Kinking of carotid arteries is not a mechanism of cerebral ischemia: a functional evaluation by Doppler echography.

AIM: The aim of this paper was to evaluate the hemodynamic behavior of carotid kinking, as assessed by color Doppler ultrasonography at baseline and during neck movements, and their relation to neurological symptoms. METHODS: In this cross-sectional study, 60 consecutive patients with non-atheromatous carotid kinking in whom diagnostic color Doppler ultrasonography investigation of neck vessels had been requested for clinical suspicion of atherosclerotic disease were evaluated. To evaluate if there were significant changes of blood velocities as a consequence of kinking, for each carotid artery we recorded systolic and diastolic velocities both in the segments proximal to kinking, as well as intra-kinking. The effects of postural changes and neck movements on carotid blood flow were also studied. RESULTS: Flow in carotid arteries with kinking was always normal, and no differences were found between flow velocity measured at the level of kinking compared to the normal tract of the vessel. During head rotation tests, flow remained largely unaffected, a substantial reduction in the velocities in the ophthalmic artery was found in 13.5% of the cases, while an increase was recorded in 27%; and no symptoms or events were recorded during the study. None of the patients referred symptoms, nor were neurological events or signs detected during the maneuvers. CONCLUSION: Our results show that carotid kinks are not a mechanism of acute cerebral ischemia, and therefore are unlikely to be a cause of neurological events or symptoms.

Inapparent myocarditis and sudden death in pediatrics. Diagnosis by immunohistochemical staining.

We analyzed the anatomopathological findings in two cases of sudden death related to myocarditis in pediatric patients. Since the diagnosis of myocarditis depends either upon histologic and histochemical techniques or the manner the sample was obtained, we describe a more specific immunohistochemical method to stain samples and more accurately diagnose and qualify cellular lymphoid strains in the inflammatory reaction of the myocardium thus allowing a correct diagnosis of myocarditis.

Carotid atherosclerosis. Immunocytochemical analysis of the vascular and cellular composition in endarterectomies.

Papers dealing with rupture of carotid plaque surface are few in spite of the growing importance of the subject. The aim of this study was to analyze the cellular and vascular components of surgically excised carotid endarterectomies in order to obtain information about their role in the pathogenesis of the plaque rupture and intraplaque hemorrhage. Seventy-six surgical specimens of carotid endarterectomies were used for this study. The findings of immunophenotyping of the cellular constituents of the plaques were: 1) endothelial lining: the fibrous cap at the site of the rupture showed an eroded surface with loss of the endothelial lining. Conversely, in the remaining surface a continuous, not damaged row of endothelial cells stained with anti-CD31 and anti-CD34 was observed; 2) fibrous cap: the collagenous fibrous cap at the site of erosion was attenuated and the phenotypic characterization of the cells showed inflammatory components consisting mainly of macrophages (CD68 positive), 2/3 of the total infiltration. The remaining 1/3 was composed of T-lymphocytes and scarce B-lymphocytes. A close interaction between macrophages and capillaries and macrophages and T-lymphocytes was observed; 3) lipid cores: two different types of lipid cores could be depicted. Avascular or mildly vascularized lipid cores and highly vascularized, with neoformed vessels stained with CD34 and CD31. CD34 stained endothelia of all kind of vessels; conversely, neoformed vessels showed a weak stain with CD31. T-lymphocytes were found to be in close contact with neoformed vessels, and in some cases, migrating through the endothelial cells; 4) deeper layers of the plaque: the base and the shoulder of the plaques showed in 28/76 cases neoformed vessels, thin or thick walled, CD34 positive, generally surrounded by mild to extensive mononuclear infiltrates. Atherosclerotic plaques were found to belong to six different lesions: plaque rupture plus thrombosis (18/76, 23.6%), plaque rupture plus intraplaque hemorrhage plus thrombosis (18/76, 23.6%), intraplaque hemorrhage without plaque rupture (16/76, 21.0%), plaque rupture plus intraplaque hemorrhage (5/76, 6.5%), stable calcified non complicated plaque (14/76, 18.4%) and unstable, soft, non complicated plaque (5/76, 6.5%). The first four lesions were considered as "complicated lesions". Complicated plaques presented neoformed vessels in the periphery, shoulder and base of the plaque in 22/57 (38.5%) cases. Conversely only 1/14 (7.1%) of non complicated, stable calcified plaques presented neoformed vessels, (p < 0.05). Of note, the 5 causes of unstable, soft non complicated plaque presented neoformed vessels surrounding the plaque. In 10/57 (17.5%) complicated plaques unequivocal histological signs of old hemorrhages were found surrounding those vessels. Irrespective of presenting no rupture, 11/35 plaques showed a mononuclear infiltrate in the fibrous cap. In conclusion, rupture of carotid plaques (50% of the cases), is characterized by the presence of a macrophagic infiltration of the caps and by the direct apposition of T-lymphocytes to macrophages and a close relation of these cells to endothelial cells. This highly suggests a cell-to-cell interaction, which results in an inflammatory process. Intraplaque hemorrhage without rupture represented 21% of the endarterectomies. These lesions are not related to cap erosion, but to plaque vascularization. Most lipid cores were highly vascularized with neoformed vessels with macrophages and T-cells in close contact and in some cases disrupting the endothelium. The abrupt growing of the lipid core and/or an overproduction of oxygen free radicals could lead to the breakdown of core vessels and intraplaque hemorrhage.

