Search for Coxsackievirus B3 RNA in idiopathic dilated cardiomyopathy using gene amplification by polymerase chain reaction

Inflammatory dilated cardiomyopathy : Etiology and clinical management

Inflammatory dilated cardiomyopathy (DCMi) is a syndrome, not an etiological disease entity. The infective etiology and the immunopathology can be best determined through endomyocardial biopsy with a complete work-up by light microscopy, immunohistology, and polymerase chain reaction for microbial agents. This review focuses on the methodological advances in diagnosis in the past few years and exemplifies the importance of an etiology-orientated treatment in different case scenarios. In fulminant nonviral myocarditis, immunosuppressive treatment together with hemodynamic stabilization of the patient via mechanical circulatory support (e.g., microaxial pumps, extracorporeal membrane oxygenation, left ventricular assist device) can be life-saving. For viral inflammatory cardiomyopathy, intravenous immunoglobulin treatment can resolve inflammation and often eradicate the virus.

[102 patients with suspected myocarditis : Clinical presentation, diagnostics, therapy and prognosis]

INTRODUCTION

Myocarditis is a disease which is difficult to diagnose and which includes a risk of the development of dilated cardiomyopathy and sudden cardiac death.

METHODS AND PATIENTS

In this study 102 patients were included from the time period 2003-2013 after diagnosis or suspected diagnosis of myocarditis in the department of internal medicine at the University Hospital Halle (Saale).

RESULTS

Of the study participants 77.5% were male and the average age was 35.5 ± 14.1 years. The symptoms reported by the patients were angina in 46.1%, dyspnea in 38.2%, performance deterioration in 29.4%, palpitations in 9.8% and syncope in 8.8%. In 45.1% of patients, symptoms were preceded by a respiratory infection. All patients underwent an echocardiogram and in 36.5% it was possible to demonstrate a regional wall motion abnormality and in 20.4% a pericardial effusion. A myocardial biopsy was performed in 15.6% of the patients. The presence of cardiotropic viruses was investigated in 37.3% of patients but was detected in only 5.9%. Cardiac magnetic resonance imaging (MRI) was performed in 82 patients of whom 33.3% showed a late enhancement and 11.9% a wall movement disorder. In this study four patients, all male, died and three suffered recurrent myocarditis.

CONCLUSION

This study showed the wide range of symptoms in myocarditis. Myocarditis is rarely severely manifested and in this study the mortality was 3.9%. For further optimization of the diagnostic and treatment algorithms, prospective, randomized studies would be desirable.

Analysis of formalin-fixed and frozen myocardial autopsy samples for viral genome in childhood myocarditis and dilated cardiomyopathy with endocardial fibroelastosis using polymerase chain reaction (PCR)

Viral infection of the myocardium is implicated in the pathogenesis of myocarditis and dilated cardiomyopathy (DCM). Enteroviruses have been considered the most common viral etiologic agents, based on peripheral culture and serologic methods. Recently, polymerase chain reaction (PCR) has been shown to be useful in the detection of viral genomes from various infected organs and body fluids. In this study, myocardial samples from autopsy specimens (formalin fixed and fresh frozen) were examined for enteroviral and DNA viral (adenovirus, herpes simplex virus [HSV], and cytomegalovirus (CMV]) genome by PCR. The specimens studied were from 58 patients with myocarditis, 28 patients with DCM and endocardial fibroelastosis [EFE], and 22 controls. Viral genome was detectable in 34 of the 58 (59%) autopsy-proven myocarditis samples (18 adenovirus, 12 enterovirus, 2 CMV, 2 HSV) and 6 of the 28 samples from patients with DCM and EFE (6 adenovirus). We conclude that PCR is effective in the rapid amplification of virus from frozen and formalin-fixed myocardial samples and that adenovirus is an important etiologic agent in viral myocarditis as well as DCM with EFE.

Classification and histological, immunohistochemical, and molecular diagnosis of inflammatory myocardial disease

