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Biomedical subjects

D C Miller

Publications and source records attributed to D C Miller.

At least 343 records · Page 19Linked to original sources
PubMed1984

Performance characteristics of the Starr-Edwards Model 1260 aortic valve prosthesis beyond ten years.

The Starr-Edwards non-cloth-covered silicone ball (Model 1260) aortic valve prosthesis has been widely used for over 15 years and remains a standard against which newer values are compared. To define more completely the performance characteristics of this prosthesis, this study (including 449 patients) analyzed the long-term function of this specific valve over a cumulative total of 2,896 patient-years (pt-yrs) of follow-up which extended beyond 13 years. Expressed in both actuarial (% [+/- standard error of the mean] free at 10 years) and linearized (%/pt-yr) terms, respectively, valve-related complications occurred at the following rates: thromboembolism, 76 +/- 3 and 2.7; anticoagulant-related hemorrhage, 74 +/- 3 and 3.1; prosthetic valve endocarditis, 92 +/- 2 and 0.9; reoperation, 90 +/- 2 and 1.1; valve failure, 82 +/- 2 and 2.2; all valve-related morbidity and mortality, 51 +/- 3 and 6.0; and valve-related death, 88 +/- 2 and 1.3. Thirteen percent of hospital and 18% of late deaths were due to valve-related causes. No case of structural failure was documented. This prosthesis has an admirable structural durability record out to 13 years, and its long-term performance is satisfactory, albeit not optimal. Despite the indestructable design and construction of this mechanical valve substitute, 12% +/- 2% of patients had died of valve-related complications by 10 years, and fully 49% +/- 3% had had some form of serious valve-related complication. The long-term data reported herein can be used for analytical comparison when follow-up of patients with newer mechanical prostheses and tissue bioprostheses reaches 10 years to elucidate whether or not these newer valves truly represent improvements and which type of valve substitute proffers the most possible net benefit to the patient.

Actuarial Analysis↗
PubMed1983

Proliferative variability of endothelial clones derived from adult bovine aorta: influence of fibroblast growth factor and smooth muscle cell extracellular matrix.

Four endothelial cell clones derived from adult bovine aorta were examined with respect to their proliferative characteristics in vitro. Three of these clones, derived in the absence of fibroblast growth factor (FGF), displayed variable basal proliferative rates. One of these non-FGF derived clones grew at a maximal rate which could not be further enhanced with FGF. The other two clones grew at a suboptimal rate which was stimulated by low doses of FGF (10-50 ng/ml) and inhibited by higher doses (100-250 ng/ml). The fourth clone, derived in the presence of FGF, was stimulated by FGF in a dose-dependent manner (10-250 ng/ml) and was not growth inhibited at high FGF concentrations (250-1,000 ng/ml). Growth of all four clones on extracellular matrix (ECM) derived from bovine aortic smooth muscle (BASM) cells was optimal in the absence of FGF. ECM-coated dishes also significantly increased the sensitivity of all clones by at least fivefold to mitogenic stimulation by serum. The proliferative lifespans of the clones ranged between 60 and 120 generations with the most actively proliferating clones attaining the greatest lifespan. Continuous subculture of two of the endothelial clones in the presence of FGF or on ECM-coated dishes did not induce a dependence of the cells on either factor for subsequent growth in its absence. The results indicate that aortic endothelial cells display considerable clonal variability in ther basal proliferative rate and in their response to FGF. This clonal variability is not observed when the cells are maintained on ECM-coated dishes derived from vascular smooth muscle cells.

Animals↗
PubMed1983

Veno-venous allografts: patency, subendothelial proliferation, and the role of platelet-active agents.

Patency and histology of 81 vein allografts and 10 autografts in the canine femoral venous system were compared and the effect of platelet active agents in altering patency rates and subendothelial proliferation in allografts was examined. It was found that allografts thrombose at a predictable interval after operation (18 +/- 7 days) and have significantly worse survival than autografts (P less than 0.001). Platelet-active agents did not alter allograft patency rate of the incidence of subendothelial proliferation in this model.

Animals↗
PubMed1983

Villous adenoma of the urinary bladder: a morphologic or biologic entity?

Villous adenomas in the urinary bladder are rare neoplasms whose malignant potential is unclear. A case of a morphologically benign non-invasive mucin producing papillary neoplasm of the urinary bladder associated with cystitis glandularis is presented. Absence of A tissue isoantigen from the neoplastic and metaplastic cells and the presence of H tissue isoantigen in both neoplastic and metaplastic cells is observed in a patient whose blood type is A, indicating incomplete maturation of surface coat constituents. The histologically benign appearance of this lesion may belie a malignant potential.

