Subendocardial ischemic myocardial lesions associated with severe coronary atherosclerosis

Morphologic changes in the subendocardial myocardium that appeared to be caused by severe, chronic subendocardial ischemia were studied in patients with fatal ischemic heart disease admitted to the Specialized Center of Research for Ischemic Heart Disease at the University of Alabama in Birmingham in the period 1970--1977. Thirteen patients were selected for this report on the basis that they had the lesions in the subendocardial myocardium we believe to have been caused by subendocardial ischemia and had no evidence of acute or remote myocardial infarction or other conditions that may have contributed to their terminal illness or death. Clinical findings were unstable angina, congestive heart failure, usually no increase in plasma enzymes indicative of myocardial damage, and electrocardiographic changes consistent with subendocardial ischemia. All 13 patients had 75% or greater stenosis of the three major coronary arteries; none had acute thrombotic or embolic coronary artery occlusion. The left ventricle in all cases was hypertrophied. The subendocardial myocardium showed circumferential pallor, hyperemia, or focal fibrosis without perceptible loss of volume in papillary muscles or trabeculae carneae. Microscopically, acute lesions showed one to two layers of preserved myofibers adjacent to the endocardium, vacuolar change in the deeper fibers, and focal areas of coagulation necrosis of variable size in the myocardium external to the fibers with vacuolar change. Coagulation necrosis was extensive in some cases and usually was not associated with infiltration of neutrophils. The repair reaction involved removal of necrotic sarcoplasm by mononuclear phagocytes, resulting in a reticular-appearing tissue without evidence of stromal collapse. Granulation tissue was not seen. Collagen fibers appeared to be deposited within the area of previous sarcolemmal sheaths. The distribution and morphology of subendocardial myocardial lesions associated with severe coronary atherosclerosis are distinctive and can be distinguished from myocardial necrosis or fibrosis associated with acute total occlusion of a coronary artery.

[Pathological patterns of reperfused myocardial infarction. Experimental study (author's transl)]

The effect of the reperfusion on the pathological appearance of experimental myocardial infarction has been studied in the rat (87 animals). Following permanent ischemia (33 animals sacrified after 1, 6, 24 and 48 hours), there appeared a reproducible extended transversal infarction marked by a uniform sequence of histologic, histoenzymatic and ultrastructural changes. Following temporary ischemia (54 animals), the pathological patterns were marked by myofibrillar degeneration (contraction band necrosis), cellular edema, calcium deposits and interstitial hemorrhages. These changes appeared after reperfusion of short duration (10 minutes). Sarcolemmal and capillary permeability alterations could be the main factor involved in the reperfusion injury. Similar tissue damage have been found in clinical conditions in subendocardial hemorrhagic necrosis after cardiopulmonary by-pass, and in reperfused infarction.

Histopathology of endomyocardial biopsies from patients with idiopathic cardiomyopathy; quantitative evaluation based on multivariate statistical analysis

In order to evaluate the histological changes in endomyocardial biopsies from 121 patients with idiopathic cardiomyopathy, quantitation of histological findings was performed and analysed by univariate and multivariate statistical analysis. Several findings, i.e. (1) disarray of myofibers, (2) hypertrophy of myofibers, (3) scarcity of myofibrils, (4) nuclear changes, (5) vacuolization, (6) proliferation of collagen fibers, (7) endocardial thickening, (8) interstitial edema, (9) cell infiltration, (10) fatty infiltration and (11) basophile degeneration, were graded in five degrees (- to 4+) or two degrees (- or +) depending upon the severity and the extent of each finding. The univariate analysis of the graded histological findings revealed no remarkable difference between the biopsies from HCM and CCM pts, except for nuclear changes, which appeared to be more prevalent in CCM (p less than 0.05). In the categorical principal component analysis of the first six histological findings listed above, three principal components could be extracted. The first principal component was characterized by all six histological findings, the second by vacuolization and proliferation of collagen fibers, and the third by hypertrophy of myofibers. The mean values of the first principal scores indicated that, in either LVB or RVB histological changes were more severe in CCM than in HCM, and in fatal cases than in survivors. The second principal scores indicated that fatal cases had more collagenosis but less severe vacuolization than survivors. The histological findings in RVB appeared to be significantly correlated (r = 0.41, p less than 0.05) with those in LVB obtained from the same heart, but some differences were noted, myofiber hypertrophy and vacuolization being more prominent in LVB than in RVB.