In the WHO 1996 classification of cardiomyopathies, myocarditis is defined as an "inflammatory disease of the myocardium associated with cardiac dysfunction" and is listed among "specific cardiomyopathies". Myocarditis is diagnosed on endomyocardial biopsy (EMB) by established histological, immunological, and immunohistochemical criteria, and molecular techniques are recommended to identify viral etiology. Infectious, autoimmune, and idiopathic forms of inflammatory cardiomyopathy are recognized that may lead to dilated cardiomyopathy. According to Dallas criteria, myocarditis is diagnosed in the setting of an "inflammatory infiltrate of the myocardium with necrosis and/or degeneration of adjacent myocytes, not typical of ischemic damage associated with coronary artery disease". The majority of experts in the field agree that an actual increase in sensitivity of EMB has now been reached by using immunohistochemistry together with histology. A value of >14 leukocytes/mm(2) with the presence of T lymphocytes >7 cells/mm(2) has been considered a realistic cut off to reach a diagnosis of myocarditis. The development of molecular biological techniques, particularly amplification methods like polymerase chain reaction (PCR) or nested-PCR, allows the detection of low copy viral genomes even from an extremely small amount of tissue such as in EMB specimens. Positive PCR results obtained on EMB should always be accompanied by a parallel investigation on blood samples collected at the time of the EMB. According to the recent Association for European Cardiovascular Pathology guidelines, optimal specimen procurement and triage indicates at least three, preferably four, EMB fragments, each 1-2 mm in size, that should immediately be fixed in 10 % buffered formalin at room temperature for light microscopic examination. In expected focal myocardial lesions, additional sampling is recommended. Moreover, one or two specimens should be snap-frozen in liquid nitrogen and stored at -80 °C or alternatively stored in RNA-later for possible molecular tests or specific stains. A sample of peripheral blood (5-10 ml) in EDTA or citrate from patients with suspected myocarditis allows molecular testing for the same viral genomes sought in the myocardial tissue.

Viral myocarditis: diagnosis, aetiology and management

Myocarditis is an inflammatory disease of the cardiac muscle caused by myocardial infiltration of immunocompetent cells following any kind of cardiac injury. Classic myocarditis mainly occurs as a result of the host's immune response against organisms that cause common infectious illnesses, as a manifestation of hypersensitivity or as a toxic reaction to drug therapy. Chronic inflammatory events may survive successful clearance of initial cardiotoxic agents, be triggered or amplified by autoimmunological processes, or develop in the context of systemic diseases. If the underlying infectious or immune-mediated causes of the disease are carefully defined by clinical and biopsy-based tools, specific immunosuppressive and antiviral treatment options may improve the prognosis of patients with acute and chronic 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.

Frontiers in viral diagnostics

Dilated cardiomyopathy (DCM) is a fatal myocardial disease with an incidence of 40:100,000. In recent years, viral infection as a causative agent for myocarditis followed by DCM has become a main topic of research. On the one hand, the virus violates the myocardial integrity itself; on the other hand, the virus induces inadequate local humoral and cellular defense reaction resulting in cardiomyocyte death, fibrosis, and overall cardiac dysfunction. Classical virological approaches are no longer sufficient to detect and identify the virus in the heart. The possibility of endomyocardial biopsies, as well as the further development of new high-specific and sensitive molecular approaches including real-time PCR or sequencing, allows us to detect and to identify the patient- specific causal virus and to predict the progression of disease and hopefully, in the future, to develop virus-specific treatment strategies.

Invited for debate: is virus persistence a determinant for disease progression?

Evidence-based medicine is not based on assumptions or extrapolations from experimental data in animal models but on solid evidence obtained from randomized clinical trials. There is today experimental and clinical proof of the capability of viruses to invade, persist, and replicate in the myocardium, where they can induce chronic damage. However, the pathogenetic role of viruses detected on endomyocardial biopsies is not clear, and clinical observational data published in the literature on the prognostic implications of this finding are non-uniform and need further elucidation in randomized trials, such as the currently ongoing Betaferon in Chronic Viral Cardiomyopathy (BICC) study. This is the first large randomized trial that evaluates the importance of antiviral therapy in patients with inflammatory cardiomyopathy with presence of viral genome in the myocardium. The results of the BICC trial might supply the needed scientific evidence for the clinical use of a targeted antiviral therapy for prevention of the progression of myocardial dysfunction and reversal of myocardial damage.

Myocarditis and inflammatory cardiomyopathy: histomorphological diagnosis

Myocarditis is a non-ischemic inflammatory disease of the myocardium associated with cardiac dysfunction. It most often results from infectious agents, hypersensitivity responses, or immune-related injury. In spite of the development of various diagnostic modalities, early and definite diagnosis of myocarditis still depends on the detection of inflammatory infiltrates in endomyocardial biopsy specimens according to Dallas criteria. Routine application of immunohistochemistry (for characterization of inflammatory cell infiltration) and Polymerase Chain Reaction PCR analysis (for identification of infective agents) has become an essential part of the diagnostic armamentarium for a more precise biopsy report. A new morphological classification is advanced to overcome the limits of Dallas criteria. A semiquantitative assessment of myocyte damage/inflammation (grading) as well as of fibrosis (staging) is indicated, thus providing histopathological diagnosis useful to the clinician for more appropriate patient risk stratification and for the application of new therapies. Consequently, the final diagnosis of myocarditis should be mainly based on three features: etiology, grade, and stage of the disease.

Detection of viruses in myocardial tissues by polymerase chain reaction. evidence of adenovirus as a common cause of myocarditis in children and adults

OBJECTIVES

The purpose of this study was to analyze cardiac tissue and blood for viral genomes using polymerase chain reaction (PCR) to define the common viral etiologies of myocarditis by age group.

