifestations of this condition. Neonatal lupus is a model of passively acquired autoimmunity and is responsible for the majority of clinical cases of congenital heart block (CHB). This review will focus on the presentation, pathophysiology, and the long-term follow-up of CHB associated with neonatal lupus, and discuss important diagnostic tests, familial implications, and pacemaker issues associated with the care of an adult with CHB.

Pathogenicity and proteomic signatures of autoantibodies to Ro and La

Ro/SSA and La/SSB comprise a linked set of autoantigens that are clinically important members of the extractable nuclear antigen family and key translational biomarkers for lupus and primary Sjögren's syndrome. Autoantibodies directed against the Ro60 and La polypeptide components of the Ro/La ribonucleoprotein complex, and the structurally unrelated Ro52 protein, mediate tissue damage in the neonatal lupus syndrome, a model of passively acquired autoimmunity in humans in which the most serious manifestation is congenital heart block (CHB). Recent studies have concentrated on two distinct pathogenic mechanisms by which maternal anti-Ro/La autoantibodies can cause CHB: by forming immune complexes with apoptotic cells in developing fetal heart; and/or by acting as functional autoantibodies that cross-react with and inhibit calcium channels. Although the precise role of the individual autoantibodies is yet to be settled, maternal anti-Ro60 and anti-Ro52 remain the most likely culprits. This article will discuss the molecular pathways that culminate in the development of CHB, including the recent discovery of β2 glycoprotein I as a protective factor, and present a proteomic approach based on direct mass spectrometric sequencing, which may give a more representative snapshot of the idiotype repertoire of these autoantibodies than genomic-based technologies.

Prolonged corrected QT interval in anti-Ro/SSA-positive adults with systemic lupus erythematosus

OBJECTIVE

To examine whether anti-Ro/SSA antibodies are associated with an increased risk of corrected QT (QTc) prolongation, and to study the stability of this relationship over time.

METHODS

Patients fulfilling the American College of Rheumatology (ACR) criteria for systemic lupus erythematosus (SLE) were invited to undergo a 12-lead resting electrocardiogram (EKG) in the pilot phase of our project, performed between February 2002 and March 2005. The same study population was used to perform a second similar analysis with a larger sample between April 2005 and May 2007. Multivariate logistic regression models were fit to estimate the cross-sectional association between anti-Ro/SSA and other demographic and clinical variables on QTc prolongation. The other potentially associated factors examined included age, sex, disease duration, lupus activity (Systemic Lupus Erythematosus Disease Activity Index 2000 update), damage (Systemic Lupus International Collaborating Clinics/ACR Damage Index), potassium and magnesium levels, and medications with the potential to prolong the QTc interval.

RESULTS

Cross-sectional analysis of the pilot data (n = 150 patients) showed an association of prolonged QTc with the presence of anti-Ro/SSA (adjusted odds ratio [OR] 12.6; 95% confidence interval [95% CI] 2.3, 70.7). In the second larger study (n = 278), the association was replicated, with a narrower 95% CI (adjusted OR 5.1; 95% CI 1.5, 17.4). In the 118 patients with 2 EKG assessments, the results were consistent over time.

CONCLUSION

Anti-Ro/SSA was associated with QTc prolongation in both our pilot data and a larger SLE cohort sample. Patients positive for anti-Ro/SSA may benefit from EKG testing and appropriate counseling should be considered for those identified with QTc prolongation.

Pregnancy outcomes in patients with autoimmune diseases and anti-Ro/SSA antibodies

Anti-Ro/SSA antibodies are associated with neonatal lupus (congenital heart block (CHB), neonatal transient skin rash, hematological and hepatic abnormalities), but do not negatively affects other gestational outcomes, and the general outcome of these pregnancies is now good, when followed by experienced multidisciplinary teams. The prevalence of CHB, defined as an atrioventricular block diagnosed in utero, at birth, or within the neonatal period (0-27 days after birth), in the offspring of an anti-Ro/SSA-positive women is 1-2%, of neonatal lupus rash around 10-20%, while laboratory abnormalities in asymptomatic babies can be detected in up to 27% of cases. The risk of recurrence of CHB is ten times higher. Most of the mothers are asymptomatic at delivery and are identified only by the birth of an affected child. Half of these asymptomatic women develop symptoms of a rheumatic disease, most commonly arthralgias and xerophtalmia, but few develop lupus nephritis. A standard therapy for CHB is still matter of investigation, although fluorinated corticosteroids have been reported to be effective for associated cardiomyopathy. Serial echocardiograms and obstetric sonograms, performed at least every 1-2 weeks starting from the 16th week of gestational age, are recommended in anti-Ro/SSA-positive pregnant women to detect early fetal abnormalities that might be a target of preventive therapy.

