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H van Urk

Publications and source records attributed to H van Urk.

At least 73 records · Page 4Linked to original sources
PubMed1995

Subfascial endoscopic ligation in the treatment of incompetent perforating veins.

OBJECTIVES: To assess the technique of subfascial endoscopic ligation of incompetent perforatory veins by use of a mediastinoscope. DESIGN: Prospective open clinic study. SETTING: Two Departments of Surgery. MATERIALS AND METHODS: Thirty-eight consecutive patients (40 legs) with recurrent or protracted venous ulceration of the lower leg were treated. Through a short, transverse incision of the skin and fascia in the proximal 1/3 of the lower leg a mediastinoscope (length 18 cm, diameter 12 mm) is inserted after which the perforating veins are ligated by haemoclips under direct vision. MAIN RESULTS: All legs showed signs of incompetent perforating veins by clinical examination, confirmed with continuous wave ultrasonography and in 31 legs there was associated deep vein incompetence. Sixteen patients had active ulceration at the moment of operation and 22 had a history of recent or recurrent ulceration. One patient developed an inflammatory reaction at the wound and in two legs a subfascial infection occurred, necessitating surgical drainage. No postoperative mortality was seen. All 16 ulcers healed within 2 months (mean: 34 days; range: 21-55 days). During a mean follow-up of 3.9 (range: 2-5) years only one out of 38 patients (2.5%) developed a recurrent ulcer. CONCLUSIONS: Subfascial endoscopic ligation of incompetent perforating veins by use of a mediastinoscope is a relatively simple technique with a low postoperative complication rate and a low recurrent ulcer rate which makes it a valuable method for treating incompetent perforating veins.

Bandages↗
PubMed1994

Safety of dobutamine-atropine stress echocardiography in patients with suspected or proven coronary artery disease.

The purpose of this study was to establish the safety of high-dose dobutamine-atropine stress echocardiography in patients with suspected or proven coronary artery disease. Six hundred fifty consecutive examinations were completed. Mean age of patients was 61 years; 300 had a previous myocardial infarction. Heart rate increased from 73 to 129 beats/min during stress testing, blood pressure did not change significantly (from 140/81 to 150/80 mm Hg). Atropine was added to dobutamine in 239 patients when no ischemia was induced with dobutamine alone and the peak heart rate was < 85% of the theoretical maximal heart rate. Atropine was more frequently administered to patients taking beta blockers (77 vs 27%, p < 0.001). New wall motion abnormalities developed in 243 patients (37%). Significant or symptomatic cardiac tachyarrhythmias, or both, developed during 24 examinations: 1 patient developed ventricular fibrillation, 3 patients developed sustained ventricular tachycardia, 12 patients experienced nonsustained ventricular tachycardia (< 10 beats) and 8 patients had paroxysmal atrial fibrillation. Cardiac arrhythmias were more frequent in patients with a history of ventricular arrhythmias (ventricular tachycardia and fibrillation) (odds ratio 9.9, 2.0 to 45) or left ventricular dysfunction at rest (wall motion score > 1.12) (odds ratio 2.9, 1.1-7.6), but not associated with atropine addition. No death or myocardial infarction occurred. The full dose was not given to 13 patients despite absence of signs or markers of ischemia for limiting side effect, yielding an overall feasibility of the stress test of 98%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Increase in copy number of an integrated vector during continuous culture of Hansenula polymorpha expressing functional human haemoglobin.

Recombinant human haemoglobin A (rHbA) was produced by a leucine-requiring strain of Hansenula polymorpha which had been transformed with an integration vector containing the Saccharomyces cerevisiae LEU2 gene and cDNAs for the expression of alpha and beta globin each driven by the H. polymorpha MOX promoter. After 40 generations in a chemostat it was found that the integrated vector had become amplified in the host strain. In some cases this led to an increase in LEU2 gene dosage, but a loss of globin expression cassettes. In other cases the globin gene dosage also increased. These changes coincided with an increase in rHbA production in the culture, which was reversed when the dilution rate was increased. Isolates from a chemostat culture producing elevated levels of rHbA were grown in fed-batch fermentations, resulting in higher productivities than when inoculated with the parent strain. The rHbA produced was purified and characterized. Oxygen binding studies and electrospray mass spectrometry showed that the rHbA had been processed and assembled correctly, and behaved as a fully functional co-operative tetramer.

Genetic Vectors↗
PubMed1994

Temporal averaging for quantification of lumen dimensions in intravascular ultrasound images.

