Three-dimensional Ultrasound Volume and Conventional Ultrasound Diameter Changes are Equally Good Markers of Endoleak in Follow-up after Endovascular Aneurysm Repair

INTRODUCTION

The main disadvantages of computed tomography angiography in follow-up after endovascular aneurysm repair are the risks of contrast-induced renal impairment and radiation-induced cancer. Three-dimensional ultrasound is a new technique for volume estimation of the aneurysm sac. Some studies have reported promising results. The aim of this study was to evaluate the accuracy and precision of three-dimensional ultrasound aneurysm sac-volume estimates, and to explore whether volume and/or diameter changes on ultrasound can be used as markers of endoleak.

METHODS

A single-center diagnostic accuracy study was performed. 92 Patients planned for endovascular aneurysm repair were prospectively and consecutively enrolled (2013-2016). Aneurysm sac diameter and volume were measured using computed tomography angiography, conventional ultrasound, and three-dimensional ultrasound preoperatively and 1, 6, 12, and 24 months postoperatively. Three-dimensional ultrasound was performed with a commercially available electromechanical transducer. Patients with endoleak were observed 5 years after endovascular aneurysm repair.

RESULTS

79 men and 13 women were included. Mean age was 74 years (57-92). Median follow-up was 24 months. Endoleak cases were observed for up to 55 months. Diameter measurements on conventional ultrasound correlated well with CT diameters (r = 0.9, P < 0.05, n = 347), and Bland-Altman analyses showed an upper limit of agreement of +0.5 cm and a lower limit of agreement of -0.8 cm. The mean difference was -0.13 cm ± 0.36 cm. Three-dimensional ultrasound volumes had a correlation with computed tomography angiography diameters of r = 0.8 (P < 0.05, n = 347) and with three-dimensional computed tomography volumes of r = 0.8 (P < 0.05, n = 155). Receiver operating characteristic analyses showed that the diameter and volume changes which led to reintervention were most accurate at 24-month follow-up, with area-under-the-curve percentage changes of 0.98 (two-dimensional ultrasound), 0.97 (three-dimensional ultrasound), and 0.97 (two-dimensional computed tomography).

DISCUSSION

Both diameter and volume changes can be used as markers for endoleak with excellent areas under the curve on receiver operating characteristic analyses. However, three-dimensional ultrasound volumes did not add any further diagnostic information. Conventional 2D diameter measurements were as accurate as volume changes as markers of endoleak.

CONCLUSION

Type II endoleaks can safely be followed up using a simple diameter measurement on conventional ultrasound.

Rat Plasma Clearance Rate and Organ Distribution of β-Hexosaminidase Isoenzymes from Human Serum

beta-Hexosaminidase (EC 3.2.1.30) is markedly increased in human serum in liver disease, chronic alcoholism, and pregnancy. Knowledge of the clearance rate of plasma/serum beta-hexosaminidase is necessary to evaluate this increase. We studied the plasma clearance of beta-hexosaminidase isoenzymes (purified from human serum and placenta) after their infusion into rat circulation. A recently developed enzyme immunoassay method was used to measure the human beta-hexosaminidase isoenzymes; this method relies on both immunoreactivity and enzyme activity, so intact human isoenzymes were measured. In comparison with the placental isoenzymes (t1/2 less than 2 min), the serum forms showed a considerably slower clearance (t1/2 = 2-4 h). However, desialylation of the serum forms resulted in their rapid clearance (t1/2 less than 2 min). The organ localization of the enzyme eliminated from the circulation was investigated 24 h after infusion. Placental and native serum isoenzymes accumulated mainly in the liver and the spleen. Desialylated serum forms were almost exclusively localized to the liver.

HbA1c predicts long-term postoperative mortality in patients with unknown glycemic status at admission for vascular surgery: An exploratory study

BACKGROUND

Peripheral arterial disease (PAD) and diabetes mellitus (DM) represent major public health challenges and are tightly associated. To facilitate early diagnosis, HbA1c has been implemented as the preferred diagnostic tool for the diagnosis of type 2 DM. In this study, we compared and evaluated HbA1c, fasting plasma glucose (FPG), and 2-hour post-load glucose values to determine which test best predicted mortality in patients with PAD.

METHODS

In all, 273 PAD patients with unknown glycemic status admitted to Haukeland University Hospital for elective surgery between October 2006 and September 2007 were included in the study. All 273 patients underwent a standard oral glucose tolerance test (OGTT) in addition to determination of HbA1c; patients were then grouped into those with DM, intermediate hyperglycemia, and normoglycemia according to World Health Organization and International Expert Committee criteria.

RESULTS

All-cause mortality was 40% over a 9-year follow-up period. After adjusting for age, sex, and relevant medication, HbA1c was a predictor for mortality (hazard ratio [HR] 1.54; 95% confidence interval [CI] 1.03-2.32]; P = 0.04). The association did not achieve statistical significance in a fully adjusted Cox regression model, although the effect estimation of HbA1c on all-cause mortality remained largely unchanged (HR 1.39; 95% CI 0.92-2.09; P = 0.13). The OGTT was not a predictor of long-term mortality.

CONCLUSIONS

The results indicate that HbA1c is a useful marker in the preoperative screening of patients of unknown glycemic status at the time of admission for vascular surgery, and may identify people at high risk of long-term mortality following surgical treatment for PAD.

