Similar prevalence of enteroviral genome within the myocardium from patients with idiopathic dilated cardiomyopathy and controls by the polymerase chain reaction

Myocarditis: diagnosis and treatment

OPINION STATEMENT

Myocarditis is a condition that can have a very wide clinical spectrum ranging from asymptomatic forms to fatal disease, but mostly presenting as new onset heart failure with reduced left ventricular ejection fraction, with or without viral syndrome. This condition is an important cause of sudden cardiac death in young patients. High risk features include second and third degree atrioventricular block or malignant arrhythmias. The diagnostic work-up may be challenging, but non-invasive imaging, primarily cardiac magnetic resonance, plays an increasingly important role, although endomyocardial biopsy is still considered a gold standard for diagnosis. Most importantly, myocarditis can transition to non-ischemic cardiomyopathy with eventually poor outcome. In this review, we will summarize the data on different diagnostic and treatment modalities of this disease.

Molecular evaluation of enteroviruses in the pathogenesis of idiopathic dilated cardiomyopathy

BACKGROUND

There is great disparity in the literature as to the presence and relevance of enterovirus in heart tissue from patients with dilated cardiomyopathy (DCM). Published estimates of enteroviral positive tissue in DCM range from 0 to 50%. Very little sequence information is so far available on those samples which are positive.

HYPOTHESIS

Re-examination of fresh biopsy material from patients previously tested, plus 13 new cases of DCM, and sequencing the products would yield information on the validity of the technique and on the type of virus being detected.

METHODS

RNA from biopsy or explant tissue was tested for the presence of enterovirus using reverse transcriptase polymerase chain reaction (PCR). The nucleotide sequences of all positive PCR products were determined by direct sequencing.

RESULTS

Positive PCR signals were found in 10% of samples from patients with DCM and in 16% of control tissues. Two DCM and 12 control samples gave the same nucleotide sequence, which was different from the CB3 used as a positive control. The other 4 DCM samples all produced multiple bands on sequencing.

CONCLUSION

The results do not support a major role for enterovirus in DCM. There is need for some caution, however, as a review of the literature shows that studies using single biopsies, such as this one, produce consistently lower estimates for enterovirus than do those wherein multiple biopsies are examined.

Myocarditis

Viruses are the most common cause of myocarditis in economically advanced countries.

Enteroviruses and adenoviruses are the most common etiologic agents.

Viral myocarditis is a triphasic process. Phase 1 is the period of active viral replication in the myocardium during which the symptoms of myocardial damage range from none to cardiogenic shock. If the disease process continues, it enters phase 2, which is characterized by autoimmunity triggered by viral and myocardial proteins. Heart failure often appears for the first time in phase 2. Phase 3, dilated cardiomyopathy, is the end result in some patients. Diagnostic procedures and treatment should be tailored to the phase of disease.

Viral myocarditis is a significant cause of dilated cardiomyopathy, as proved by the frequent presence of viral genomic material in the myocardium, and by improvement in ventricular function by immunomodulatory therapy.

Myocarditis of any etiology usually presents with heart failure, but the second most common presentation is ventricular arrhythmia. As a result, myocarditis is one of the most common causes of sudden death in young people and others without preexisting structural heart disease.

Myocarditis can be definitively diagnosed by endomyocardial biopsy. However, it is clear that existing criteria for the histologic diagnosis need to be refined, and that a variety of molecular markers in the myocardium and the circulation can be used to establish the diagnosis.

Treatment of myocarditis has been generally disappointing. Accurate staging of the disease will undoubtedly improve treatment in the future. It is clear that immunosuppression and immunomodulation are effective in some patients, especially during phase 2, but may not be as useful in phases 1 and 3. Since myocarditis is often selflimited, bridging and recovery therapy with circulatory assistance may be effective. Prevention by immunization or receptor blocking strategies is under development.

Giant cell myocarditis is an unusually fulminant form of the disease that progresses rapidly to heart failure or sudden death. Rapid onset of disease in young people, especially those with other autoimmune manifestations, accompanied by heart failure or ventricular arrhythmias, suggests giant cell myocarditis.

Peripartum cardiomyopathy in economically developed countries is usually the result of myocarditis.

High prevalence of viral genomes and multiple viral infections in the myocardium of adults with "idiopathic" left ventricular dysfunction

BACKGROUND

For a long time, enteroviruses have been considered to be the most common cause of acute viral myocarditis (MC), with possible transition from MC to dilated cardiomyopathy (DCM). Recent investigations have shown, however, that other viruses are also frequently encountered in MC patients, suggesting that persistence of various virus species may play a pathogenic role in the transition from MC to DCM. The purpose of this study was to screen endomyocardial biopsies (EMBs) from patients with "idiopathic" DCM for the presence of viral genomes by using polymerase chain reaction (PCR) to assess the frequency of cardiac viral infections that may be involved in the pathogenesis of the disease.

METHODS AND RESULTS

EMBs were obtained for PCR analysis from 245 consecutive patients (median left ventricular ejection fraction, 35.0%; range, 9% to 59%). PCR and reverse transcription-PCR were performed to detect the genomic sequences of enterovirus (EV), adenovirus (ADV), human cytomegalovirus (HCMV), herpes simplex virus, Epstein-Barr virus (EBV), human herpesvirus 6 (HHV-6), parvovirus B19 (PVB19), and influenza A and B viruses. Myocardial inflammation was assessed by histological and immunohistological analyses. Viral genomes could be amplified from EMBs of 165 (67.4%) of the 245 DCM patients: EV=23 (9.4%), ADV=4 (1.6%), PVB19=126 (51.4%), HHV-6=53 (21.6%), EBV=5 (2.0%), HCMV=2 (0.8%), including n=45 cases (27.3%) with multiple infections. Active or borderline myocarditis according to the Dallas classification did not exist in any case. Lymphocyte and macrophage infiltrates were not significantly different in virus-positive versus virus-negative patients.