[Pathology of cardiac lesions induced by radiofrequency ablation in an experimental model]. / Patología de las lesiones cardíacas provocadas por la corriente ablativa de radiofrecuencia en un modelo experimental.

Radiofrequency catheter ablation is increasingly being used for the treatment of several tachyarrhythmias. The main aim of this paper is to describe the lesional pathology produced by this type of current. Fourteen Wistar rats (mean weight 300 g) were subjected to discharges of a 700 KHz, pure, unmodulated, sine-wave radiofrequency generator. Three rats, through open chests, received epicardial shocks and were immediately sacrificed ("acute" lesions). The remaining 11 rats received shocks through percutaneously plunged tungsten wires, and were sacrificed 1 to 4 weeks after the procedure ("chronic" lesions). Hearts were fixed in buffered (pH7) 10% formalin solution. Selected slices were stained with hematoxilin-eosin and Mallory trichrome. Other slices were fixed in 3% glutaraldehyde and post-fixed in osmium tetroxyde, dehydrated and included in Polybed 812. Ultrathin slices were stained with uranil acetate and lead citrate and examined in a JEOL JEM-100 C electronic microscope. "Acute" specimens showed small coagulation necrosis areas, well delimited by carbonization and hemorrhages. Neighbouring myocardium showed one o two rows of moderate cell lesions which consisted of cytoplasmic homogeneization and increased contracture bands. " Chronic" lesions showed granulation tissue with mononuclear infiltrates and neoformation vessels surrounding a central necrosis area. The older the lesion, the larger the number of fibroblasts and mature collagen tissue. Ultrastructural studies showed irreversible myocardial changes in the lesional borders, with cytosolic and myofibrillar edema, contracture bands and rupture of mitochondrial crests. Radiofrequency lesions are limited, shallow and with net borders, which makes them almost ideal for subendocardial ablation of small arrhythmogenic areas.

Effect of vitamins A and E on ischemia-reperfusion damage in rabbit heart.

The aim of this study was to test the effect of vitamins A and E in reducing oxyradical effects and myocardial damage after ischemia-reperfusion in the rabbit heart. Oxyradical effects were indirectly assessed by hydroperoxide initiated chemiluminescence and myocardial damage was evaluated by qualitative and quantitative electron microscopy. Left anterior coronary artery was ligated in control and vitamin-treated rabbits for 30 min and then reperfused for 10 min. Rabbits were pretreated with 150 mg vitamin E and 60,000 IU vitamin A 24 h before surgery. After 10 min of reperfusion full-thickness needle samples were obtained from five different myocardial areas (three ventricular and two septal areas) and used for the determination of hydroperoxide-initiated chemiluminescence and ultrastructural damage. In the control group, hydroperoxide-initiated chemiluminescence was 18,400 +/- 500 cpm/mg protein for the non-ischemic and non-reperfused ventricular areas, and 40,500 +/- 1,800 cpm/mg protein for ischemic-reperfused ventricular areas. In the vitamin-treated group, hydroperoxide-initiated chemiluminescence was decreased by 8% in the non ischemic and non reperfused ventricular areas and by 51-75% in the ventricular ischemic and reperfused areas. The two septal areas in the control group gave chemiluminescences of 6,800 +/- 1,200 cpm/mg protein (non ischemic-non reperfused) and 17,000 +/- 2,000 cpm/mg protein (ischemia-reperfusion). In the vitamin-treated group, chemiluminescence decreased by 4 and 58%, respectively. The ischemia-reperfused areas showed extensive edema, margination of nuclear chromatin and swollen mitochondria with disrupted cristae including rupture of the inner and outer mitochondrial membranes.(ABSTRACT TRUNCATED AT 250 WORDS)

