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Biomedical subjects

K Craig Kent

Publications and source records attributed to K Craig Kent.

At least 73 records · Page 4Linked to original sources
PubMed2003

Use of cine magnetic resonance angiography in quantifying aneurysm pulsatility associated with endoleak.

OBJECTIVE: Persistent aneurysm perfusion or endoleak is associated with pulsatility of abdominal aortic aneurysm (AAA) after endovascular repair. However, the resultant pulsatile change in aneurysm diameter may be difficult to quantify, and therefore its significance is unknown. In this study cine magnetic resonance angiography (MRA) was used to quantify aneurysm wall motion during the cardiac cycle and to correlate it with the presence and type of endoleak. METHODS: Cine MRA was performed in 16 patients undergoing endovascular repair of AAA. A 1.5 T magnet and post-processing with GEMS 4.0 Fiesta computerized video image analysis software were used to calculate maximum aortic diameter during systole and diastole. Changes in aortic diameter were determined from these measurements. Cine MRA was performed on aneurysms before treatment and in patients with and without endoleak after endovascular repair. Type of endoleak was confirmed at angiography in all cases. Four patients had antegrade (type I) endoleak, and eight patients had retrograde (type II) endoleak; no endoleak was present in four patients. Endovascular grafts with stent support throughout the entire length of the graft (Talent) were used in all cases (14 bifurcated grafts, 2 tube grafts). RESULTS: Cine MRA demonstrated significantly greater wall motion and resultant change in aneurysm diameter in patients with type I endoleak compared with patients without endoleak (type I, 2.14 +/- 1.28 mm vs no endoleak, 0.12 +/- 0.09 mm, P =.001). Change in aneurysm diameter in patients with type II endoleak was not significantly greater than in patients with no endoleak (type II, 0.26 +/- 0.21 mm vs no endoleak, 0.12 +/- 0.09 mm, P = NS). Untreated aneurysms demonstrated the greatest change in diameter during the cardiac cycle (3.51 +/- 0.79 mm). CONCLUSION: Cine MRA may be used to accurately quantify AAA wall motion before and after endovascular stent-graft treatment. The extent of change in diameter corresponds to the type of endoleak, with antegrade (type I) endoleak generating greater pulsatile change in diameter than retrograde-collateral (type II) endoleak or no endoleak. Cine MRA may provide a noninvasive means of assessing the success of endovascular treatment of AAA. Further studies will be necessary to confirm the utility and efficacy of cine MRA in postoperative assessment of endovascular aneurysm repair.

Aged↗
PubMed2003

Surgical treatment and outcomes of patients with primary inferior vena cava leiomyosarcoma.

BACKGROUND: The inferior vena cava (IVC) is a rare site for primary soft tissue sarcoma. There are limited data in the literature regarding surgical management of the IVC and longterm survival of these patients. STUDY DESIGN: From 1982 to 2002, a total of 25 patients with primary IVC leiomyosarcoma was treated as inpatients and followed in a prospective database at Memorial Sloan-Kettering. Presenting symptoms, tumor characteristics, operative management, postoperative morbidity, and disease-specific survival were assessed for each patient. RESULTS: The 25 patients with primary IVC leiomyosarcoma accounted for 0.5% of all adult patients with soft tissue sarcoma treated during this time. The median patient age was 56 years (range 41 to 79 years). The three most common presenting symptoms were abdominal pain (52%), distention (20%), and deep venous thrombosis (12%). Of the patients, 21 (84%) underwent complete resection of the tumor. The IVC was managed in one of three ways: ligation (n = 11), primary/patch repair (n = 8), and expanded polytetrafluoroethylene tube grafting (n = 2). Among patients undergoing IVC ligation and primary/patch repair (n = 19), 11% had severe postoperative edema and none had worsening renal function. Local recurrence occurred in 33% of patients and distant recurrence occurred in 48% of patients. Patients undergoing complete resection had 3-year and 5-year disease-specific survival rates of 76% and 33%, respectively. There were no 3-year survivors among patients with incomplete resections. CONCLUSIONS: Complete resection of primary IVC leiomyosarcomas is feasible and associated with improved survival. The IVC can be managed by primary repair or ligation with a low risk of severe postoperative edema.