CONCLUSIONS

Viral genomes were frequently detected in EMBs of patients with systolic left ventricular dysfunction. Our data suggest that myocardial persistence of various viruses, often presenting as multiple infections, may play a role in the pathogenesis of DCM far more frequently than suspected so far.

Selective human enterovirus and rhinovirus inhibitors: An overview of capsid-binding and protease-inhibiting molecules

The absence of effective vaccines for most viral infections highlights an urgent necessity for the design and development of effective antiviral drugs. Due to the advancement in virology since the late 1980s, several key events in the viral life cycle have been well delineated and a number of molecular targets have been validated, culminating in the emergence of many new antiviral drugs in recent years. Inhibitors against enteroviruses and rhinoviruses, responsible for about half of the human common colds, are currently under active investigation. Agents targeted at either viral protein 1 (VP1), a relatively conserved capsid structure mediating viral adsorption/uncoating process, or 3C protease, which is highly conserved among different serotypes and essential for viral replication, are of great potential to become antipicornavirus drugs.

Immunomodulatory treatment strategies in inflammatory cardiomyopathy: current status and future perspectives

Chronic autoimmunity and viral persistence constitute prognostic factors for adverse outcome in dilated cardiomyopathy patients. Inflammatory cardiomyopathy is a specific cardiomyopathy entity diagnosed in approximately 50% of dilated cardiopmyopathy patients by immunohistological quantification of immunocompetent infiltrates and cell adhesion molecule abundance. Patients with autoimmune inflammatory cardiomyopathy benefit from immunosuppressive treatment and immunoadsorption by improvement of left ventricular ejection fraction and heart failure symptoms, paralleled by a significant suppression of intramyocardial inflammation. However, dilated cardiomyopathy patients with viral persistence do not respond favorably to immunosuppression.

Immunomodulatory effect of pentoxifylline in suppressing experimental autoimmune myocarditis

Although a recent clinical study reported the beneficial effects of pentoxifylline (PTX), a phosphodiesterase inhibitor, on both symptoms and cardiac function in dilated cardiomyopathy (DCM), the precise mechanism of the drug has not been delineated. This study examined the efficacy of PTX in the treatment of experimental autoimmune myocarditis (EAM), as a model of the autoimmune mechanism involved in DCM. Oral PTX, or saline as control, was administered to Lewis rats at 150mg/kg body weight per day bid daily from 5 days before immunization with cardiac myosin until death on Day 21. Histological examination of the hearts showed PTX significantly reduced the severity of EAM. mRNA expression of tumor necrosis factor (TNF)-alpha, interleukin (IL)-4, IL-6, and IL-10 was significantly reduced in peripheral blood mononuclear cells, but expression of IL-4 and IL-6 was upregulated in heart tissue. PTX in vitro could suppress T cell proliferation and inhibit TNF-alpha and interferon-gamma production. In conclusion, the immunomodulatory effects of PTX had a significant therapeutic result in EAM. This is the first report to describe such an effect of PTX in a specific animal model for DCM.

Absence of viral nucleic acids in early and late dilated cardiomyopathy

OBJECTIVE

To investigate whether viral infection acts as a trigger factor for the development of dilated cardiomyopathy in genetically predisposed individuals with a family history of disease.

SETTING

Patients attending the cardiomyopathy unit in a cardiac tertiary referral centre.

DESIGN

Nested polymerase chain reaction (nPCR) was used to determine whether enteroviral, adenoviral, or cytomegaloviral nucleic acids were detectable in the myocardium of 19 asymptomatic relatives of patients with dilated cardiomyopathy; all these relatives had echocardiographic abnormalities thought to represent early disease. Explanted hearts from patients with end stage dilated cardiomyopathy were also studied and were compared with 25 controls (ischaemic heart disease (21), valvar heart disease (2), hypertrophic cardiomyopathy (1), restrictive cardiomyopathy (1)). Myocardial tissue from two fatal cases of culture positive coxsackie myocarditis was used as a positive control.

RESULTS

No viral nucleic acid was detected in any group other than in those with myocarditis. Spiking of random wells with purified recombinant viral nucleic acids confirmed the sensitivity and reproducibility of the assays.

CONCLUSIONS

Myocardial viral infection is not detectable in relatives of patients with dilated cardiomyopathy who are suspected of having early disease. There is no evidence that viruses act as a trigger factor for initiating the dilated cardiomyopathy in these patients.