BACKGROUND

Enteroviruses are considered the most common cause of myocarditis at all ages. Diagnosis relies on viral cultures, serology, and cardiac histology, which lack sensitivity, as well as PCR. However, in many cases enteroviruses are not detected.

METHODS

Cardiac samples were obtained for PCR analysis from patients with myocarditis (n = 624) and dilated cardiomyopathy (DCM) (n = 149). Patients were analyzed by age group, including neonates (n = 116), infants (n = 191), toddlers (n = 87), children (n = 110), adolescents (n = 92), and adults (n = 177). After nucleic acids had been extracted from an endomyocardial biopsy, an explant, or autopsy samples, PCR and reverse transcription PCR were performed to detect the genomic sequences of enterovirus, adenovirus, cytomegalovirus (CMV), herpes simplex virus (HSV), Epstein-Barr virus (EBV), parvovirus, respiratory syncytial virus (RSV), and influenza A virus.

RESULTS

Viral genome was amplified (adenovirus = 142, enterovirus = 85, CMV = 18, parvovirus = 6, influenza A = 5, HSV = 5, EBV = 3, RSV = 1) from 239 (38%) of the 624 samples from myocarditis patients, including 26 patient samples in which dual infection was found. Virus was detected in 30 (20%) of 149 DCM patient samples; only adenovirus (n = 18) and enterovirus (n = 12) were detected.

CONCLUSIONS

Polymerase chain reaction identified adenovirus as the most common virus in the myocardium of children and adults with myocarditis and DCM. Although enteroviruses are also found in these patients, they appear to be a less common cause of myocarditis than adenovirus.

Interferon-beta treatment eliminates cardiotropic viruses and improves left ventricular function in patients with myocardial persistence of viral genomes and left ventricular dysfunction

BACKGROUND

Viral infections are important causes of myocarditis and may induce cardiac dysfunction and finally lead to dilated cardiomyopathy. We investigated whether interferon (IFN)-beta therapy is safe and may achieve virus clearance and prevent deterioration of left ventricular (LV) function in patients with myocardial virus persistence.

METHODS AND RESULTS

In this phase II study, 22 consecutive patients with persistence of LV dysfunction (history of symptoms, 44+/-27 months) and polymerase chain reaction-proven enteroviral or adenoviral genomes were treated with 18x10(6) IU/week IFN-beta (Beneferon) subcutaneously for 24 weeks. Histological and immunohistological analysis of endomyocardial biopsies was used to characterize myocardial inflammation. LV diameters and ejection fraction were assessed by echocardiography and angiography, respectively. During the treatment period, IFN-beta was well tolerated by all patients. No patient deteriorated. Clearance of viral genomes was observed in 22 of 22 of patients after antiviral therapy. Virus clearance was paralleled by a significant decrease of LV end diastolic and end systolic diameters, decreasing from 59.7+/-11.1 to 56.5+/-10.0 mm (P<0.001) and 43.2+/-13.6 to 39.4+/-12.1 mm (P<0.001), respectively. LV ejection fraction increased from 44.6+/-15.5% to 53.1+/-16.8% (P<0.001).

CONCLUSIONS

A 6 months, IFN-beta treatment was safe in patients with myocardial enteroviral or adenoviral persistence and LV dysfunction and resulted in elimination of viral genomes (22 of 22 patients) and improved LV function (15 of 22 patients).

Viral causes of cardiac inflammation

Over the past year there have been few significant breakthroughs in the understanding of the etiologies of viral myocarditis or dilated cardiomyopathy (DCM). One interesting trend has been the increasing number of reports of myocarditis associated with parvovirus B19 infection. Whether this is simply a result of improved diagnostics, or reflects an underlying change in the etiology is unclear. However, studies of the underlying mechanisms of these disorders have resulted in several reports linking the acquired and viral forms. Over the past few years the cytoarchitecture has been a focus of study for familial DCM. During the last year, one key molecule, dystrophin, has been shown to be disrupted in patients with end-stage cardiomyopathy, irrespective or etiology, mutated in patients with sporadic forms of disease and identified as a potential susceptibility gene for viral infection of the myocardium. The shared cellular receptor, the Coxsackievirus B-Adenovirus receptor (CAR), for the two most common viral agents associated with acquired myocarditis and DCM, was shown to be up-regulated in patients with DCM, potentially making the expression of this protein a marker of susceptibility to virus infection. However, a study of the CAR gene in patients with DCM or myocarditis did not identify any genetic mutations in these patients. Finally a receptor for viral double stranded RNA (TLR-3) was identified. The role of this receptor in the innate immune response against cardiotropic viruses has yet to be elucidated.

