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Biomedical subjects

W D Edwards

Publications and source records attributed to W D Edwards.

At least 127 records · Page 7Linked to original sources
PubMed1992

Percutaneous polymeric stents in porcine coronary arteries. Initial experience with polyethylene terephthalate stents.

BACKGROUND: To test the feasibility of percutaneous deployment of intracoronary polymeric stents, a prototype polyethylene terephthalate (PET) stent and a catheter-based delivery system were developed. METHODS AND RESULTS: Polymeric stents were deployed in the coronary arteries of 11 Yucatan swine: six stents were placed in the left anterior descending coronary artery, four stents were placed in the circumflex artery, and one stent was placed in the right coronary artery. Stent deployment was achieved by withdrawal of an outer delivery sheath, thus allowing the PET stent to self-expand to a preformed configuration. Two animals died during surgery, one during stent placement and the other several hours after implantation due to intracoronary thrombus formation. Two animals were electively sacrificed within 24 hours of stent implant to examine the adequacy of stent deployment within the coronary vessel. The remaining seven animals survived until the termination of the study 4-6 weeks later. Light microscopic examination of the stented vessels showed an extensive neointimal proliferative response with vessel occlusion in all animals who survived initial stent placement. There were two distinct types of histological responses to the PET stent--a chronic foreign body inflammatory response around the stent tines and a neointimal proliferative response in the center of the occluded vessel lumen. The histological response seen in the central area of the vessel was morphologically similar to that seen in patients with restenosis after successful percutaneous transluminal coronary angioplasty, whereas the morphological response seen at the periphery of the stent tine was similar to that exhibited by a chronic foreign body reaction and was not typical of that seen in a restenosis lesion. A ventricular aneurysm also developed in the area of myocardium that was previously supplied by the occluded vessel. CONCLUSIONS: This study demonstrates that percutaneous deployment of polymeric stents in the coronary arteries is technically feasible. The use of PET polymer was associated with an intense proliferative neointimal response that resulted in complete vessel occlusion. Histological examination of the stented segments of the vessel revealed no evidence that dissection of the vessel wall had occurred at the time of initial stent deployment. Although the PET polymer was of similar quality to that used in the manufacture of balloon angioplasty catheters, a toxic chemical or contaminant effect cannot be completely excluded as the stimulus to intimal proliferation. This finding may have relevance to the selection of materials for use as intravascular devices.

Animals↗
PubMed1992

Carcinoid disease of the heart. Surgical management of ten patients.

Between 1982 and 1989, 10 patients with carcinoid heart disease underwent tricuspid valve replacement with a mechanical prosthesis at our institution. Pulmonary valvectomy was performed in nine patients and pulmonary valve replacement with a pulmonary homograft was performed in one. Two patients had carcinoid tumor metastatic to the heart, involving the right atrium in one case and both ventricles in the other. One patient had concomitant coronary artery bypass with the saphenous vein, and one patient had a quadruple valve replacement for histologically proved carcinoid disease of all four valves. The 30-day mortality was 10% and the late mortality was 30%. The remaining six patients were alive 4, 4, 4, 7, 24, and 46 months postoperatively. A review of the English literature identified 28 additional patients who underwent tricuspid valve replacement for carcinoid heart disease. There was no significant difference in the survival of patients with a bioprosthesis versus a mechanical valve in the tricuspid position. The 4-year survival for the 38 patients undergoing tricuspid valve replacement for carcinoid heart disease was 48% +/- 13%. Symptomatic patients who have carcinoid heart disease and whose metastatic malignant disease is not an imminent threat to life should be offered valve replacement. Operating soon after the onset of increasing cardiac symptoms, before the often rapid deterioration in right ventricular failure, optimizes the benefits.

Bioprosthesis↗
PubMed1992

Histopathologic abnormalities of the sinus node compared with electrocardiographic evidence of sinus node dysfunction after the modified Fontan operation: an autopsy study of 14 cases.

Autopsy specimens from 14 patients who had undergone a modified Fontan operation were evaluated to correlate the extent of histopathologic disruption of the sinus node with electrocardiographic findings of sinus node dysfunction. Patients with sinus node dysfunction (n=7) and those without (n=7) were similar in age, complexity of cardiac malformation, and number of postoperative days at time of death. The degree of fibrosis, local hemorrhage, necrosis, lymphocytic infiltration, and focal calcification of the sinus node and perinodal tissue was also similar in both groups. These findings, which showed a comparable amount of sinus node disruption in patients with normal sinus rhythm and in those with sinus node dysfunction, indicate a lack of correlation between the extent of histopathologic abnormality of the sinus node and electrocardiographic evidence of sinus node dysfunction.

Journal Article↗
PubMed1992

Primary cardiac angiosarcoma: a clinicopathologic study of six cases.