Detection of enteroviruses ribonucleic acid sequences in endomyocardial tissue from adult patients with chronic dilated cardiomyopathy by a rapid RT-PCR and hybridization assay

A rapid reverse transcription polymerase chain reaction (RT-PCR) and microwell capture hybridisation assay with general specificity for enteroviruses was developed and compared with an improved nested RT-PCR for the detection of enteroviral RNA sequences in endomyocardial tissue from patients with chronic dilated cardiomyopathy. This method could detect as few as 20 genomic RNA copies per 100 mg of heart tissue homogenate and results could be obtained within 8 hours. Of the 55 biopsy specimens aseptically collected from the explanted hearts of 55 patients, 21 (38.2%) were positive by RT-PCR microplate assay, whereas only 19 (34.5%) were positive by nested RT-PCR assay and none were positive by classical cell culture assays. No enterovirus was detectable by RT-PCR or classical cell culture assays in any of the 55 heart biopsy specimens taken from organ donors without any known heart disease. Moreover, the nucleotide sequences of EV nested RT-PCR products showed greatest similarity to group B Coxsackieviruses [CVB3 (n = 12) or CVB5 (n = 3)], but also to group A Coxsackieviruses (CVA21 (n = 1) or CVA9 ( n= 3)]. The described RT-PCR and microwell capture hybridisation assay can be applied to the virological diagnosis of human enteroviral cardiac infections. Moreover our findings suggest that group B and group A Coxsackieviruses can persist in heart tissue from patients with end-stage chronic cardiomyopathy, supporting the hypothesis that these viruses could be implicated in the etiology of idiopathic dilated cardiomyopathy.

Characterization of T cell receptor beta chains of accumulating T cells in chronic ongoing myocarditis demonstrated by heterotopic cardiac transplantation in mice

Autoimmne mechanisms have been implicated in the pathogenesis of chronic ongoing mycarditis. An earlier study of murine chronic ongoing myocarditis reported that infiltrating T cells and macrophages were prominent in the normal donor heart, in a heterotopic cardiac transplantation model. It was demonstrated that myocarditis was transferred to a normal heart transplanted into a mouse with chronic myocarditis. The present study investigated an autoimmune link to the pathogenesis of chronic ongoing myocarditis by analyzing the T cell clonalities in the model. To characterize the accumulating T cells in the donor heart, the T cell receptor beta genes (TCRBG) were amplified by reverse transcriptase-polymerase chain reaction (RT-PCR) from mRNA in the donor hearts and accumulating TCRBG clonotypes were contrasted with those from recipient hearts. Inbred 3-week-old A/J mice were inoculated intraperitoneally with Coxsackievirus B3 (Nancy strain), 2 x 10(4) PFU, and housed for more than 60 days. Normal A/J mouse hearts were transplanted into the same strain of mice without myocarditis, as well as into the mice with chronic ongoing myocarditis. Both recipient and donor hearts were evaluated histologically 2 weeks after the transplantation. TCRBG were amplified by RT-PCR from mRNA of recipient and donor hearts and spleens. The specific accumulating TCRBG clonotypes were identified by their single strand conformation polymorphism. Multiple clonotypic accumulations occurred in the donor heart after cardiac transplantation. Distinct oligoclonal accumulation of TCR Vbeta1, 10, and 13 T cells was found in both recipient and donor hearts in 3 of 4 mice. Moreover, these clonotypes were not observed in spleen cells of the recipient mice. T specific cells expanding clonotypes of TCRBG are responsible for transferring myocarditis to the donor heart. An autoimmune response may, therefore, play a key role in the progression of chronic ongoing myocarditis.

Evaluation of viral infection in the myocardium of patients with idiopathic dilated cardiomyopathy

OBJECTIVES

The aim of this study was to evaluate the viral etiology of idiopathic dilated cardiomyopathy (DCM).

BACKGROUND

The demonstration of enteroviral genome in hearts with DCM has reinforced the importance of enteroviruses in the pathogenesis of DCM. However, there is uncertainty about the character and activity of enteroviruses detected in the myocardium. Recently, the association of hepatitis C virus or adenovirus with DCM has been reported.

METHODS

Myocardial specimens from 26 patients with idiopathic DCM, which were obtained at partial left ventriculectomy (PLV), were examined virologically. Strand-specific detection of enteroviral RNA was performed to differentiate active viral replication from latent persistence. Polymerase chain reaction was used to detect genomic sequences of hepatitis C virus, adenovirus, cytomegalovirus, influenza viruses, mumps virus, herpes simplex viruses, varicella-zoster virus and Epstein-Barr virus.

RESULTS

Plus-strand enteroviral RNA was detected in 9 (35%) of the 26 patients. Minus-strand enteroviral RNA was determined in seven (78%) of these nine plus-strand RNA-positive patients. Sequence analysis revealed that the enteroviruses detected were coxsackie B viruses, such as coxsackievirus B3 and B4. However, genetic material from other viruses was not detected. Six (86%) of seven minus-strand enteroviral RNA-positive patients died of cardiac insufficiency within the first six months after PLV.

CONCLUSIONS

Coxsackie B viruses were seen in hearts with idiopathic DCM. Active viral RNA replication appeared to be present in a significant proportion of these cases. Minus-strand coxsackieviral RNA in the myocardium can be a marker for poor clinical outcome after PLV. There was no evidence of persistent infection by other viruses in hearts with DCM.

Cardiomyopathy in childhood, mitochondrial dysfunction, and the role of L-carnitine

Cardiomyopathy in childhood is associated with high morbidity and mortality rates. Many metabolic causes have been identified, including genetic or acquired defects in mitochondrial energy production affecting beta-oxidation, carnitine transport, and the electron transport chain. Combining conventional inotropic and antiarrhythmic therapy with metabolic interventions has improved overall outcome. L-carnitine, a natural substance involved in mitochondrial transport of fatty acids, is one such therapy and plays a central role in the regulation of the inner mitochondrial supply of free coenzyme A. Carnitine deficiency can be caused by both genetic and environmental causes with resultant signs and symptoms of metabolic disease, including cardiomyopathy. Administration of L-carnitine can result in improvement or resolution of the cardiomyopathy.