Quantitative analysis of arterial dimensions from high frequency intravascular ultrasound images (30 MHz) may be hampered by strong blood scattering. Replacement of blood by saline is one method to provide a clear view of the arterial lumen; another method is that of temporal averaging of successive ultrasound images. The accuracy of this latter method was tested by comparing the lumen area measurements on the temporal-averaged image, with the data of the same cross-section obtained from the single-frame and saline-filled images. The mean lumen area measured on the temporal-averaged images was similar to that measured on the single-frame images (mean difference: -0.02 +2- 1.16 mm2; p = ns). The mean lumen area of the saline-filled images was 8% larger than the values obtained from the temporal-averaged and single-frame images (mean difference: -1.14 +/- 0.85 mm2, p < 0.05), probably due to the difference in sound velocity between saline and blood. Intraobserver variation in the averaging method were 2.4 times smaller than the measurements of the single-frame images and close to the data obtained by saline injection (variation coefficient: single-frame: 8.8%; temporal-averaged: 3.6%; saline-filled: 2.9%). It is concluded that analysis from temporal-averaged images is more efficient, enabling accurate and reproducible measurement of the luminal dimensions from images containing blood scattering echoes. This technique is suitable to replace the laborious saline injection method and facilitates off-line quantitative analysis.

Aged↗
PubMed1994

Dobutamine-atropine stress echocardiography for assessment of perioperative and late cardiac risk in patients undergoing major vascular surgery.

OBJECTIVE: To determine the value of dobutamine-atropine stress echocardiography and clinical variables to predict perioperative and late cardiac events in patients scheduled for elective major non-cardiac vascular surgery. DESIGN: Blinded prospective study. PATIENTS: Patients (n = 187 mean age 69 yrs). MEASUREMENTS: Dobutamine-atropine stress test was performed preoperatively. Results were not used for clinical management. The clinical risk profile was evaluated by Detsky's score. RESULTS: Technically adequate images were obtained in 185/187 patients, one major complication occurred (ventricular fibrillation) and four tests were prematurely stopped due to side effects. Data from 181 patients were analysed. The stress test was positive (new or worsened wall motion abnormality) in 56/181 patients. Perioperative cardiac events were: five fatal myocardial infarctions, three non-fatal myocardial infarctions, nine unstable angina pectoris and one pulmonary edema. All patients with a cardiac event had a positive stress test (18/56). No event occurred in patients with a negative stress test. By multivariate analysis only a new wall motion abnormality during the stress test (odds ratio 45.0, 6-369) was a significant predictor of cardiac events. Patients (n = 154) were followed after operation for 16 +/- 9 months. Twenty-four cardiac events occurred in 21 patients: six fatal myocardial infarctions, three non-fatal myocardial infarctions, six unstable angina pectoris, three ventricular arrhythmias and six congestive heart failures. The stress echo was positive in 19/21 patients with late cardiac events. The cardiac events correlated by multivariate analysis with a history of myocardial infarction (odds ratio 9.6, 1.9-47.7) and new wall motion abnormalities (odds ratio 6.2, 1.5-25.1). CONCLUSION: Dobutamine-atropine stress echocardiography is a relatively safe and useful test to identify patients at risk of perioperative and late postoperative cardiac events.

Aged↗
PubMed1994

A new "closed" in situ vein bypass technique.

AIM: We have developed a new closed technique using a co-axial catheter embolisation system for intraoperative coil embolisation of the side branches of in situ vein bypass grafts in order to avoid long skin incisions. TECHNIQUE: After completion of the proximal anastomosis, disruption of the valves and completion of the distal anastomosis, the catheter is introduced via a proximal side branch of the greater saphenous vein. Under fluoroscopic control the side branches are identified, selectively catheterised and an embolisation coil is positioned in each side branch. PATIENTS: In 14 patients (eight men, six women), 16 in situ bypasses were performed (12 below knee femoro-popliteal, four femoro-crural). RESULTS: Once mastered the embolisation procedure took less than 1 hour. In four cases persistent arteriovenous fistulae had to be treated in the postoperative period. Two major wound complications occurred and there were three early failures. One late failure occurred due to a rupture of the venous bypass 6 weeks postoperatively. The remaining 12 bypasses are patent, with a median follow-up of 16 (3-26) months. CONCLUSION: These preliminary results suggest that the "closed" technique is feasible and that long term occlusion of AV-fistulae can be achieved without ligation via incisions.

