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Biomedical subjects

M D Silver

Publications and source records attributed to M D Silver.

At least 55 records · Page 3Linked to original sources
PubMed1988

Late strut fracture of the Beall model 105 disc valve prosthesis.

Strut fracture, with embolization of the disc occluder, caused the death of a 64-year-old man who had a Beall model 105 heart valve prosthesis in the mitral position for 13 years. Scanning electron microscopy of the fractured surface revealed evidence of a fatigue failure mechanism in the metal wire. The case is unique in that strut fractures affecting this prosthesis had only been observed previously in the range of 141 to 342 days after implantation. Morphological changes in this valve prompted reexamination of three other model 105 prostheses that had been recovered from the mitral area at necropsy or surgery 9 to 10 years after insertion in 1972 or 1973. All had been kept in dry storage. The three prostheses and the valve described above showed previously unrecognized cracks in the pyrolytic carbon coating of the struts, which form the cage that limits occluder movement. The defects were located at or near the base of struts, where they entered the sewing ring and were bent to pass into the strut supporting ring. We believe that the cracks in the carbon coating precede total strut fracture and postulate that they are needed for the metal wire to be subject to a fatigue failure mechanism.

Adult↗
PubMed1987

Cardioversion and defibrillation using a catheter electrode: myocardial damage assessed at autopsy.

A technique has been described for countershock in an intensive care setting using a catheter electrode in patients with recurrent ventricular tachyarrhythmias. During defibrillation or cardioversion an electrode in the superior vena cava acts as an anode and an electrode in the right ventricular apex is the cathode. This report describes the resultant changes in the hearts of four men who died with recent, large myocardial infarcts and who had received eight to 55 countershocks of 2.5-50 joules through the catheter. Mural thrombus and/or focal endothelial hemorrhage was found in three hearts at the anode site. Thrombus was seen at the cathode site in two hearts. Myocardial necrosis, secondary to the catheter, was present in only one heart which had a 2 mm rim of granulation tissue around the distal electrode. It is unlikely that this focal area of right ventricular damage would be clinically important. We conclude, therefore, that repeated countershocks delivered through the catheter system produce little myocardial damage.

Aged↗
PubMed1987

Anomalous mitral arcade: a rare cause of mitral valve disease in an adult.

Anomalous mitral arcade is a rare congenital abnormality of the mitral valve not previously described in an adult. Familiarity with this anomaly may facilitate interpretation of left ventricular abnormalities detected with echocardiography or contrast ventriculography in patients with evidence of mitral valve disease.

Adult↗
PubMed1986

Estimation of the abrasive wear coefficient in Lillehei-Kaster cardiac valve prostheses.

An approximate hemodynamic theory, which predicts the opening dynamics of the Lillehei-Kaster heart valve, is used in conjunction with an abrasive wear model to predict the wear process on the shields. The hemodynamic theory predicts markedly different opening dynamics between the mitral and aortic positions and is shown to give excellent correlation with the experimental results of other investigations. The abrasive wear model is also shown to give excellent correlation with the experiments of others when the abrasive wear coefficient is taken as k = 6.4 X 10(-6). The theoretical results of this effort and the experimental data from clinical explants of other investigators is used to predict that occluder dislodgement is unlikely in less than 90 yr for either the mitral or aortic positions (for a mean cardiac output of 3.8 l.min-1 and a mean heart rate of 70 beats min-1).

Heart Valve Prosthesis↗
PubMed1986

Acquired coronary arterial aneurysms: an autopsy study of 52 patients.

