Corrected QT interval in anti-SSA-positive adults with connective tissue disease: Comment on the article by Lazzerini et al

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.

The Role of Autoantibodies in Arrhythmogenesis

PURPOSE OF REVIEW

The role of autoantibodies in arrhythmogenesis has been the subject of research in recent times. This review focuses on the rapidly expanding field of autoantibody-mediated cardiac arrhythmias.

RECENT FINDINGS

Since the discovery of cardiac autoantibodies more than three decades ago, a great deal of effort has been devoted to understanding their contribution to arrhythmias. Different cardiac receptors and ion channels were identified as targets for autoantibodies, the binding of which either initiates a signaling cascade or serves as a biomarker of underlying remodeling process. Consequently, the wide spectrum of heart rhythm disturbances may emerge, ranging from atrial to ventricular arrhythmias as well as conduction diseases, irrespective of concomitant structural heart disease or manifest autoimmune disorder. The time has come to acknowledge autoimmune cardiac arrhythmias as a distinct disease entity. Establishing the autoantibody profile of patients will help to develop novel treatment approaches for patients.

Cardiac Conduction Defects in Systemic Lupus Erythematosus

Systemic autoimmune conditions may cause morbidity and mortality. Systemic lupus erythematosus (SLE) is a prominent example of such diseases. It can result in conduction abnormalities due to accelerated atherosclerosis, vasculitis, or autoantibodies-induced myocarditis. Cardiac conduction abnormalities may produce sinus tachycardia, sinus bradycardia, prolonged QT intervals, atrial fibrillation, or atrioventricular (AV) nodal blocks. Neonatal lupus is sometimes associated with anti-Ro/SSA and anti-La/SSB antibodies, but their role remains a matter of controversy in adults.

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.

Prolonged Tpeak-Tend interval in anti-Ro52 antibody-positive connective tissue diseases

Patients with connective tissue diseases (CTDs) may have prolonged corrected QT interval which indicates increased risk for ventricular arrhythmias. However, a more sensitive measure of ventricular repolarization, T-peak-to-end (Tpe) interval, has not been studied in CTDs. We aimed to investigate the relationship between ventricular repolarization abnormalities and anti-Ro52-positivity in subjects with connective tissue diseases (CTDs). We enrolled patients with anti-Ro52-positive CTDs, ANA-positive CTDs, and healthy subjects in this cross-sectional study. We excluded conditions potentially affecting the QT interval. We compared the ECG measures between the groups and performed analyses to define factors associated with ventricular repolarization measures. 15 ANA and anti-Ro52-positive, 39 ANA-positive and anti-Ro52-negative, and 22 healthy subjects were enrolled. None of the subjects had rhythm or conduction disturbances. Corrected QT intervals were similar between the groups. Tpe (84, 77.3, and 69.4 msn, respectively) and QT-dispersion (40, 27.2, and 20.1 msn, respectively) were higher in anti-Ro52-positive subjects compared with the ANA-positive and healthy subjects. Anti-Ro52 titers were correlated with Tpe and QT-dispersion (r = 0.52 and p < 0.001 for each). ANA and anti-Ro52-positivity were independently associated with higher Tpe (OR = 7.7, p = 0.001 and OR = 6.9, p = 0.001, respectively), corrected Tpe (OR = 11.3, p = 0.001 and OR = 8.4, p = 0.003, respectively), QT dispersion (OR = 7, p = 0.008 and OR = 13, p < 0.001, respectively), and QTc dispersion (OR = 9.1, p = 0.001 and OR = 14.1, p < 0.001, respectively). This study provides evidence that ANA positivity, especially when concomitant anti-Ro52-positivity is present, significantly deteriorates ventricular repolarization. The aforementioned ventricular repolarization abnormalities may render these subjects susceptible to serious rhythm or conduction disorders in the setting of predisposing conditions.

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.

