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Biomedical subjects

K C Kent

Publications and source records attributed to K C Kent.

87 records · Page 5Linked to original sources
PubMed1992

Role of superficial femoral artery puncture in the development of pseudoaneurysm and arteriovenous fistula complicating percutaneous transfemoral cardiac catheterization.

Of 13,203 transfemoral diagnostic and therapeutic cardiac catheterization procedures performed between January 1, 1980 and December 31, 1990, 73 (0.55%) were complicated by pseudoaneurysm (PA) formation, and 15 (0.11%) by arteriovenous fistulas (AVF). The rate of PA increased progressively from 0.44% (1980-1987), to 0.59% (1987-1989), to 0.92% (1990), with no corresponding change in the incidence of AVF. The rising incidence of PA complicating transfemoral cardiac catheterization was associated closely with the use of larger diameter catheters and aggressive antiocoagulation during coronary interventions, but findings during surgical repair suggested that puncture of the superficial femoral (SFA), rather than the common femoral artery (CFA), was an important avoidable cause of some PA and AVF. A technique for fluoroscopic localization of the puncture site to avoid inadvertent SFA puncture and the associated increased risk of complication is proposed.

Aneurysm↗
PubMed1992

Optimal seeding conditions for human endothelial cells.

An in vitro model of endothelial cell seeding has been developed to individually evaluate the steps required for seeding arterial prostheses. Human saphenous vein endothelial cells are radiolabeled with tritiated thymidine and seeded onto 4 mm polytetrafluoroethylene grafts. Grafts are then placed into a perfusion circuit for determination of cellular retention. Using this model, the following variables were studied: (1) graft coating (fibronectin versus serum versus plasma); (2) time of incubation of cells with graft (0, 20, 90 minutes); (3) density of the initial seeding solution (4 x 10(3)-6 x 10(5) cells/cm2). The data suggest that incubation of a graft with plasma provides an adhesive surface that is as effective as fibronectin for enhancing cell retention. With this particular model, seeding densities between 1 and 2 x 10(5) cells/cm2 produce a confluent monolayer with optimal utilization of cells. A shorter 20 minute incubation period resulted in the retention of only half of the seeded cells, while postperfusion attachment increased significantly with a 90 minute incubation period. Data derived from this system can be used to construct a protocol that may be useful for clinical in vivo seeding trials.

Blood Vessel Prosthesis↗
PubMed1992

Peripheral directional atherectomy: 4-year experience.

Directional atherectomy alone or with supplemental percutaneous transluminal angioplasty was used to treat peripheral vascular lesions in 77 patients (85 procedures). Lesions involved 17 iliac arteries, 45 infrainguinal arteries, and 23 laser extremity vein bypass grafts. Technical success, defined as reduction of stenosis diameter to 30% or less of the normal vessel diameter, was achieved in 78 of 85 (92%) cases. The complication rate was 21% (18 of 85 procedures). Most complications were minor and were related to puncture sites. Patients underwent noninvasive follow-up studies, including measurement of ankle-brachial index and segmental pressures, plethysmography, and clinical examination. The mean follow-up period was 13.5 months. The probability of 1-, 2-, and 3-year patency for lesions treated with atherectomy alone was 92%, 84%, and 84%, respectively. Kaplan-Meier survival analysis revealed no difference in 2- to 3-year patency rate on the basis of lesion location or presence of calcification, eccentricity, or ulceration. Diabetic patients, however, had a higher restenosis rate than did patients who were not diabetic (P less than .03).

Aged↗
PubMed1991

Magnetic resonance imaging: a reliable test for the evaluation of proximal atherosclerotic renal arterial stenosis.

Symptomatic renal artery stenosis is a significant and treatable clinical problem. A reliable and accurate noninvasive method of screening for renal artery stenosis has not yet been found. We used magnetic resonance imaging to study 37 patients who had undergone recent renal angiography. Fourteen patients had normal renal arteries by angiography. In 23 patients either unilateral or bilateral stenosis or occlusion was present. The disease process in all patients appeared to be atherosclerosis. The average age of the 37 patients was 68 years. The magnetic resonance scans and angiograms were read independently by two different radiologists, each of whom was blinded to the clinical history and the results of the other study. Renal arterial stenoses found on angiogram and magnetic resonance scans were graded as absent (0% to 24%), mild (25% to 49%), moderate (50% to 74%), or severe (75% to 99%). The magnetic resonance imaging results concurred with the angiographic findings in 70 of 77 arteries (91%). Magnetic resonance imaging predicted the presence of a greater than 50% stenosis of the renal artery with a sensitivity of 100% and a specificity of 94%. Magnetic resonance imaging may prove to be the best noninvasive screening test for proximal atherosclerotic renal arterial stenosis.