Autopsy or surgical specimens from six patients with primary cardiac angiosarcoma seen at the Mayo Clinic (all in men) between 1939 and 1988 were studied (patients' ages, 31 to 80 years; mean 50 years). The symptoms were nonspecific and included dyspnea and thoracoabdominal pain in six; anorexia in five; fatigue, hemoptysis, or orthopnea in four; nausea and vomiting, fever, or weight loss in three; and night sweats in two. Cardiomegaly was present in five, and a pericardial effusion or density, a mass adjacent to the heart, or nonspecific ST-T wave changes were present in three. All six neoplasms arose from the right atrium and exhibited epicardial or endocardial extension; three produced obstructive intracavitary right atrial masses. Pulmonary metastatic lesions were noted in five patients. The cardiac neoplasm was diagnosed by computed tomography or magnetic resonance imaging in the three most recent patients, and surgical resection was performed in two of them. Mean survival was 6 months after presentation. Causes of death were pulmonary hemorrhage in three, thoracic metastasis in two, and hemopericardium in one. The diagnosis of primary cardiac angiosarcoma was established at operation in two patients and at autopsy in four. Despite diagnosis by noninvasive imaging procedures and aggressive early surgical intervention, survival was less than 6 months. Thus optimal therapy is unclear.

Adult↗
PubMed1991

Value and limitations of two-dimensional echocardiography in predicting myocardial infarct size.

To investigate the quantitative relations between the severity of regional wall motion abnormalities and segmental infarct size and between the severity of overall left ventricular dysfunction and global infarct size, a clinicopathologic study was undertaken of 30 patients who had a 2-dimensional (2-D) echocardiogram within 7 days before death. The severity of regional wall motion abnormalities was graded for each segment with a 2-D echocardiographic 14-segment model. The severity of global left ventricular dysfunction was calculated as the mean of the visualized regional wall motion scores. On pathologic examination of autopsy specimens, segmental infarct size was estimated as a percentage of the segmental cross-sectional area. The global infarct size was expressed as a percentage of the total left ventricular mass. At the segmental level, regional wall motion score was positively correlated (r = 0.53) with the segmental infarct size. The sensitivity and specificity of detecting infarcted segments by abnormal wall motion scores were 81 and 71%, respectively. All dyskinetic segments revealed infarct size of greater than or equal to 10%. The wall motion score index was positively correlated (r = 0.52) with the global infarct size. The mean global infarct size was 7% for the 8 patients with a wall motion score index of less than 2, which was significantly lower than the mean of 27% for the 22 patients with a wall motion score index of greater than or equal to 2 (p less than 0.001). A 2-D echocardiogram is sensitive and specific in detecting infarcted segments and can be useful in quantitating myocardial damage after myocardial infarction.

Aged↗
PubMed1991

Degenerative aortic stenosis. One effect of the graying of America.

Degenerative calcific aortic stenosis is evolving as a common geriatric problem. Once symptoms develop, it is a highly lethal disease that does not respond well to medical therapy. Aortic balloon valvuloplasty may offer palliation but is unlikely to alter the overall course of the disease. Aortic valve replacement is the therapy of choice, but high perioperative morbidity and mortality rates can be expected in the very elderly. The presence of other appreciable cardiac disorders may contribute to the occurrence of postoperative complications. Patients with asymptomatic aortic stenosis and normal left ventricular function can be treated medically and followed with serial aortic valve area determinations using Doppler echocardiography.

Aged↗
PubMed1991

Lipomatous hamartoma of the tricuspid valve: echocardiographic-pathologic correlations.

We report the eighth example of a cardiac valvular hamartoma (five mitral, three tricuspid). An intracavitary right atrial mass was present in a 76-year-old man and was characterized echocardiographically by a mobile cystic structure involving the septal tricuspid leaflet. Microscopically, the affected leaflet was comprised predominantly of mature adipose tissue. Formation of a valvular windsock in this case was attributed to the chronic effect of right ventricular pressure on tissue that was weaker than a normal leaflet. Valvular hamartomas should be included in the differential diagnosis of lesions that produce prolapsing, cystic, or windsock malformations of atrioventricular valves.

Aged↗
PubMed1991

Microscopic pulmonary tumor embolism causing subacute cor pulmonale: a difficult antemortem diagnosis.

Microscopic pulmonary tumor embolism is difficult to diagnose. The most common initial clinical symptom is subacute progressive dyspnea, and the initial laboratory evaluation typically shows hypoxemia in a patient with clear lung fields on a chest roentgenogram. Another distinguishing feature may be hepatic abnormalities. In general, pulmonary angiography discloses no evidence of emboli, but multiple subsegmental peripheral perfusion defects are noted on ventilation-perfusion lung scans. The diagnosis of microscopic pulmonary tumor embolism can be confirmed by open-lung or transbronchial lung biopsy or by microvascular pulmonary cytology, a less invasive procedure that could be performed at the time of pulmonary angiography. Herein we describe two patients with unsuspected microscopic pulmonary tumor embolism that eventuated in subacute cor pulmonale and death. These cases illustrate the characteristic findings of this entity and emphasize the need for early diagnosis.