In the past decade most studies of coronary arterial aneurysms have been clinical; few have focused on morphology and etiopathogenesis. The subjects of the present autopsy study were 52 patients, 5 months to 80 years of age, with coronary arterial aneurysms. Patients were divided into two groups: 38 with atherosclerotic coronary aneurysms and 14 with aneurysms secondary to inflammation. Of the 38 patients with atherosclerotic aneurysms, 20 (53 per cent) had histories of ischemic heart disease; the aneurysms were in the right coronary artery in 18 (47 per cent), the left coronary artery in 13 (35 per cent), and in the right and left coronary arteries in seven (18 per cent). Of the four major coronary arteries, the average number of severely narrowed arteries (reduction of more than 75 per cent) in cross-sectional luminal area) was 1.8/patient; aortic aneurysms were present in eight of these patients (24 per cent). Of the 14 patients with coronary aneurysms secondary to inflammation, four had histories of ischemic heart disease; 10 had histories of an influenza-like syndrome. Isolated left coronary arterial aneurysms were seen in six of these patients (43 per cent), while eight (51 per cent) had multiple right and left coronary arterial aneurysms. The average number of severely narrowed coronary arteries in this group was 1.5/patient, and only one patient had an aortic aneurysm. Therefore, patients with atherosclerotic aneurysms are more often symptomatic; they have increased heart weights and equal numbers of coronary arterial aneurysms in the right and left vessels, and the majority (89 per cent) have single aneurysms with thrombi in the lumen. Patients with coronary arterial aneurysms secondary to inflammation are younger; the majority of these patients have a prodromal influenza-like syndrome, a low incidence of ischemic heart disease, and multiple coronary arterial aneurysms.

Adolescent↗
PubMed1985

Nemaline myopathy with associated cardiomyopathy. Report of clinical and detailed autopsy findings.

We describe the clinical features and autopsy findings of an adult patient who had nemaline myopathy and an associated progressive cardiomyopathy. The spinal cord and the results of morphometric analysis of multiple peripheral nerves were normal. There was probable intrafusal fiber involvement, in addition to the typical histopathologic features of extrafusal fibers. Cardiac dysfunction was a prominent clinical and autopsy feature, but it has been infrequently recognized in this entity. Our findings suggest that there is a poor correlation between clinical and pathologic features in this disorder, and they support the need for careful cardiac evaluation of affected patients. Furthermore, the constellation of features favors a myopathic basis for the disease, in contradistinction to some previously expressed views.

Adult↗
PubMed1985

Metal wear in Lillehei-Kaster heart valve prostheses.

Ten Lillehei-Kaster heart valve prostheses, in situ for up to 10 years and recovered at surgery or necropsy, were examined by light and scanning electron microscopy. All showed metal wear on the luminal aspect of their struts. The volume of wear related to the duration a prosthesis had been in situ. The worn metal showed distinct, transverse surface corrugations, which became more obvious with time. Aortic prostheses wore more and faster than mitral ones. One strut usually showed more wear than the other, a change likely due to specific manufacturing methods. It is believed that the pattern of wear is caused by a velocity-controlled stick-slip abrasive wear process, resulting from an interaction between the edge of the moving pyrolytic carbon disc, the struts' titanium surface, and the protein coat covering that surface. None of the patients had prosthesis dysfunction attributable to metal wear. Disc escape seems unlikely considering the degree of wear observed after 10 years. Furthermore, the surface corrugations did not appear to cause disc sticking or other problems. However, clinicians might consider monitoring patients who have borne these prostheses for greater than 10 years.

Aortic Valve↗
PubMed1985

Vasculature in the walls of human coronary arteries.

Casts were produced of the arterial networks of 25 human hearts obtained at autopsy from subjects who were not diagnosed as having cardiovascular disease. Many casts showed imprints of atherosclerotic plaques, remnants of calcified masses, and fine vascular meshes near the lumen of the major coronary arteries. Of 25 casts produced, 14 contained one or more of these anomalies, seven contained vascular meshes, and five of these related to imprints and/or calcified masses. Analysis of these findings in the context of atherosclerosis, intramural hemorrhage, and vascular spasm, suggests possible relationships between them. The findings support the hypothesis that neovasculature in the walls of coronary arteries may play a role in the pathogenesis of vascular disease and malfunction.

Adult↗
PubMed1984

Radionuclide angiography and endomyocardial biopsy in the assessment of doxorubicin cardiotoxicity.

Thirty-eight patients with a mean age of 53.2 years (19 to 75 years of age), who were receiving doxorubicin (D) for malignant disease, were studied in order to determine the relationship between functional and morphologic myocardial changes at different dose levels. Serial patient evaluations included physical examination, chest x-ray, electrocardiogram (ECG), endomyocardial biopsy (EMB), and rest-exercise gated nuclear angiography (GNA), at doses of D ranging from 144 to 954 mg/m2 (mean, 426 mg/m2). Physical examination, chest x-ray, and ECG proved to be insensitive predictors of D cardiotoxicity. Correlation of GNA and EMB in 31 patient evaluations, exclusive of known heart disease, did not reveal any false-positive angiograms, and all abnormal GNAs were associated with abnormal biopsies. Use of stress GNA uncovered six abnormal ventricles which could have been missed with a rest GNA alone. It has been suggested that: (1) GNA is a reliable monitor of D therapy; (2) an exercise study should be performed when the rest ejection fraction is normal, but is unnecessary when the rest EF is abnormal; (3) all patients with a resting ejection fraction of less than 45%, exclusive of other cardiac disease, should have D discontinued; and (4) endomyocardial biopsy is useful in assessing D cardiotoxicity in patients with other possible causes of an abnormal GNA.