Detection of enteroviral RNA in end-stage dilated cardiomyopathy in children and adolescents

Medical records and archival myocardial specimens of 33 children and adolescents with end-stage idiopathic dilated cardiomyopathy (IDCM) were collected to evaluate retrospectively the potential role of enteroviral persistence in the pathogenesis of IDCM. The clinical history and laboratory assessment of each patient were reviewed carefully in order to obtain information on the nature and etiology of infections in the past and at the time of diagnosis of cardiomyopathy. Sixty-four formaldehyde-fixed, paraffin-embedded myocardial specimens, obtained from endomyocardial biopsies (n = 5), explanted hearts (n = 10), or autopsies (n = 49), were studied by the polymerase chain reaction (PCR) and by in situ hybridization to detect enteroviral RNA in the specimens. Control specimens included 34 formaldehyde-fixed, paraffin-embedded myocardial specimens from children with other cardiomyopathies, metabolic diseases, structural heart defects, or various noncardiac malignancies. The presence of cellular RNA in the specimens was confirmed by amplification of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA or beta-actin mRNA as positive controls. Only one specimen from the 32 IDCM patients with appropriate myocardial specimens was positive for enteroviral RNA by PCR. Sequence analysis of the amplified viral segment showed a significant degree of homology between the viral sequence and echovirus 1. One specimen from the control patients also appeared positive by PCR, but sequence analysis of the amplified viral segment revealed it as rhinovirus 16. The results do not indicate any significant role for enteroviral persistence in end-stage childhood IDCM, although they need to be confirmed using a prospective study with fresh frozen specimens. However, mechanisms other than viral persistence may be more important in the progression of IDCM to end-stage heart failure in this age group.

Idiopathic dilated cardiomyopathy: lack of association with hepatitis C virus infection

OBJECTIVE

To determine whether there is an association between hepatitis C virus (HCV) infection and dilated cardiomyopathy in a well defined area of north western Greece; such an association has been reported elsewhere.

DESIGN

Evaluation of consecutive patients with chronic HCV infection for the presence of clinical or subclinical manifestations of dilated cardiomyopathy by history, physical examination, and non-invasive laboratory procedures (ECG, chest x ray, and echocardiography) before the initiation of interferon alpha treatment; investigation for HCV infection markers in patients with dilated cardiomyopathy by enzyme and immunoblot assays (antibodies to HCV) and the reverse transcriptase polymerase chain reaction (HCV RNA).

SETTING

A tertiary referral centre for patients with chronic hepatitis and dilated cardiomyopathy.

PATIENTS

102 patients with well defined chronic HCV infection and 55 patients with well established dilated cardiomyopathy were evaluated.

MAIN OUTCOME MEASURES

The need for HCV testing in patients with dilated cardiomyopathy, or follow up for heart disease in patients with chronic HCV infection.

RESULTS

None of the patients with chronic HCV infection had clinical or subclinical evidence of dilated cardiomyopathy from history and laboratory findings. None of the patients with dilated cardiomyopathy was positive for antibodies to HCV or viraemic on HCV RNA testing.

CONCLUSIONS

The study neither confirms the findings of other investigators, nor indicates a pathogenic link between HCV and dilated cardiomyopathy. For this reason, at least in Greece, testing for HCV in patients with dilated cardiomyopathy or follow up for heart disease in HCV patients appears unnecessary. Genetic or other factors could be the reason for this discrepancy if previously reported associations between HCV and dilated cardiomyopathy or hypertrophic cardiomyopathy were not coincidental.

Meta-analysis of the association of enteroviruses with human heart disease

The role of viruses in the genesis of both dilated cardiomyopathy (DCM) and acute myocarditis remains uncertain. Modern molecular techniques such as polymerase chain reaction (PCR) and in situ hybridisation are sensitive means of detecting viral genomic material in human myocardial tissue and may help to resolve the quest. Meta-analysis of the papers in the literature records studies of both acute myocarditis and DCM where molecular techniques were used to demonstrate enteroviruses. This review studies information from the published literature as well as statistical analysis of the cumulative molecular data relating enteroviruses to DCM, and to compare these findings with the information available on the role of enteroviruses in acute myocarditis. Twelve papers reported studies in acute myocarditis, of which 11 found higher percentages of enteroviral RNA positivity in the diseased population, giving an overall odds ratio of 4.4. Seventeen papers reported studies in DCM, with 11 recording higher positivity rates in these patients. Cumulative analysis of these data suggests an overall odds ratio of 3.8. The causative role of enteroviruses in acute myocarditis, particularly in children, is supported by meta-analysis of the available literature. The data on DCM is suggestive of an association but a proportion of the studies are negative.

