Search PubMed⌕ Search

Biomedical subjects

A D Callow

Publications and source records attributed to A D Callow.

At least 73 records · Page 4Linked to original sources
PubMed1984

Complement activation by synthetic vascular prostheses.

Morphologic evaluation of synthetic grafts (both seeded and unseeded) harvested within 2 weeks of implantation has revealed heavy infiltration with polymorphonuclear leukocytes (PMNs). Since complement-activated PMNs are known to damage endothelial cells, we hypothesized that complement activation might prove a barrier to optimal endothelial cell seeding of prosthetic grafts. To determine whether synthetic vascular prostheses activate complement and whether the type of graft material influences the degree of activation, we assayed the plasma of 10 healthy donors for complement activity following incubation with short segments of knitted Dacron and polytetrafluoroethylene (PTFE) graft material. C5a generation was measured by radioimmunoassay and granulocyte aggregometry. Standard hemolytic assays were used to determine depletion of functional classical pathway (CH50 and C4) alternative pathway (APH50) activity. Results indicated substantial complement activation by Dacron and virtually none by PTFE. Activation by Dacron appeared to occur via both complement pathways. Such complement "reactivity" may have important implications for the performance of prosthetic materials as small-caliber vascular grafts, whether seeded with endothelial cells or not.

Blood Vessel Prosthesis↗
PubMed1984

The clinical implications of acute thrombosis of the inferior vena cava.

A review of the clinical records of 25 patients with IVC thrombus, proved by cavography during a ten year period, showed that this form of venous thrombosis accounted for less than 5 per cent of all phlebographically documented DVT at this institution. Before phlebography was performed, only eight patients (32 per cent) were suspected clinically of having IVC thrombus because of the absence of classic signs of bilateral lower extremity edema and pain in the majority of patients. Five patients presented with an acute PE, one being fatal. The majority of patients, 19 of 25 (80 per cent), had IVC thrombus contiguous with either iliofemoral (eight patients) or infrainguinal (11 patients) DVT. Nineteen patients were given anticoagulation therapy with heparin, and three patients underwent IVC compartmentalization. No subsequent PE developed in either group. Despite the potential for large lethal PE, heparin therapy appears to be the appropriate form of treatment for patients with IVC thrombus.

Acute Disease↗
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

The impact of coronary artery disease on carotid endarterectomy.

In a series of 531 CENDX, preoperative cardiac risk was categorized by clinical criteria. Patients with CAD (history of previous MI, angina, congestive heart failure, and/or electrocardiographic evidence of CAD were selected for more invasive studies based on clinical criteria. The overall incidence of postoperative myocardial infarction was 2.5% and increased slightly to 4% in patients with symptomatic cardiac disease. More importantly, the overall mortality was 0.9% and only 3 of 13 (23%) postoperative myocardial infarctions were fatal. Neurologic complications averaged 1.4% and approximately 70% were related to preceding cardiac events. Twenty-two patients or 4% of the entire series underwent carotid endarterectomy combined with coronary artery bypass graft and this approach was associated with one death and one stroke. Therefore, we conclude that a selective approach to coronary arteriography and subsequent CABG based on clinical criteria is associated with an acceptably low mortality and cardiac morbidity.

Arteriosclerosis↗
PubMed1983

Above-knee polytetrafluoroethylene femoropopliteal bypass graft: Is it a reasonable alternative to the below-knee reversed autogenous vein graft?

To determine whether an above-knee polytetrafluoroethylene (AK-PTFE) femoropopliteal bypass graft might be an acceptable alternative to a below-knee reversed autogenous saphenous vein (BK-ASV) bypass graft, we compared 51 AK-PTFE grafts to 39 concurrently performed BK-ASV grafts. All patients were staged by preoperative noninvasive vascular laboratory criteria into limiting claudication or limb salvage groups and by intraoperative arteriography according to degree of runoff. There was no significant difference in the primary graft patency at 36 months between the AK-PTFE group (63%) and the BK-ASV group (72%). Secondary graft patency among the AK-PTFE group was improved by minor distal graft revision to 88% at 36 months. The preoperative noninvasive hemodynamic evaluation status was an influential factor; the graft patency rate among the patients with limiting claudication was superior to that among the limb salvage group, but the degree of runoff as shown by intraoperative angiography did not appear to have an effect on cumulative patency. Resting Doppler ankle/brachial artery pressure ratios did not predict subsequent occlusion of AK-PTFE grafts. Atherosclerosis is a progressive and systemic disease that frequently involves both the coronary and tibial vessels. AK-PTFE spares autogenous saphenous vein so that it can be reserved for use in coronary artery bypass or in subsequent treatment of more distal tibial vessel disease.

Arteriosclerosis↗
PubMed1982

Recurrent stenosis after carotid endarterectomy.

