Arrhythmogenic and inotropic effects of interferon investigated in perfused and in vivo rat hearts: influences of cardiac hypertrophy and isoproterenol

Autoimmune congenital heart block: a case report and review of the literature related to pathogenesis and pregnancy management

Autoimmune congenital heart block (ACHB) is a passively acquired immune-mediated disease characterized by the presence of maternal antibodies against components of the Ro/SSA and La/SSB ribonucleoprotein complex that mainly affects the cardiac conducting system. ACHB occurs in 2% of women with positive anti-Ro/SSA and anti-La/SSB antibodies and causes a high risk of intrauterine fetal death, neonatal mortality, and long-term sequelae. In this review, we first describe a case of ACHB to provide preliminary knowledge. Then, we discuss the possible pathogenic mechanisms of ACHB; summarize the pregnancy management of patients with positive anti-Ro/SSA and anti-La/SSB antibodies and/or rheumatic diseases, the prevention of ACHB, and the treatment of ACHB fetuses; and propose routine screening of these antibodies for the general population. Careful follow-up, which consists of monitoring the fetal heart rate, is feasible and reassuring for pregnant women with positive anti-Ro/SSA and/or anti-La/SSB antibodies to lower the risk of ACHB in fetuses. Moreover, maternal administration of hydroxychloroquine may be useful in preventing ACHB in pregnant women with anti-Ro/SSA and/or anti-La/SSB antibodies.

Interferons and innate immune activation in autoimmune congenital heart block

Autoimmune congenital heart block (CHB) may develop in foetuses of women carrying anti-Ro/SSA and La/SSB autoantibodies and is characterized by disruption of signal conduction at the atrioventricular (AV) node, resulting in partial or complete AV block. If not fatal in utero, complete CHB typically requires lifelong cardiac pacing. No treatment has so far been unequivocally demonstrated to prevent or treat autoimmune CHB, and the relatively low incidence (1%-5%) and recurrence (12%-16%) rates of second/third-degree AV block add to the complexity of managing pregnancies in women with anti-Ro/La antibodies. Altogether, a better understanding of events leading to development of autoimmune CHB is needed to improve surveillance and treatment strategies. In the past decade, studies have started to look beyond the role of maternal autoantibodies in disease pathogenesis to assess other contributing factors such as foetal genetics and, more recently, immune responses in foetuses and neonates of anti-Ro/La antibody-positive women. In this review, we provide an update on the epidemiology, clinical presentation and current treatment approaches of autoimmune CHB, summarize the previously proposed pathogenic mechanisms implicating maternal autoantibodies, and discuss the recent findings of type I interferon (IFN) and innate immune activation in foetuses with autoimmune CHB and in neonates of anti-Ro/La antibody-positive mothers, and how these may contribute to autoimmune CHB pathogenesis.

ClC-3 chloride channel is involved in isoprenaline-induced cardiac hypertrophy

Isoprenaline, an activator of β-adrenergic receptor, has been found to induce cardiac hypertrophy in vivo and in vitro, but the exact mechanism is still unclear. ClC-3 is a member of the chloride channel family and is highly expressed in mammalian myocardium. In the present study, the role of ClC-3 in isopronaline-induced cardiac hypertrophy was investigated. We found that ClC-3 expression was reduced in isoprenaline-induced hypertrophic H9c2 cells, primary rat neonatal cardiomyocytes and myocardium of C57/BL/6 mice, and this reduction was prevented by the pretreatment of propranolol. Adeno-associated virus 9 (AAV9)-mediated ClC-3 expression in myocardium decreased heart mass index, thinned interventricular septum and left ventricular wall and lowered the mRNA expression of natriuretic peptide type A (ANF) and β-myosin heavy chain (β-MHC). Our results showed that ClC-3 played an important role in β-adrenergic cardiac hypertrophy which could be associated with ANF and β-MHC, and all these findings suggested that ClC-3 may be a novel therapeutic target for the prevention or treatment of myocardiac hypertrophy.

Sick sinus syndrome induced by interferon and ribavirin therapy in a patient with chronic hepatitis C

The therapeutic effect of interferon (IFN) on chronic hepatitis C and its adverse effects have been well documented. Although the incidence of IFN-related cardiotoxicity is low, careful observation is necessary because of its possible fatal outcome. We describe a 45-year-old woman who suffered from sinus node dysfunction after the combination therapy of pegylated IFN-alpha and ribavirin for chronic hepatitis C. Despite the cessation of IFN therapy, sinus node dysfunction was not reversible, and led her to the implantation of permanent pacemaker. Physicians should therefore be aware of the possibility of sinus node dysfunction in patients receiving IFN therapy. <Learning objective: Pegylated interferon-alpha has been widely used to treat hepatitis C virus infection, which is associated with a wide variety of adverse effects. There is a limited number of case reports regarding suspected interferon-induced cardiotoxicity, especially bradyarrhythmia. We report a case with chronic hepatitis C who developed sick sinus syndrome after interferon-alpha therapy.>.

Is combination therapy for chronic hepatitis C toxic for cardiac function?