Editor's Choice - The National Norwegian Carotid Study: Time from Symptom Onset to Surgery is too Long, Resulting in Additional Neurological Events

OBJECTIVE/BACKGROUND

The objective was to observe for 1 year all patients in Norway operated on for symptomatic carotid stenosis with respect to (i) the time from the index event to surgery and neurological events during this time; (ii) the level in the healthcare system causing delay of surgical treatment; and (iii) the possible relationship between peri-operative use of platelet inhibitors and neurological events while awaiting surgery.

METHODS

This was a prospective national multicentre study of a consecutive series of symptomatic patients. Patients were eligible for inclusion when referred for surgery. An index event was defined as the neurological event prompting contact with the healthcare system. All 15 departments in Norway performing carotid endarterectomy (CEA) participated.

RESULTS

Three hundred and seventy one patients were eligible for inclusion between 1 April 2014 and 31 March 2015, and 368 patients (99.2%) were included. Fifty-four percent of the patients contacted their general practitioner on the day of the index event. Primary healthcare referred 84.2% of the patients to hospital on the same day as examined. In hospital median time from admission to referral for vascular surgery was 3 days. Median time between referral to the operating unit and actual CEA was 5 days. Overall, 61.7% of the patients were operated on within 2 weeks of the index event. Twelve patients (3.3%) suffered a new neurological event while awaiting surgery. The percentage of patients on dual antiplatelet therapy was lower (25.0%) in this group than among the other patients (62.6%) (p = .008). The combined 30 day mortality and stroke rate was 3.8%.

CONCLUSION

This national study with almost complete inclusion and follow-up shows that the delays occur mainly at patient level and in hospital. The delay is associated with new neurological events. Dual antiplatelet therapy is associated with reduced risk of having a new neurological event before surgery.

Abdominal aortic aneurysms--glycaemic status and mortality

AIMS

The prevalence of diabetes mellitus (DM) and mortality with respect to glycaemic status in patients with abdominal aortic aneurysms (AAA) was evaluated. Glycaemic status was assessed by an oral glucose tolerance test (OGTT) and by HbA1c.

METHODS

Sixty-six patients with AAA admitted to the vascular surgery unit for elective surgery between October 2006 and September 2007 were included. Seven patients had previously known DM. OGTT and HbA1c results were available from 58 patients. The patients were categorized as having DM, prediabetes and normoglycaemia according to the WHO's and American Diabetes Association's criteria.

RESULTS

The prevalence of newly diagnosed DM according to the OGTT and HbA1c results were 12% and 14% respectively. Mean follow-up time was 68 months and all-cause mortality 43%. HbA1c was an independent predictor for mortality in the DM category. Hazard ratio of all-cause mortality in the DM category defined by the HbA1c values was 6.35, 95% [CI 1.49-27.1]; p = 0.01.

CONCLUSIONS

DM defined by HbA1c ≥ 6.5% is an important determinant of mortality following surgical treatment for AAA. Half the patients with AAA and DM were unaware of their DM diagnosis. All patients with AAA should be tested for DM using HbA1c. The results should be confirmed in a larger prospective study.

HbA₁c versus oral glucose tolerance test as a method to diagnose diabetes mellitus in vascular surgery patients

Background

The diagnosis of diabetes mellitus (DM) is based on either fasting plasma glucose levels or an oral glucose tolerance test (OGTT). Recently, an HbA_1c value of ≥ 48 mmol/mol (6.5%) has been included as an additional test to diagnose DM. The purpose of this study was to validate HbA_1c versus OGTT as a method to diagnose DM in vascular surgery patients.

Methods

The study population consisted of 345 patients admitted consecutively due to peripheral arterial disease. Sixty-seven patients were previously diagnosed with DM. Glucose levels of OGTT and HbA_1c values were analyzed in 275 patients. The OGTT results were categorized into three groups according to the World Health Organization 1999 criteria: 1) DM defined as fasting plasma glucose (FPG) ≥ 7.0 mmol/L and/or two-hour value (2-h-value) ≥ 11.1 mmol/L; 2) intermediate hyperglycaemia, which consists of IGT (FPG < 7.0 mmol/L and a 2-h-value between 7.8 mmol/L and 11.1 mmol/L), and IFG (fasting glucose value between 6.1 mmol/L and 7.0 mmol/L with a normal 2-h-value); and 3) normal glucose metabolism defined as FPG < 6.1 mmol/L and a 2-h-value < 7.8 mmol/L.

Results

Of the 275 patients on whom OGTT was performed, 33 were diagnosed with DM, 90 with intermediate hyperglycaemia and 152 had normal glucose metabolism. An HbA_1c value of ≥ 48 mmol/mol (6.5%) detected DM with a 45.5% sensitivity and a 90% specificity compared with the OGTT results. Combining the measurements of the HbA_1c value with the fasting plasma glucose level (≥7.0 mmol/L) increased the sensitivity to 64%. The total prevalence of DM and intermediate hyperglycaemia was 85% based on HbA_1c values and 45% based on the OGTT.

Conclusions

Compared with the OGTT the HbA_1c cut-off value of ≥ 48 mmol/mol (6.5%) had a 45.5% sensitivity to diagnose DM in patients with peripheral arterial disease. OGTT and HbA_1c categorized different individuals with DM and intermediate hyperglycaemia. The total prevalence of pathologic glucose metabolism was substantially higher based on HbA_1c values than based on OGTT. The high prevalence of DM and intermediate hyperglycaemia when using HbA_1c in this study may reflect a high chronic glycaemic burden in patients with peripheral arterial disease. Further studies on vascular surgery patients are needed to identify which method, OGTT or HbA_1c, is the better in predicting DM and future clinical development of vascular disease.