Adult↗
PubMed1984

Morphologic and morphometric analyses of muscle in the neonatal myotonic dystrophy syndrome.

Autopsy studies of three premature siblings who died soon after birth with the neonatal myotonic dystrophy syndrome revealed pulmonary hypoplasia and congenital pleural effusions. Neither of these findings has been described previously in this condition. New ultrastructural findings include focal diaphragmatic myofiber degeneration and necrosis, which were attributed to over-stretching of the fetal diaphragm. In addition, abnormally small stores of free and intravesicular glycogen were observed in skeletal muscle fibers. The morphometric features of control fetal and neonatal skeletal muscle were recorded for comparison with muscle fiber measurements in the three infants. Fiber diameters in the latter were much smaller than expected for body weights. The morphologic and morphometric findings support the concept that fetal muscle maturation is severely retarded in this syndrome.

Brain↗
PubMed1984

Isobutyl-2-cyanoacrylate pulmonary emboli associated with occlusive embolotherapy of cerebral arteriovenous malformations.

Three patients had cerebral arteriovenous malformations (AVM) treated by occlusive embolotherapy using isobutyl-2-cyanoacrylate (IBC). At necropsy two had asymptomatic IBC pulmonary emboli. The numbers of emboli and the size of pulmonary vessels occluded correlated roughly with an increasing frequency and volume of injectate made in the cerebral tissue. The extent of pulmonary vascular occlusion in one case suggests that pulmonary vascular hypertension could develop as a complication of this form of treatment.

Adult↗
PubMed1984

Gamna body of the heart.

A patient with cerebral strokes had a cardiac tumour excised. Histologically, it was an infarcted myxoma with features of a Gamna body. Findings are compared with other cardiac Gamna bodies reported in the literature. Most probably represent unusual degenerative changes in a myxoma.

Aged↗
PubMed1982

Carcinoid heart disease: diagnosis by two-dimensional echocardiography.

We prospectively studied 14 patients with the carcinoid syndrome to determine if two-dimensional echocardiography could detect the nature and extent of valvular abnormalities. Eight of the 14 patients had definite abnormalities of the right-sided cardiac valves. The tricuspid valve had a characteristic appearance, similar to previously described pathologic findings. The leaflets appeared diffusely thickened, shortened and stiff without evidence of commissural fusion. Saline contrast studies demonstrated tricuspid regurgitation, which corresponded to the severity of the tricuspid valve involvement. The pulmonary valve could only be adequately assessed in seven of 14 patients, and morphologic abnormalities similar to those in the tricuspid valve were found. Follow-up studies have shown progression of cardiac disease in six of eight patients. We conclude that two-dimensional echocardiography can detect the characteristic cardiac abnormalities in the carcinoid syndrome and may be a useful tool for following their progression.

Adult↗
PubMed1981

The morphology of the human newborn ductus arteriosus: a reappraisal of its structure and closure with special reference to prostaglandin E1 therapy.

The ductus arteriosus was examined in 103 fetuses and infants to define the normal structure, development, and morphologic features of the functional and anatomic phases of ductal closure. New contributions include ultrastructural observations and the light microscopic definition of the junctional regions of the ductus with the pulmonary artery and aorta. Observations relating to ductal closure include hyperemia of the ductal vasa vasorum, the presence of longitudinal muscle bands in the inner media, necrosis of the inner ductal wall, and organization of intraluminal thrombi. We found that a ductus arteriosus that fails to close normally is liable to show morphologic lesions, including intimal fibrinous deposits, medial hemorrhages, and dissecting aneurysms. The findings were used comparatively to investigate whether prostaglandin E1 infusion, given to maintain ductal patency in 7 infants with ductus dependent congenital heart disease, was associated with specific morphologic features. We could not delineate specific changes attributable to its use.

Age Factors↗