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Biomedical subjects

M D Silver

Publications and source records attributed to M D Silver.

At least 73 records · Page 4Linked to original sources
PubMed1980

Calcification in porcine xenograft valves in children.

Calcification developed in the degenerating collagen of the cusps of three porcine xenograft heart valves implanted in children for less than 4 years. The morphologic features and effects of this calcification are presented. Calcification of porcine xenografts seems to occur more frequently and at an earlier stage after insertion in children than in adults. Host factors, possibly related to calcium homeostasis, may promote calcification; hence, these valves may not be appropriate for use in children.

Adolescent↗
PubMed1980

Malignant hyperthermia susceptibility. A light and electron microscopic study of endomyocardial biopsy specimens from nine patients.

Cardiomyopathy develops in some individuals who have a susceptibility to malignant hyperthermia. We studied right ventricular endomyocardial biopsy specimens from nine patients defined as having this disorder because of positive caffeine contracture tests on skeletal muscle biopsy specimens. Three patients had clinical evidence of cardiomyopathy and six did not. Light microscopy showed cytoplasmic contraction bands, perinuclear clearing, and a mild to moderate variation in myocyte and nuclear size. Ultrastructurally cytoplasmic contraction bands were associated with cardiac villi, myofiberlysis, and myofibrillolysis. These changes and occasional breaks in the sarcolemma were regarded as artefacts of the biopsy procedure. Megamitochondriosis with accompanying degenerative changes in the mitochondria were also seen and probably indicate increased cell metabolism; vacuolation of the cytoplasm was regarded as an "aging" phenomenon. Thus, the biopsy specimens were abnormal, but the changes were artefactual or nonspecific and were not unique to this group of patients. Biopsy did not provide a morphological explanation for abnormal cardiac function.

Adolescent↗
PubMed1980

Electrophoretic profiles of nonhistone nuclear proteins of human hearts with muscular subaortic stenosis.

Muscular subaortic stenosis (MSS) is a genetically determined cardiomyopathy, whereas right ventricular infundibular hypertrophy (IH) apparently is an acquired condition. Since genetic expression in eukaryotic cells may be regulated primarily by DNA-associated proteins, we isolated and characterized the proteins of heart nuclei from nine patients with MSS, eight with IH, and two with normal (N) hearts. More than 150 proteins could be identified by two-dimensional polyacrylamide gel electrophoresis. Proteins in the entire region from pH 7.0 to 9.0 with molecular weights (Mr) ranging from 35,000 to 41,000 and a protein focusing from pH 5.2 to 5.3 with Mr of 55,000 were strikingly reduced in MSS. Again the electrophoretic patterns of N and IH were similar. The electrophoretic patterns of nonhistone nuclear protein (NHNP) in MSS relative to N showed a striking resemblance to those demonstrated previously for the early stage (myolytic phase) of hamster cardiomyopathy relative to the matched control. Since NHNP interacting with DNA appears to play a major role in genetic expression, it is possible that some of the manifestations of MSS could be due to different components of NHNP in the affected hearts.

Animals↗
PubMed1980

Clinicopathological correlations in patients who received an isolated model 104 Beall mitral valve.

Following reports of accelerated wear in the model 104 Beall prosthetic valve, the authors initiated a recall and prospective follow-up study of patients who received Beall valves. In the 3 years of the follow-up program, 12 patients who had an isolated Beall mitral valve implanted have had elective replacement of the prosthesis. Cinefluoroscopy was the most accurate preoperative method of predicting the degree of pathologic wear. The serum lactic dehydrogenase value was the next most helpful measurement. Change in functional class, mitral regurgitation murmur, hemodynamic status, echocardiography and the duration of the valve in situ were not sensitive indicators.

Adult↗
PubMed1980

Wear in Björk-Shiley heart valve prostheses recovered at necropsy or operation.

Thirteen Björk-Shiley prostheses, in situ for up to 27 months, were examined for wear. The discs showed "burnish marks" which did not erode the surface or "wear marks" which did. The metal cages were worn on the "arms" of the inlet strut or at the "hook" of the outlet strut, with metal wear presenting as scored areas or as beveling. This wear is minor and comparable to that seen following accelerated cycle testing in vitro. It is unlikely to seriously affect prosthesis function in the normal lifetime of an individual, but metal wear might cause disc flutter and change auscultatory findings associated with a prosthesis.

Heart Valve Prosthesis↗
PubMed1980

Preliminary results of transluminal dilation in the treatment of peripheral arterial occlusive disease.

The results of our pathologic studies demonstrated that a Grüntzig catheter does not damage arteries in vitro, and our clinical results confirm the observations made by Grüntzig and indicate that this technique has a role in management of certain patients with peripheral arterial occlusive disease. Although long term results are not available, we believe that this technique widens the scope of management for certain patients with peripheral vascular disease but will not replace conservative medical management or surgical treatment. At present, it probably has an intermediate role between the two and replaces neither.

Arterial Occlusive Diseases↗
PubMed1979

Morphological findings in idiopathic calcification of the ascending aorta and aortic valve affecting a young woman.

The pathology of a case of idiopathic calcification affecting the ascending aorta in a young woman is presented. A varying width of media throughout the aorta and extending into its proximaques of calcium, found in the acellular media, were confined to the ascending aorta. No inflammatory or reparative reaction was seen in the vessel wall. Electron microscopically, the calcium seemed to have an affinity for elastic tissue elements of all sizes and the mode of deposition appeared to be by 'avenues' of the microfibrillar component. Possible pathogenetic mechanisms are discussed.

Adolescent↗
PubMed1979

The porous-surfaced electrode: a new concept in pacemaker lead design.