Long QT Syndrome: An Emerging Role for Inflammation and Immunity

The long QT syndrome (LQTS), classified as congenital or acquired, is a multi-factorial disorder of myocardial repolarization predisposing to life-threatening ventricular arrhythmias, particularly torsades de pointes. In the latest years, inflammation and immunity have been increasingly recognized as novel factors crucially involved in modulating ventricular repolarization. In the present paper, we critically review the available information on this topic, also analyzing putative mechanisms and potential interplays with the other etiologic factors, either acquired or inherited. Accumulating data indicate inflammatory activation as a potential cause of acquired LQTS. The putative underlying mechanisms are complex but essentially cytokine-mediated, including both direct actions on cardiomyocyte ion channels expression and function, and indirect effects resulting from an increased central nervous system sympathetic drive on the heart. Autoimmunity represents another recently arising cause of acquired LQTS. Indeed, increasing evidence demonstrates that autoantibodies may affect myocardial electric properties by directly cross-reacting with the cardiomyocyte and interfering with specific ion currents as a result of molecular mimicry mechanisms. Intriguingly, recent data suggest that inflammation and immunity may be also involved in modulating the clinical expression of congenital forms of LQTS, possibly triggering or enhancing electrical instability in patients who already are genetically predisposed to arrhythmias. In this view, targeting immuno-inflammatory pathways may in the future represent an attractive therapeutic approach in a number of LQTS patients, thus opening new exciting avenues in antiarrhythmic therapy.

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.

Anti-Ro/SSA-associated corrected QT interval prolongation in adults: the role of antibody level and specificity

OBJECTIVE

Recent evidence suggests that anti-Ro/SSA antibodies, strongly associated with the development of congenital heart block, may also be arrhythmogenic for the adult heart. In fact, anti-Ro/SSA-positive patients with connective tissue disease (CTD) frequently display corrected QT (QTc) prolongation associated with an increase in ventricular arrhythmias. However, QTc prolongation prevalence markedly differs throughout the studies (10-60%), but the reason why is not yet clear. The aim of this study was to evaluate whether anti-Ro/SSA-associated QTc prolongation in adult patients with CTD is related to antibody level and specificity.

METHODS

Forty-nine adult patients with CTD underwent a resting 12-lead electrocardiogram recording to measure QTc interval, and a venous withdrawal to determine anti-Ro/SSA antibody level and specificity (anti-Ro/SSA 52 kd and anti-Ro/SSA 60 kd) by immunoenzymatic methods and Western blotting.

RESULTS

In our population, a direct correlation was demonstrated between anti-Ro/SSA 52-kd level and QTc duration (r = 0.38, P = 0.007), patients with a prolonged QTc had higher levels of anti-Ro/SSA 52 kd with respect to those with a normal QTc (P = 0.003), and patients with a moderate to high level (≥50 units/ml) of anti-Ro/SSA 52 kd showed a longer QTc interval (P = 0.008) and a higher QTc prolongation prevalence (P = 0.008) than those with a low positive/negative level (<50 units/ml). On the contrary, no association was found between QTc and anti-Ro/SSA 60-kd level.

CONCLUSION

In anti-Ro/SSA-positive adult patients with CTD, the occurrence of QTc prolongation seems strictly dependent on the anti-Ro/SSA 52-kd level. This finding, possibly explaining the different QTc prolongation prevalence reported, strengthens the hypothesis that an extremely specific autoimmune cross-reaction is responsible for the anti-Ro/SSA-dependent interference on ventricular repolarization.

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.

Anti-Ro/SSA antibodies and cardiac arrhythmias in the adult: facts and hypotheses

It is well established that the passive trans-placental passage of anti-Ro/SSA antibodies from mother to foetus is associated with the risk to develop an uncommon syndrome named neonatal lupus (NLE), where the congenital heart block represents the most severe clinical feature. Recent evidence demonstrated that also adult heart, classically considered invulnerable to the anti-Ro/SSA antibodies, may represent a target of the arrhythmogenicity of these autoantibodies. In particular, the prolongation of the QTc interval appears the most frequent abnormality observed in adults with circulating anti-Ro/SSA antibodies, with some data suggesting an association with an increased risk of ventricular arrhythmias, also life threatening. Moreover, even though the association between anti-Ro/SSA antibodies and conduction disturbances is undoubtedly less evident in adults than in infants, from the accurate dissection of the literature data the possibility arises that sometimes also the adult cardiac conduction tissue may be affected by such antibodies. The exact arrhythmogenic mechanisms involved in foetus/newborns and adults, respectively, have not been completely clarified as yet. However, increasing evidence suggests that anti-Ro/SSA antibodies may trigger rhythm disturbances through an inhibiting cross-reaction with several cardiac ionic channels, particularly the calcium channels (L-type and T-type), but also the potassium channel hERG, whose different expression and involvement in the cardiac electrophysiology during lifespan might account for the occurrence of age-related differences.