Female↗
PubMed2003

Is carotid angioplasty and stenting more cost effective than carotid endarterectomy?

OBJECTIVE: Carotid angioplasty and stenting (CAS) has been advocated as a minimally invasive and inexpensive alternative to carotid endarterectomy (CEA). However, a precise comparative analysis of the immediate and long-term costs associated with these two procedures has not been performed. To accomplish this, a Markov decision analysis model was created to evaluate the relative cost effectiveness of these two interventions. METHODS: Procedural morbidity/mortality rate for CEA and costs (not charges) were derived from a retrospective review of consecutive patients treated at New York Presbyterian Hospital/Cornell (n = 447). Data for CAS were obtained from the literature. We incorporated into this model both the immediate procedural costs and the long-term cost of morbidities, such as stroke (major stroke in the first year = $52,019; in subsequent years = $27,336/y; minor stroke = $9419). We determined long-term survival rate in quality-adjusted life years and lifetime costs for a hypothetic cohort of 70-year-old patients undergoing either CEA or CAS. Our measure of outcome was the cost-effectiveness ratio. RESULTS: The immediate procedural costs of CEA and CAS were $7871 and $10,133 respectively. We assumed major plus minor stroke rates for CEA and CAS of 0.9% and 5%, respectively. We assumed a 30-day mortality rate of 0% for CEA and 1.2% for CAS. In our base case analysis, CEA was cost saving (lifetime savings = $7017/patient; increase in quality-adjusted life years saved = 0.16). Sensitivity analysis revealed major stroke and death rates as the major contributors to this differential in cost effectiveness. Procedural costs were less important, and minor stroke rates were least important. CAS became cost effective only if its major stroke and mortality rates were made equivalent to those of CEA. CONCLUSION: CEA is cost saving compared with CAS. This is related to the higher rate of stroke with CAS and the high cost of stents and protection devices. To be economically competitive, the mortality and major stroke rates of CAS must be at least equivalent if not less than those of CEA.

Aged↗
PubMed2003

Guidelines for the reporting of renal artery revascularization in clinical trials.

Although the treatment of atherosclerotic renal artery stenosis with use of percutaneous angioplasty, stent placement, and surgical revascularization has gained widespread use, there exist few prospective randomized controlled trials (RCTs) comparing these techniques to each other or against the standard of medical management alone. To facilitate this process as well as help answer many important questions regarding the appropriate application of renal revascularization, well-designed and rigorously conducted trials are needed. These trials must have clearly defined goals and must be sufficiently sized and performed so as to withstand intensive outcomes assessment. Toward this end, this document provides guidelines and definitions for the design, conduct, evaluation, and reporting of renal artery revascularization RCTs. In addition, areas of critically necessary renal artery revascularization investigation are identified. It is hoped that this information will be valuable to the investigator wishing to conduct research in this important area.

Comment↗
PubMed2003

Management strategy for compartment syndrome of the upper extremity arising during anticoagulation or thrombolytic therapy: an increasingly common surgical dilemma.

Compartment syndrome is a documented and potentially lethal complication of thrombolytic therapy. With the increasing use of catheter-directed thrombolytic therapy, a high index of suspicion for the potential occurrence of this surgical emergency must be maintained. Errors of omission in the diagnosis of compartment syndrome, even for a few hours, may lead rapidly to limb loss, renal failure, and possibly death. The authors present a case of compartment syndrome arising in the forearm of a patient being treated with continuous catheter-directed thrombolytic therapy for an occluded arterial bypass graft associated with an ischemic lower extremity. Specific to this presentation is their management of compartment syndrome during thrombolytic therapy as well as previously unreported use of a homograft (cadaveric skin) to control ongoing blood loss from a fasciotomy site in this fully anticoagulated patient. The authors think their management in this case may help to provide direction to others faced with a similar, increasingly common, surgical dilemma.