The true incidence of recurrent carotid stenosis is unknown. Most reports provide only anecdotal data. Reported incidences, which range from 0.6% to 9.8%, reflect the care with which the search for recurrent stenosis was made by individual reporters. Early restenosis occurring within less than 24 months is characterized by a fibrous hyperplastic reaction, whereas stenoses occurring beyond this time are usually caused by typical atherosclerotic lesions. Although no clear risk factors can be identified, surgical trauma and inadequate endarterectomy are likely predisposing causes. Reoperation is technically more difficult and a patch graft, preferably vein, is often necessary. Careful postoperative evaluation and a search for the possibility of recurrent stenosis is recommended, especially in view of the increasing frequency of prophylactic carotid endarterectomy.

Carotid Arteries↗
PubMed1982

Prophylactic carotid endarterectomy for asymptomatic bruit. A look at cardiac risk.

We assessed the influence of preoperative cardiac risk factors in 57 patients undergoing 70 prophylactic carotid endarterectomies (PCE) and found that: (1) 47 (83%) had at least one cardiac risk factor and (2) nine of 15 deaths occurring in the late follow-up period (40 to 120 months) were due to cardiac causes. Perioperatively, one patient sustained a mild stroke. Although the cumulative stroke-free occurrence rate was kept to less than 6% over the five-year period, cardiac morbidity and mortality greatly influenced the quality of life after PCE. Therefore, PCE is suggested only for patients who have minimal preoperative cardiac risk factors or for those patients whose cardiac risk factors can be improved by medical therapy.

Aged↗
PubMed1982

Platelet--arterial synthetic graft interaction and its modification.

We compared the in vivo platelet reactivity of two commonly used clinical grafts, Dacron and expanded polytetrafluoroethylene (PTFE), with that of a control autogenous artery graft and assessed whether platelet reactivity was modified by the platelet-antiaggregating agent prostacyclin (PGI2) (epoprostenol). Grafts were randomly placed into the carotid arteries of 21 baboons. Platelets labeled with indium 111 were infused within one hour after implantation graft for gamma camera scanning of platelet uptake. The accumulation of platelets on Dacron grafts began almost immediately after injection and reached a peak after one to two hours. The PTFE and control autogenous artery grafts accumulated comparable small amounts of platelets. Prostacyclin was then infused in a second series of baboons with Dacron grafts, at a rate of 150 to 200 ng/kg/min. It prevented the usual platelet uptake when administered concomitant with graft implantation and reduced previously established platelet activity.

Animals↗
PubMed1982

Chronic intestinal ischemia associated with oral contraceptive use.

A 48-yr-old woman with chronic intestinal ischemia and a long history of oral contraceptive use is reported. She presented with a 6-month history of severe diarrhea, abdominal pain, and weight loss. Abdominal arteriography revealed occlusion of the celiac axis at its origin and 90% stenosis of the superior mesenteric artery. This chronic arterial lesion has not been previously noted in association with the use of oral contraceptive agents in otherwise healthy women. The patient's isolated arterial lesions proved amenable to successful surgical bypass. Postoperatively she became completely asymptomatic and has remained so on long-term follow-up.

Adult↗
PubMed1982

Ultrastructural and capillary adaptation of gastrocnemius muscle to occlusive peripheral vascular disease.

The effect of chronic occlusive peripheral vascular disease (PVD) on the histochemistry and capillarity of the gastrocnemius muscle was studied in 129 biopsies taken from 93 subjects. Sixty-three patients underwent biopsy during surgical procedures, and data related to walking distance and ankle systolic pressure. Thirty biopsies taken from normal subjects post mortem served as a control group, and data were analyzed for fiber type distribution, fiber area, fiber type grouping, and fiber capillarity. Fiber type distribution did not alter significantly between the patients with PVD and the control group, but the mean fiber area of the type 1 fiber in male patients with intermittent claudication (IC) was reduced when compared to that in age-matched controls (4608 +/- 1181 mu 2, IC +/- 1 SD; 5795 +/- 1771 mu 2, controls +/- 1 SD) (P less than 0.05). When bilateral biopsies were taken from the gastrocnemii of patients with unilateral occlusions, the type 2 fibers in the diseased leg were significantly smaller than fibers of the control group (2821 +/- 953 mu 2, IC +/- 1 SD; 4318 +/- 1504 mu 2, controls +/- 1 SD) (P less than 0.02). Fiber type grouping, evidence of denervation and reinnervation of muscle, appeared to be more common in patients with more severe limb ischemia. Overall capillary numbers did not appear to alter with degree of ischemia, but fiber shrinkage appeared to compensate for any loss of capillaries in the more ischemic muscle. These data suggest that the limb of the untrained patient with IC does not adapt to ischemia by adjusting its exercise capacity but merely shows evidence of disuse. These adaptations suggest that there may be much to be gained by nonsurgical methods of treating IC.

Adaptation, Physiological↗
PubMed1981

Intraoperative prereconstruction arteriography.