Adult↗
PubMed1991

Evaluation of the extracranial carotid arteries: correlation of magnetic resonance angiography, duplex ultrasonography, and conventional angiography.

We compared duplex scanning, "bright blood" and "black blood" magnetic resonance angiography, and conventional angiography for evaluation of the extracranial carotid arteries. All three methods were applied to 39 vessels in 20 patients. Duplex scanning was inaccurate when compared to conventional angiography in six instances. In three instances the degree of stenosis was overgraded by the scanner, and in three cases the stenosis was undergraded. Magnetic resonance angiography was inaccurate when compared to conventional angiography in three instances. In all cases magnetic resonance angiography overgraded the degree of stenosis. By use of a greater than 70% stenosis as a positive study, the sensitivity of magnetic resonance angiography was 100% and the specificity 92%. With use of the same criteria, the sensitivity of duplex scanning was 86%, and specificity was 84%. In those evaluations where the results of the magnetic resonance angiography and duplex scanning were in agreement, the correlation with conventional angiography was 100%. We conclude that magnetic resonance angiography is an alternative means to duplex scanning for noninvasive carotid imaging. A combination of bright and black blood magnetic resonance angiography is precise in delineating lesions of the extracranial carotid artery and may ultimately eliminate the need for conventional angiography in the evaluation of carotid stenosis.

Angiography, Digital Subtraction↗
PubMed1990

Abdominal aorta and renal artery stenosis: evaluation with MR angiography.

A blinded, prospective study with magnetic resonance (MR) angiography was performed to study patients who had undergone abdominal aortography. In 55 renal arteries among 25 patients, MR angiography had a sensitivity of 100% for detecting renal artery stenosis of 50% or greater and a specificity of 92%. With MR angiography, the degree of renal artery stenosis was overgraded in four of 55 renal arteries: Mild stenosis was overgraded as moderate stenosis in two arteries and as a severe stenosis in one, and a moderate stenosis was overgraded as a severe stenosis in one. The number of renal arteries was correctly determined in all cases. The renal arteries could be well evaluated only in the proximal third of the vessel, precluding detection of more distal stenoses. Atherosclerotic plaque uniformly appeared dark on gradient-echo images and was easily differentiated from bright, flowing blood in the aortic lumen. MR angiography enabled correct grading of the presence of atherosclerotic plaque and stenoses of the abdominal aorta in 22 of 25 patients (88%). The authors conclude that MR angiography has the potential to be a useful screening technique for patients with suspected renal artery stenosis and disorders of the abdominal aorta, but further clinical studies are warranted.

Angiography↗
PubMed1990

Simultaneous occurrence of superficial and deep thrombophlebitis in the lower extremity.

Forty-two consecutive patients diagnosed with superficial phlebitis were seen during a 5-year period. Thirty-five of the 42 patients were outpatients. The diagnosis of superficial phlebitis was made by the presence of palpable subcutaneous cords in the course of the greater saphenous vein or its tributaries in association with tenderness, erythema, and edema. The presence of concurrent deep venous thrombosis (DVT) was assessed by impedance plethysmography in 37 patients, compression venous ultrasonography in 3 patients, and venography in 8 patients. Five of the 42 patients (12%) had DVT. Four of these five patients had a positive impedance plethysmographic or ultrasonographic test result followed by a confirmatory venogram. The fifth patient had a positive ultrasonographic test result, but no venogram was performed. Two of the five patients had clots that involved the popliteal or femoral veins. Four of 23 patients (17%) with superficial phlebitis at or above the knee had DVT. Only 1 of the 19 patients (5%) with superficial phlebitis below the knee had DVT. Three of the five patients with both superficial phlebitis and DVT had undergone surgery recently. All but 3 of the 42 patients (93%) had varicose veins. No patients had clinically apparent pulmonary emboli. DVT occurred in 17% of the patients with above-knee extension of the superficial phlebitis. In the clinical management of superficial lower-limb thrombophlebitis, noninvasive tests should be performed to guide therapy. When superficial phlebitis develops after recent surgery or the superficial phlebitis extends above the knee, diagnostic surveillance should be especially strict. When the noninvasive test results are equivocal, phlebography is indicated to rule out DVT.