Adenoma↗
PubMed1983

Digital subtraction angiography of aortic dissection.

Digital subtraction angiography (DSA) was used to study six patients with aortic dissection, five of whom had undergone surgical repair. One patient had both pre- and postoperative evaluations. DSA with intravenous contrast administration is a relatively noninvasive procedure that provides diagnostic images in projection format allowing assessment of the extent of aortic dissection and involvement of important aortic branches. Postacquisition reprocessing techniques unique to DSA optimize the imaging information regarding flow dynamics of the true and false channels.

Aortic Dissection↗
PubMed1983

Discriminant analysis of the changing risks of coronary artery operations: 1971-1979.

The risk of perioperative myocardial infarction (PMI) and operative mortality (OM) associated with coronary artery bypass grafting (CABG) has declined since the introduction of this procedure 15 years ago. Rigorous scientific investigation of the reasons for this trend has been hindered by the complex interactions between changing indications for operation, criteria for patient selection, and management methods. Using univariate and multivariate logistic regression analyses, we investigated the effects of 42 variables on PMI and OM for two cohorts undergoing CABG between 1971 and 1975 (Group A) and 1977 and 1979 (Group B). According to previously identified risk factors, Group B patients were at higher potential risk than those in Group A. Nevertheless, the PMI and OM rates declined from 8.7% +/- 0.9% to 4.6% +/- 0.7% (p = 0.005) and from 2.4% +/- 0.5% to 1.2% +/- 0.4% (p = 0.07), respectively. In calendar year 1979 (N = 438), the PMI and OM rates were 2.8% +/- 0.8% and 0.7% +/- 0.4%. More importantly, the independent determinants of PMI and OM for the two time intervals were distinctly different. Factors which affected the PMI rate in Group A were no longer determinants of PMI in Group B; with the exception of emergency operation and, to a modest extent, congestive heart failure (CHF), predictors of OM in Group A were not determinants of OM in Group B. Thus the adverse impact of multiple patient-related and disease-related determinants of PMI and OM has been neutralized over this decade by the real improvements in patient management. The specific factors and management concepts responsible for these superior results in sicker patients remain uncharacterized; however, in general terms, more sophisticated medical, anesthetic, and nursing management and more refined surgical expertise have essentially nullified the concept of high-risk candidates. Furthermore, the more propitious early results being attained currently may translate directly into parallel long-term improvements in functional benefit and survival.

Coronary Artery Bypass↗
PubMed1983

Aneurysm of the diverticulum of the ductus arteriosus in the adult. Successful surgical treatment in five patients and review of the literature.

Sixteen aneurysms of the diverticulum of the ductus arteriosus in adults have been previously reported. Ten patients died of rupture of the aneurysm or died at surgical exploration. Only one previous patient underwent successful aneurysmectomy. Five new cases of aneurysm of the adult ductal diverticulum, all diagnosed preoperatively and successfully repaired, are presented. All five patients are alive 6 to 33 months postoperatively. Our experience with these patients suggests several important features of these aneurysms: (1) Diagnosis may be difficult and may require multiple-view aortography or computed tomographic (CT) scanning to differentiate from tumor. (2) The operative approach, either left thoracotomy or median sternotomy, may be determined by the necessity for concomitant procedures. (3) Unlike true atherosclerotic aneurysms of the aortic arch, these aneurysms can be repaired effectively by aneurysmorrhaphy. (4) Because of their critical location and the high incidence of complications in reported cases, aneurysms greater than 3 cm in diameter, those producing symptoms, or those showing progressive enlargement should be surgically resected.

Aged↗
PubMed1982

Intravenous arteriography using digital subtraction techniques.

The application of digital computers to electronic x-ray imaging devices has rejuvenated interest in the field of intravenous arteriography. By utilizing computer image subtraction techniques, digital roentgenographic systems based on fluoroscopy or computed tomography (scanned projection radiography) provide significantly improved vascular imaging compared with conventional film subtraction methods. Digital subtraction angiography schemes isolate contrast media in the vessel by detecting differences in images obtained before and after the injection of contrast medium or changes in the relative attenuation of contrast media at different x-ray energies. Present applications include carotid and peripheral arteriography, thoracic and abdominal aortography, pulmonary arteriography, and ventriculography. Future applications may include intracerebral and coronary arteriography. These systems should provide low-risk outpatient screening arteriography.