Trial registration

REK vest 14109

Improved patency and reduced intimal hyperplasia in PTFE grafts with luminal immobilized heparin compared with standard PTFE grafts at six months in a sheep model

AIM

The aim of this study was to compare the performance of polytetrafluoroethylene (PTFE) grafts with luminal coating of immobilized heparin to that of standard PTFE grafts at six months.

METHODS

Twenty-eight common carotid arteries in fourteen sheep were bypassed with heparin-coated PTFE grafts (6 mm diameter, 6 cm length) on one side and standard PTFE grafts on the other. The grafts were explanted after six months. The thickness of intimal hyperplasia (IH) in open grafts was measured with histomorphometrical methods.

RESULTS

Two of 14 heparinized PTFE grafts and nine of 14 grafts in the control PTFE-group were occluded at explantation (P=0.006). Six-month patency rates for heparinized PTFE grafts and for standard PTFE grafts were 86% and 36%, respectively. Mean graft anastomotic IH thickness in open grafts were 0.074 mm for heparinized PTFE grafts and 0.259 mm for PTFE-grafts (P=0.006).

CONCLUSION

PTFE grafts with luminal coating containing immobilized heparin had significantly better patency and recruited less intimal hyperplasia than standard PTFE grafts at six months.

[Intermittent claudication--diagnosis and treatment]

BACKGROUND

Intermittent claudication occurs in 5% of the population over 60 years, and may involve reduced walking distance, pain and a reduced quality of life. The mortality rate is 5% per year and the annual amputation rate 1%. This review article gives an update on diagnosis and medical, endovascular and surgical treatment of intermittent claudication.

MATERIAL AND METHODS

The article is based on publications found on Pubmed, supplemented by clinical experience.

RESULTS AND INTERPRETATION

The aims of medical, endovascular and surgical treatments are to enable the patient to walk further, obtain an improved quality of life and to live longer. Patients should first be treated medically. Endovascular treatment or open surgery, are options for patients with reduced quality of life due to limited walking distance. The treatment choice depends on the location of the arterial lesions and if the patient has any other illness.

Treatment of a Hepatic Artery Aneurysm by Endovascular Stent-Grafting

Aneurysms of the visceral arteries are rare. Traditional treatment has been surgical or endovascular with coil embolization. Recently, however, reports on endovascular therapy with stent-grafts have been published. We report the case of a 61-year-old man who was successfully treated with a stent-graft for a symptomatic combined celiac/hepatic artery aneurysm.

Flow measurement before and after papaverine injection in above-knee prosthetic femoropopliteal bypass

OBJECTIVE

To investigate the value of intraoperative blood flow measurements on early and long-term patency of above-knee prosthetic femoropopliteal bypass.

METHODS

Flow was measured with a transit time flowmeter before (basal flow) and after an intragraft injection of papaverine (papaverine flow) in 87 operations (86 patients) between January 1990 and December 2001. Sixty-one grafts were of polyester, and 26 were of polytetrafluoroethylene. The operations were done under epidural anesthesia. The preoperative angiographic run-off score and clinical risk factors were recorded. Patency rates were analyzed with the product limit method and compared with the log-rank test. Variables found to be near significantly related to patency rates (P < .1) were included in a multivariate analysis performed with the Cox proportional hazard model.

RESULTS

Basal flow measurements were not related to patency. The 2- and 5-year patency rates for grafts with a papaverine flow < or = 500 mL/min were 48% and 18% compared with 66% and 52% for grafts with a papaverine flow > or = 500 mL/min. These differences were statistically significant (P = .012, hazard ratio, 2.6). Two- and 5-year patency rates for smokers vs nonsmokers were 44% and 18% vs 69% and 54%. The patency rates for patients with poor vs good run-off were 42% and 27% vs 66% and 31%. Smoking (P = .008, hazard ratio, 2.75) and poor run-off score (P = .009, hazard ratio, 2.38) were found to be independent risk factors for reduced patency rates. Poor run-off score did not correlate with low values of measured basal or papaverine flow.

CONCLUSIONS

Papaverine flow of < or = 500 mL/min is associated with reduced mid- and long-term patency rates. Additional antithrombotic medication and frequent follow-up for these grafts should be considered. The inferior patency rates of smokers and patients with poor run-off indicate that prosthetic bypass is less suitable for these groups of patients.

Homocysteine Levels, Haemostatic Risk Factors and Patency Rates After Endovascular Treatment of the Common Iliac Arteries

OBJECTIVES

To investigate the impact of clinical risk factors, plasma homocysteine and haemostatic variables on the results after endovascular treatment of symptomatic atherosclerosis of the common iliac artery.

DESIGN

Prospective observational study.

SETTING

University hospital.

PATIENTS AND METHOD

The study included 139 technically successful interventions in 103 patients. Technical success was defined as < or = 30% residual stenosis as seen on the post treatment angiogram. Blood samples for analyses of fasting plasma values of homocysteine, fibrinogen, D-dimer, activated protein C resistance were drawn upon admission. Median follow-up for all procedures was 22 months (range 0-55 months). Patency was defined as freedom from > or = 50% restenosis or reocclusion.

RESULTS

The technical success rate for all procedures was 93%. The 1-year cumulative primary patency rate based on intention to treat was 85%. Multivariate analysis revealed a significant independent association between patency rates and levels of fibrinogen and homocysteine and the nature of the lesion treated (stenosis vs. occlusion).