Aged↗
PubMed2003

Gadodiamide administration causes spurious hypocalcemia.

PURPOSE: To evaluate the prevalence of spurious hypocalcemia after gadodiamide-enhanced magnetic resonance (MR) imaging. MATERIALS AND METHODS: Eight hundred ninety-six inpatients with available serum calcium data obtained before and after gadodiamide-enhanced MR imaging were identified. Changes in serum calcium measurements following gadodiamide administration in 1,049 MR imaging examinations performed in these patients were correlated with gadodiamide dose, renal function, and time between gadodiamide administration and phlebotomy. RESULTS: Following 42 gadodiamide-enhanced examinations, serum calcium measurements spuriously decreased by more than 2 mg/dL (0.5 mmol/L), resulting in laboratory reports of "critical" hypocalcemia (ie, calcium level < 6 mg/dL [1.5 mmol/L]) in 25 examinations. These reduced calcium measurements were correlated with serum creatinine level (r = 0.39, P <.001), gadodiamide dose (r = 0.37, P <.001), and time between gadodiamide injection and phlebotomy (r = -0.28, P <.001). Spurious reductions in calcium measurements after administration of 0.1 mmol of gadodiamide per kilogram of body weight were greater in patients with renal insufficiency (0.6 mg/dL [0.15 mmol/L] +/- 0.5 [0.125, SD]) than in those with normal renal function (0.14 mg/dL [0.035 mmol/L] +/- 0.4 [0.1]) (P <.001). After administration of more than 0.2 mmol/kg of gadodiamide, spurious calcium measurement decreases were greater in patients with renal insufficiency (2.4 mg/dL [0.6 mmol/L] +/- 3.6 [0.9]) than in those with normal renal function (0.4 mg/dL [0.1 mmol/L] +/- 0.7 [0.175]) (P <.001). Patients with renal insufficiency had spuriously low calcium measurements up to 4(1/2) days after gadodiamide administration. Seven patients were inappropriately treated with intravenous calcium and eleven with oral calcium in response to false-positive laboratory reports of critical hypocalcemia. No patient had characteristic symptoms of hypocalcemia or injuries attributed to the inappropriate medical treatment. CONCLUSION: Gadodiamide administration causes spurious hypocalcemia, particularly at doses of 0.2 mmol/kg or higher and in patients with renal insufficiency.

Calcium↗
PubMed2003

Filter devices for cerebral protection during carotid angioplasty and stenting.

The risk of embolization during carotid artery stenting (CAS) has been the foremost reason for the cautious acceptance of this percutaneous alternative to carotid endarterectomy. To address this issue, numerous embolic protection devices are being evaluated as an adjunct to CAS for neuroprotection. Among the 3 main categories of these devices, distal filters, which trap embolic debris while maintaining distal cerebral perfusion, have attracted the most corporate interest. This review focuses on the emerging field of embolic protection filters for use in CAS.

Angioplasty, Balloon↗
PubMed2002

Microinjection of DNA into the nuclei of human vascular smooth muscle cells.

BACKGROUND: It is challenging to successfully transfect human vascular cells by conventional techniques. We evaluated the efficiency of transfection of human smooth muscle cells (SMC) using a method of direct nuclear microinjection of DNA constructs. MATERIALS AND METHODS: The nuclei of explanted human saphenous vein SMC were microinjected with the plasmid pCMVbeta, containing the lacZ gene for beta-galactosidase (beta-gal). Efficiency of injection and expression were assessed by histochemical staining for beta-gal. Injected SMC were subjected to standard assays of viability and migration. RESULTS: Parameters affecting the conditions of injection were systematically analyzed to achieve optimal transfection efficiency. A vertical injection resulted in a twofold increase in expression of beta-gal compared to a horizontal approach. A DNA concentration of 100 ng/microl (390 copies/injection) provided a maximal rate of expression. No further increase in expression was evident at higher concentrations. Maximal expression was achieved with a time of injection of 200-500 ms, an injection pressure of 5-10 psi, and a pipette tip size of 0.6 microm, resulting in an injection volume of 0.03 pl. Cytoplasmic injection did not result in gene expression. The ability of SMC to migrate under videomicroscopy was not altered by the injection process. Optimizing all injection parameters resulted in cell viability >95% and efficiency of injection of 59%. CONCLUSION: DNA encoding a variety of intracellular proteins can be efficiently microinjected into human vascular SMC. Coupled with the use of videomicroscopy, this technique can allow for the evaluation of genes that might modulate important cellular processes such as proliferation and migration.