[Ischemia-reperfusion experimental model in the rabbit: ligation of the circumflex coronary artery versus ligation of the anterior descending coronary artery]. / Modelo experimental de isquemia-reperfusión en el conejo: ligadura de la arteria coronaria circunfleja versus ligadura de la arteria coronaria descendente anterior.

INTRODUCTION AND OBJECTIVES: The myocardial damage during ischemia and reperfusion in the rabbit was studied, in order to compare two different models: the occlusion of the circumflex coronary artery (Cx) vs the occlusion of the left anterior descending coronary artery (LAD). METHODS: Each group consisted of 10 New Zealand rabbits; after 50 minutes of occlusion the artery was reopened for 20 minutes and then a biopsy from the area at risk and another from the perfused area were obtained. The specimens were used for chemiluminiscence and electron microscopy. Electrocardiograms were taken throughout the experience. Transverse sections of both ventricles were used for light microscopy. RESULTS: In both groups elevations of the ST segment, more important in the Cx group (p < 0.001) were observed. In the LAD group, the QRS complexes were enlarged in three animals, in 4 rabbits there were reperfusion arrhythmias, but the experimental mortality was zero. In the other group, 50% of the animals died during the experiment. In the LAD group the chemiluminiscence of the area at risk was greater than that of the perfused area (p < 0.001). No differences could be demonstrated between the samples of the Cx group, probably because of the extensive necrotic areas unable to generate photoemission. Ultrastructural and microscopic characteristic lesions of the ischemia-reperfusion phenomena were found in both groups, particularly severe in the Cx group with extensive areas of necrotic tissue. CONCLUSIONS: This experience shows that the myocardial necrosis, the mortality and the malignant arrhythmias were quantitatively different according to which coronary artery was occluded. This fact may be taken into account when an animal model for ischemia-reperfusion is selected.

Beneficial effects of cloricromene in ischemic reperfused myocardium.

Cloricromene (Clo) has been used to prevent myocardial damage after transient occlusion of the circumflex coronary artery (Cx). Twenty rabbits were injected for 4 days with a single dose of Clo (0.25 mg/kg i.v.) or placebo. On the 5th day, the Cx was occluded, and Clo (6.4 micrograms/kg/min) or placebo was continuously infused. After 50 min, the occlusion was removed and after 20 min of reperfusion, the rabbits were sacrificed. In the placebo group, all rabbits showed marked ST segment changes and severe ischemic arrhythmias (6/10 animals). In 5 of them, ventricular fibrillation was followed by death. In the Clo group smaller ST segment elevations were observed, and in 2 rabbits ventricular fibrillation spontaneously reversed as did ST segment elevations. A significant reduction of the necrotic area was also observed in the Clo group by postmortem examination.

The hypertrophied myocardium and coronary disease. Structural changes in patients submitted to aortocoronary bypass surgery.

Seventeen patients with coronary disease submitted to myocardial revascularization were studied. Ten patients had a hypertrophied ventricle, and 7 had normal ventricular mass. Myocardial biopsies were obtained before ischemia and at the time of reperfusion and were assessed for: volume fraction of fibrous tissue, myocyte diameter, morphometric mitochondrial studies and ultrastructural changes. The volume fraction of fibrous tissue in patients with hypertrophied ventricle was 1.9 +/- 0.04, and in patients with normal ventricular mass was 0.9 +/- 0.01 (p less than 0.05). The diameter of the myocyte was 23 +/- 0.3 microns and 18 +/- 1.2 microns for patients with hypertrophied and normal ventricular mass, respectively (p less than 0.01). The value of volumetric density for pre-ischemia samples in patients with a hypertrophied ventricle was 23 +/- 2.2 and in patients with normal ventricular mass was 35 +/- 2.7 (p less than 0.02). Grades 3 and 4 of damaged mitochondria were significantly increased in reperfusion samples from patients with a hypertrophied ventricle compared to pre-ischemia samples. Collagen growth was increased in hypertrophied hearts which were also more sensitive to the ischemia/reperfusion mechanism.