Detection of enteroviral infection in myocardial tissues by polymerase chain reaction (PCR)

OBJECTIVE: To determine if enteroviral infection is linked to myocarditis and dilated cardiomyopathy. Enteroviruses, especially coxsackieviruses, appear to be the most common agents of viral myocarditis. METHODS: We collected 53 endomyocardial biopsies and two autopsy specimens from 41 patients affected by myocarditis or dilated cardiomyopathy. The patients were diagnosed clinically, hemodynamically, virologically and histologically (Dallas classification). We tested for the presence of enteroviral sequences by PCR, using 5prime prime or minute non-coding (coxsackievirus B3, CB3, map position 450--474, 584--603) derived primers. Specificity was confirmed using the Southern blot. We used a fraction of CB3 acutely infected mouse myocardial tissue as a control. RESULTS: We detected enteroviral sequences in four patients with active myocarditis, borderline myocarditis or cardiomyopathy. The patient with active myocarditis had shown neutralizing antibodies in serologic analysis for coxsackievirus B3 and B5. CONCLUSIONS: The data support a weak link of enteroviral infection to human myocarditis and dilated cardiomyopathy, at least when using a PCR assay on biopsies.

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.

Myocardial inflammatory cell infiltrates in cases of dilated cardiomyopathy as a determinant of outcome following partial left ventriculectomy

Partial left ventriculectomy (PLV) can be used to treat refractory congestive heart failure caused by dilated cardiomyopathy (DCM). In order to understand the relationship between the underlying myocardial injury and early clinical outcomes after PLV, histopathologic, immunohistochemical and virologic studies of the resected myocardium were performed. The posterolateral left ventricular walls from 27 patients with idiopathic DCM were examined. Cardiomyocyte diameter, degree of myocardial fibrosis, degree of cardiomyocyte degeneration, and degree of inflammatory cell infiltration were compared with mortality rates. Polymerase chain reaction was performed to detect enterovirus genome in the myocardium. Some patients had inflammatory cell infiltrates with focal accumulations of lymphocytes and macrophages, including both cytotoxic/suppressor T-cells and helper/inducer T-cells. The number of inflammatory cells (activated lymphocytes plus macrophages/mm2) was significantly greater in patients who died of cardiac insufficiency after surgery (27.8 +/- 5.7; n = 7) than in the survivors (11.1 +/- 2.5; n = 15). There was no significant difference in the degree of myocardial fibrosis, cardiomyocyte diameter or degree of cardiomyocyte degeneration between the 2 groups. Enterovirus genome was detected in the myocardium of 9 (38%) of 24 patients examined and 5 of these enterovirus-positive hearts had severe inflammatory cell infiltrates (37.9 +/- 2.5/mm2). Early survival in patients undergoing PLV for DCM is significantly affected by the degree of myocardial inflammation, so patients with more severe or ongoing inflammation may have poor clinical outcomes. Chronic myocarditis may play an important role in the etiology and pathophysiology of idiopathic DCM.

Association of viral genome with graft loss in children after cardiac transplantation

BACKGROUND

The survival of recipients of cardiac allografts is limited by rejection, lymphoproliferative disease, and coronary vasculopathy. The purpose of this study in children who had received heart transplants was to evaluate the cardiac allografts for myocardial viral infections and to determine whether the presence of viral genome in the myocardium correlates with rejection, coronary vasculopathy, or graft loss.

METHODS

We enrolled heart-transplant recipients 1 day to 18 years old who were undergoing evaluation for possible rejection and coronary vasculopathy. Endomyocardial-biopsy specimens were evaluated for evidence of rejection with the use of standard criteria and were analyzed for the presence of virus by the polymerase chain reaction (PCR).

RESULTS

PCR analyses were performed on 553 consecutive biopsy samples from 149 transplant recipients. Viral genome was amplified from 48 samples (8.7 percent) from 34 patients (23 percent); adenovirus was found in 30 samples, enterovirus in 9 samples, parvovirus in 5 samples, cytomegalovirus in 2 samples, herpes simplex virus in 1 sample, and Epstein-Barr virus in 1 sample. In 29 of the 34 patients with positive results on PCR (85 percent), an adverse cardiac event occurred within three months after the positive biopsy, and 9 of the 34 patients had graft loss due to coronary vasculopathy, chronic graft failure, or acute rejection. In 39 of the 115 patients with negative results on PCR (34 percent), an adverse cardiac event occurred within three months of the negative PCR finding; graft loss did not occur in any of the patients in this group. The odds of graft loss were 6.5 times as great among those with positive results on PCR (P=0.006). The detection of adenovirus was associated with considerably reduced graft survival (P=0.002).

CONCLUSIONS

Identification of viral genome, particularly adenovirus, in the myocardium of pediatric transplant recipients is predictive of adverse clinical events, including coronary vasculopathy and graft loss.