Intraoperative arteriography was performed in 57 patients undergoing arterial reconstructive surgery of the lower extremity prior to selection of the site for the distal anastomosis. In 42 patients (74%), this procedure proved to be of significant benefit. Prereconstructive intraoperative arteriography influenced surgery for seven patients in the following ways: (1) two patients had visualization of vessels not demonstrated on the preoperative arteriogram; and (2) five patients had demonstration of occlusive disease that favored selection of a more distal site of anastomosis. In the remaining 35 patients, the tibial vessels and arch were visualized more clearly, so that the degree and extent of disease were better appreciated. This may have important prognostic significance. On postreconstructive arteriography, an additional five patients were shown to have an anastomotic defect that was corrected in the operating room. Intraoperative arteriography is a rapid, safe, and simple procedure that should be considered as an adjunct in reconstructive surgery of the lower extremity.

Angiography↗
PubMed1981

Management of combined segment disease.

Eighty-five of 148 inflow procedures were performed for combined segment disease. Our study shows that aortofemoral bypass is clinically and functionally superior to axillofemoral bypass in limbs with combined segment disease and hemodynamic criteria for limb salvage. The results of these two procedures are comparable for claudicant limbs. A derivative of segmental plethysmography, the predictive index, can select preoperatively those limbs that will fail to respond to aortofemoral bypass alone. Finally, either in limbs selected for aortofemoral bypass with both ischemic tissue lesions and a predictive index greater than 0.2 or in limbs selected for axillofemoral bypass with ischemic tissue lesions alone, a synchronous procedure can be performed with relatively low morbidity and excellent early functional results.

Ankle↗
PubMed1980

Management of variceal hemorrhage: results of a standardized protocol using vasopressin and transhepatic embolization.

We reviewed the courses of 40 patients with variceal bleeding treated with a standardized protocol, including intravenous (IV) vasopressin (Pitressin) and transhepatic embolization. Twelve of the 32 patients with acute episodes of massive variceal bleeding responded to the administration of IV vasopressin alone. Of the 20 patients who did not respond to vasopressin therapy, emergency transhepatic portography with embolization produced cessation of bleeding in ten (50%). The remaining ten patients who failed to respond to either IV vasopressin therapy or transhepatic embolization died, regardless of whether they were treated with aggressive medical therapy or emergency portosystemic shunt. Transhepatic embolization in both the emergent and elective situation demonstrated a thrombotic complication rate of 20%, which limited or precluded eventual therapy with elective portosystemic shunt. Because of this relatively high incidence of occult portal thromboses after transhepatic embolization, transhepatic portography should be obtained routinely prior to elective portosystemic shunts in those patients who have a history of transhepatic embolization.

Adult↗
PubMed1980

Below-knee amputation: is the effort to preserve the knee joint justified?

The records of 50 patients (31 men and 19 women, ranging in age from 49 to 89 years) undergoing definitive below-knee amputation for ischemia from May 1971 to May 1979 were reviewed. Forty-three (86%) had ulceration or necrosis involving the foot or toes. Seven had rest pain without tissue loss. Overall healing rate was 86%. Seven patients (14%) failed to heal and required reamputation above the knee; the functional status of the remaining 43 patients was graded preoperatively and at the time of late follow-up (mean, 3.4 years). Twenty-five of 35 (71%) unilateral below-knee amputees could walk with a prosthesis; ten could not. Seventeen patients (34%) either required an additional, higher amputation or did not use the knee joint to increase mobility. The patient with marginal circulation and marked preoperative functional limitations may have the above-knee level as the chosen site for amputation.

Actuarial Analysis↗
PubMed1980

David M. Hume Memorial Lecture. An overview of the stroke problem in the carotid territory.

In a review of 1,000 carotid endarterectomies performed over a 20 year period, there was relief of transient ischemic attacks in approximately 85% of patients, an operative mortality of 1.3%, due almost exclusively to myocardial infarction, and a recurrent stenosis rate of 3.1%. Coexisting cardiac disease constitutes the greatest operative hazard. Continuous electroencephalographic monitoring is a reliable method of detecting inadequate cerebral perfusion during carotid cross clamping and for the selective use of a temporary inlying carotid shunt. An atherosclerotic plaque in the carotid system constitutes a greater risk than elsewhere in the peripheral arterial system and should not be considered an innocent lesion. Prophylactic carotid endarterectomy can be performed with almost no mortality and morbidity. Antiplatelet agents, while useful in reducing the incidence of transient ischemic attacks, do not seem to provide equal protection against stroke and death from stroke.

Anticoagulants↗
PubMed1980

A primate model for the study of the interaction of 111In-labeled baboon platelets with Dacron arterial prostheses.

This paper presents early experience with a primate model for the noninvasive study of the interaction of circulating platelets with healing arterial prostheses. These experiments demonstrate that baboon platelets can be isolated and labeled with 111Indium with high efficiency using a sterile technique. Platelets subjected to this process have a linear life span similar to that of 51Chromium-labeled baboon platelets. The high energy gamma emission of 111Indium oxine allows for external scanning using a standard gamma camera. The small quantity of 111Indium-labeled platelets in the region of the graft can be discriminated from the surrounding blood vessel and quantitated by gamma camera imaging and computer analysis. There was a significant increase in the platelet deposition on prosthetic surfaces observed 5--48 hours after graft implantation and injection of 111Indium-labeled autologous platelets.

Animals↗