CONCLUSION

The aetiology of restenoses and reocclusions is probably multifactorial. Procoagulant activity, the nature of the lesion treated and homocysteine levels within and above the upper range of normal limits are important risk factors for failure after endovascular treatment of the common iliac arteries.

Homocysteine Levels, Haemostatic Risk Factors and Patency Rates after Endovascular Treatment of the Above-Knee Femoro-Popliteal Artery

OBJECTIVES

To investigate the relationship between plasma homocysteine and other haemostatic variables and restenoses or reocclusions after endovascular treatment of symptomatic atherosclerosis of the above-knee femoro-popliteal artery.

DESIGN

Prospective observational study.

SETTING

University hospital.

PATIENTS AND METHODS

The study included 103 patients (116 limbs), treated with subintimal angioplasty in 58 cases (50%) and with intraluminal PTA in 58 (50%): 39 (34%) patients were treated for critical limb ischaemia. Blood samples for analyses of fasting plasma values of homocysteine, fibrinogen, D-dimer, activated protein C resistance were drawn upon admission. Median follow-up for all procedures was 11 months (range 0-42 months). Outcome events (arterial patency) were defined as > or =50% restenosis or reocclusion in the treated arterial segment. Patency rates were estimated with the product limit method and Kaplan-Meier curves. Variables found to be related significantly to patency were included in multivariate analysis performed with the Cox proportional hazard model.

RESULTS

The 1-year cumulative primary patency rate for all procedures was 48%. One-year limb salvage rate in cases of critical ischaemia was 74%. Multivariate analysis demonstrated significant independent associations between patency rates and plasma D-dimer, diabetes mellitus, the nature of the lesion treated (stenosis vs. occlusion) and antithrombotic therapy with aspirin after the procedure. Plasma levels of homocysteine, fibrinogen or activated protein C resistance were not associated with patency rates. Homocysteine levels were higher in patients with critical limb ischaemia than those with intermittent claudication.

CONCLUSIONS

Early restenosis or reocclusion after endovascular intervention of lesions in the above-knee femoro-popliteal artery was more frequent following treatment of occlusion (versus stenosis), for patients with diabetes, patients with elevated D-dimer and those without antithrombotic therapy after the procedure. Plasma homocysteine did not appear to influence the outcome of endovascular intervention.

Homocysteine Levels, Haemostatic Risk Factors and Restenosis after Carotid Thrombendarterectomy

OBJECTIVES

To investigate the effect of elevated serum homocysteine and haemostatic as well as clinical risk factors on the tendency to restenosis after carotid artery thrombendarterectomy.

DESIGN

A prospective, observational study.

PATIENTS AND METHODS

In the period from October 1999 to October 2002, 86 patients were subjected to 96 carotid endarterectomies because of internal carotid artery stenoses. The carotid stenoses were symptomatic in 86 cases (90%). Fasting plasma homocysteine, fibrinogen, D-dimer and activated protein C resistance were measured the day before surgery. Follow-up was done 1, 3, 6, 12 and 18 months postoperatively and yearly thereafter with clinical assessment and triplex ultrasonography. The median follow-up time was 17 months (range 9-42 months). Freedom from restenosis was estimated with Kaplan-Meier curves, using log-rank test for comparison between groups. Variables found to be significantly related to restenosis rates were included in a multivariate analysis performed with the Cox proportional hazards model. Comparison of means of continuous data between two groups was done with Student's t-test and more than two groups with one-way analysis of variance.

RESULTS

Restenoses within 12 months of the operation occurred in 11 cases (11%). Univariate analysis revealed that plasma homocysteine values < or =10 micromol/l and freedom from ischaemic heart disease were both significantly associated with an increased risk of restenosis (p=0.0076 and 0.0059). However, multivariate analysis showed that only plasma homocysteine values <10 micromol/l were independently and significantly associated with an increased risk of restenosis (p=0.046). There were no associations between the degree of atherosclerotic affection of the precerebral circulation or symptoms on one hand and the levels of homocysteine, fibrinogen, D-dimer and activated protein C resistance on the other.

CONCLUSION

There seems to be an independent, significant association between homocysteine values within the lower two thirds of the normal range and restenosis after carotid endarterectomy. Studies on the biological properties of human endothelial cells from different types of vasculature and different locations, specifically with respect to homocysteine metabolism and its effect, are warranted.

Outcome of treatment of ruptured abdominal aortic aneurysms depending on the type of hospital

OBJECTIVE

To compare the outcome of patients operated on acutely for ruptured abdominal aortic aneurysms (AAA) or otherwise symptomatic aortic aneurysms in a university hospital and in two county hospitals by the same group of vascular surgeons.

DESIGN

Retrospective study.

SETTING

1 university and 2 county hospitals, Sweden.

SUBJECTS

108 patients operated on urgently for AAA, 81 at the university hospital, and 27 at the county hospitals between January 1992 and December 1998.

INTERVENTION

Repair of the AAA.

MAIN OUTCOME MEASURES

Morbidity and mortality.

RESULTS

21 of the 81 patients having urgent repair of an AAA at the university hospital (26%) had been transferred from the county hospitals. Thirteen patients were not operated on, 7 because of their poor general condition and great age (median 84 years), 3 who refused operation, and 3 in whom the diagnosis was incorrect. During the same time period a further 27 haemodynamically unstable patients were operated on by the same vascular surgeons at the county hospitals. The on-table mortality for patients with ruptured AAA and shock was 5/43 (12%) at the university hospital and 4/27 (15%) at the county hospitals. The corresponding in-hospital rates were 11/43 (26%) and 11/27 (41%). Mortality was significantly higher if the operation was delayed by more than 45 minutes. The incidence of postoperative complications was the same in both hospitals.

