Myocardial indium-111 antimyosin uptake in patients with idiopathic dilated cardiomyopathy: its relation to haemodynamics, histomorphometry, myocardial enteroviral infection, and clinical course

Coronary endothelial dysfunction and myocardial cell damage in chronic stable idiopathic dilated cardiomyopathy

Impairment of endothelium-dependent vasodilatation in response to acetylcholine reflects an abnormal endothelial function. Labelled indium-111 monoclonal antimyosin antibodies enable detection of myocardial cell damage. We analysed whether endothelial dysfunction correlates with myocardial antimyosin uptake in a selected group of patients with idiopathic dilated cardiomyopathy.

METHODS

Twenty-two consecutive patients with chronic stable idiopathic dilated cardiomyopathy (18 males and four females) were included. The duration of heart failure symptoms was 46+/-34 months. At inclusion, the functional class of New York Heart Association was 2.1+/-0.7. Endothelial function was evaluated using intracoronary graded concentrations of acetylcholine. Vasomotor responses of the left anterior descending coronary artery were measured by quantitative coronary analysis. Myocardial uptake of antimyosin antibodies was quantified by means of a heart-to-lung ratio (HLR).

RESULTS

Eighteen patients showed endothelial dysfunction (82%) and the remaining four patients showed a normal endothelial function. There were no statistically significant differences between patients with and without endothelial dysfunction in relation to clinical, echocardiographic and hemodynamic parameters. In addition, these variables did not correlate with the magnitude of the vasomotor response to acetylcholine. Eighteen patients (82%) showed abnormal antimyosin uptake; 15 of them (83%) showed endothelial dysfunction. The global mean HLR of antimyosin uptake was 1.73+/-0.24. The coronary vasomotor response to acetylcholine correlated with the intensity of uptake of antimyosin antibodies (r=-0.45, P<0.04).

CONCLUSIONS

Coronary endothelial dysfunction and myocardial antimyosin uptake was found in a high percentage of patients with chronic stable idiopathic dilated cardiomyopathy. The abnormal vasomotor response seems to be related to the degree of myocardial damage.

Antimyosin scintigraphy and immunohistologic analysis of endomyocardial biopsy in patients with clinically suspected myocarditis--evidence of myocardial cell damage and inflammation in the absence of histologic signs of myocarditis

OBJECTIVES

This study compares the results of antimyosin scintigraphy in patients with clinically suspected myocarditis with histologic and immunohistologic findings in the endomyocardial biopsy.

BACKGROUND

In patients with clinically suspected myocarditis, antimyosin scintigraphy often demonstrates myocardial cell damage but histologic evaluation of the endomyocardial biopsy often fails to show evidence of myocarditis. Recently developed immunohistologic techniques appear to be more sensitive for the detection of myocardial inflammation than histologic analysis alone. Studies comparing antimyosin scintigraphy and immunohistologic analysis of the endomyocardial biopsy in patients with clinically suspected myocarditis are not yet available.

METHODS

Sixty-five patients with clinically suspected myocarditis underwent antimyosin scintigraphy. Antimyosin antibody uptake was correlated with histologic and immunohistologic findings in the endomyocardial biopsy.

RESULTS

Antimyosin scintigraphy showed evidence of myocardial cell damage in 36 (55%) of the 65 patients and was negative in 29 (45%) patients. Histologic analysis of the endomyocardial biopsy revealed myocarditis in nine patients: six had a positive and three had a negative antimyosin scan, respectively. Thirty (83%) of 36 patients with evidence of myocardial cell damage on antimyosin scintigraphy were histologically negative for myocarditis. Immunohistologic analysis showed evidence of myocarditis in 31 (86%) of 36 patients with a positive antimyosin scan and also in 17 (59%) of 29 patients with a normal scan (p < 0.047).

CONCLUSIONS

Antimyosin scintigraphy often shows myocyte injury in patients with clinically suspected myocarditis. Histologic analysis of the endomyocardial biopsy alone is often negative, but additional immunohistologic analysis of the endomyocardial biopsy frequently provides evidence of myocardial inflammation in these patients. With immunohistologic analysis as the reference method, antimyosin scintigraphy has a high specificity but a lower sensitivity for the detection of myocarditis.

Ischemic and non-ischemic myocyte damage and antimyosin monoclonal imaging

Antimyosin monoclonal antibody is a specific marker of impaired sarcolemmal integrity resulting not only from ischemia but also from non-ischemic myocardial injury, such as infection, inflammatory, or immunologic reactions, and alcohol or drug intoxication. In addition, antimyosin accumulation has been demonstrated in some forms of cardiomyopathy with unknown as well as known etiologies. Antimyosin positivity appears to indicate precisely the extent of myocardial necrosis and to reflect cardiac dysfunction in an acute stage of active myocardial damage caused by ischemia and inflammation. However, the correlation is not necessarily good in the chronic stages of the disease or in idiopathic cardiomyopathic hearts; in other words, cardiac antimyosin uptake can be detected even in myocardial tissue with a normal histologic appearance independent of the presence of inflammatory responses, myocyte necrosis, or functional or morphologic deterioration. Thus, antimyosin is useful not only for detecting and quantifying acute myocardial necrosis but also for specifically identifying ongoing or latently progressing myocardial degeneration and sarcolemmal disruption, which will certainly lead to myocardial necrosis. These characteristics may contribute to the early detection of myocardial damage and lead to the investigation of pathophysiologic mechanisms. Further progress in immunologic and radiolabeling techniques is necessary for better specificity and less antigenicity against humans in antimyosin monoclonal antibody imaging.

Antimyosin antibody imaging in clinical myocarditis and cardiomyopathy: principle and application

When cardiac myocytes fall into necrosis, their cell membrane integrity will be lost and myosin heavy chains inside the cells will be exposed to the circulation. Then, antimyosin antibody specifically binds to these exposed myosin molecules when they are injected into the patients. Myocardial imaging using indium-111 labeled antimyosin monoclonal antibody was performed in 26 patients. Forty-eight hours after the injection of radiolabeled antimyosin antibody, planer and single-photon emission computed-tomographic (SPECT) images were obtained. In myocarditis, all three patients at the acute stage showed positive scans, whereas six out of seven patients at the chronic stage showed negative, suggesting that antimyosin imaging may be used for evaluating whether myocarditis is active or healed. In dilated cardiomyopathy, seven out of 10 patients showed positive scans, and the ejection fraction of these patients was significantly lower than that of patients who showed negative. In hypertrophic cardiomyopathy, six out of seven patients showed positive scans. In particular, patients with dilated ventricle showed strongly positive, suggesting a correlation between antimyosin uptake and poor prognosis. Taken together, indium-111 antimyosin antibody imaging may be useful for evaluating diagnosis and prognosis of patients with myocarditis and cardiomyopathies.

Scintigraphic detection of inflammatory heart disease

Inflammatory diseases of the heart encompass myocarditis, endocarditis and pericarditis. This paper discusses the diagnostic potential of scintigraphy in these entities. In myocarditis, indium-111 antimyosin Fab imaging can visualize active myocyte damage and thus contribute substantially to the diagnosis. Antimyosin uptake is also seen in a large subset of patients with dilated cardiomyopathy, indicating ongoing myocyte injury in these cases. In endocarditis, immunoscintigraphy using monoclonal technetium-99m-labelled antigranulocyte antibodies provides useful diagnostic information in patients with equivocal echocardiographic findings. Immunoscintigraphy seems to indicate the floridity of the inflammatory process in endocarditis and may be used to monitor antibiotic therapy. In pericarditis, the clinical value of scintigraphy has not been convincingly demonstrated.