Biomedical subjects

W C Mackey

Publications and source records attributed to W C Mackey.

62 records · Page 4Linked to original sources

PubMed1985

Ultrasound characteristics of recurrent carotid disease: hypothesis explaining the low incidence of symptomatic recurrence.

The true incidence of recurrent disease after carotid endarterectomy (CENDX) is unknown, but noninvasive hemodynamic testing shows a paradox between the incidence of hemodynamically significant recurrent stenosis (RS) and the presence of symptomatic disease. We have shown that real-time B-mode ultrasound imaging can demonstrate the gross pathology of the arterial wall and plaque and their surface characteristics. Therefore we reviewed the clinical data and B-mode studies performed 6 months to 15 years after 276 carotid endarterectomies. Preoperative and perioperative risk factors and associated symptoms on follow-up were stored on computer. The patients were divided into three groups by the anatomy of their B-mode study. The majority of the studies were normal (203 [73.5%]), 42 (15.2%) showed mild disease, and 34 (12.3%) demonstrated significant RS. The RS group had a statistically significant increase in incidence of known lipid abnormalities (p less than 0.05), associated peripheral vascular disease, previous myocardial infarctions, and ulcerated plaque on the original carotid endarterectomy (p less than 0.01). The site of RS appeared related to the time of detection by B-mode ultrasound imaging. Internal carotid RS developed late (greater than 4 years), as did RS of the bifurcation. By contrast, stenosis at the common carotid level developed earlier. These findings suggest different pathogenic mechanisms--for the former, redevelopment of atherosclerosis; for the latter, accentuation of preexisting atherosclerosis perhaps by hemodynamic factors. Finally, in the 26 vessels with RS without occlusion, there was an 8% incidence of plaque ulcer or hemorrhage vs. a 62% incidence in 79 primary atherosclerotic plaques previously studied by both B-mode and pathologic examination. The low incidence of plaque characteristics associated with symptomatic disease may account for the low incidence of symptomatic disease associated with RS.

Arterial Occlusive Diseases↗

PubMed1984

A baboon flow-regulated shunt for the study of small caliber vascular grafts.

Synthetic vascular grafts often occlude when used in low-flow high-resistance reconstructions. In order to study the pathophysiology of graft failure a flow-regulated ex vivo shunt was designed for insertion into the baboon femoral artery and vein. Synthetic graft materials (4 mm i.d.) can be placed into the shunt circuit and studied at known rates of flow for uptake of 111In-labeled platelets. Segments of the grafts can be removed from the shunt circuit at specified time intervals for morphologic study with scanning electron microscopy (SEM). In this paper the shunt model is described in detail and early experiments with it are reported. Labeled platelet uptake and SEM studies suggest that flow rate and graft composition influence the deposition of platelets and other blood components on graft surfaces. At high-flow knitted Dacron attracts large numbers of platelets, and becomes covered with a nearly confluent platelet-protein carpet within 1 hr. At low flow platelet uptake and development of the platelet-protein carpet is slower. Polytetrafluoroethylene (PTFE) attracts few platelets at high-flow rates, but at lower-flow rates begins to develop a platelet-protein carpet similar to that seen on knitted Dacron. Flow-related factors influencing platelet deposition are discussed and further experiments to be carried out with this model are described.

Animals↗

PubMed1984

Aspirin decreases platelet uptake on Dacron vascular grafts in baboons.

The influence of a single dose of aspirin (5.4-7.4 mg/kg) on platelet uptake on 4-mm Dacron interposition grafts was studied in a baboon model using gamma camera scanning for 111-Indium labeled platelets. In vitro assessment of platelet function after aspirin administration revealed that in the baboon, as in the human, aspirin abolished arachidonic acid-induced platelet aggregation, prolonged the lag time between exposure to collagen and aggregation, and decreased plasma thromboxane B2 levels. Aspirin also prolonged the template bleeding time. Scans for 111-Indium labeled platelets revealed that pretreatment with a single dose of aspirin decreased platelet uptake on 4-mm Dacron carotid interposition grafts. This decrease in platelet uptake was associated with a significant improvement in 2-hour graft patency and with a trend toward improved 2-week patency.

Animals↗

PubMed1983

Infrarenal aortic occlusion: a reassessment of surgical indications.