Cell Movement↗
PubMed2002

Endarterectomy vs stent angioplasty: what is the optimal treatment of carotid stenosis?

Very few operations have been subject to more scientific scrutiny than carotid endarterectomy (CEA). Since its introduction in the 1950s, CEAs have been performed in great numbers with the goal of preventing ischemic stroke. In the mid 1980s concern about over utilization of CEA and reports of excessive perioperative stroke morbidity and mortality prompted the initiation of several multicenter, randomized trials designed to evaluate the efficacy of CEA. As the results of these trials became available, the number and frequency of CEA in the United States increased significantly. However, now a new wave of uncertainty has arisen related to the availability of an alternative to CEA, carotid angioplasty and stent (CAS). Now, more than ever, there is uncertainty as to the proper management of carotid artery stenosis. In this review we summarize the existing data regarding the efficacy of CEA and compare these data to a critical analysis of the recent results of CAS.

Angioplasty↗
PubMed2002

Guidelines for the reporting of renal artery revascularization in clinical trials.

Although the treatment of atherosclerotic renal artery stenosis with use of percutaneous angioplasty, stent placement, and surgical revascularization has gained widespread use, there exist few prospective randomized controlled trials (RCTs) comparing these techniques to each other or against the standard of medical management alone. To facilitate this process as well as help answer many important questions regarding the appropriate application of renal revascularization, well-designed and rigorously conducted trials are needed. These trials must have clearly defined goals and must be sufficiently sized and performed so as to withstand intensive outcomes assessment. Toward this end, this document provides guidelines and definitions for the design, conduct, evaluation, and reporting of renal artery revascularization RCTs. In addition, areas of critically necessary renal artery revascularization investigation are identified. It is hoped that this information will be valuable to the investigator wishing to conduct research in this important area.

Angioplasty, Balloon↗
PubMed2002

The signaling protein Rho is necessary for vascular smooth muscle migration and survival but not for proliferation.

BACKGROUND: The small GTPase Rho has been implicated in a variety of cellular processes. Vascular smooth muscle cell (SMC) migration, proliferation, and apoptosis are important events that contribute to the formation of intimal hyperplasia. To better understand the importance of Rho in intimal hyperplasia, we evaluated the necessity of Rho for these 3 cellular processes. METHODS: We used for these studies a recombinant C3 exoenzyme (C3), which selectively adenosine diphosphate-ribosylates and, thus, functionally inactivates Rho. SMC migration was determined by scratch and modified Boyden chamber assays, proliferation by tritiated-thymidine incorporation, and apoptosis by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling. RESULTS: Pretreatment of human SMC with C3 overnight resulted in adenosine diphosphate-ribosylation and inactivation of Rho. Inactivation of Rho completely eliminated SMC migration in response to platelet-derived growth factor (PDGF)-AB. Furthermore, C3 blocked phosphorylation of focal adhesion kinase, tensin, and paxillin, which are essential for cellular migration. In contrast, C3 did not significantly affect DNA synthesis in response to PDGF-AB or activation of mitogen-activated protein kinase, a signaling mediator of PDGF-stimulated proliferation. However, prolonged inactivation of Rho by C3 induced apoptosis of SMC. CONCLUSIONS: The small GTPase Rho is necessary for vascular SMC migration and cell survival but not for proliferation. Manipulation of Rho might have therapeutic value in modulating intimal hyperplasia.