Enterovirus heart disease of adults: a persistent, limited organ infection in the presence of neutralizing antibodies

Detection of enterovirus RNA in endomyocardial biopsies (EMB) by reverse transcription/polymerase chain reaction (RT-PCR) is currently the preferred diagnostic procedure in suspected enterovirus heart disease (EHD), which can present clinically as myocarditis, dilated cardiomyopathy (DCM), and arrhythmogenic right ventricular cardiomyopathy (ARVC). EMB and peripheral blood mononuclear cells (PBMC) of 44 patients with suspected EHD were examined by nested RT-PCR to investigate whether the myocardial enterovirus infection is limited to the heart or is generalized. Enterovirus RNA was detected in EMB, but not in PBMC, of 8 patients (3 of these suffered from ARVC), whereas EMB of 16 controls and PBMC of 45 controls were negative. In addition, enterovirus RNA was demonstrated in PBMC, but not in EMB, of a single patient with suspected EHD. A high sequence homology of the amplicons to coxsackievirus B3 was demonstrated in 7 patients, and to coxsackievirus B2 in two patients. In order to evaluate whether the myocardial enterovirus infection was acute or persistent, neutralization and complement fixation tests were performed for antibodies against the serotypes indicated by the nucleic acid sequences. Neutralizing antibodies were detected in the sera of all 9 patients, but complement fixing antibodies were demonstrated only in one EHD patient and in the patient positive for enterovirus RNA in PBMC. In conclusion, the molecular and serological data demonstrate that CVB3 predominates as cardiotropic enterovirus, and that the enterovirus replication is limited to the heart in EHD. Serological results support the hypothesis of myocardial enterovirus RNA persistence in spite of neutralizing antibodies.

Enteroviral RNA and virus-like particles in the skeletal muscle of patients with idiopathic dilated cardiomyopathy

The role of chronic viral infection in the etiopathogenesis of idiopathic dilated cardiomyopathy (IDC) has generated considerable research. Enteroviruses were the favorite candidates as etiologic agents of IDC. However, enteroviruses were rarely demonstrated in affected hearts. We investigated whether enteroviral infection persists in the heart and in extracardiac sites, particularly in skeletal muscle, in patients with IDC. Blood and myocardial and skeletal muscle samples were collected at cardiac transplantation from 31 IDC patients, 24 non-IDC heart disease patients, and 3 heart donors. Samples underwent ultrastructural studies and ribonucleic acid (RNA) extraction. RNA was reverse-transcribed, and 2 nested fragments (bps 179 and 126) were amplified in the highly conserved 5' noncoding region of enteroviral genomic RNA. Enteroviral RNA was found in the skeletal muscle of 12 cases, whereas only 4 hearts (2 of which with positive skeletal muscle) were positive. Of the 24 controls, 2 were positive (1 muscle and heart, 1 muscle only). Automated sequencing confirmed the enteroviral nature of the amplified products. Ultrastructural study showed enterovirus-like particles in 4 of the enterovirus-positive muscles, and myopathic changes in all enterovirus-positive cases. Skeletal muscle hosts chronic enteroviral infection in more than one third of patients with sporadic IDC. Two hypotheses may explain this link. Myocardial damage may derive directly from recurrent subclinical heart infections caused by enteroviruses harbored in skeletal muscle. Alternatively, enterovirus-related myopathy may trigger an autoimmune response to antigens shared by muscle and myocardium. Further studies are needed to assess the importance of these, non-mutually exclusive mechanisms in IDC pathogenesis.

Myocardial damage assessed by indium-111-antimyosin: correlation with persistent enteroviral ribonucleic acid in dilated cardiomyopathy

The persistence of enteroviral ribonucleic acid (RNA) in the myocardium has been implicated as a pathogenetic factor in idiopathic dilated cardiomyopathy. Enteroviral persistence may lead to myocardial cell membrane damage, resulting in increased uptake of antimyosin antibodies. To further evaluate this hypothesis, a direct comparison of myocardial antimyosin uptake with the presence of enteroviral RNA was performed in ten patients (one female, nine male; 53+/-8 years) with chronic dilated cardiomyopathy. Planar antimyosin images were obtained 48 h after the injection of indium-111-labelled antimyosin Fab. Using a region of interest technique, the heart to lung uptake ratio (HLR) was calculated as a semiquantitative parameter of myocardial tracer uptake. Cardiac catheterization was performed to assess left ventricular function and to obtain myocardial biopsy samples. In the biopsy samples, gene amplification by polymerase chain reaction (PCR) was used to specifically detect enteroviral RNA. In the ten patients, the left ventricular ejection fraction was 39%+/-11% and the end-diastolic volume 131+/-46 ml/m2. The HLR was 1.72+/-0.21 and showed no correlation with functional parameters. In two patients with a positive PCR consistent with persisting enteroviral RNA, the HLR was not higher than that in eight patients with a negative PCR (1.46+/-0. 18 vs 1.78+/-0.18, respectively). These results suggest that increased uptake of 111In-antimyosin in chronic idiopathic dilated cardiomyopathy cannot be explained by pure persistence of enteroviral RNA. Other pathogenetic factors such as myocardial autoantibodies or microvascular spasm may be responsible for myocyte membrane damage detected by antimyosin.

Inflammatory myocardial diseases and cardiomyopathies

Inflammatory myocardial disease has been associated with a variety of infectious and noninfectious etiologies. It is associated with the development of dilated cardiomyopathy in some patients. Given its imprecise diagnosis, varied clinical presentation and undefined natural history, it is quite difficult to make broad generalizations regarding its evaluation and treatment. It is hoped continued application of new molecular biological and other techniques will shed further light on the pathophysiologic mechanisms of myocarditis in humans, thus pointing to therapeutic interventions.