Arteriovenous Shunt, Surgical↗
PubMed1993

[Good results of subfascial endoscopy as treatment of communicating vein insufficiency].

Incompetent communicating or perforating veins are often responsible for recurrent varicose veins with skin changes at the lower leg, especially in the postthrombotic syndrome. Subcutaneous and subfascial surgical explorations carry a 35% complication rate. We used a new endoscopic technique to locate and ligate communicating veins with the objective to decrease this complication rate. Through a short skin incision on the anteromedial side of the proximal 1/3 of the lower leg the fascia is incised over 2 cm and the subfascial space opened by finger dissection. A mediastinoscope (length 18 cm; diameter 12 mm) is inserted and pushed down beneath the fascia to the level of the malleolus. Under direct vision the communicating veins crossing this space are located and ligated with haemoclips. In 48 patients, 15 male and 33 female, with a mean age of 53 (22-73) years, 54 legs were treated: 40 legs showed recurrent varicose veins, due to incompetent communicating veins with severe skin changes and ulcers, and 14 had primary varicosis. All patients complained of fatigue and pain. In 49 legs (44 patients) relief of preoperative complaints was obtained and in 5 (4 patients) there was no change. Two indurated wounds and 1 dehiscent wound were treated conservatively. One patient, operated on both legs, developed a severe subfascial infection on both sides necessitating a reintervention. The advantages of the subfascial endoscopic technique, a fast operative procedure, fewer postoperative wound infections (9.3%), a good cosmetic effect, and a low (2.5% after 3.8 years) recurrent ulcer rate make it a valuable new method for treating incompetent communicating veins.

Adult↗
PubMed1993

Intravascular ultrasonography before and after intervention: in vivo comparison with angiography.

PURPOSE: To compare the additional capacity of intravascular ultrasonography versus angiography to assess morphologic features and lumen dimension, 37 patients undergoing vascular intervention of the common iliac or superficial femoral artery were studied. A total of 181 ultrasonic cross sections were analyzed (94 before and 87 after intervention). METHODS AND RESULTS: Before intervention intravascular ultrasonography distinguished normal cross sections (n = 17) from cross sections with a lesion (n = 77): soft (51%) versus hard (31%) lesions, and eccentric (75%) versus concentric (7%) lesions. After intervention intravascular ultrasonography documented dissection (43%), plaque rupture (10%), and internal elastic lamina rupture (8%). A good correlation between ultrasonography and angiography was found for the recognition of eccentric or concentric lesions and dissections. The degree of stenosis was assessed semiquantitatively by visual estimation of the degree of luminal narrowing from the angiograms and intravascular ultrasonic images and was categorized into four classes: (1) normal, (2) less than 50% stenosis, (3) 50% to 90% stenosis, and (4) greater than 90% stenosis. Intravascular ultrasonographic assessment of stenosis was in agreement with angiography in 78% of cases and showed more severe lesions in 22% before intervention. Similar data were observed after intervention, with 72% of results being in agreement and 28% of cases showing more severe lesions. The degree of stenosis was also quantitatively evaluated by computer-aided analysis of the intravascular ultrasonic images. The semiquantitative analysis by intravascular ultrasonography corresponded well with the quantitative analysis done by the computer-aided system. When both echography and angiography suggested that arteries were normal, quantitative intravascular ultrasonography identified lesions that occupied an average of 18% of the cross-sectional area of the vessel. CONCLUSIONS: This in vivo study shows that intravascular ultrasonography is capable of documenting detailed morphologic features. Semiquantitative ultrasonic data correlate closely with those of angiography, albeit stenoses were assessed as more severe on ultrasonography.

Aged↗
PubMed1993

Dobutamine stress echocardiography for assessment of perioperative cardiac risk in patients undergoing major vascular surgery.