Detection of adenoviral genome in the myocardium of adult patients with idiopathic left ventricular dysfunction

BACKGROUND

The use of molecular biological techniques has demonstrated the importance of enteroviral infection of the myocardium in the pathogenesis of myocarditis and dilated cardiomyopathy in adults and adenovirus and enterovirus infection in children. The aim of this study was to determine the frequency of adenoviral infection of the myocardium of adults with impaired left ventricular function of unknown origin.

METHODS AND RESULTS

Nested polymerase chain reaction (nPCR) was used to determine the frequency of detection of adenoviral DNA and enteroviral RNA in myocardial tissue samples from 94 adult patients with idiopathic left ventricular dysfunction and 14 control patients. Histological and immunohistological analyses were performed to detect myocardial inflammation. Adenoviral genomic DNA was detected by nPCR in 12 of the 94 patients with left ventricular dysfunction (in each case, adenovirus type 2), whereas enteroviral RNA was detected in another 12 patients. All control samples were negative for both viruses. In all patients, active myocarditis was excluded according to the Dallas criteria. However, there was significantly decreased CD2, CD3, and CD45RO T lymphocyte counts in the adenovirus-positive group compared with the adenovirus-negative group (P<0.05), whereas no differences were associated with enterovirus infection.

CONCLUSIONS

Although enteroviruses are an important causative agent in the pathogenesis of myocarditis and dilated cardiomyopathy, this study shows that adenovirus infection is also important in the pathogenesis of left ventricular failure in adults. However, the pathogenetic basis of disease associated with adenovirus infection may be different than that after infection with other agents, particularly with respect to activation of the host immune response.

Enteroviral genome in native hearts may influence outcome of patients who undergo cardiac transplantation

The Enterovirus may be the most common agent responsible for viral myocarditis and cardiomyopathy. Very little of the literature is available concerning the follow-up of patients who underwent transplantation with enteroviral positivity in native hearts. In the present study, 45 explanted hearts from patients who underwent orthotopic heart transplant at University of Padova were studied by reverse transcriptase (RT)-polymerase chain reaction (PCR): 27 patients had dilated cardiomyopathy (DC), 12 had ischemic cardiopathy (IC), 2 had valvular disease (VD), 2 had arrhythmogenic right ventricular cardiomyopathy (ARVC), 1 had giant cell myocarditis (GCM), and 1 had lymphocytic myocarditis (LM). Two sets of PCR primers from the highly conserved region of Enterovirus and Rhinovirus were used. Samples of both ventricles and septum were analyzed in every patients. The RT-PCR and nucleotide sequencing of amplicons were also performed on all post-transplantation follow-up biopsies in patients with Enterovirus positivity in the native heart. The viral genome was detectable in only 1 of 27 patients with DC (3%) and in 1 patient with LM. Nucleotide sequence analysis of the amplified product showed differences in nucleotide sequence of PCR samples compared with the sequence of the coxsackievirus B3 used in the current study. The patient with Enterovirus-positive DC showed a higher index of severe rejection (>3A) in the first 6 months, compared with the other patients tested. The patient with Enterovirus-positive LM died of disease recurrence 2 months after transplantation. The present study reveals a scarce presence of Enterovirus in the myocardium of patients with chronic myocardial disease. Because Enterovirus infection was predictive of a poor prognosis in these two patients, molecular studies are useful in excluding viral involvement in native hearts of transplanted patients.

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.

Characterization of Coxsackie B virus RNA in myocardium from patients with dilated cardiomyopathy by nucleotide sequencing of reverse transcription-nested polymerase chain reaction products

This study was performed to detect and characterize the enterovirus present in myocardium of some patients with heart muscle disease by nucleotide sequencing of polymerase chain reaction (PCR) products after amplification with enterovirus group-specific primers. Enterovirus sequences have been detected previously in myocardium of patients with myocarditis or dilated cardiomyopathy and seem causal, although the particular virus serotypes involved have not been identified. In a prospective study of endomyocardial biopsy specimens from 35 consecutive patients with suspected heart muscle disease, enterovirus sequences from the 5' nontranslated region were amplified by reverse transcription-nested PCR using group-specific primers. This region contains both conserved and variable sequence motifs, characteristic of particular enterovirus serotypes. The nucleotide sequences of individual PCR products were determined by cycle sequencing and compared with all known sequences (GenBank/EMBOL), using the GCG software package. Endomyocardial biopsy specimens from 9 of 21 (42.9%) patients with a histologically confirmed diagnosis of dilated cardiomyopathy were positive for enterovirus by PCR, compared with only 1 of 14 (7.1%) patients with other myocardial pathological conditions (Fisher's exact probability=0.0275: odds ratio=9.75; 95% confidence interval=1.31-72.78). The nucleotide sequence of the PCR products differed, indicating no cross-contamination. However, computerized comparison showed that each had greatest homology with the 5' nontranslated region of Coxsackie B virus but contained up to 11% sequence variations compared with the prototype Coxsackie B3 strain Nancy. Parallel investigation of tissue from our mouse model of Coxsackievirus B3-induced myocarditis showed that nucleotide sequence changes are not introduced by reverse transcription or PCR. These data support the link between enteroviral infection and dilated heart muscle disease and suggest that Coxsackie B serotypes are the enteroviruses most frequently involved.