Role of calcium channels in congenital heart block

Congenital heart block (CHB) is a conduction abnormality that affects hearts of foetuses and/or newborn to mothers with autoantibodies reactive with the intracellular soluble ribonucleoproteins 48-kD La, 52-kD Ro and 60-kD Ro. CHB carries substantial mortality and morbidity, with more than 60% of affected children requiring lifelong pacemakers. Several hypotheses have been proposed to explain the pathogenesis of CHB. These can be grouped under three main hypotheses: Apoptosis, Serotoninergic and Ca channel hypothesis. Here, we discuss these hypotheses and provide recent scientific thinking that will most likely dominate the future of this field of research.

Congenital heart block: identification of autoantibody binding site on the extracellular loop (domain I, S5-S6) of alpha(1D) L-type Ca channel

Congenital heart block (CHB) is an autoimmune disease associated with autoantibodies against intracellular ribonucleoproteins SSB/La and SSA/Ro. The hallmark of CHB is complete atrioventricular block. We have recently established that anti-SSA/Ro -SSB/La autoantibodies inhibit alpha(1D) L-type Ca current, I(Ca-L), and cross-react with the alpha(1D) Ca channel protein. This study aims at identifying the possible binding sites on alpha(1D) protein for autoantibodies from sera of mothers with CHB children. GST fusion proteins of the extracellular regions between the transmembrane segments (S5-S6) of each of the four alpha(1D) Ca channel protein domains I-IV were prepared and tested for reactivity with sera from mothers with CHB children and controls using ELISA. Sera containing anti-Ro/La autoantibodies from 118 mothers with CHB children and from 15 mothers with anti-Ro/La autoantibodies but have healthy children, and from 28 healthy mothers without anti-Ro/La autoantibodies and healthy children were evaluated. Seventeen of 118 (14.4%) sera from mothers with CHB children reacted with the extracellular loop of domain I S5-S6 region (E1). In contrast, only 2 of 28 (7%) of sera from healthy mothers (-anti-Ro/La) and healthy children reacted with E1 loop and none (0 of 15) of sera from healthy mothers (+anti-Ro/La) and healthy children reacted with the E1 loop. Preincubation of E1 loop with the positive sera decreased the O.D reading establishing the specificity of the response. Electrophysiological characterization of the ELISA positive sera and purified IgG showed inhibition (44.1% and 49.8%, respectively) of the alpha(1D) I(Ca-L) expressed in tsA201 cells. The inhibition was abolished when the sera were pre-incubated with E1 fusion protein. The results identified the extracellular loop of domain I S5-S6 of L-type Ca channel alpha(1D) subunit as a target for autoantibodies from a subset of mothers with CHB children. This novel finding provides insights into the potential development of therapeutic peptides that could bind to the pathogenic antibodies and prevent CHB.

Arrhythmias and conduction defects in rheumatological diseases--a comprehensive review

OBJECTIVES

To review the clinical aspects of cardiac arrhythmias and conduction disturbances in several common and less encountered adult rheumatic diseases and to underline the importance of prompt diagnosis and management in these patients.

METHODS

The PubMed database was searched for articles published between the years 1960 and 2008 for keywords referring to autoimmune diseases. All relevant English-written articles were reviewed. Most were uncontrolled series and case reports, due to the lack of prospective studies and randomized trials.

RESULTS

Rheumatologic conditions may affect the cardiovascular system and increase morbidity and mortality. Rhythm and conduction defects are usually mild but may be life-threatening; in certain diseases, such as in systemic lupus erythematosus they may resolve following therapy with corticosteroids. Conduction defects occur frequently in patients with spondyloarthropathies and in those with various forms of vasculitis. Enhanced variation of the QT interval may be a sensitive marker of a higher arrythmogenic tendency in patients with autoimmune conditions.

CONCLUSIONS

It is important to identify patients at high risk for cardiac arrhythmias. Treating such patients with arrhythmias should not differ fundamentally from other patients. Nevertheless, appropriate clinical attention and judgment should be applied to exclude the possibility that arrhythmias reflect uncontrolled myocardial inflammation.

[Fetal ultrasonography and Doppler in isolated congenital heart block]

Isolated congenital heart block is linked to transplacental passage of maternal anti-SSA/Ro and/or anti-SSB/La antibodies that may be related to a connective tissue disease. Ultrasonography and Doppler are essential to screen fetus at risk. They allow the diagnosis of first- and second-degree blocks which are probably preliminary stages in conducting tissue's injury. In these situations, a maternal treatment by fluorinated steroids can be proposed because of its possible effect on partial blocks. However, these early signs of nodal injury can be lacking: some fetus present a complete heart block without previously detected less advanced block. Moreover, the significance of first-degree block is unclear since it could reverse spontaneously. Other markers of nodal injury would be valuable. In case of complete congenital heart block, ultrasonography is useful to detect congestive heart failure and help the obstetrical management when unfavorable prognostic signs occur.