Preservation of the myocardial collagen framework by human growth hormone in experimental infarctions and reduction in the incidence of ventricular aneurysms.

We administered human growth hormone to a group of rats with experimental myocardial infarctions, in order to observe its action on the connective tissue repair process and the consequent effect on postinfarction ventricular aneurysms. Myocardial connective tissue displays a complex layout around each myocyte and among neighboring ones. It has been shown to be highly vulnerable to acute coronary ischemia which affects its diverse components in accordance with a precise timetable. The ultimate consequence of ischemia on connective tissue is the disappearance of intermyocytic links and the collagen weave that surrounds each cell. Damage to this collagen framework of the heart is responsible for the final disarray of myocytes, with a parallel effect to the myocytolytic actions of ischemia within the very structure of each cell. Hence, the appearance of postinfarction ventricular aneurysms seems to be related to failure in normal repair processes resulting from maturation of new collagen tissue into the area of myocardial necrosis. It has been shown that, besides the well-known actions on chondrocytes, hypothalamic-hypophyseal human growth hormone and somatomedins activate the fibroblasts. Administration of human growth hormone resulted in a significant decrease in the incidence of ventricular aneurysms. Scanning electron microscopy showed a good preservation of connective tissue components of myocardium. A different histological pattern of necrosis resulted in the treated group.

Endomyocardial biopsies in chronic chagasic cardiomyopathy. Immunohistochemical and ultrastructural findings.

Mononuclear cellular infiltrates and extensive fibrosis, with or without apical ventricular aneurysms, are the usual morphological findings in chronic chagasic cardiomyopathy. These lesions are thought to be mediated by immune phenomena rather than by continuing parasitic invasion of the heart. In the present report, we correlated clinical, immunohistochemical and ultrastructural findings in 30 endomyocardial biopsies from patients with chronic chagasic cardiomyopathy. In 12 of these biopsies, immunocytochemical techniques were used to identify and count leukocytes (common leukocyte antigen, CLA), T lymphocytes (UCHL-1 antibody) and B lymphocytes (L-26 antibody). The biopsy specimens showed variable degrees of myocardial hypertrophy and mononuclear infiltrates. No tissue forms of trypanosomes were found. The endocardium averaged 24 +/- 12.6 microns (mean +/- SD) in thickness. The mean myocyte diameter was 20 +/- 7.33 microns. The hearts were severely fibrotic containing a mean of 24.1 +/- 12.8% of fibrous tissue (range 8.2-49%), mast cells were scarce. Mononuclear cell infiltrates were found in 25 of the 30 biopsies. In 12 biopsies, immunohistochemical studies showed that the majority of the lymphocytes were T lymphocytes and associated with necrotic or degenerating myocytes. 10 of the 12 biopsy samples showed 5 or more CLA-positive mononuclear cells/high power field. In these 10 patients, T and B lymphocytes represented 32 and 13% of the total mononuclear infiltrating cells, respectively. The remaining cells were monocytes and macrophages.

Electrophysiologic-structural correlations in chagasic aneurysms causing malignant arrhythmias.

We studied the structure and ultrastructure of three chagasic aneurysms, the excision of which abolished malignant arrhythmias. Chronic recurrent ventricular tachycardia often occurs in patients with chagasic aneurysms, and ventricular mapping indicates that these arrhythmias originate in regions adjacent to those aneurysms. In our patients, ventricular tachycardia had been refractory to medical treatment. During surgery, epicardial and endocardial mapping showed abnormal potentials. Sutures were placed in the areas of resection, their sizes approximating those of earliest activation so that these sites could be identified. The myocardium showed chronic inflammatory reaction, myocytolysis and fibrosis. The presence of "islets" was common (normal, "early" damaged or "established" necrotic myocytes surrounded by fibrous tissue). The "early" lesions were predominant at the previously identified areas of arrhythmogenic activity. The ultrastructural studies showed hypertrophy of myocytes and partial or complete loss of myofibrils, swelling of mitochondria and disruption of mitochondrial cristae, accumulation of lipofuscin granules, and intracellular oedema. A most striking alteration was the thickening of the basement membranes of myocytes and vascular endothelial and smooth muscle cells. The interlaced fronts of respectively healthy (fast conducting) and "early" damaged (slow conducting) myocytes seen in serial sectioning produced an ideal configuration for reentry circuits. The final proof that the arrhythmias originated in these endocardial regions was their abolition by resection of the aneurysm.