Stereologic analysis of dystrophic chicken muscle

Stereologic methods have been used to estimate the volume and surface densities of sarcoplasmic reticulum (SR) and T tubules of normal and dystrophic chicken pectoralis muscle fibers. The surface and volume densities of the T system in dystrophic muscle fibers showed large increases compared with normal muscle fibers; the surface and volume densities of the SR showed large decreases. In addition, the SR and T system in dystrophic fibers undergo changes in shape. The tubules of the free SR become much narrower; the T system becomes dilated and vesiculated. Dystrophic fibers, on the average, are much larger than normal but maintain the same sarcolemmal surface/fiber volume ratio as normal fibers. Alterations in the surface and volume densities of the dystrophic sarcotubular system may account for some of the altered contractile properties of these muscles.

The non-specific nature of the myocardial wavy fibre

Wavy myocardial fibres were found in about half each of a series of 28 normal and 31 infarcted human hearts, as well as in the normal heart of an infant. Such fibres were also seen in rather more than half of a series of normal rat hearts. Thus, the wavy fibre is not a specific feature of acute ischaemic heart disease. Some experimental evidence was obtained that patchy loss or preservation of ATP promotes the formation of wavy fibres.

[Electron microscopic studies in enzootic muscular dystrophy in cattle]

Electron microscopy was used to examine the sekeletal muscles of young cattle, aged between 13 and 24 months, with spontaneous enzootic myodystrophy (nutritional myodegeneration due to selenium deficiency, white muscle disease). The animals had been received from Sumava District, Southern Bohemia, an area known for shortage of selenium. Outbreaks of clinical illness were recorded from them between four and 18 days from the beginning of grazing. Most of the ultrastructural changes included decomposition of myofibrils and hyalinisation of fibres as well as defective fibril synthesis (Z-striation abnormality), some of the latter phenomena recordable even from regenerating fibre. However, minor disorders only were established from the mitochondria, sarcoplasmic reticulum, components of sarcoplasm, and vessels. There were far-reaching ultrastructural similarities to nutritional myodegeneration of sheep. The changes recorded are likely to suggest a specific role played by selenium in the formation and preservation of myofibril proteins.

[Electron microscopic findings in the skeletal musculature of broilers with nutritional encephalomalacia]

Sings of myopathy were recorded by means of electron microscopy from the skeletal muscles of 20 broiler chickens, aged five and six weeks and suffering from spontaneous nutritional encephalomalacia. Focal deposits of osmiophilic, granular or amorphous matter, intermixed also with membrane fragments and condensed to homogenous osmiophilic bodies, were found quite often in the sarcoplasm. Those deposits were interpreted as lipoproteid complexes (pigmentation due to vitamin E deficit). Also observed were degenerative disorders of compensatory reactions of membraneous fibre organelles (sarcoplasmic reticulum, mitochondria) as well as decomposition of myofibrils and fibre hyalinization. Fibre regeneration and vascular damage occurred less often. Pathogenetically, the changes are interpreted particularly with regard to a membrane-stabilising anti-oxidant action of vitamin E and compared to the selenium-dependent myopathies of ruminants from which primary myofibrillar damage was recordable but no pigment accumulation.

Effects of insulin on experimental catecholamine cardiomyopathy

We have recently shown that insulin attenuates norepinephrine (NE) dose-response curves in both isolated cardiac muscle and intact heart preparations. Accordingly, an intact rabbit model was used to determine if insulin would reduce the extent of myocardial damage following a standard NE infusion. Each animal was given pentobarbital, 30 mg/kg, and heart rate, arterial pressure, glucose, blood gases, and pH were measured. NE (2 microgram/min/kg) was given intravenously for 90 minutes. After 48 hours the rabbits were killed and the hearts were examined microscopically and assigned a histologic score. Florid lesions were present in 17 of 24 sections (71%) from 12 animals. They were characterized by myofiber necrosis and an intense cellular reaction. However, only 5 of 40 sections (12.5%) from 20 rabbits given insulin (10 units/kg) 30 minutes before the NE infusion showed advanced lesions (P less than 0.001). The mean histologic score was reduced from 1.7 to 1.0 (P less than 0.001). The frequency of advanced lesions increased to 86% in animals given a higher dose of NE (3 microgram/kg/min) and was reduced to 53% by pretreatment with insulin. A dosage of 5 units/kg was as effective as 10 units/kg, but rabbits given 1 unit/kg manifested cardiomyopathic changes identical to those in rabbits not pretreated with insulin. No differences in heart rate, arterial pressure, PO2, or pH were evident between the groups. It is concluded that large doses of insulin reduce myocardial damage produced by NE in this model. This may be linked with the phenomenon of insulin inhibition of the inotropic action of NE.