Female↗
PubMed1989

What is the proper role of polytetrafluoroethylene grafts in infrainguinal reconstruction?

Polytetrafluoroethylene grafts have been used extensively for infrainguinal vascular reconstruction either as the conduit of choice or as a substitute when saphenous vein is unavailable. Although numerous studies have shown satisfactory early patency rates, the long-term efficacy of these grafts in a large number of patients for specific indications and in various positions has been less well defined. From 1977 to 1987 we used four PTFE grafts from three different manufacturers to perform 300 infrainguinal reconstructions on 240 patients on our vascular service. The indications for surgery were disabling claudication in 28% and limb salvage in 72%. The 30-day operative mortality of 1% was not different from the 1.4% associated with infrainguinal autogenous vein grafting. The 5-year cumulative patency rate achieved with all infrainguinal polytetrafluoroethylene grafts was 35%, significantly higher for grafts placed for claudication (57%) than those placed for limb salvage (24%). There were no significant differences between the above-knee and below-knee locations for distal anastomoses regardless of indication, but femoropopliteal grafts provided significantly higher 5-year patency (37%) than infrapopliteal grafts (12%). Comparison of the 5-year patency rates among the three manufacturers of polytetrafluoroethylene grafts showed no significant differences. Fifty-four polytetrafluoroethylene grafts that failed underwent 67 revisions after catheter thrombectomy or thrombolysis, which resulted in a minimal 11% 5-year patency rate. Based on this experience, it is concluded that infrainguinal polytetrafluoroethylene prostheses provide significantly inferior results when compared with autogenous reconstruction.

Adult↗
PubMed1989

Short-term and midterm results of an all-autogenous tissue policy for infrainguinal reconstruction.

Saphenous vein is the optimal conduit for infrainguinal vascular reconstruction. In instances in which this vein is unavailable or of "poor quality," reliance has been placed on a variety of prosthetic materials for bypass grafting. However, long-term patency with these prosthetic grafts has been disappointing. In January 1985 we instituted a policy of using exclusively autogenous tissue for infrainguinal arterial reconstruction. During the ensuing 3-year period, 203 patients underwent 266 arterial operations below the inguinal ligament, with a prosthetic graft used in only 11 instances (4%). No patient was denied surgery for limb salvage because of a lack of available autogenous vein. Thirty-three percent of procedures were performed for failure of prior revascularization and 73% for limb salvage. The 3-year cumulative primary patency rate for all autogenous procedures was 72%. Procedures were divided into those that used greater saphenous vein (patency 77%) vs autogenous alternatives such as bypass with arm vein or lesser saphenous vein, vein patch angioplasty, and endarterectomy (patency 64%). The operative mortality rate was 1.4% and the 3-year limb salvage rate was 89%. Autogenous infrainguinal reconstruction can be performed in almost every instance with acceptable results, suggesting that the need for prosthetic bypass grafts in the lower extremity is less than has been previously reported.

Adult↗
PubMed1989

Species variation and the success of endothelial cell seeding.

In vivo seeding of vascular grafts in dogs has resulted in the formation of a confluent luminal monolayer and increased patency. Results of similar trials in humans have been mixed. Interspecies variation of the harvest, attachment, and growth of vascular endothelium might explain these apparent differences. Endothelial cells were harvested by standard enzymatic techniques from bovine aorta (n = 7), canine external jugular vein (n = 9), and human saphenous vein (n = 8). Growth curves were generated by means of a replicate microwell technique and then compared with the following observations: Harvest of endothelium from human saphenous vein provides a lower yield of viable endothelial cells. When compared to bovine or canine cells, the lag phase of the growth curve of human cells is prolonged and the doubling time in the growth phase is increased. These results suggest that in humans there are fewer available cells, and conditions for endothelial cell growth may be more stringent than for other species. It may be necessary to develop alternative methods of seeding before success in humans can be achieved.