CONCLUSION

If a patient with a ruptured AAA and shock is admitted to the county hospital and operated on by a specialist vascular surgeon the outcome is fully acceptable. The difference seems to be related to the postoperative period. To what extent the delay caused by the surgeon's journey to the county hospital has any influence on the outcome is not possible to evaluate.

Intraoperative contamination of synthetic vascular grafts. Effect of glove change before graft implantation. A prospective randomised study

OBJECTIVES

to investigate the incidence of intraoperative graft contamination, bacterial species and the influence of change of surgeon's gloves on contamination.

DESIGN

a prospective randomised study.

MATERIALS AND METHODS

forty patients had implantation of synthetic vascular grafts. All patients received intraoperative cloxacillin (2.0 g) or clindamycin (0.6 g) intravenously. The procedures were randomised to two groups: Group 1 - surgeons changed the gloves before the first contact with the vascular prosthesis and Group 2 - operation without glove change. The growth of all bacterial species from graft segments and from the gloves was recorded. The susceptibility to antibiotics was tested.

RESULTS

the number of contaminated grafts was similar in the two groups. Growth of bacteria was recorded from 92.5% (37/40) of the graft segments and 33% (51/156) of glove imprints. Of the cultured species, 75% and 47%, respectively, were identified as coagulase-negative staphylococci (CNS). Twenty-eight per cent of CNS were resistant to cloxacillin, 15% to clindamycin, and 10% to cloxacillin and clindamycin. In all, 25% of the CNS strains were resistant to the prophylactic antibiotic used. In 50% of cases, the antibiogram of the CNS strain recovered from gloves agreed with that of the strain harvested from the graft.

CONCLUSIONS

a high incidence of graft contamination was found which was not reduced by changing gloves. However, changing gloves did seem to reduce the number of bacterial species.

Percutaneous transluminal angioplasty with or without stenting for femoropopliteal occlusions? A randomized controlled study

BACKGROUND

To investigate the-one year outcome of PTA and stenting and PTA alone for femoropopliteal occlusions.

DESIGN

Randomized prospective study

METHODS

32 patients with femoropopliteal occlusions were randomized into two treatment groups: PTA and Strecker-stent (n=15) and PTA alone (n=17). The median age of the patients was 71 years. All patients had chronic limb ischaemia, 66% had tissue loss, 19% had rest pain and 15% had disabling claudication. The median ABPI was 0.45. The occlusion was confined to the superficial femoral artery in 30 cases and to the popliteal artery in 2 cases. The median length of the occlusions was 7.3 cm. Aspirin (ASA), 160 mg daily, was administrated postoperatively but no anticoagulation was used. The follow-up included: clinical examination, measurement of ABPI and control angiography at 12 months or earlier when necessary (20 patients).

RESULTS

There was no mortality or limb loss as a consequence of the treatment. There were six (16%) immediate major complications in five patients. In the PTA group, one patient had a myocardial infarction and three patients needed arteriography due to bleeding. In the stent group, one patient required arteriography and embolectomy. The one-year mortality was 6% and there were no amputations. Four patients (two in each group) were operated on with a femorodistal bypass. The rate of clinical improvement was 71% after PTA and stent and 60% after PTA alone (p=0.17). An increased ABPI (>0.10) was shown in 50% of the stent group and 61% in the PTA group (p=0.17). Angiographic re-occlusions were seen in 33% and 75% in the stent and PTA groups respectively (p=0.17), while the rate of restenosis was significantly higher in the stent group (50% vs 25%) (p=0.033).

CONCLUSIONS

Stenting following PTA for femoropopliteal occlusions does not significantly improve neither the clinical state nor the clinical/angiographic patency. The results do not justify any routine placement of stent following PTA in the successfully recanalized femoropopliteal arteries. The low rate of acceptance of a follow-up angiography indicates that this kind of study should preferably use duplex scanning instead of angiography for follow-up.

Magnetic resonance imaging and MR angiography of endoluminally treated abdominal aortic aneurysms

OBJECTIVES

To evaluate magnetic resonance imaging (MRI) with gadolinium-based contrast medium-enhanced MR angiography (MRA) for the follow-up of endoluminally treated abdominal aortic aneurysms.

DESIGN

MRI/MRA, angiography and computed tomography (CT) were performed 1 month after endoluminal stent-graft placement. MRI/MRA was repeated at 6 and 12 months and angiography and CT were added to confirm unexpected findings.

MATERIALS

Fifteen male patients with endoluminally treated abdominal aortic aneurysms.

METHODS

MRI with MRA, spiral CT with transverse images and angiography were performed.

RESULTS

MRI/MRA demonstrated changes of stent-graft morphology, aortic neck- and aneurysmal diameter, stent-graft blood flow, stent-graft leakage, blood flow in lumbar arteries, intra-aneurysmal thrombus, periaortic inflammation and vertebral body infarction. For most of these features MRI/MRA provided more information than angiography and/or CT. MRI was the only method demonstrating thrombus reorganisation and vertebral body infarction.

CONCLUSIONS

MRI with MRA provides the relevant information needed for follow-up of endoluminally treated abdominal aortic aneurysms (AAA). This may be the method of choice because of its use of contrast media with very low nephrotoxicity, lack of ionising radiation and non-invasiveness.