BACKGROUND: The purpose of this study was to determine the predictive value of dobutamine stress echocardiography for perioperative cardiac events in patients scheduled for elective major noncardiac vascular surgery. METHODS AND RESULTS: Patients (n = 136; mean age, 68 years) unable to exercise underwent a dobutamine stress test before surgery (incremental dobutamine infusion [10-40 micrograms.kg-1.min-1] continued with atropine [0.25-1 mg i.v.] if necessary to achieve 85% of the age-predicted maximal heart rate without symptoms or signs of ischemia). The clinical risk profile was evaluated by Detsky's modification of Goldman's risk factor analysis. Echocardiographic images were evaluated by two observers blinded to the clinical data of the patients, and results of the test were not used for clinical decision making. Technically adequate images were obtained in 134 of 136 patients, one major complication occurred (ventricular fibrillation), and three tests were discontinued prematurely because of side effects. Finally, data from 131 patients were analyzed with univariate and multivariate methods. The dobutamine stress test was positive (new or worsened wall motion abnormality) in 35 of 131 patients. In the postoperative period, five patients died of myocardial infarction, nine patients had unstable angina, and one patient developed pulmonary edema. All patients with cardiac complications (15 patients) had a positive dobutamine stress test. No cardiac events occurred in patients with negative tests. Five patients with a technically inadequate or prematurely stopped test were operated on without complications. By multivariate analysis (logistic regression), only age > 70 years and new wall motion abnormalities during the dobutamine test were significant predictors of perioperative cardiac events. CONCLUSIONS: Dobutamine stress echocardiography is a feasible, safe, and useful method for identifying patients at high or low risk of perioperative cardiac events. The test yields additional information, beyond that provided by clinical variables, in patients who are scheduled for major noncardiac vascular surgery.

Adult↗
PubMed1993

Octreotide scintigraphy for the detection of paragangliomas.

Paragangliomas have neuroendocrine characteristics. We previously described successful in vivo visualization of various tumors of neuroendocrine origin after injection of the radiolabeled somatostatin analogue octreotide. In this study, we report the results of 111In-octreotide scintigraphy in 34 patients referred because of known paragangliomas or in whom a paraganglioma was suspected and compared the results of octreotide scintigraphy with the outcomes of other imaging techniques used in the diagnosis or follow-up of these patients. Fifty of 53 (94%) known localizations in 25 patients with paragangliomas were visualized. In two patients, three localizations were missed during octreotide scintigraphy. Unexpected additional paraganglioma sites, not detected or not investigated with conventional imaging techniques, were found in 9 of 25 patients (36%) with known paragangliomas. In four of them, the supposed tumor localizations were thereafter also demonstrated with other imaging modalities. In eight of nine patients who were referred because of symptoms consistent with paraganglioma or follow-up after surgical removal of a paraganglioma, neither routine imaging nor octreotide scintigraphy revealed any abnormalities indicative of paraganglioma. We conclude that: (1) virtually all paragangliomas can be visualized using in vivo 111In-octreotide scintigraphy and (2) because conventional imaging is usually limited to the site where a paraganglioma is clinically suspected, octreotide scintigraphy, because of the information it provides on potential tumor sites in the whole body, may be useful in detecting multicentricity or metastases in patients with paraganglioma.

Abdominal Neoplasms↗
PubMed1992

Winner of the ESVS Prize 1991. European Prospective Randomised Multi-centre Axillo-bifemoral Trial.

In vitro and in vivo studies revealed significantly better haemodynamic properties for a newly designed axillo-bifemoral bypass graft, with a flowsplitter at the bifurcation. In order to analyse the clinical relevance of these improved haemodynamic properties a prospective randomised clinical trial was performed. The patency rates of two different axillo-bifemoral bypass grafts, differing only in the configuration of the bifurcation: one with a contralateral branch at an angle of 90 degrees and one with a flowsplitter, were analysed. In 19 centres, 117 patients were randomised, 59 receiving a prosthesis with a flowsplitter, and 58 a prosthesis with a 90 degrees bifurcation. Indications and risk factors were equally distributed in both groups. Final analysis after 3 years with a mean follow-up of 12 months (range 3-36 months) showed that the prosthesis with a flowsplitter had a significantly better patency rate after 2 years of 84% compared to the patency rate of the prosthesis with a 90 degrees-angled bifurcation of 38% (log-rank test, p less than 0.0001). These data were not significantly influenced by the indication for the operation, associated risk factors (e.g. diabetes mellitus, hypertension or myocardial infarction), outflow tract or anti-coagulant therapy. Other endpoints such as death and graft infection did not differ significantly.

Aged↗
PubMed1992

Effect of balloon angioplasty on femoral artery evaluated with intravascular ultrasound imaging.