BACKGROUND

Many types of cardiovascular complications such as; cardiac arrhythmias, impaired cardiac function, myocardial ischemia and decreased left ventricular function, have been attributed to interferon therapy.

OBJECTIVES

The aim of this study was to evaluate the effects of combination therapy pegylated interferon and ribavirin on left ventricular systolic and diastolic functions in patients with a chronic hepatitis C infection.

PATIENTS AND METHODS

A total of 120 patients, eligible for hepatitis C virus (HCV) treatment with pegylated interferon and ribavirin, were included in this study. All patients underwent a full cardiovascular baseline examination including; detailed medical history, thorough clinical examination, 12 lead electrocardiogram (ECG), and echocardiography. A cardiac evaluation was performed at the beginning and six months after starting combination therapy.

RESULTS

No significant changes regarding cardiac symptoms including; shortness of breath, cough, palpitations, chest pain and hypertension, were found during or six months after starting the combined therapy. ECG findings showed statistically non-significant decreases in the QT interval, while corrected QT showed statistically non-significant increases six months after beginning combined therapy, when compared to their values before treatment. Also with regard to the echocardiography findings, there was no statistically significant difference found between any of the echocardiography parameters six months after starting combined therapy compared to their values before treatment.

CONCLUSIONS

The results of our study suggest that, combination therapy does not cause a significant deterioration in cardiac function in patients with a chronic hepatitis C infection, and it may be used safely in patients without cardiac disease.

Cardiac arrhythmia induced by interferon beta-1a

Cardiac adverse effects have never been reported with interferon (INF) beta. We report a case of left bundle branch block in a 35-year-old woman treated with INF beta-1a for multiple sclerosis. Five years after INF therapy, she presented loss of consciousness, retrosternal pains, short breath and lowered tolerance of effort. ECG and Holter 24-h ECG monitoring revealed permanent complete left bundle branch block. Nine months after stopping INF, no abnormalities were found at ECG and echocardiogram examination.

Pathophysiological basis for monitoring of whole heart conductance by 2-lead system

BACKGROUND

The defibrillation threshold (DFT) is elevated during myocardial ischemia, but the underlying mechanism remains to be elucidated. The hypothesis tested by the present study was that whole heart conductance (WHC) is a determinant of DFT.

METHODS AND RESULTS

WHC was monitored across the longest diameter of the isolated perfused rat heart, using a 2-electrode instrument under various conditions including ischemia-reperfusion (IR). In the control study, WHC was influenced by the conductivity and flow rate of the solution. In IR, WHC decreased immediately after the onset of perfusion arrest in a single exponential manner, then declined again gradually. The second decrease was augmented and accelerated by pretreatment with 1.0 mmol/L heptanol (p<0.005) or high-[Ca2+]e (p<0.001), and was attenuated and delayed by pretreatment with 1.0 micromol/L verapamil (p<0.01). WHC after reperfusion was greater than the pre ischemic level. The postischemic increase in WHC was proportional to the ischemic interval and tissue water content as assessed by desiccation method.

CONCLUSION

Although time-dependent alterations in DFT in ischemic hearts may be attributable at least in part to dynamic changes in WHC, WHC should be interpreted carefully because it reflects many physiological factors such as coronary perfusion, electrical coupling of cardiac myocytes and tissue edema.

Influence of Interferon Therapy on Signal-Averaged and Ambulatory Electrocardiograms in Patients With Chronic Active Hepatitis

Although interferon (IFN) shows cardiotoxicity and arrhythmogenesis, the influence of IFN on signal-averaged electrocardiography remains to be clarified. The aim of this study was to test a clinical hypothesis that IFN therapy for hepatitis C virus may induce ventricular late potentials (LPs) and related arrhythmias in patients with chronic active hepatitis. Signal-averaged and ambulatory electrocardiograms were recorded sequentially in patients with chronic active hepatitis C (n = 22) throughout the entire period of IFN therapy. The filtered QRS duration (fQRS) and low amplitude (< 40 microV) signal duration (LAS40) were significantly increased (95.5 +/- 8.5 to 99.6 +/- 9.4 msec, P < 0.0001, and 32.8 +/- 3.1 to 36.3 +/- 3.0 msec, P < 0.0001, respectively), whereas the root mean square voltage in the terminal 40 msec of the fQRS (RMS40) was significantly decreased (25.5 +/- 5.4 to 22.3 +/- 5.2 microV, P < 0.005) 1 month after starting the IFN therapy. The ventricular LP was negative in all subjects before starting therapy, but became positive in 7 patients after the therapy commenced. There were no differences in clinical baseline characteristics between the LP-positive (n = 7) and LP-negative (n = 15) groups. Significant increases in mean heart rate, fQRS, and LAS40 were observed after starting the therapy, irrespective of the appearance of the ventricular LP, whereas a decrease in RMS40 was observed only in the LP-positive group. No sustained ventricular arrhythmias were documented in the ambulatory electrocardiography and no cardiac events were encountered in the follow-up period. Therefore, the results indicate a reversible and subclinical risk of IFN-induced arrhythmogenesis.