[Endovascular technique in aortic aneurysm. A promising alternative to open surgery]

The article consists in a presentation of endovascular surgery for abdominal aortic aneurysm repair in 23 cases. Two cases required conversion to open surgery, but the procedure could be completed in the remaining 21 cases, with a current duration of follow-up of up to 30 months. There was early leakage in one case, and late leakage in five cases. Late conversion has been necessary in three instances, and supplementary endovascular measures have been required in a further two instances. All complications have occurred in those cases operated during the first half of the study period. Modification of the endoprosthesis used and increasing skill have reduced both operation time and the complication rate. Intensive care is no longer required, and the median duration of hospitalisation is three days. Follow-up with magnetic resonance imaging has yielded new and important information.

Biological responses differ considerably between endovascular and conventional aortic aneurysm surgery

OBJECTIVES

To determine the inflammatory responses in endovascular abdominal aortic aneurysm (AAA) repair and their relation to clinical findings.

DESIGN

Prospective non-randomised study.

SETTING

University Hospital, Department of Surgery.

PATIENTS AND METHODS

Seven patients treated with an endoluminal procedure (AAA-E) and seven patients undergoing conventional surgery (AAA-C) were included. Inflammatory parameters were assessed by measurements of the cytokines interleukin (IL)-1 beta, IL-6, IL-8 and Tumour Necrosis Factor-alpha (TNF-alpha); analyses of complement proteins C1q, C4, C3, C5a and Terminal Complement Complexes (TCC); haematologic parameters and determination of C-reactive protein (CRP).

RESULTS

In six of seven patients in the AAA-E group blood pressure decreases were recorded during introduction of the device. IL-6 and CRP levels were found to be significantly higher in AAA-C patients compared to the AAA-E group. On the other hand, high TNF-alpha levels were recorded in the AAA-E group. Less consumption of the complement proteins C1q, C4 and C3 was observed in AAA-E compared to AAA-C patients. Increased C5a levels were recorded in the AAA-C group, whereas only slight fluctuations were noticed in the AAA-E group. TCC levels were unchanged in both groups.

CONCLUSION

Endovascular aortic aneurysm repair induced a significant inflammatory response, mainly involving TNF-alpha and differing from the findings during open AAA repair. These inflammatory responses were probably related to blood pressure decreases during the procedures. On the other hand, conventional repair induced responses related to the more extensive surgical trauma and reperfusion injury.

Healing characteristics of polymer-coated or collagen-treated Dacron grafts: an experimental porcine study

The healing characteristics of polymer-coated Dacron grafts with or without heparin-bonding and collagen-coated Dacron grafts are compared with standard knitted Dacron grafts by implanting eight of each graft into pig iliac arteries. The grafts were implanted at random bilaterally with end-to-side anastomoses. The grafts were explanted after 1, 2 and 4 weeks and prepared for histological evaluation by in vivo fixation. Graft segments were investigated by light microscopy, scanning electron microscopy and transmission electron microscopy. The endothelial coverage, intimal thickness and healing characteristics were subjected to one-way analysis of variance. One week after surgery endothelial-like cells appeared close to the anastomoses and after 2 weeks a clear growing endothelial edge was observed in the collagen-coated grafts. After 4 weeks' implantation all grafts were patent and endothelial cells covered the grafts to a various extent. Collagen-coated grafts had significantly greater endothelial cell coverage compared with Dacron and polymer-coated grafts without heparin bonding (P < 0.05). Evaluation by transmission electron microscopy revealed the luminal coverage of the collagen-coated grafts to consist of organized smooth muscle cells and endothelial cells containing Weibel-Palade bodies. The smooth muscle cells in the other grafts were less organized and were covered by endothelial cells to a lesser degree. No differences were noted regarding the inflammatory response of the graft materials and no further positive effects were encountered by the addition of heparin to the polymer coating. The study demonstrates that various coating procedures and surface modulation of knitted Dacron grafts produce a graft which is impervious to blood but still allows tissue incorporation.(ABSTRACT TRUNCATED AT 250 WORDS)

The adhesion of labelled neutrophils on synthetic vascular grafts. An experimental porcine study

The adhesion of neutrophils onto different vascular grafts was studied in vivo in a pig model. In acute experiments autologous 111In-labelled neutrophils were reinfused after end-to-side implantation of 5 cm, 6 mm internal diameter grafts. The dynamic deposition on each graft was determined for 300 min in vivo. Static measurements in vitro concluded the study. The adhesion was greater in Dacron and collagen coated Dacron grafts compared to expanded polytetrafluoroethylene (ePTFE) and to Dacron grafts coated with a polymer. The segmental activity along all the grafts increased towards the distal anastomosis. The results suggest different inflammatory response to various graft materials.

Liver regeneration following 68% partial orthotopic liver transplantation in the rat

Liver regeneration following transplantation in 'small for size' conditions is not fully understood. We therefore evaluated the regenerative response of transplanted partial liver grafts in outbred rats without the use of immunosuppression and compared it to liver regeneration following resection. The transplanted livers showed enhanced regeneration compared to controls. We suggest that this is caused by activation of the immune system.