Adenocarcinoma↗
PubMed1991

Differential histopathology of primary atherosclerotic and restenotic lesions in coronary arteries and saphenous vein bypass grafts: analysis of tissue obtained from 73 patients by directional atherectomy.

Vascular tissue obtained using a directional percutaneous atherectomy device was examined microscopically. Tissue was obtained from coronary arteries without prior instrumentation (primary lesions, n = 31), aortocoronary saphenous vein bypass grafts with primary lesions (n = 8), coronary arteries with lesions developing after prior balloon angioplasty or mechanical atherectomy (restenotic lesions, n = 30) and vein bypass grafts with restenotic lesions (n = 4). Primary lesions were characterized by dense intimal fibrosis with necrotic debris (83% of intimal tissue) and foam cells typical of atherosclerosis. These lesions frequently contained cholesterol crystals (45% of coronary arteries, 50% of vein grafts) and calcium deposits (65% of coronary arteries, 38% of vein grafts). Restenotic lesions were characterized by an increased proportion of loose fibroproliferative tissue (45% of coronary artery intima, 35% of vein graft intima). Immunohistochemical stains confirmed this proliferative tissue to be primarily smooth muscle cells. Thrombus was rarely observed. Comparison of resected tissues indicated that dense fibrosis and necrosis are significantly more common in primary than in restenotic lesions (83% versus 56% of intimal tissue, p = 0.0005), whereas smooth muscle cell hyperplasia is more common in restenotic than in primary lesions (44% versus 17% of intimal tissue, p less than 0.0005). Partial-thickness resection of medial tissue or full-thickness resection of media with associated adventitial tissue occurred in 27 (56%) of 39 primary atheromatous lesions and 16 (47%) of 34 restenotic lesions; subintimal tissue obtained from primary lesions appeared identical to that obtained from restenotic lesions. These data indicate that the histopathologic characteristics of the neointimal layer of restenotic lesions differ from those of the intimal layer of primary atherosclerotic lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Constriction, Pathologic↗
PubMed1991

Can anatomical left ventricular mass be estimated reliably by M-mode echocardiography? A clinicopathological study of ninety-three patients.

To evaluate the accuracy of M-mode echocardiography in the assessment of left ventricular mass, we compared various echocardiography-derived regression equations for left ventricular mass to postmortem left ventricular weights in 93 patients (mean age 68 +/- 11 years) who had autopsy within 30 days of technically adequate two-dimensional guided M-mode echocardiography and who had normal left ventricular shape. The left ventricle was enlarged in 36 patients (39%) and was involved by chronic ischemic disease in 48 patients (52%). Only a modest correlation was found between M-mode echocardiography and anatomical left ventricular mass (range of correlation coefficients, 0.58 to 0.67). Each echocardiographic formula demonstrated increasing deviations as left ventricular mass increased. A previously suggested correction formula lessened overestimation, but considerable data dispersion remained. Regional wall-motion abnormalities, present in 22%, did not affect the correlation. We conclude that M-mode echocardiography, performed with standard methods, does not reliably estimate anatomical left ventricular mass, especially in patients with large hearts.

Aged↗
PubMed1991

Theoretical studies on mechanism of MPTP action: ET interference by MPP+ (1-methyl-4-phenylpyridinium) with mitochondrial respiration vs. oxidative stress.

This report demonstrates that ease of electron uptake by 1-methyl-4-phenylpyridinium (MPP+), apparently the active agent derived from MPTP, is influenced by conformation of the phenyl ring. From quantum mechanical calculations on MPP+, electron affinity is most negative for the nearly coplanar arrangement, indicating that the molecule is most readily reduced in this geometry. Ionization potential is largest in the perpendicular conformation, thus making for most facile oxidation in that form. Site binding would be expected to alter conformation in comparison with the situation in solution, and, hence, to influence reduction potential. We suggest that electron transfer by MPP+ may play a role in inhibition of mitochondrial respiration and in oxidative stress.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1990

Theoretical calculations on calcium channel drugs: is electron transfer involved mechanistically?

Theoretical studies were done on calcium channel drugs in order to gain insight into the mode of action. Empirical force field calculations with nifedipine, a calcium channel antagonist, indicate that the E-conformation at the ring juncture is lower in energy than the Z-conformation. This energy difference is only 0.2 kcal/mol when the esters in the 3- and 5-positions of the dihydropyridine (DHP) ring are both synperiplanar (sp, sp). Molecular orbital calculations on the ground and excited states in the Z-conformation with the esters in the (ap, sp) conformation show a low lying excited state with substantial intramolecular electron transfer (ET) character. This excited state is only 1.8 eV higher in energy than the ground state and corresponds to a transfer of approximately 0.3 electron from the DHP ring to the nitrobenzene moiety. We suggest that ET may play an important role in the mechanism of action, either intramolecular or, as previously proposed, intermolecular, along with lipophilicity and steric effects.

Calcium Channel Blockers↗