Stem cell factor in mast cells and increased mast cell density in idiopathic and ischemic cardiomyopathy

BACKGROUND

We compared cardiac mast cell (HHMC) density and the immunological and nonimmunological release of mediators from mast cells isolated from heart tissue of patients with idiopathic dilated (DCM) (n=24) and ischemic cardiomyopathy (ICM) (n = 10) undergoing heart transplantation and from control subjects (n = 10) without cardiovascular disease.

METHODS AND RESULTS

HHMC density in DCM (18.4+/-1.6 cells/mm2) and ICM (18.4+/-1.5 cells/mm2) was higher than that in control hearts (5.3+/-0.7 cells/mm2; P<.01). The histamine and tryptase contents of DCM and ICM hearts were higher than those of control hearts. The histamine content of the hearts was correlated with mast cell density (r(s)=.91; P<.001). Protein A/gold staining of heart tissue revealed stem cell factor (SCF), the principal growth, differentiating, and activating factor of human mast cells, in HHMC secretory granules. Histamine release from cardiac mast cells caused by immunological (anti-IgE and rhSCF) and nonimmunological stimuli (Ca2+ ionophore A23187) was higher in patients with DCM and ICM compared with control subjects. Immunological activation of HHMC induced a significantly greater release of tryptase and LTC4 in patients with DCM and ICM compared with control subjects.

CONCLUSIONS

Histamine and tryptase content and mast cell density are higher in failing hearts than in control hearts. SCF, present in secretory granules of HHMC, might represent an autocrine factor sustaining mast cell hyperplasia in heart tissue in these patients. The increased local release of fibrogenic factors (eg, histamine, tryptase, and leukotriene C4) might contribute to collagen accumulation in the hearts of patients with cardiomyopathy.

Detection of intrauterine viral infection using the polymerase chain reaction

Intrauterine viral infection commonly presents as nonimmune hydrops fetalis or intrauterine growth restriction. Cytomegalovirus (CMV) and parvovirus are commonly recognized causes of fetal infection using serology and cultures. We used the polymerase chain reaction (PCR) to evaluate the frequency of fetal viral infection and the associated clinical course and outcome. Specimens (amniotic fluid, fetal blood, pleural fluid, tissue) from 303 abnormal pregnancies at risk for viral infection and 154 controls were analyzed using primers for CMV, herpes simplex virus, parvovirus B19, adenovirus, enterovirus, Epstein-Barr virus, and respiratory syncytial virus. Viral genome was detected in 144/371 samples (39%) or 124/303 patients (41%), with adenovirus (n = 74 patients; 24%), CMV (n = 30 patients; 10%), and enterovirus (n = 22 patients; 7%) most common. Only 4/154 (2.6%), unaffected control patients' samples were PCR positive. We conclude that diagnosis of fetal viral infection by PCR is common in abnormal pregnancies. Adenovirus and enterovirus may cause fetal infection that have been previously unrecognized.

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.

Association of parvovirus B19 genome in children with myocarditis and cardiac allograft rejection: diagnosis using the polymerase chain reaction

BACKGROUND

Inflammatory diseases of the heart, including myocarditis and cardiac transplant rejection, are important causes of morbidity and mortality in children. Although viral infection may be suspected in either of these clinical conditions, the definitive etiology is often difficult to ascertain. Furthermore, the histology is identical for both disorders. Coxsackievirus has long been considered the most common cause of viral myocarditis; however, we previously demonstrated by polymerase chain reaction (PCR) analysis that many different, and sometimes unexpected, viruses may be responsible for myocarditis and cardiac rejection. In this study, we describe the association of parvovirus genome identified through PCR analysis of cardiac tissue in the clinical setting of myocarditis and cardiac allograft rejection.

METHODS AND RESULTS

Myocardial tissue from endomyocardial biopsy, explant, or autopsy was analyzed for parvovirus B19 using primers designed to amplify a 699-base pair PCR product from the VP1 gene region. Samples tested included those obtained from patients with suspected myocarditis (n=360) or transplant rejection (n=200) or control subjects (n=250). Parvoviral genome was identified through PCR in 9 patients (3 myocarditis; 6 transplant) and no control patients. Of the 3 patients with myocarditis, 1 presented with cardiac arrest leading to death, 1 developed dilated cardiomyopathy, and the other gradually improved. Four of the 6 transplant patients had evidence of significant rejection on the basis of endomyocardial biopsy histology. All transplant patients survived the infection.