On skeletal muscle pathology in trichinosis

A study was carried out on the pathology of trichinosis in human muscle biopsy sample and comparatively in experimental trichinosis in the rat, by current microscopic techniques and Troitsky's method of block silver impregnation of the nerve endings. Stress is laid upon the incipient changes in the parasitized muscle fibers, the sarcolemmic origin of the parasite capsule, the myogenic nature of certain periparasitary but intracapsular clear cells of precocious appearance and other associated, non-specific lesions, such as common myositis changes or giant myogenic foreign-body cells. The intimate relationships between parasitized muscle fibres, cellular interstitial reactions, local new-growth vessels and proliferation of the nerve endings are also described. The morpho-functional significance of such morphological synergic manifestations is discussed as an adaptation to the new local conditions brought about by the appearance of the peculiar muscle fibre-parasite unit in trichinosis.

Experimental investigations in acute myocardial ischaemia. Note II. Studies concerning morphophysiologie alterations of the ischaemic myocardium under vascularization conditions

The biology of the myocardial fiber was studied under experimental conditions similar to angina and the premonitory syndrome of myocardial infarction. The morphophysiologic data obtained particularly concerning the mitochondria demonstrated that affection of the myocardium by progressive ischaemia induced less severe lesions than the abrupt onset of ischaemia, also lowering the frequency of ventricular fibrillations.

Nemaline myopathy

Nemaline myopathy occurred sporadically in a 59-year-old woman. She had slowly progressive weakness. A muscle biopsy specimen showed nemaline rods, increased variation in fiber size, apparent loss of Type IIb fiber differentiation, and a "moth-eaten" pattern of the intermyofibrillar network. At least 44 cases of this disorder have been reported. Clinically, they showed several different modes of onset, patterns of muscle group involvement, and rates of progression. There was a suggestion of familial involvement in at least half. In addition to the presence of nemaline rods, pathological abnormalities of muscle biopsy specimens were quite variable. Results of recent biochemical studies have shown abnormal myosin in a patient with rod myopathy. A hypothesis is proposed that relates the diverse clinical and histological features of this disease to a hereditary molecular abnormality of myosin synthesis.

[A case of nemaline myopathy studied over a period of nine years (author's transl)]

We report a case of a boy of 13 who was born with muscular hypotony which has tended to improve over the course of the years. We was examined for the first time when he was 4 years old and a diagnosis was made of "congenital myopathy". Examination showed curved feet, gothie palate, severe laxity of the ligaments, and spider fingers which evoked Marfan's syndrome. The present myopathy is concentrated in the shoulder girdle and the E.M.G. showed "myogenic" tracings. Biopsy of the deltoid showed the presence of large numbers of rods in all muscle fibers stained with Engel's modified trichromic stain, localized mainly under the sarcolemma. Histochemical staining showed no evidence of differences in the fibers, all of which had the same enzymatic activity. A diagnosis was made of nemaline myopathy. As we were able to follow clinical progress in this case for nine consecutive years we could confirm that not only was the disease non-progressive but that it was regressing in this patient.

Pathogenesis of isoproterenol-induced myocardial lesions: its reation to human 'coagulative myocytolysis'

Animals develop 'infarct-like' lesions when injected with isoproterenol (ISP), a potent synthetic catecholamine. These lesions are morphologically similar to those of 'coagulative myocytolysis' (COAM) or myofibrillar degeneration, one of the findings described in acute myocardial infarction and sudden death in man. Wistar rats were divided into 8 groups: some were injected with 10 mg/kg ISP i.p. plus 5 muCi of tritiated ISP, while others served as control. Animals were sacrified at 5 and 30 min and 24 and 72 h. The ISP-induced lesions were studied by means of light microscopy, histochemistry, autoradiography and electron microscopy. Myofibrillar degeneration, positive tests for ischemia, increase of succinic dehydrogenase enzymes, hypercontraction and widening of Z bands of sarcomers were correlated with the rapid distribution of ISP. These lesions were minimized by prenylamine, a drug which inhibits catecholamine effects by slowing down Ca transport. It is concluded that myocardial necrosis induced by ISP is probably due to a primary act on the sarcolemmal membrane, followed by stimulation of adenylate cyclase, activation of Ca and Na channels, exaggreated Ca inflow, excess of excitation-contraction coupling mechanism, energy consumption and cellular death. The close resemblance of human COAM to ISP-induced lesions suggests that similar mechanisms may be involved.