[Acute myocardial infarction and bronchoalveolar carcinoma. Association or coincidence?]. / Infarto agudo del miocardio y carcinoma bronquioalveolar. Asociación o casualidad?

The aim of this paper is to report for the first time the association between bronchiolo-alveolar carcinoma and acute myocardial infarction (AMI). Two patients suffering from this association were studied. A 59 year old male, diabetic, alcoholic and smoker was admitted because a diaphragmatic AMI. An interventricular septal defect and papillary posterior muscle rupture were confirmed at autopsy. A 0.8 cm diameter friable mass was found in the right lung superior lobe. The second case was a 69 year old male, smoker, who presented with a diaphragmatic and right ventricular posterior wall AMI. A round 1 cm diameter tumor was observed at the right lung superior lobe. It had a caseous aspect lying over a fibrous scar. Both cases had severe right coronary artery narrowings with recent occlusive thrombi. The cardiac valves were free of non-bacterial thrombotic endocarditis. Therefore the possibility of coronary embolization was discarded. As lung carcinomas produce vasospastic and thrombogenic mucins, these substances could have been responsible for the acute coronary thrombosis.

Histopathology of specialized and ordinary myocardium and nerves in chronic Chagas disease, with a morphometric study of inflammation and fibrosis.

Chagas disease, in the chronic phase, is known to be characterized by cardiac failure, and/or arrhythmias. To assess the involvement of the conduction system and of the working myocardium, morphometric and immunohistochemistry studies have been carried out on 4 autoptic hearts of chronic chagasic myocardiopathy. The characterization of interstitial infiltrates was performed by lymphocyte immunophenotyping with immunocytochemical techniques. These infiltrates were more prominent in the working myocardium and in the left branch of the His bundle. The infiltrates consisted of about 50% of macrophages and 50% of T-lymphocytes. Mast cells would not play a role in the chronic stages of the disease. Eosinophils were present in no more than the 5% of the inflammation. The fibrosis, especially of the conducting system seems to be facilitated by an impaired lymphatic outflow, whereas the evidence of neuroganglionic involvement was variable.

Morphometry of skeletal muscle involvement in mice infected or preimmunized with live attenuated Trypanosoma cruzi.

A morphometric study was undertaken in the quadriceps muscle of Swiss mice in order to assess the effects of immunization with attenuated T. cruzi upon tissue lesions. interfascicular lymphocytic infiltration, presence of amastigote nests, vascular lesions, degeneration and fibrosis were evaluated independently. Each of these alterations was drastically prevented in preimmunized animals. These results indicate that immunity against T. cruzi not only reduces circulating parasites but also clears most of the organic damage caused by infection.

Morphometry of skeletal muscle involvement in mice infected or preimmunized with live attenuated Trypanosoma cruzi

A morphometric study was undertaken in the quadriceps muscle of Swiss mice in order to assess the effects of immunization with attenuated T. cruzi upon tissue lesions. interfascicular lymphocytic infiltration, presence of amastigote nests, vascular lesions, degeneration and fibrosis were evaluated independently. Each of these alterations was drastically prevented in preimmunized animals. These results indicate that immunity against T. cruzi not only reduces circulating parasites but also clears most of the organic damage caused by infection.

Morphometry of skeletal muscle involvement in mice infected or preimmunized with live attenuated Trypanosoma cruzi.

A morphometric study was undertaken in the quadriceps muscle of Swiss mice in order to assess the effects of immunization with attenuated T. cruzi upon tissue lesions. interfascicular lymphocytic infiltration, presence of amastigote nests, vascular lesions, degeneration and fibrosis were evaluated independently. Each of these alterations was drastically prevented in preimmunized animals. These results indicate that immunity against T. cruzi not only reduces circulating parasites but also clears most of the organic damage caused by infection.

Morphometry of skeletal muscle involvement in mice infected or preimmunized with live attenuated Trypanosoma cruzi.

A morphometric study was undertaken in the quadriceps muscle of Swiss mice in order to assess the effects of immunization with attenuated T. cruzi upon tissue lesions. interfascicular lymphocytic infiltration, presence of amastigote nests, vascular lesions, degeneration and fibrosis were evaluated independently. Each of these alterations was drastically prevented in preimmunized animals. These results indicate that immunity against T. cruzi not only reduces circulating parasites but also clears most of the organic damage caused by infection.