CONCLUSIONS

Parvovirus is associated with myocarditis in a small percentage of children and may be a potential contributor to cardiac transplant rejection. PCR may provide a rapid and sensitive method of diagnosis.

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.

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.

The elusive search for fetal infection. Changing the gold standards

Two percent to four percent of all newborns have a major structural malformation of which only a small percentage can be explained by either aneuploidy or a single-gene disorder. No other mammal has a similar reproductive problem. It is the suggestion that previously unrecognized viral infection accounts for a large percentage of these abnormalities by interfering with appropriate embryonic cell migration, reducing hyperplasia, or damaging the precursor structure by means of an inflammatory mechanism.

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.

Technical report: Part 2. Basic requirements for designing optimal PCR primers

Designing optimal polymerase chain reaction (PCR) primer sequences is one of the critical factors for successful PCR with sensitive, specific, and assay-to-assay reproducible results. In this review, all the requirements of PCR primer sequences are summarized, such as location, size of amplicon, length of primers, nucleotide composition, Tm, 3' terminal hybridization strength and frequency, hairpin formation energy, primer-to-primer interaction, specificity, and location of mismatches to sequences of cross-hybridization. The report also discusses how to explore these various types of information for more advanced PCR applications, which include nested PCR, multiplex PCR, competitive PCR, long PCR, point mutation detection, degenerate primers, and PCR cloning.

Myocardial enterovirus infection with left ventricular dysfunction: a benign disease compared with idiopathic dilated cardiomyopathy

OBJECTIVES

Endomyocardial biopsy samples from patients with idiopathic dilated cardiomyopathy were screened for the presence of enterovirus genome. Patients with enterovirus-positive samples were further studied with regard to disease course, histologic variables and response to interferon-alpha treatment.

BACKGROUND

Studies of patients with idiopathic dilated cardiomyopathy have reported widely divergent clinical outcomes, suggesting that there is no unique underlying pathogenetic mechanism.

METHODS

Five left ventricular endomyocardial biopsy samples were screened for the presence of the enterovirus genome by an established in situ hybridization technique in combination with a histologic, histomorphometric and immunohistologic workup. The course of the disease was then prospectively followed for up to 50 months. Virus-positive patients whose condition deteriorated were treated with interferon-alpha.

RESULTS

Of 77 patients, 20 (26%) had enterovirus-positive and 57 (74%) enterovirus-negative biopsy samples. During a mean follow-up period of 25.8 +/- 13.7 months, 1 patient in the enterovirus-positive group and 11 in the enterovirus-negative group died. Four patients in the enterovirus-negative group underwent heart transplantation (p < 0.05). The surviving 19 enterovirus-positive patients had a decrease in mean left ventricular end-diastolic diameter from 66 to 61 mm (p < 0.05) and a mean increase in left ventricular ejection fraction from 0.35 to 0.43 (p < 0.05). In contrast, enterovirus-negative patients had no significant change in end-diastolic diameter or left ventricular ejection fraction. Four patients in the enterovirus-positive group whose condition deteriorated were treated with a 6-month course of subcutaneous interferon-alpha (3 x 10(6) U every second day). This treatment induced hemodynamic improvement in all four patients and eliminated the persistent enteroviral infection in two.

CONCLUSIONS

Enterovirus-positive patients have a better heart transplantation-free survival rate and hemodynamic course, with fewer histologic changes, than do enterovirus-negative patients. In addition, enterovirus-positive patients respond favorably to interferon-alpha treatment. These observations indicate that myocardial enteroviral infection with associated left ventricular dysfunction is a distinct disease entity with a benign course.

Reverse transcription PCR to detect enteroviruses in surface water

We have developed a simple, fast, and efficient procedure to detect enteroviruses in water samples. Aliquots of water are subjected to two-step filtration, with the second filter containing a positively charged nylon membrane that holds back virus particles. Viruses thus adsorbed are directly lysed, and RNA is isolated by hybridization to specific oligonucleotides bound to magnetic beads. The solution used contains guanidine thiocyanate, which lyses virus particles, inactivates enzymes, e.g., RNases, allows mild hybridization conditions, and does not influence biotin-streptavidin interaction on magnetic beads. Detection and specific identification are accomplished by reverse transcription PCR of the highly conserved noncoding region at the 5' end of virus RNA combined with Southern hybridization. The system was tested with tap water artificially spiked with poliovirus vaccine and yielded a detection limit of 20 50% tissue culture infective doses per liter. We used the same procedure to investigate the water quality of surface water at public beaches by rivers and lakes. Of 40 samples tested, 7 were positive for enteroviruses. A comparison with enterobacterial contamination determined by PCR and classical microbiological methods in parallel showed that enteroviruses were found only in samples also positive for Escherichia coli. In conclusion, this procedure can easily be adapted to test large water samples and is simple enough to be used for routine determinations of water quality in terms of virus contamination.