A congenital myopathy of unknown origin

Parallel with the clinical and histochemical investigations, an ultrastructural examination of a muscle biopsy specimen was made, in order to detect any slight cellular alterations which cannot possibly be discovered through any other methods, and to identify a muscle disease of unknown origin.

Left atrial ultrastructure in mitral valvular disease

Light microscopic and ultrastructural observations were made on left atrial tissues obtained from 14 patients at the time of operation for correction of mitral valvular disease. Cardiac muscle cells varied in size but most frequently were hypertrophied. In fibrotic areas, present in all left atria, the muscle cells tended to be isolated from adjacent cells and exhibited degenerative changes of varying severity. These changes consisted or proliferation of Z-band material and cytoskeletal filaments, myofibrillar loss, proliferation of elements of free and extended junctional sarcoplasmic reticulum, variations in size and number of mitochondria, occurrence of abnormal mitochondria, dissociation of intercellular junctions, formation of spherical microparticles, and accumulation of lysosomal degradation products. Hypertrophy was considered to lead to cellular degeneration, with decrease or loss of contractile function. Atrial fibrillation was associated with severe cellular degeneration. The severity of degeneration was greater in patients with mitral regurgitation, with or without associated mitral stenosis, than in patients with pure mitral stenosis.

Time course of electron microscopic alterations in the hypertrophied myocardium of Goldblatt rats

In Goldblatt rats, electron microscopic investigations of morphological changes in heart tissue during the compensatroy stage of pressure induced cardiac hypertrophy were performed. Myocardial cellular size enlarged considerably within the first 4 weeks after renal artery coarctation. An enlargement of the T-tubular system is particularly striking. The ratio of myofibril volume to total cell volume is significantly increased from the 4th-24th week and can at least partially explain a rise in developed tension which occurs in spite of a frequent disarrangement of myofibrils. In later stages severe changes in the vessel walls take place and there is an augmentation of connective tissue which impairs a correlation between myocardial cell alterations and mechanical parameters.

Cellular changes in mechanically overloaded heart

From the ultrastructural aspects of the myocardial cell in different types of heart overloading, several points concerning the adaptation of the myocardial cell were briefly summarized: the respective role of hypertryphy and hyperplasia in heart enlargement, the nature of the myofibrillar changes; the changes in the volume, number and size of mitochondria, and the dependence of the cellular lesions on the severity of the load.

[Familial form of centronuclear myopathy in the adult]

Two adult cases of centronuclear myopathy are described in a family from French Guyana. One of them, aged 23, has a slight weakness despite hypertrophic muscles. A typical picture of centronuclear myopathy was seen on muscle biopsy with atrophy of type I fibers and hypertrophy of II A fibers. His uncle, aged 53, had a progressive weakness of the lower limbs for the last 25 years, with also a pattern of centronuclear myopathy, but with more dystrophic features and atrophy of both type I and II A fibers. The mode of inheritance is dominant. These two cases are compared with the previously published reports. The pathogenesis of centronuclear myopathy is discussed.

Changes in motor innervation and histochemical pattern of muscle fibers in some congenital myopathies

Changes in motor innervation were compared with histologic and histochemical pattern of muscle fibers in three biopsies of central core disease, four biopsies of nemaline myopathy, one biopsy of myotubular myopathy, and three biopsies of mitochondrial myopathy. Evidence of collateral reinnervation was obtained only in one biopsy from central core disease. In other biopsies, no structural or ultrastructural abnormality of axis cylinders, myelin, or myoneural junction suggesting denervation were observed. The only relevant change found in centronuclear myopathy and to a lesser extent in nemaline myopathy was an unusual smallness and simplication of motor endings, suggesting delayed or impaired maturation. Muscle fibers strongly reactive for both adenosinetriphosphatase and nicotinamide-adenine dinucleotide diaphorase, observed in central core disease and mitochondrial myopathy, were not associated with increased terminal innervation ratio.