Citing a high incidence of proximal propagation of aortic thrombosis, several authors have advocated aortic reconstruction for all patients with infrarenal aortic occlusion irrespective of their preoperative symptoms and potential operative risks. To test this thesis, the records and follow-up data of 38 patients seen at our institution between 1965 and 1982 with infrarenal aortic occlusion were analyzed. Twenty-four of the 38 patients were treated surgically (Group I); 16 (42 percent) had an aortobifemoral graft and 8 (21 percent) had an axillofemoral bypass graft. When the 14 patients who did not have surgery (Group II) and the 8 patients who had an axillofemoral graft were combined, 22 patients (58 percent) did not have aortic reconstruction (Group III), thus the aortic thrombus was left in situ. There was no significant difference in cumulative survival between the three groups at 4 year follow-up. Of 13 patients in Group III who were followed for more than 6 months (mean 48 months), none died from proximal propagation of aortic thrombosis. The decision for surgical intervention in patients with distal aortic occlusion should be arrived at, as in other patients with aortoiliac occlusive disease, by weighing preoperative symptoms and operative risks and not primarily by the level of risk of proximal propagation of thrombosis.

Aorta, Abdominal↗

PubMed1983

A fifty year experience with Meckel's diverticulum.

Four hundred and two patients with Meckel's diverticulum are reviewed. Symptoms referable to the diverticulum occurred in 68 patients or 16.9 per cent of the group. Obstruction of the small intestine, inflammation and lower gastrointestinal tract bleeding accounted for 90 per cent of the presenting symptoms. A 10.3 per cent mortality and a 17.6 per cent morbidity rate were noted for symptomatic diverticuli. Patients most likely to have symptoms develop were 40 years of age, or younger; those whose diverticuli were 2 centimeters or more in length; those whose diverticuli contained heterotopic mucosa, and, probably, those who were males. Patients more than 40 years of age with diverticuli less than 2 centimeters in length with no heterotopic mucosa and who were females constitute a lower risk group. The decision to perform an incidental Meckel's diverticulectomy should be based upon the risk of the individual patient having symptoms develop from the diverticulum.

Adolescent↗

PubMedDate not supplied

The interaction of blood components with PDMS (polydimethylsiloxane) and LDPE (low-density polyethylene) in a baboon ex vivo arteriovenous shunt model.

The interaction of 111Indium-labeled platelets, and other blood components with the luminal surface of polydimethylsiloxane (PDMS) and low-density polyethylene (LDPE) was determined using an ex vivo arteriovenous shunt in the baboon. Both PDMS and LDPE showed little platelet accumulation at either high (200 cc/min) flow rates. PDMS accumulated more platelets at low than at high flow. When the surfaces of PDMS and LDPE were examined under scanning electron microscopy after 2.5 h of flow in the shunt circuit, red and white blood cells were attached. Platelets appeared to be confined to patchy areas covered by a fibrinlike network. The low platelet reactivity of LDPE and PDMS suggests their potential use as coatings for conventional, more platelet reactive vascular graft materials.

Animals↗

PubMedDate not supplied

A biocultural analysis of circumcision.

The phenomenon of circumcision may well serve a range of religious and symbolic functions. In addition to these conceptual categories, we argue that circumcision also serves a more mundane, practical function of lowering excitability and distractibility quotients--sexual arousal--of pubescent males, i.e., biasing young males more toward increased tractability which would enhance group efforts and less toward individual goals of amorous exchanges. Neurological data suggest that early lesions of the prepuce/foreskin tissues would generate a re-organization/atrophy of the brain circuitry. This re-organization/atrophy, in turn, is suggested to lower sexual excitability. Epithelial data indicate that keratinization of the more exposed glans penis would lower the sensibility, hence sexual excitability, of the circumcised male's genitalia. In addition, circumcision removes the foreskin-prepuce which, by secreting smegma, would also minimize any pheromonic qualities which the smegma may generate. Inferential data support the hypothesis that a practical consequence of circumcision, complementary to any religious-symbolic function, is to make a circumcised male less sexually excitable and distractible, and, hence, more amenable to his group's authority figures.

Circumcision, Male↗

PubMedDate not supplied

Costs and benefits of prosthetic vascular surgery.

For a variety of reasons, primary amputation is often advised in the elderly individual with a severely ischemic leg. Reinforcing this recommendation is the perception that reconstructive arterial surgery in this group is far more expensive than the primary amputation. Living more than only one more year after amputation, professional nursing care cost approaches $100,000. In two recent studies, the cost for patients undergoing primary below the knee amputations plus rehabilitation was almost identical to the mean patient cost for arterial reconstruction. In addition, under the prospective payment systems, substantial financial loss accrues to hospitals caring for these patients.

Actuarial Analysis↗