Bivalent effects of human growth hormone in experimental myocardial infarcts. Protective when administered alone and aggravating when combined with beta blockers.

Human growth hormone (hGH) administered alone revealed itself as a useful drug to prevent ventricular aneurysm formation in experimental myocardial infarctions in rats and is also able to diminish and change the usually expected pattern of wall necrosis. A protective action on the collagen framework of myocytes has been confirmed as one of the main causes responsible for the above mentioned findings. There are other positive metabolic actions on the myocardial cell although not completely known yet. These actions are revealed by an atypical picture of infarction which appears regionally reduced and with a patchy intracellular distribution. In an opposite fashion, when hGH was administered together with beta blockers, a rapid and extensive deleterious action occurred at the ventricular wall, a very high incidence of ventricular aneurysms and an increased extension of myocardial infarcts were the most outstanding features. The histologic picture in this series resembles that of a rapidly evolving diabetic cardiomyopathy.

[Histologic findings in laser radiation of myocardial pericrater in dogs]. / Hallazgos histológicos en la irradiación por laser sobre el miocardio canino pericrater.

Laser beam constitutes a potential therapy in modern cardiology. Although its myocardial effects are known, they have been insufficiently evaluated at the surviving myocytes zone surrounding the evaporated crater. In order to assess myocyte cellular and organelar damage, we studied 8 isolated canine hearts radiated with different intensities by a CO2He laser beam 2.4, 3.5, 5, 15, 25, 30 and 40 Watts, varying the exposition time from 1 to 6 sec. Color photographs from the post-radiated lesions on front and depth were obtained. Their volumes were measured applying the cylinder and the cut out-conus formulas according to the shape of the lesions and then the involved tissues were embedded in paraffin for histological studies. Previously, samples of the lesions were fixed in glutaraldehyde for ultrastructural studies. Volumes of the craters were from 0.0004 to 19.57 mm3. Three layers were observed: a) a carbonized internal lining which measured x 15 microns in thickness; b) a coagulation necrotic zone ("gruyere cheese-like"), 70 microns thickness; c) finally more peripherally, a layer consisting of myocytes with patchy homogeneous cytoplasm, and scare positivity for the Barbeito López Trichome Stain (a positive technique in cases of myocardial damage). Ultrastructurally, crater peripherical cells showed cytosol and mitochondrial edema without membrane disruptions. These findings suggest that myocytes surrounding the laser beam crater, show reversible lesions. Therefore laser beam apperrs a safe procedure to be used in myocardium.

Immunohistochemical staining of lymphocytes for the reliable diagnosis of myocarditis in endomyocardial biopsies.

Interobserver variability in the interpretation of pathologic endomyocardial biopsies for detecting myocarditis has been widely reported. Thus, conflicting reports about the therapeutic benefit of immunosuppressive treatment in myocarditis may be due to differences in the interpretation of the biopsy findings. In doubtful cases, scattered interstitial cells may be present between myocytes and can be misinterpreted as true lymphocytes. In our study, a further characterization of interstitial cells in endomyocardial biopsies previously diagnosed as showing 'myocarditis' was performed by lymphocyte immunophenotyping with immunocytochemical techniques for membrane and cytoplasmic antigens. Common leukocyte antigen (CLA), kappa and lambda light immunoglobulin chains and T lymphocyte antigens were made visible by an indirect immunoperoxidase technique. A previous diagnosis of 'myocarditis' had been established histologically in 27 patients by the presence of an inflammatory cell infiltrate associated with focal acute cellular damage. These specimens were selected for further study using an immunoperoxidase technique. The number of negative and positive mononuclear cells for each marker was counted on all fields at a magnification of X 400. These numbers were correlated with the extent of interstitial fibrosis and/or myocyte damage on each sample. According to previous studies, 5.0 lymphocytes/high-power field were considered as the lower limit of myocarditis if they were associated with myocyte injury. From the 27 samples previously diagnosed histologically as 'myocarditis' only 14 showed 5 or more CLA-positive mononuclear cells/X 400 field. In 6 out of 8 selected cases having less than 5 CLA-positive cells, no T-antigen-positive cells could be detected. The remaining samples showed T lymphocytes localized in acute infiltrated areas.(ABSTRACT TRUNCATED AT 250 WORDS)