Angiography↗
PubMed1982

Early events in calcium-induced liposome fusion.

Calcium-induced interaction of liposomes composed of pure phosphatidylserine (PS) has been studied using a rapid-mixing, rapid-freeze device. Freeze-fracture electron microscopy of this material revealed that liposomes react very rapidly after addition of calcium ions. After only 10 ms (the resolution of the technique) vesicle fusion was apparent. At the same time, however, vesicles also collapsed, and appeared as aggregates of flattened membranes. This may explain controversies which have arisen over vesicle fusion studied with more indirect methods.

Calcium↗
PubMed1982

Two-dimensional echocardiographic analysis of segmental left ventricular wall motion before and after coronary artery bypass surgery.

Twenty patients with coronary artery disease were studied with two-dimensional echocardiography the day before saphenous vein bypass graft surgery. Serial studies were obtained 7.4 +/- 2.5 (+/- SD) and 43.4 +/- 13.1 days postoperatively to qualitatively assess the effect of bypass surgery on regional wall motion. Changes in segmental wall motion were assessed semiquantitatively by assigning a segmental wall motion score to each of nine echocardiographically defined segments. Preoperatively, 18% of the segments moved abnormally. The mean overall segmental wall motion score did not change significantly, as shown by comparing the postoperative studies with the preoperative study. However, there was a significant worsening in the septal motion (apical and basal) and a significant improvement in posterior wall motion (apical and basal) after bypass surgery. Anterior and lateral wall motion were not significantly changed. Nonseptal segments that were normal preoperatively usually remained normal; abnormal nonseptal segments usually improved or were unchanged by surgery. The motion of septal segments, however, generally worsened postoperatively whether they were normal or abnormal preoperatively. We conclude that segmental wall motion assessed by two-dimensional echocardiography may improve after revascularization surgery, but the interventricular septum shows impaired motion. This effect of coronary artery bypass on wall motion is better demonstrated relatively late after operation than early in the postoperative course, as has been done in some previous studies.

Aged↗
PubMed1982

Diagnosis of arterial prosthetic graft infection by indium-111 oxine white blood cell scans.

Early and accurate diagnosis of infected prosthetic arterial grafts is difficult, despite the application of diverse diagnostic modalities. Delay in making the diagnosis is largely responsible for the high amputation and mortality rates associated with this complication. In nine patients with suspected graft infections, indium-111 white blood cell scanning was useful and accurate. Graft infection was proved in five cases and ruled out in three. One false-positive scan was due to a sigmoid diverticular abscess overlying the graft. Indium-111 white blood cell scans may improve the accuracy of diagnosing infected prosthetic grafts, which may result in better limb and patient salvage rates.

Adult↗
PubMed1982

The durability of porcine xenograft valves and conduits in children.

One hundred four patients younger than 20 years of age underwent intracardiac xenograft valve replacement (n = 41) or extracardiac conduit implantation (n = 63). Long-term follow-up averaged 4.5 and 4.3 years, respectively, and cumulative follow-up totaled 344 patient-years (pt-yr). Thirty patients were followed more than 5 years. Functional results and survival were satisfactory, but valve failure and conduit failure prompted 23 reoperations at linearized rates of 10.1 +/- 2.6% and 4.1 +/- 1.5%/pt-yr, respectively. The rate of valve failure due to leaflet fibrocalcification (primary tissue failure [PTF] was 8.1 +/- 2.4%/pt-yr. Among patients who underwent valve replacement, 52 +/- 13% were free of reoperation at 5 years (59 +/- 13% for PTF only), as were 80 +/- 9% of patients who received an extracardiac conduit. There were no deaths associated with the 22 late reoperations or with the 21 reoperations for PTF. Valve failure was due to PTF in 80% of cases; conversely, isolated valvular PTF was the cause of conduit failure in only one of eight patients. The most common cause of conduit failure was exuberant pseudointimal proliferation in the proximal conduit, which was seen in six of eight patients (75%) with or without other sites of obstruction and responsible for nine of the 15 obstructions (60%). These results underscore the palliative nature of these procedures, militate against indiscriminant use of conduits, prompt consideration of alternative nonconduit techniques where possible, and reemphasize the clinical need for superior valve substitutes and biomaterials for use in the pediatric age group.

Adolescent↗