Autoimmune response in chronic ongoing myocarditis demonstrated by heterotopic cardiac transplantation in mice

BACKGROUND

Autoimmune mechanisms have been implicated in the pathogenesis of chronic ongoing myocarditis. To investigate this relation, we used an A/J mouse model inoculated with coxsackievirus B3 and determined whether myocarditis would be transferred to normal hearts that were heterotopically transplanted.

METHODS AND RESULTS

Inbred 3-week-old A/J mice were inoculated intraperitoneally with coxsackievirus B3 (Nancy strain; 2 x 10(4) plaque-forming units) and housed for > 60 days. The presence of the viral genome in the myocardium was determined by the polymerase chain reaction with primers specific for the 5' end of the coxsackievirus B3 genome performed at 40, 50, or 60 days after inoculation. Normal A/J mouse hearts were transplanted into the same strain of mice without myocarditis (group A) and into mice with chronic ongoing myocarditis (group B). The hearts were evaluated histologically 2 weeks after transplantation. Conventional histological examination of infiltrated T cells and macrophages was performed, and the expression of intercellular adhesion molecule-1, major histocompatibility complex (MHC) class I antigen, and MHC class II antigen was evaluated by immunoenzymatic staining. The concentrations of interleukin-1 alpha (IL-1 alpha) and tumor necrosis factor (TNF-alpha) in the grafts were measured with an ELISA. The viral RNA genomes were not detected in the mice with chronic ongoing myocarditis, but their transplanted hearts did show myocarditis. In the hearts with induced myocarditis, infiltrated mononuclear cells consisted of CD4+ T cells, CD8+ T cells (CD4+ cell number > CD8+ cell number), and macrophages. Intercellular adhesion molecule-1, MHC class I antigen, and MHC class II antigen were expressed in the vascular endothelial cells and myocardial cells in and around the infiltrated lesions. The concentrations of IL-1 alpha and TNF-alpha in group B were significantly higher than those in group A (group A versus group B: IL-1 alpha, 125 +/- 35 versus 180 +/- 34 pg/mL; TNF-alpha, 45 +/- 15 versus 96 +/- 40 pg/mL; P < .05).

CONCLUSIONS

Results suggest that an autoimmune response may play a key role in the progression of chronic ongoing myocarditis.

Recognition and optimum management of myocarditis

Myocarditis is a poorly understood condition and its prevalence is largely underestimated. A significant proportion of cases may be subclinical and chronic, leading to dilated cardiomyopathy, which represents the first cause of heart transplantation worldwide. Although inflammation of the myocardium can be associated with various causes, particularly viruses, myocarditis is usually idiopathic. Present evidence suggests that some 'idiopathic' and chronic 'postviral' myocarditis cases may be autoimmune, whereas others with acute self-limited disease or with persisting pathogenic virus by molecular methods may represent viral myocarditis. The major obstacle in identifying a specific therapy in myocarditis lies in the difficulty of a thorough clinical characterisation of individual patients in relation to viral and autoimmune involvement. This also explains the inconclusive results of trials of immunosuppressive drugs in myocarditis/dilated cardiomyopathy. Diagnosis is based upon endomyocardial biopsy. Management of myocarditis requires avoidance of agents that exacerbate myocarditis or depress myocardial function, and conventional therapy for heart failure (diuretics, ACE inhibitors and, if indicated, digoxin) and arrhythmias. Although at present the use of immunosuppressive therapy cannot be recommended on a routine basis, the recent Myocarditis Treatment Trial, where an aetiologically heterogeneous patient population was treated without significant adverse effects, provides some rationale for applying the same immunosuppression protocol to selected patients, e.g. those with active biopsy-proven myocarditis, unresponsive to conventional therapy, prior to transplantation, and those with idiopathic giant cell myocarditis.

Evidence for autoimmunity to myosin and other heart-specific autoantigens in patients with dilated cardiomyopathy and their relatives

Autoimmune disease is characterised by the presence of circulating autoantibodies in the affected patients and in a proportion of their relatives. These antibodies are generally not pathogenic but are reliable markers of immune-mediated tissue damage. In organ-specific autoimmune disease, the destruction process is largely restricted to one organ within the body and the autoantibodies react with autoantigens which are unique to the diseased target organ. At least in a patient subset, myocarditis and dilated cardiomyopathy (DCM) may represent the acute and chronic stages of a progressive organ-specific autoimmune disease of the myocardium. Autoimmune features in patients with myocarditis/DCM include: familial aggregation, a weak association with HLA-DR4, abnormal expression of HLA class II on cardiac endothelium on endomyocardial biopsy, and detection of organ- and disease-specific cardiac autoantibodies, by immunofluorescence and absorption techniques, in the affected patients and in a proportion of their symptom-free relatives from both familial and non-familial DCM pedigrees. The organ-specific cardiac autoantibodies detected by immunofluorescence are directed against multiple antigens. One of these, first identified using immunoblotting and confirmed by ELISA, is the cardiac-specific alpha-myosin isoform. Myosin fulfils the expected criteria for organ-specific autoimmunity, in that immunisation with cardiac but not skeletal myosin reproduces, in susceptible mouse strains, the human disease phenotype of DCM; in addition, alpha-myosin is entirely cardiac-specific and is only expressed in the myocardium. Using ELISA, high titer organ- and disease-specific anti alpha-myosin antibodies have been found in 16% of the symptom-free relatives of DCM patients and in 38% of the pedigrees of the same cohort of relatives studied by immunofluorescence. The ELISA results provide additional evidence for autoimmunity in a subset of DCM families, and emphasise the importance of alpha-myosin as a target antigen.