ADP Ribose Transferases↗
PubMed2002

The cost-effectiveness of a "quick-screen" program for abdominal aortic aneurysms.

BACKGROUND: The incidence of abdominal aortic aneurysm (AAA) is increasing, and the prognosis of ruptured AAA remains dismal. Early diagnosis and intervention are crucial. We designed this study to determine whether selected population screening with a brief "quick-screen" ultrasound could be cost-effective. METHODS: A series of 25 patients with risk factors for AAA were evaluated in a blinded fashion by a quick-screen ultrasound and a full conventional study. Times and accuracy for the 2 approaches were compared. An analysis of the cost-effectiveness of screening for AAA was then performed using a Markov model. We determined the long-term survival in quality-adjusted life years and lifetime costs for a hypothetical cohort of 70-year-old males undergoing either AAA screening or not. Our measure of outcome was the cost-effectiveness ratio (CER). RESULTS: The average time for a quick screen was one-sixth that of a conventional study (4 vs 24 minutes). The accuracy of the quick screen was 100%. In our base-case analysis, screening for AAA was cost-effective with a CER of $11,215. Society usually is willing to pay for interventions with CER of less than $60,000 (eg, CER for coronary artery bypass grafting, $9500; breast cancer screening, $16,000). In sensitivity analysis, reducing the cost of screening from $259 (approximate Medicare reimbursement) to $40 (the quick screen) improved the CER to $6850. Moreover, screening populations with increased prevalence of AAA (eg, male with family history [18%]) further improved the CER. CONCLUSIONS: Our analysis demonstrates that ultrasound screening for AAA should be offered to all males above the age of 60. Widespread screening for AAA should be adopted and reimbursed by Medicare and other insurers.

Aged↗
PubMed2002

Why insurers should reimburse for compression stockings in patients with chronic venous stasis.

BACKGROUND: Chronic venous stasis ulcers produce substantial morbidity rates and result in a significant expense to society. Fortunately, compression stockings (CS) have been found to reduce the rate of recurrence in patients with previous ulceration. Surprisingly, Medicare and other insurers do not reimburse the expense associated with CS or with patient education (Ed), which is essential to ensure compliance. METHODS: A Markov decision analysis model was used for analysis of the cost-effectiveness of a strategy of reimbursement for CS and Ed (prophylaxis) versus one that does not supply these resources in a 55-year-old patient with prior venous stasis ulceration. The mean time to ulcer recurrence (53 months with CS+Ed; 18.7 months without prophylaxis), the mean time for ulcer healing (4.6 months), the probabilities of hospitalization (12%) and amputation (0.4%) after the development of an ulcer, and quality-adjustment factors (0.80 during ulcer treatment) were derived from the literature. The cost of CS ($300/year) and Ed ($93 for initial evaluation; $58/year; $40/recurrence) and the medical cost of ulcer treatment (average cost, $1621/recurrence) were calculated from our hospital cost accounting system. RESULTS: A strategy of CS and Ed was cost saving, with 0.37 quality-adjusted life years and $5904 saved, compared with a strategy that does not provide these resources. The inclusion of loss of revenue related to absence from work in the analysis increased cost savings to $17,080 during the patient's lifetime. With sensitivity analysis, CS and Ed remained cost-effective (lifetime cost per quality-adjusted life year saved, <$60,000) if amputations and the cost of ulcer treatment were eliminated or if the cost of prophylaxis was increased to 600% of the base-case. The mean time to recurrence in patients with CS and Ed needed to be reduced from 53 months to 21.1 months before this strategy was no longer cost-effective. CONCLUSION: Prophylactic CS and Ed in patients with prior venous stasis ulceration are cost saving, even with the most conservative of assumptions. Insurers should routinely reimburse for these interventions.

Bandages↗
PubMed2002

Recommended standards for reports dealing with arteriovenous hemodialysis accesses.