BACKGROUND: Intravascular ultrasound was used to assess the immediate effect of balloon angioplasty on the superficial femoral artery. METHODS AND RESULTS: In 16 consecutive patients, corresponding ultrasonic cross sections (n = 72) before and after balloon angioplasty were qualitatively and quantitatively analyzed. The qualitative data were compared with angiographic findings. Before intervention, the angiographically demonstrated obstructive lesions were confirmed by intravascular ultrasound. Ultrasound enabled discrimination between soft (n = 43) and hard (n = 29) lesions, as well as between eccentric (n = 57) and concentric (n = 15) lesions. After balloon angioplasty, the presence of a dissection assessed angiographically in 14 patients was confirmed by intravascular ultrasound. Additional morphological information provided by ultrasound included plaque rupture in 14 patients and internal lamina rupture in six patients. Quantitative ultrasound data revealed an increase in free lumen area from 9.7 +/- 4.7 to 18.3 +/- 7.0 mm2 (p less than or equal to 0.01), an increase in minimal lumen diameter from 2.8 +/- 0.7 to 3.6 +/- 1.2 mm (p less than or equal to 0.01), and an increase in media-bounded area from 21.7 +/- 5.4 to 28.3 +/- 5.8 mm2 (p less than or equal to 0.01). The lesion area for the majority of cases (n = 32) remained unchanged (13.0 +/- 4.9 mm2 versus 12.9 +/- 4.6 mm2), or the lesion disappeared partially (from 9.1 +/- 0.9 to 4.3 +/- 1.4 mm2, n = 4, p less than or equal to 0.01) or totally (from 10.1 +/- 4.2 to 0 mm2, n = 6). Stretching of the arterial wall was further evidenced by medial thinning from 0.55 +/- 0.19 to 0.34 +/- 0.11 mm (p less than or equal to 0.01). CONCLUSIONS: Luminal enlargement by balloon dilatation is achieved primarily by overstretching the arterial wall, with the lesion volume remaining practically unchanged. Overstretching is accompanied almost always by dissection and plaque rupture and occasionally by an internal lamina rupture.

Aged↗
PubMed1992

Extrinsic compression of the superficial femoral artery at the adductor canal: evaluation with intravascular sonography.

Balloon angioplasty of the superficial femoral artery was performed in 15 consecutive patients with obstructive atherosclerotic disease near the adductor hiatus. After angioplasty, extrinsic compression of the femoral artery at the adductor hiatus was shown on intravascular sonograms in five patients (33%). In retrospect, this inward deformation of the arterial wall was thought to be present in only one case before angioplasty. After angioplasty, intravascular sonography was used successfully to differentiate between residual stenosis due to residual plaque and that due to extrinsic compression of the wall of the femoral artery near the adductor hiatus. We conclude that intravascular sonography may be a useful adjunct to angiography for determining the cause of residual stenosis.

Angioplasty, Balloon↗
PubMed1992

Intraoperative angiography and endovascular ultrasound imaging.

Endovascular ultrasound imaging is a new technique that can be used to monitor intraoperatively the effects of balloon angioplasty or to inspect the quality of vascular reconstruction, such as endarterectomy or bypass surgery. The technique is based on high frequency ultrasonic imaging (30-40 MHz) using a rotating single element transducer mounted in an 8F catheter tip, providing 360 degrees cross-sectional real time images. The clinical application is based on the high correlation between the ultrasonic images and the histological characteristics of the corresponding vessel wall tissue and lumen geometry, as has been established in previous in vitro studies. Endovascular ultrasound assessment of percutaneous angioplasty procedures or intraoperative vascular reconstruction has become an adjunct to angiographic and/or angioscopic monitoring.

Angiography↗
PubMed1991

Assessment of medial thinning in atherosclerosis by intravascular ultrasound.

This study investigated the in vitro (40 MHz) and in vivo (30 MHz) feasibility of intravascular ultrasound to document the influence of atherosclerotic lesions on the typical 3-layered appearance of muscular arteries. The in vitro images of 39 arteries were compared with the corresponding histologic sections. Media and lesion thickness were measured at the areas of minimal and maximal lesion thickness. The median media thickness was 0.8 mm in the absence of a lesion, decreasing to 0.3 mm in the area of maximal atherosclerosis. The ultrasonic data correlated closely with histologic measurements (0.6 and 0.3 mm, respectively). The in vivo study was performed in 29 patients undergoing coronary or peripheral vascular procedures. A total of 150 still-frames were selected for quantitative analysis. The median media thickness was 0.6 mm in the absence of a lesion, decreasing to 0.1 mm in the area with maximal atherosclerosis. This study revealed that intravascular ultrasound imaging accurately determines that media thickness of muscular arteries is inversely related to lesion thickness. In vitro data, verified with histology, can be translated to humans in vivo.

Arteries↗