Molecular detection and differentiation of enteroviruses in endomyocardial biopsies and pericardial effusions from dilated cardiomyopathy and myocarditis

Enteroviruses (EVs), especially group B coxsackieviruses, have been implicated in the pathogenesis of myocarditis and dilated cardiomyopathy (DCM). To determine whether a specific type of EV is present in DCM hearts, we examined the genotypes of EVs detected in endomyocardial biopsies and pericardial effusions by polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) analysis. Positive PCR results were obtained from biopsies in 6 (19 percent) of 31 patients with DCM, 5 (18 percent) of 28 with myocarditis, 5 (22 percent) of 23 with other cardiac diseases, and from pericardial effusions in 4 (57 percent) of 7 patients with pericarditis. SSCP profiles of most of the clinical samples were different and were not identical to any of the standard group B coxsackie viruses. Our findings suggest that EV genomes are involved in the myocardium of patients with various cardiac conditions and that a particular type of EV is not present in DCM hearts.

Detection of enteroviral RNA by polymerase chain reaction in endomyocardial tissue of patients with chronic cardiac diseases

Enteroviruses are suspected to be etiologic agents in myocarditis and cardiomyopathy. The prevalence of enteroviral (EV) heart infection in patients with chronic cardiomyopathy was determined through detection of specific EV genomic sequences using reverse transcription and polymerase chain reaction (RT-PCR) followed by slot blotting. Endomyocardial biopsies from the explanted hearts of 19 patients with dilated cardiomyopathy (DCM) and 14 patients with chronic coronary disease (CCD) were examined. EV genome was detected in 11 of 19 patients with DCM and in 8 of 14 patients with CCD. Ventricular biopsies from the control group, which included 35 healthy heart patients and 33 patients with myocardial infarction, were negative by EV RT-PCR. The percentage of patients showing presence of EV-RNA was almost similar in the DCM (57.9%) and CCD (57.1%) groups. The present study demonstrates that enterovirus RNA sequences persist in the myocardium in a significant proportion of patients suffering from end-stage ischaemic and dilated cardiac diseases and supports the hypothesis of a possible direct link between EV infection and the pathogenesis of chronic heart disease.

Persistence of virus and viral genome in myocardium after coxsackievirus B3-induced murine myocarditis

Following infection with Coxsackievirus B3 (CVB3), A-strain mice develop ongoing myocarditis that persists after the virus ceases to be cultivatable from heart tissue. We studied the natural history of this virus-induced but apparently autoimmune inflammation by means of in situ hybridization (ISH) and by polymerase chain reaction (PCR). Both ISH and culture allowed detection of virus up to 2 weeks post-infection in virtually all heart tissues. In contrast, PCR revealed the presence of viral genome for a substantially longer period of time, i.e. at least 34 days after CVB3 infection. Similarly, the majority of mice showed myocardial inflammation at this time point. However, the persistence of virus did not correlate with ongoing myocarditis, and vice versa. Most mice with ongoing myocarditis produced heart myosin autoantibodies, most probably as a result of tissue damage. The lack of correlation between presence of ongoing inflammation and persistence of virus supports our previous view that the late phase of CVB3-induced myocarditis is mediated by autoimmunological mechanisms.

Mitochondrial DNA deletions in dilated cardiomyopathy: a clinical study employing endomyocardial sampling

OBJECTIVES

The aim of this study was to assess the occurrence of the two most commonly encountered mitochondrial DNA (mtDNA) deletions in the hearts of patients with idiopathic dilated cardiomyopathy.

BACKGROUND

The mutation frequency of mtDNA is high, and sporadic cases of cardiomyopathies associated with mtDNA deletions have been described. Reports of increases in mtDNA deletions with advancing age also exist.

METHODS

We studied 15 consecutive patients with typical signs of idiopathic dilated cardiomyopathy, without a family history, together with 16 control hearts obtained at autopsy from patients who died of noncardiac causes. The patients underwent both right and left heart catheterization, during which endomyocardial biopsy samples were taken. The mtDNA in these samples and in the control hearts was analyzed by the polymerase chain reaction technique for the occurrence and proportion of 5- and 7.4-kilobase (kb) deletions (Cambridge sequence map positions from nucleotides 8469 to 13447 and 8637 to 16084, respectively).

RESULTS

The 5-kb mtDNA deletion was observed in the hearts of all of the patients with idiopathic dilated cardiomyopathy, accounting for 0.32 +/- 0.05% (mean +/- SEM) of the total mtDNA. The 7.4-kb deletion was found in 7 of the 15 patients with idiopathic dilated cardiomyopathy and comprised 0.28 +/- 0.08% of the total. The 5- and 7.4-kb deletions were detected in 12 and 9 control hearts, respectively, quantitatively similar to the patients with idiopathic dilated cardiomyopathy. A sigmoidal age dependency of the mtDNA deletions was found both in the patients with cardiomyopathy and in the control hearts, but after elimination of the confounding age variable, there was no difference between these groups.

CONCLUSIONS

Because of the similarity of the age-dependent increase in the frequency of mtDNA deletions in cardiomyopathic and control hearts, the deletions have no causal relation with idiopathic dilated cardiomyopathy. The present results confirm the notion of an increase in mtDNA deletions with advancing age and show that endomyocardial tissue sampling is a feasible method for detecting mtDNA defects in affected hearts.