An expanded phenotype of maternal SSA/SSB antibody-associated fetal cardiac disease

OBJECTIVES

Conventional manifestations of fetal Sjogren's antibodies (SSA/SSB) associated cardiac disease include atrioventricular block (AVB), transient sinus bradycardia, endocardial fibroelastosis (EFE) and dilated cardiomyopathy. We describe other manifestations of cardiac disease.

METHODS

We describe three fetuses with unique myocardial and conduction system disease.

RESULTS

One had isolated EFE with subsequent mitral and tricuspid valve chordal avulsion, the second had sinoatrial and infrahissian conduction system disease, and in both, neonatal progression to life threatening disease occurred. The third had sinus node dysfunction and atrial flutter.

CONCLUSION

These findings expand the clinical phenotype of maternal SSA/SSB antibody associated fetal cardiac disease.

Rapid progression of atrioventricular nodal blockade in a patient with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a multisystem disorder with numerous potential adverse effects on the cardiovascular system. These complications likely develop in most patients with SLE at some time during the course of their disease, in part due to the decreased mortality associated with SLE as a result of modem medical management. Conduction disturbances have been reported in the literature to occur primarily from the progression of SLE and secondarily from pharmacotherapy used to treat SLE and may first be evident on the electrocardiogram in the emergency department (ED) setting. Electrocardiogram abnormalities such as borderline first-degree heart block may be clues to more significant cardiac disease brought upon by years of chronic inflammation, myocarditis, vasculitis, and fibrosis that are often the result of longstanding autoimmune disease. It is essential that patients with autoimmune disease be screened carefully in the ED setting for underlying myocardial disease, particularly given the increased potential for atherosclerosis, ischemia, arrhythmias, and myocardial conduction defects in these patients.

Cardiac arrhythmias and conduction disturbances in autoimmune rheumatic diseases

Rhythm and conduction disturbances and sudden cardiac death (SCD) are important manifestations of cardiac involvement in autoimmune rheumatic diseases (ARDs). In patients with rheumatoid arthritis (RA), a major cause of SCD is atherosclerotic coronary artery disease, leading to acute coronary syndrome and ventricular arrhythmias. In systemic lupus erythematosus (SLE), sinus tachycardia, atrial fibrillation and atrial ectopic beats are the major cardiac arrhythmias. In some cases, sinus tachycardia may be the only manifestation of cardiac involvement. The most frequent cardiac rhythm disturbances in systemic sclerosis (SSc) are premature ventricular contractions (PVCs), often appearing as monomorphic, single PVCs, or rarely as bigeminy, trigeminy or pairs. Transient atrial fibrillation, flutter or paroxysmal supraventricular tachycardia are also described in 20-30% of SSc patients. Non-sustained ventricular tachycardia was described in 7-13%, while SCD is reported in 5-21% of unselected patients with SSc. The conduction disorders are more frequent in ARD than the cardiac arrhythmias. In RA, infiltration of the atrioventricular (AV) node can cause right bundle branch block in 35% of patients. AV block is rare in RA, and is usually complete. In SLE small vessel vasculitis, the infiltration of the sinus or AV nodes, or active myocarditis can lead to first-degree AV block in 34-70% of patients. In contrast to RA, conduction abnormalities may regress when the underlying disease is controlled. In neonatal lupus, 3% of infants whose mothers are antibody positive develop complete heart block. Conduction disturbances in SSc are due to fibrosis of sinoatrial node, presenting as abnormal ECG, bundle and fascicular blocks and occur in 25-75% of patients.

Autoantibody-mediated cardiac arrhythmias: mechanisms and clinical implications

Cardiac arrhythmias, including conduction defects and tach- yarrhythmias, represent an important source of morbidity and mortality in industrialized countries. Among the different pathophysiological mechanisms involved in the arrhythmogenesis, an inappropriate activation of the immune system represents a field of recent increasing interest. In fact, a large amount of studies suggest that specific autoantibody may be significantly involved in the pathogenesis of cardiac arrhythmias not only in the course of systemic autoimmune disease, but also in a number of rhythm disorders currently classified as "idiopathic." Although the strongest evidence concerns the relationship between anti-Ro/SSA antibodies and the development of congenital heart block in foetus and newborn, other specific autoantibodies demonstrated the aptitude to affect directly the myocardial tissue, thus producing interference in its bioelectric activity thereby leading to rhythm disorders, also life-threatening. The identification of an immunological autoantibody-mediated mechanism opens new perspectives in the treatment and prevention of cardiac arrhythmias in such patients, including the use of immunosuppressive agents and/or the removal of autoantibodies by immuno-adsorption technique.