Three major problems which may be encountered with endocardial pacemaker electrodes are a lack of stable position, a chronic increase in stimulation threshold, and a diminishing magnitude of the sensed endocardial signal. These problems are particularly manifest in the atrium. Having previously shown that porous metal surfaces can support stable tissue ingrowth in both bloodstream and soft tissue environments, we set out todetermine the performance of porous-surfaced endocardial pacing electrodes in the atrial position. In two groups of six dogs each, J-shaped atrial leads with Elgiloy electrode tips (2.3 mm. in diameter, 2.3 mm. in length), having either conventional smooth surfaces (control) or porous surfaces (20 to 50 micron particle size) produced by powder metallurgy techniques, were positioned in the right atrial a-pendage. Stimulation thresholds and P-wave amplitude were repeatedly measured until the dogs were put to death 30 w-eks following implantation. The presence or absence of electrode fixation was observed and the atrial tissue reaction was examined grossly and by both light and scanning electron microscopy (SEM). The porous-surfaced electrodes demonstrated superior long-term stimulation thresholds which, at 30 weeks, averaged less then one third of those in the control group. In addition, the porous group showed a small but significant improvement in the amplitude of the sensed P wave. None of the smooth-surfaced electrodes showed fixation, and the tissue reaction consisted of a thick layer of granulation and fibrous tissue on the underlying endocardium, widely separating the electrode from the myocardium. In contrast, all of the porous-surfaced electrodes were fexed to the endocardium by fibrous tissue ingrowth into the surface pores. This tissue fixation of the electrode tip in close proximity to underlying myocytes explains their superior performance.

Animals↗
PubMed1978

Bacterial endocarditis of the mitral valve associated with annual calcification.

Bacterial endocarditis, caused mainly by Staphylococcus aureus, was found at autopsy in five patients who had a calcified posterior mitral valve annulus. Clincopathologic correlation indicates that the infection should be suspected in elderly patients with a calcified mitral annulus, the murmur of mitral insufficiency, fever, anemia, polymorphonuclear leukocytosis and a positive blood culture, regardless of evidence of peripheral embolism or of another disease that could cause the last four features. Pertinent pathologic findings are a calcified mitral valve annulus, vegetations of bacterial endocarditis towards the base of the posterior leaflet associated with leaflet perforation and an annulus abscess, and no other valvular disease. The infection may develop on the atrial aspect of a leaflet ulcerated by the calcium mass or may begin on its ventricular aspect, subsequently perforating the leaflet and infecting its atrial surface.

Aged↗
PubMed1978

Aneurysms of the septum primum in adults.

Sixteen aneurysms of the septum primum were found at autopsy among 1,578 adults. Most occurred in individuals in their fifth or sixth decade. All aneurysms were asymptomatic and none were diagnosed before death. Fourteen bulged into the right ventricle. The aneurysm may develop in patients with a raised intra-atrial pressure but most seemed associated with normal intra-atrial pressures. A particular morphology of the fossa ovalis region may predispose the septum to aneurysm formation. Echocardiographic and angiographic features of the aneurysm need definition to distinguish them from those caused by other lesions.

Adult↗
PubMed1978

Late complications of prosthetic heart valves.

Iatrogenic lesions induced during prosthesis insertion are likely to be encountered by a pathologist examining a patient who died of late complications of heart-valve prosthesis. The lesions are classified as those that may occur in any patient who has had a heart-valve prosthesis inserted, including the iatrogenic type and those that are uniquely associated with a particular prosthesis because of its structure or design.

Death, Sudden↗
PubMed1977

Strokes: A complication of mitral-leaflet prolapse?

During a prospective trial of platelet-inhibiting drugs in patients with transient ischaemic attacks (T.I.A.s), 14 patients had serious neurological dysfunction and normal cerebral angiograms. The patients (mean age 37 years) had neurological episodes over a period of 1-4 years consisting of acute non-progressive strokes with residual symptoms. In 3 patients, the two cerebral hemispheres were involved on different occasions. Cerebral angiograms showed no significant atheromatous disease in the intracranial or extracranial vessels. 3 patients had mid-systolic clicks, 5 had systolic murmurs, and 2 patients had both a click and a murmur. Holter electrocardiographic monitoring revealed atrial, junctional, or ventricular extrasystoles (5 patients), paroxysmal atrial fibrillation (3), and paroxysmal ventricular tachycardia (1). Left ventricular angiography confirmed mitral-leaflet prolapse in all the patients. The focal nature of the T.I.A.s suggests an embolic event, the embolus arising from the abnormal mitral valve. In a patient not included in this series, a small antemortem left atrial thrombus was found at necropsy.

Adolescent↗
PubMed1977

The pathology of wear in the Beall model 104 heart valve prosthesis.

We examined 13 Beall model 104 prostheses recovered at surgery or autopsy 10 to 84 1/2 months after insertion and observed the pattern of prosthesis wear. We defined wear as "mild" when the disc was notched but neither the metal of the struts was exposed not the cloth seat torn. In "moderate" wear the disc was notched, the Teflon coating of the struts was worn away exposing the underlying metal but the cloth of the set was not torn. The cloth seat was torn in "severe" wear, exposing the metal seat and causing a different pattern of disc erosion. In one case this allowed the disc to tilt into the valve lumen and, later, to escape from its cage. Most of the prostheses studied showed "moderate" or "severe" wear. We believe that some degree of wear is inevitable. Clinical signs and symptoms were not specific but a rough correlation existed between the severity of hemolysis, as indicated by serum LDH levels, and the degree of prosthesis wear. When wear was "severe", the results of cardiac catheterization studies usually mirrored the change, but there were a few exceptions. All patients with the Beall model 104 prosthesis may eventually develop "severe" wear, and we recommend regular reassessment with a view toward prosthesis replacement.

Adult↗