Utility of immunofluorescence and electron microscopy in endomyocardial biopsies from patients with unexplained heart failure

Ultrastructural morphometric findings of cardiomyocytes in patients with impaired ventricular function--a comparative clinicopathological study

AIM

The present study aims to analyze the differences in ultrastructural changes between right ventricular myocardium in clinically determined grades of heart failure (HF) [New York Heart Association (NYHA) classes I-IV] and their value in the routine diagnostic setting.

METHODS

We investigated consecutive right ventricular endomyocardial biopsies of 12 patients presenting with HF (49±11.2years; male=10) by light microscopy and ultrastructural morphometric analysis. The patients were divided into four groups according to their NYHA classes (NYHA I: n=1, II: n=2, III: n=8, IV: n=1). We used a stereological point counting method on electron micrographs to determine the volume, surface, and numerical density of cardiomyocyte myofibrils; z-lines; mitochondria; and cristae as required. Further, secondary parameters were calculated.

RESULTS

Myofibrillar parameters increased between NYHA class I and II (P<.01), which matched with more pronounced cardiomyocyte hypertrophy on the light microscopic level. In NYHA classes III and IV, the myofibrillar parameters dropped, while parameters concerning the mitochondria and their cristae rose (P<.01). This resulted in an elevated mitochondria to myofibril ratio (P<.05) and correlated with histologically evident atrophic cardiomyocytes, perinuclear loss of myofibrils and dot-like perinuclear staining positive on peroxide acid shift.

CONCLUSION

In this present study, right ventricular myocardial ultrastructure differed between patients diagnosed with HF of different degrees in distinct subcellular changes. These findings suggest that ultrastructural analysis, while correlated with histopathological features, adds to the diagnosis in the routine diagnostic setting, specifically in lower NYHA grades, in which only minor changes are observed histologically.

High proportion of patients with end-stage heart failure regardless of aetiology demonstrates anti-cardiac antibody deposition in failing myocardium: humoral activation, a potential contributor of disease progression

AIMS

Various reports have raised the possibility of humoral immune responses as contributors for the progression of heart failure. Previous studies, however, have focused on the analysis of serum and documented circulating antibodies against a variety of cardiac proteins. However, there is little evidence on whether anti-cardiac antibodies are deposited in end-stage failing myocardium. Our objective was to determine whether or not there was evidence of deposition of anti-cardiac antibodies and/or activated complement components in end-stage failing human myocardium.

METHODS AND RESULTS

Myocardial samples were obtained from 100 end-stage heart failure patients and 40 donor control biopsies. Sections were cut and stained using standard fluorescent immunohistochemistry techniques with anti-human immunoglobulin G (IgG), IgG3, and C3c. Gel electrophoresis and protein identification by mass spectrometry were used to confirm the presence of IgG and its antigen. Immunoglobulin G was localized to the sarcolemma in 71% of patients, 48% of those being positive for the subtype IgG3. The proportion of patients with ischaemic heart disease that was positive for IgG was 65% and among those with non-ischaemic aetiologies was 76%. In a subgroup analysis, the presence of IgG and its subunits were confirmed by mass spectrometry and adenosine triphosphate synthase β subunit identified as an antigen. Complement was activated in 31% of all patients. The presence of IgG, IgG3, and C3c was directly correlated with the length of disease (r = 0.451, P = 0.006).

CONCLUSION

Evidence of anti-cardiac antibodies and complement activation was found in a large number of patients with end-stage cardiomyopathy regardless of the aetiology. Adenosine triphosphate synthase appears to be a new prominent antigenic stimulus; but more interestingly, the simultaneous co-existence of activated complement components suggests that this humoral mechanism may participate in disease progression.

The role of B-cells in heart failure

Heart failure is a complex disease that has great impact on morbidity and mortality in the general population. No recent therapies have proven to be effective; however, the discovery of new potential pathophysiological mechanisms involved in heart failure expression and progression could offer novel therapeutic strategies. A number of studies have shown that the immune system may be a central mediator in the development and progression of heart failure, and here we describe how the B-cell and B-cell-mediated pathways play specific roles in the heart failure state. Therapies aimed at B-cells, either blocking antibody production or inactivating B-cell function, may suggest potential new treatment strategies.

Current state of knowledge on aetiology, diagnosis, management, and therapy of myocarditis: a position statement of the European Society of Cardiology Working Group on Myocardial and Pericardial Diseases

In this position statement of the ESC Working Group on Myocardial and Pericardial Diseases an expert consensus group reviews the current knowledge on clinical presentation, diagnosis and treatment of myocarditis, and proposes new diagnostic criteria for clinically suspected myocarditis and its distinct biopsy-proven pathogenetic forms. The aims are to bridge the gap between clinical and tissue-based diagnosis, to improve management and provide a common reference point for future registries and multicentre randomised controlled trials of aetiology-driven treatment in inflammatory heart muscle disease.