Rat plasma clearance rate and organ distribution of beta-hexosaminidase isoenzymes from human serum

beta-Hexosaminidase (EC 3.2.1.30) is markedly increased in human serum in liver disease, chronic alcoholism, and pregnancy. Knowledge of the clearance rate of plasma/serum beta-hexosaminidase is necessary to evaluate this increase. We studied the plasma clearance of beta-hexosaminidase isoenzymes (purified from human serum and placenta) after their infusion into rat circulation. A recently developed enzyme immunoassay method was used to measure the human beta-hexosaminidase isoenzymes; this method relies on both immunoreactivity and enzyme activity, so intact human isoenzymes were measured. In comparison with the placental isoenzymes (t1/2 less than 2 min), the serum forms showed a considerably slower clearance (t1/2 = 2-4 h). However, desialylation of the serum forms resulted in their rapid clearance (t1/2 less than 2 min). The organ localization of the enzyme eliminated from the circulation was investigated 24 h after infusion. Placental and native serum isoenzymes accumulated mainly in the liver and the spleen. Desialylated serum forms were almost exclusively localized to the liver.

Surgical treatment versus thrombolysis in acute arterial occlusion: a randomised controlled study

Thrombolytic treatment has been tried in various forms for acute limb ischaemia with varying degrees of success but is also often accompanied by bleeding problems. The present investigation compares the effect of surgical thrombectomy (TE) and thrombolysis (TL) using recombinant tissue plasminogen activator (rt-PA). Twenty patients with a need for intervention owing to ischaemia lasting more than 24 h but less than 14 days were included. Patients randomised to TE were operated under epidural anaesthesia and patients in the TL group received 30 mg rt-PA during a 3 h period through a catheter placed into the thrombus and advanced as lysis was achieved. Thrombectomy resulted in an immediate restitution of blood flow in six out of nine cases, in three cases a bypass procedure was performed, and one of these failed with a resultant amputation. Thrombolysis gave a good primary result in six cases which lasted in four of them. Three had a subsequent percutaneous transluminal angioplasty. Partial lysis was seen in two cases and a further two failed. Five went to surgery with three bypass and two fogarty procedures being necessary. There was no hospital mortality and there were no bleeding complications due to the rt-PA treatment in this series. In 19 out of 20 patients the circulation was re-established. Appropriate handling of acute ischaemic conditions implies the use of both thrombolysis and appropriate surgical procedures, including distal bypass grafts.

Factors influencing the concentrations of the large neutral amino acids in the brain and in the CSF of dogs after portacaval anastomosis

Portal-systemic shunting of blood is associated with hyperammonemia, an increased glutamine concentration in brain, an altered plasma neutral amino acid pattern, and high levels of several of the large neutral amino acids in brain. Since some of these amino acids are precursors for neurotransmitters and for other potentially neuroactive substances, high CNS levels of these amino acids may contribute to the development of encephalopathy. In order to determine the relative importance of changes in brain glutamine levels and changes in competition among the neutral amino acids for blood-brain transport, we measured the concentrations of the large neutral amino acids in plasma, cisternal cerebrospinal fluid and in brain tissue from various regions of dogs after end-to-side portacaval shunt. Although the changes in CSF amino acid levels correlated partially with altered amino acid plasma competitor ratios, better correlations were observed with the elevation of CSF glutamine. These results suggest a model of blood-brain amino acid transport in which a high level of glutamine in brain extracellular fluid competes with other neutral amino acids for efflux from brain, thus raising brain amino acid levels after portal-systemic shunting.

The effects of ammonia tolerance tests on the cerebrospinal fluid concentrations of amino acids and indoleamines in patients with liver cirrhosis

To study the effect of ammonia administration on amino acids and indoleamines in cerebrospinal fluid (CSF) and on amino acids, insulin, and glucagon in plasma in humans with liver cirrhosis, we performed seven ammonia tolerance tests on six patients with stable liver cirrhosis. The grade of encephalopathy was determined by psychometric tests. Only one of the patients had pronounced encephalopathy. The other patients had no or only slight encephalopathy. The plasma concentrations of valine, leucine, isoleucine, phenylalanine, tyrosine, and methionine decreased after the ammonia load, whereas no changes were found in the plasma concentrations of glucagon and insulin. In CSF the concentrations of glutamine, aromatic amino acids, and indoleamines increased only in the patient who had pronounced encephalopathy, whereas no changes were found in the other patients. The effect of an ammonia load on the concentrations of neutral amino acids in CSF in patients with pronounced encephalopathy remains to be demonstrated.

The effect of ammonia infusion on brain monoamine metabolism in portacaval-shunted rats

The effect of ammonia infusion on monoamine metabolism was studied in the rat brain. Seven days after portocaval shunt (PCS) or sham operation animals were infused with ammonia or saline. Brain metabolism of serotonin and norepinephrine was studied after injection of a decarboxylase inhibitor (m-hydroxybenzylhydrazine, NSD 1015) which blocks the conversion of 5-hydroxytryptophan to serotonin and dihydroxyphenylalanine to dopamine. Neurologic testing was conducted before killing. Plasma and brain amino acids were measured. PCS animals infused with ammonia were in deep coma after 6 h infusion, whereas sham-operated animals were virtually unaffected. Brain amino acid analyses demonstrated increased concentrations of the aromatic amino acids and a tenfold increase in glutamine. Serotonin metabolism was diminished after 6 h. Dopamine synthesis was normal, but norepinephrine levels were low after 6h. The study suggests that hyperammonemia in PCS rats results in a depression of the serotonin synthesis rate in accordance with two previous studies but in contrast to previous hypotheses on the regulation of serotonin metabolism.