The incidence rate of treated end-stage renal disease in the united states is 180 per million and continues to rise at a rate of 7.8% per year. Arteriovenous hemodialysis access (AV access) creation and maintenance are two of the most difficult issues associated with the management of patients on hemodialysis. The 1-year complication rate of a primary prosthetic AV access for hemodialysis ranges from 33% to 99%. Various investigators report on patency and complications of AV access. However, it is rather difficult to compare outcomes because of the wide variety of access materials, configurations, locations, risk factors, and quality of inflow and outflow vessels. Although there have been reporting standards for dialysis access endovascular interventions and for central venous access placement, standards regarding surgical access placement and its revision are lacking. The "Dialysis Outcome Quality Initiative," published by the National Kidney Foundation, provides recommendations for optimal clinical practices aimed at improving dialysis outcome and patient survival. This reporting standards document is not meant to be a "practice guidelines" or "best practices" document. Rather, the purpose of this document is to provide standardized definitions related to AV access procedures and to recommend reporting standards for patency and complications, to be used by surgeons, nephrologists, and interventional radiologists, that will permit meaningful comparisons among AV access procedures. The terms, definitions, and categories featured in this article have been approved by the Committee on Reporting Standards of the Society for Vascular Surgery and the American Association for Vascular Surgery and should be observed in preparing manuscripts on AV accesses for submission to the Journal Of Vascular Surgery.

Arteriovenous Shunt, Surgical↗
PubMed2002

Prolonged administration of doxycycline in patients with small asymptomatic abdominal aortic aneurysms: report of a prospective (Phase II) multicenter study.

BACKGROUND: The primary purpose of this study was to evaluate compliance, side effects, and safety associated with prolonged administration of doxycycline in patients with small asymptomatic abdominal aortic aneurysms (AAAs). A secondary goal was to determine how treatment with doxycycline influences circulating levels of matrix metalloproteinase-9 (MMP-9) in this patient population. METHODS: Thirty-six patients with AAAs (30 men and 6 women; mean age, 69 +/- 1 years) were enrolled into a 6-month phase II study to evaluate treatment with doxycycline (100 mg orally twice a day). Aneurysm size was measured before and after treatment, and compliance and side effects were monitored. Plasma levels of doxycycline were measured midway through the study, and plasma MMP-9 concentrations were measured at baseline, 3 months, and 6 months. RESULTS: Thirty-three of the 36 patients (92%) completed 6 months of doxycycline treatment. Significant treatment-related side effects occurred in five patients (13.9%), including three with cutaneous photosensitivity reactions (8.3%), one with tooth discoloration (2.8%), and one with yeast infection (2.8%). A high rate of compliance with treatment was seen, despite minor but frequent side effects, including nonspecific gastrointestinal symptoms (25%), easily managed episodes of photosensitivity (22.2%), and reversible tooth discoloration (5.5%). The mean plasma doxycycline level after 3 months was 4.62 +/- 0.68 ug/mL (median, 3.64 microg/mL; range, 1.31 to 14.39 microg/mL; n = 23 patients). No significant change was seen in AAA diameter (42.7 +/- 1.3 mm at 6 months versus 41.0 +/- 0.9 mm at baseline), and the overall rate of AAA expansion was 0.63% +/- 0.25% per month. The mean plasma MMP-9 level (n = 19 patients) was elevated at baseline (118.9 +/- 37.9 ng/mL; upper limit of normal, 85 ng/mL) but subsequently decreased to 83.8 +/- 32.9 ng/mL at 3 months (not significant versus baseline) and to 66.4 +/- 24.2 ng/mL at 6 months (P =.022 versus baseline). Only 21% of patients had an elevated level of plasma MMP-9 after 6 months of treatment compared with 47% at baseline (P <.05). CONCLUSION: Prolonged administration of doxycycline is safe and well tolerated by patients with small asymptomatic AAAs and is associated with a gradual reduction in plasma MMP-9 levels. Further studies are needed to evaluate the long-term effects of doxycycline on the rate and extent of aneurysm growth and the potential use of plasma MMP-9 levels as a biomarker of aneurysm disease progression.

Aged↗