Animals↗
PubMed1988

Femoropopliteal reconstruction for claudication. The risk to life and limb.

The current study was undertaken to examine the results of femoropopliteal bypass grafting with intermittent claudication as the indication. Of 1173 infrainguinal reconstructions carried out on our service during the past decade, 249 (21%) consecutive femoropopliteal grafts were performed for disabling claudication in 191 patients. The primary five-year cumulative patency rates were 78% for autogenous vein and 52% for polytetrafluoroethylene grafts. There were two (0.8%) 30-day operative deaths and a subsequent five-year amputation rate of 2.4% for both groups. Femoropopliteal reconstruction for claudication may therefore be carried out with acceptably low operative mortality and a subsequent amputation rate comparable with that anticipated from the natural history of the disease. While the five-year patency rate is significantly higher utilizing autogenous vein grafts, symptomatic relief may be expected with prosthetic grafts in approximately half the patients without incurring a higher risk of limb loss.

Adult↗
PubMed1987

Evolving strategies for the repair of complex renovascular lesions.

Fifty-five patients with 59 complex renovascular lesions required two or more branch artery anastomoses during aortorenal grafting. Forty-five reconstructions involving 112 branches were facilitated using hypothermic ex vivo perfusion preservation, whereas 14 involving 28 branches were repaired in situ. Ex vivo repair was used whenever the kidney was considered unreconstructable by in situ techniques. Fibromuscular dysplasia predominated and the branched internal iliac artery was used for renal artery substitution. There were no deaths and only one kidney (ex vivo) was lost. Branch vessel occlusion occurred in two of 140 anastomoses (1.4%). Ninety-eight per cent (51/52) of the heparinized patients had cure or improvement at mean follow-up of 5 years. No late graft dysfunction occurred in postoperative angiographic follow-up. The branched internal iliac artery is uniquely suited and remains the preference of the authors for the replacement of the diseased renal artery and its branches. The in situ repair is ideally suited for lesions limited to the renal artery bifurcation. Ex vivo repair is reserved for complex or reoperative distal arterial lesions. Unique characteristics in the group include: bilateral lesions (25%), solitary kidney (22%), reoperative lesions (16%), children (9%), and coexisting significant aortic disease (7%). In situ and ex vivo repair meet all the challenges of complex renovascular disease. The strategies outlined will achieve outstanding long-term total and segmental renal salvage in the treatment of hypertension or aneurysmal disease. When ex vivo repair is required, it can be accomplished with only one additional simple maneuver, the reanastomosis of the renal vein.

Adolescent↗
PubMedDate not supplied

Piggy-back mesenteric arterial reconstruction.

Reimplantation of stenotic or occluded visceral arteries into the aorta is one solution to symptomatic chronic visceral ischemia. We report a patient in whom the associated problem of small bowel infarction precluded prosthetic reconstruction and saphenous vein was unavailable. Reimplantation of the celiac artery into the aorta was combined with piggy-back reimplantation of the superior mesenteric artery into the side of the celiac artery to provide successful revascularization of the small bowel. A 16-month angiographic and 5-year clinical follow-up is provided.

Aged↗
PubMedDate not supplied

An in vitro model for human endothelial cell seeding of a small diameter vascular graft.

A precise system was devised to measure the kinetics of attachment of human venous endothelium to a variety of materials and substrates. Cells were labelled in a postconfluent state with tritiated thymidine, harvested, and a cell suspension seeded into a 4 mm PTFE graft. After a 90 minute incubation period, one half of the graft segment was sacrificed and the remaining portion placed in a perfusion system (225 cc/min) for 1 hour. Graft segments, effluents, and seeding suspension were assayed in a beta scintillation counter. The percentage of cells that attached pre- and postperfusion were determined, as well as the retrieval of tritium from the system. Initially, 71% of seeded cells attached to grafts coated with fibronectin, with significantly less (60%) remaining attached after perfusion. Only 10% of cells initially attached to uncoated grafts, with 4% retained postperfusion. Retrieval of tritium averaged 102 +/- 10% for all experiments. This system determines both pre- and postperfusion attachment of human endothelial cells to vascular grafts following manipulation of numerous variables, including graft material, substrate, incubation time, and seeding density. An optimal seeding protocol for human trials can thus be determined.

Blood Vessel Prosthesis↗