Familial dilated cardiomyopathy

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Low frequency of detection by nested polymerase chain reaction of enterovirus ribonucleic acid in endomyocardial tissue of patients with idiopathic dilated cardiomyopathy

OBJECTIVES

The purpose of this study was to determine the prevalence of enteroviral infection in the myocardium of patients with idiopathic dilated cardiomyopathy by using a highly sensitive and specific detection technique.

BACKGROUND

Recent molecular studies have suggested that enteroviral persistence (in particular, coxsackieviruses type B) may underlie idiopathic myocarditis and dilated cardiomyopathy.

METHODS

The method used to detect enterovirus-specific ribonucleic acids (RNAs) is based on reverse transcription and nested polymerase chain reaction amplification with four pairs of primers from the conserved 5' noncoding region of the enteroviral genome. Several members of the Enterovirus genus are detectable by this assay (coxsackieviruses B1 to B6; polioviruses 1 to 3; echoviruses 9, 19 and 31), with a sensitivity threshold close to the detection of a single molecule of viral RNA in 1 mg of tissue sample. Endomyocardial tissue samples from 84 subjects were analyzed (77 samples obtained from left endomyocardial biopsies, 7 from explanted hearts). The subjects comprised 63 study patients (53 with dilated cardiomyopathy, 3 with idiopathic myocarditis, 1 with right ventricular dysplasia, 1 with restrictive cardiomyopathy, 1 with eosinophilic myocarditis, 1 with primary ventricular fibrillation and 3 with myocarditis of known etiology) and 21 control subjects with other diseases.

RESULTS

Positive signals were obtained only in samples from six study patients (four with dilated cardiomyopathy, one with right ventricular dysplasia and one with myocarditis). Samples from control subjects, uninfected rat myocardium and cultured cell lines yielded systematically negative results. Moreover, the nucleotide sequence analysis of the amplification products from patients with positive samples raised doubts about the true positivity of these samples.

CONCLUSIONS

This study suggests that the persistence of enteroviral RNA in dilated cardiomyopathy is not a major cause of the disease and that a careful analysis of polymerase chain reaction amplification products is essential in any study in which this technique is pushed to high sensitivity thresholds.

Adenovirus myocarditis: retrospective diagnosis by gene amplification from formalin-fixed, paraffin-embedded tissues

Understanding the pathogenesis of viral myocarditis is linked to the availability of sensitive assays to detect viruses in clinical material. Recent advances in molecular techniques permit direct detection of viral-specific nucleic acid in tissue samples. This report describes a protocol for DNA extraction and amplification of adenovirus genome from formalin-fixed, paraffin-embedded human tissues that detects as little as 10 copies of viral genome in a background of 0.5 micrograms of human DNA. This sensitive assay permitted the examination of archived tissues to establish a retrospective diagnosis of adenoviral myocarditis in two pediatric patients.

Acute myocarditis. Rapid diagnosis by PCR in children

BACKGROUND

The diagnosis of viral myocarditis remains difficult and generally depends on clinical and histological criteria. Viral cultures and serology are often unrewarding, with low yields. The purpose of this study was to analyze the usefulness of polymerase chain reaction (PCR) in the rapid diagnosis of acute myocarditis in children.

METHODS AND RESULTS

PCR was used to analyze 38 myocardial tissue samples from 34 patients with suspected acute viral myocarditis and 17 control patients with congenital heart disease (14) or hypertrophic cardiomyopathy (3). Myocardial samples were obtained at the time of right ventricular biopsy (13 samples), from explanted hearts (18 samples) at transplantation, and from cardiac autopsy specimens (24 samples) and were evaluated for the presence of enterovirus, cytomegalovirus (CMV), adenovirus, and herpes simplex virus (HSV) using PCR primers designed to consensus and unique sequences of these viral genomes. Blood also was obtained at the time of biopsy (11) or transplant (18). In 26 of 38 myocardial samples (68%), viral genome was detected by PCR (15 adenoviral, 8 enteroviral, 2 HSV, 1 CMV), whereas all control myocardial samples and blood samples were negative. Four patients had positive viral cultures, and these matched the PCR findings. Disagreement with histopathology occurred in 13 of 26 PCR-positive specimens, usually associated with adenovirus.

CONCLUSIONS

PCR offers a rapid, sensitive diagnostic method for myocardial viral infection. While enterovirus is an important etiological agent, adenovirus was more prevalent in this series and should be evaluated when etiology is sought. PCR used in conjunction with standard endomyocardial biopsy appears to enhance the likelihood of detecting viral genome in the myocardium of patients with clinical evidence of myocarditis.

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.