Arrhythmias presenting in neonatal lupus

Perfusion of human foetal heart with anti-Ro/SSA antibodies induces transient heart block. Anti-Ro/SSA antibodies may cross-react with T- and L-type calcium channels, and anti-p200 antibodies may cause calcium to accumulate in rat heart cells. These actions may explain a direct electrophysiological effect of these antibodies. Congenital complete heart block is the more severe manifestation of so-called "Neonatal Lupus". In clinical practice, it is important to distinguish in utero complete versus incomplete atrioventricular (AV) block, as complete AV block to date is irreversible, while incomplete AV block has been shown to be potentially reversible after fluorinated steroid therapy. Another issue is the definition of congenital AV block, as cardiologists have considered congenital blocks detected months or years after birth. We propose as congenital blocks detected in utero or within the neonatal period (0-27 days after birth). The possible detection of first degree AV block in utero, with different techniques, might be a promising tool to assess the effects of these antibodies. Other arrhythmias have been described in NL or have been linked to anti-Ro/SSA antibodies: first degree AV block, in utero and after birth, second degree (i.e. incomplete block), sinus bradycardia and QT prolongation, both in infants and in adults, ventricular arrhythmias (in adults). Overall, these arrhythmias have not a clinical relevance, but are important for research purposes.

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.

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.

Comparison of frequency of complex ventricular arrhythmias in patients with positive versus negative anti-Ro/SSA and connective tissue disease

A previous study of electrocardiography at rest showed that anti-Ro/SSA-positive patients with connective tissue disease (CTD) frequently had corrected QT (QTc) interval prolongation. Because QTc interval prolongation is a definite risk factor for arrhythmic sudden death in the general population, a 24-hour electrocardiographic monitoring study was performed to investigate the possible relation between QTc interval prolongation and incidence of ventricular arrhythmias as a possible expression of immunomediated electric instability of the myocardium in anti-Ro/SSA-positive patients with CTD. The study population consisted of 46 patients with CTD; 26 anti-Ro/SSA-positive and 20 anti-Ro/SSA-negative (control group) patients (Sjögren's syndrome, 9 and 3 patients; systemic lupus erythematosus, 4 and 9 patients; systemic sclerosis, 2 and 4 patients; undifferentiated CTD, 8 and 1 patients; mixed CTD, 2 and 2 patients, and polymyositis/dermatomyositis, 1 and 1 patient, respectively). All patients underwent ambulatory Holter electrocardiography to obtain 24-hour monitoring of the QTc interval and ventricular arrhythmias. With respect to the control group, anti-Ro/SSA-positive patients with CTD (1) commonly showed QTc interval prolongation (46% vs 5%), and this abnormality, when present, persisted for the 24 hours (global mean 24-hour QTc interval 440.5+/-23.4 vs 418.2+/-13.2 ms); (2) had a higher incidence of complex ventricular arrhythmias (i.e., Lown classes 2 to 5, 50% vs 10%) also in the absence of detectable cardiac abnormalities; and (3) in patients with CTD, there is a direct relation between global mean 24-hour QTc interval and ventricular arrhythmic load independently of age and disease duration. In conclusion, anti-Ro/SSA-positive patients with CTD seemed to have a particularly high risk of developing ventricular arrhythmias. The risk appeared related mainly to abnormalities in ventricular electrophysiologic characteristics emerging in the clinical setting as QTc interval prolongation.

Prise en charge obstétricale des patientes à risque de « lupus néonatal »

Fetuses and infants of women with anti-SSA/Ro and anti-SSB/La antibodies are at risk of neonatal lupus syndrome, featuring skin lesions, hematological and hepatic disorders, and congenital heart block (CHB) in the absence of severe cardiac malformation. The prevalence of CHB in newborns of anti-SSA/Ro positive women with known connective tissue disease is 1 to 2% and the risk of recurrence ranges from 10 to 17%. CHB is definitive and is associated with significant morbidity (pacemaker must be implanted in 2/3 of cases) and mortality (16 to 19%). Myocardial involvement may either be associated or appear subsequently. Other manifestations are discussed. For anti-SSA/Ro positive pregnant women, echocardiograms should be performed every 2 weeks from 16 to 24 weeks of gestation, and every week in case of past history of CHB. Electrocardiogram should be performed in the first days of life for all children to detect incomplete CHB. Therapy for CHB detected in utero is based on fluorinated steroids, especially betamethasone. Its efficiency is variable.