Endomyocardial biopsy--technical aspects experience and current status. An Indian perspective

Our study ellucidates the utility of endomyocardial biopsy (EMB) in various cardiac-muscle disorders seen in a tropical country like India. The procedure has been successfully performed in 501 patients (572 procedures) at our centre from April 1985 to December 1992. This included 60 infants and children. The indications were dilated cardiomyopathy (DCM) in 214, non-specific aortoarteritis in 91, rheumatic heart disease in 75, restrictive cardiomyopathy in 45, constrictive pericarditis in 14 and miscellaneous in 62 patients. There was no mortality, however, one patient developed cardiac tamponade and another sustained ventricular tachycardia requiring cardioversion. There was transient atrial fibrillation in six patients and all these had acute rheumatic heart disease. Transient complete heart block occurred in six patients with underlying left-bundle branch-block. Histological examination of EMB revealed myocarditis in 34/214 (15.4%) patients in DCM group and helped in following up these cases on immunosuppressive treatment. In the presence of restrictive haemodynamics it could identify amyloidosis in four patients. It was also helpful in differentiating between endomyocardial fibrosis and chronic constrictive pericarditis. In patients with non-specific aorto-arteritis significant histological changes of inflammatory myocarditis were observed in patients especially in congestive heart failure. Furthermore, it was helpful in identifying the nature of cardiac tumour in one patient. Its utility has also been evaluated in disorders, including rheumatic heart disease, peripartum cardiomyopathy and systemic disorders like systemic lupus erythematosis. Even in the absence of cardiac-transplant programmes at national level we have found EMB to be a useful investigation in a tropical country like India.

A prospective case-control study of antibodies to coxsackie B virus in idiopathic dilated cardiomyopathy

OBJECTIVES

This study was conducted to determine the frequency and significance of Coxsackie B virus-specific immunoglobulin-M (IgM) in patients with idiopathic dilated cardiomyopathy and compare them with the frequency in both unmatched and matched control subjects.

BACKGROUND

The principal evidence supporting a pathoetiologic role for Coxsackie B viruses in human dilated cardiomyopathy is derived from retrospective serologic studies. These studies have evaluated patients with end-stage disease and have failed to recognize the importance of assessing both matched and unmatched control subjects.

METHODS

In this prospective case-control study, we assessed sera for Coxsackie B virus-specific IgM (serotypes B1 to B5) from 114 patients with dilated cardiomyopathy at diagnosis or referral to our center, 94 healthy unmatched control subjects, 41 healthy matched control subjects from the same general practitioner and 32 members of the patients' own households.

RESULTS

A higher frequency of positive Coxsackie B virus IgM was observed in patients with dilated cardiomyopathy than in unmatched control subjects (33% vs. 5%; p = 3 x 10(-7)). In patients with dilated cardiomyopathy, the response was monotypic (84%), commonly against serotypes B2 and B5, and was not associated with any clinical or histologic feature. The frequency of positive virus-specific IgM was similar in patients with dilated cardiomyopathy and their 41 matched community control subjects (46% vs. 27%; p = 0.11) and 32 household contacts (37% vs. 28%; p = 0.59). Control subjects who tested positive for virus-specific IgM tended more commonly to be seropositive than did control seronegative subjects (community control subjects 37% vs. 18%, p = 0.32; household contacts 42% vs. 20%; p = 0.36) and had an identical serotypic response in 4 (33%) of 12 cases.

CONCLUSIONS

The frequency of Coxsackie B virus IgM was higher in patients with dilated cardiomyopathy than in unmatched control subjects but was similar in patients and control subjects who shared the same environment, indicating local spread of infection. The reason for the association between Coxsackie B virus IgM and dilated cardiomyopathy and its relevance to pathogenesis remain to be established.

Viral infection and the pathogenesis of dilated cardiomyopathy

Long-term follow-up studies of patients with suspected viral myocarditis reveal progression to dilated cardiomyopathy (DCM) in a significant number of cases. Thus, an underlying viral etiology has been hypothesized in the pathogenesis of ongoing heart disease that leads to DCM. Recent application of molecular biology in clinical diagnosis has strengthened this hypothesis. By use of probe hybridization and polymerase chain reaction, enteroviral RNA has been detected in the myocardium of patients at all stages of the disease process: myocarditis, chronic heart disease, and DCM. Experimental murine models of enterovirus-induced heart disease provide a framework for examining the pathogenic mechanisms. Viral cytotoxicity, immunological responses, viral RNA persistence, and spasm of the coronary microvasculature are all implicated in the ongoing disease process. Abnormal cardiac function and heart failure are attributed to the pathological changes that occur.

Dilated cardiomyopathy and myocarditis in Kenya: an endomyocardial biopsy study

We have studied, by light and electron microscopy, left ventricular endomyocardial biopsy specimens from 18 African patients (14 men) with idiopathic dilated cardiomyopathy in Nairobi. Nine patients (50%) had evidence of healing myocarditis, that is the presence of a mild inflammatory cell infiltration within the myocardium. Interstitial fibrosis was prominent in five patients (28%) and in all 18 specimens there were hypertrophied muscle fibres. Therefore, half of the patients with idiopathic dilated cardiomyopathy had histological signs of a previous myocarditis. There was no serological evidence of a previous or recent coxsackie infection or any other common viral infections. It seems probable that the myocarditis was due to an inappropriate immunological reaction to myocardial muscle.