Infusion of branched-chain amino acids and ammonium salts in rats with portacaval shunts

During infusion into rats with a portacaval shunt of either ammonium (NH4+) salts alone or NH4+ salts combined with the three branched-chain amino acids (BCAAs) in equimolar quantities, we assessed neurologic function and measured plasma and brain ammonia and amino acid levels and the brain content of amine neurotransmitters and their metabolites. Survival was lengthened and neurologic function was preserved longer in rats receiving BCAAs. Infusion of BCAAs resulted in lower plasma and brain ammonia concentrations compared with rats receiving NH4+ salts alone. Plasma glutamine and alanine levels were higher in rats receiving BCAAs, suggesting increased ammonia detoxification. Loss of neurologic function, regardless of which solution was infused, eventually occurred and corresponded with decreased brain norepinephrine and increased brain alanine levels. These results suggest that BCAAs can protect against hyperammonemia by stimulating the peripheral detoxification of ammonia.

Effect of hyperammonemia and methionine sulfoximine on the kinetic parameters of blood-brain transport of leucine and phenylalanine

The activity of the blood-brain neutral amino acid transport system is increased in rats infused with ammonium salts or rendered hyperammonemic by a portacaval anastomosis. This effect may be due to a direct action of ammonia or to some metabolic consequence of high ammonia levels, such as increased brain glutamine synthesis. To test these possibilities we evaluated the kinetic parameters of blood-brain transport of leucine and phenylalanine in control rats, in rats after continuous 24 h infusion of ammonium salts (NH4+ = 2.5 mmol X kg-1 X h-1), and in rats treated with methionine sulfoximine, an inhibitor of glutamine synthetase, before infusion of ammonium salts. In ammonia-infused rats without methionine sulfoximine treatment, the KD and Vmax of phenylalanine transport were increased, respectively, about 170% and 80% compared to controls, whereas the Km and Vmax of leucine transport were increased, respectively, about 100% and 200%. Electron microscopy demonstrated marked swelling of astrocytic processes around brain capillaries of ammonia-infused rats; however, capillary permeability to horseradish peroxidase apparently was not increased by ammonia infusion. Administration of methionine sulfoximine before ammonia infusion inhibited glutamine synthesis and prevented the changes in transport of leucine and phenylalanine, but apparently did not reverse the perivascular swelling. These results suggest that the ammonia-induced increase in the activity of transport of large neutral amino acids across the blood-brain barrier requires glutamine synthesis in brain, and is not a direct effect of ammonia.

Methionine sulfoximine prevents the accumulation of large neutral amino acids in brain of portacaval-shunted rats

Portal-systemic shunting and hyperammonemia lead to an accumulation of the large neutral amino acids in brain and apparently alter transport of neutral amino acids across the blood-brain barrier. It has been proposed that portal-systemic shunting leads to a high brain concentration of glutamine, a product of cerebral ammonia detoxification, and thereby affects the transport of other neutral amino acids across the blood-brain barrier. To test this hypothesis, rats with a portacaval shunt were treated with L-methionine-dl-sulfoximine (MSO), an inhibitor of glutamine synthesis. Treatment with MSO resulted in lower concentrations of the neutral amino acids in brain of portacaval-shunted rats and a higher brain ammonia concentration, compared with untreated shunted rats. These results suggest that the accumulation of neutral amino acids in brain after portacaval shunt depends on the increased synthesis of glutamine in brain.

Indole amines and amino acids in various brain regions after infusion of branched chain amino acids into hepatectomized rats

This study was designed to determine regional changes of amino acids and indole amines in the brain and possible interactions between amino acids and indole amines 18 h after hepatectomy in rats. Hepatectomy and glucose infusion alone resulted in a profound increase of most large neutral amino acids (LNAA) in plasma and in the brain except for the branched-chain amino acids (BCAA), which maintained normal or somewhat lower values in plasma. Hepatectomy and infusion of glucose combined with BCAA sharply reduced the plasma and brain amino acid concentrations of other LNAA. Simultaneously the concentrations of serotonin and 5-hydroxyindoleacetic acid were decreased in all brain regions. In both groups of hepatectomized rats there were regional variations of the amino acid and the indole amine concentrations in the brain, but the response to BCAA infusion was generally the same in all brain regions. No difference in survival between the 2 groups could be found.

Methionine sulfoximine prevents the accumulation of large neutral amino acids in brain of hyperammonemic rats

Accumulation of neutral amino acids in the brain due to altered transport across the blood-brain barrier appears to be a consequence of portal-systemic shunting and hyperammonemia. It has been suggested that high brain concentrations of glutamine, a product of cerebral ammonia detoxification, accelerates the transport of other neutral amino acids from blood to brain. To test this hypothesis, normal rats were infused with ammonium salts with or without pretreatment with L-methionine-dl-sulfoximine (MSO), an inhibitor of glutamine synthesis. Pretreatment with MSO prevented most ammonium salt-induced changes in the concentrations of the neutral amino acids in brain, suggesting that hyperammonemia alters the transport of neutral amino acids across the blood-brain barrier by causing the brain glutamine level to rise.

Effect of extragastric vagotomy on pancreatic polypeptide in dogs

The direct vagal innervation of the pancreas in dogs was interrupted by extragastric vagotomy (EGV). The response of pancreatic polypeptide (PP) to a protein meal and to hypoglycemia was compared preoperatively, after EGV and after truncal vagotomy (TV). EGV had no detectable effect on PP secretion under basal or stimulated conditions. After TV, the PP response to a protein meal was reduced and totally abolished in response to insulin hypoglycemia when compared to preoperative results. This indicates that direct innervation of the pancreas is of little importance for the release of PP but that vagal innervation of the stomach is important provided that the vagal fibers to PP cells all pass through these extragastric vagal branches.