Endovascular stroke treatment does not preclude high thrombolysis rates

BACKGROUND AND PURPOSE

In 1995 intravenous recombinant tissue plasminogen activator (IVRTPA) was the first reperfusion therapy to be approved in patients with acute ischaemic stroke (AIS). The significance and impact of IVRTPA in times of modern endovascular stroke treatment (EST) were analysed in a German academic stroke centre.

METHODS

A retrospective observational cohort analysis of 1034 patients with suspected AIS presenting at the emergency department in 2014 was performed. Patients were evaluated for baseline characteristics, reperfusion procedures, IVRTPA eligibility, clinical outcome, symptomatic intracranial haemorrhage (sICH) and mortality. Data acquisition was part of an investigator-initiated, prospective and blinded end-point registry.

RESULTS

In 718 (69%) patients the diagnosis of symptomatic AIS was confirmed. 419 (58%) patients presented within 4.5 h of symptom onset and of those 260 (62%) received reperfusion therapy (IVRTPA alone, n = 183; combination or bridging therapy, n = 60; EST alone, n = 17). Subtracting cases with absolute contraindications for IVRTPA resulted in an effective thrombolysis rate of 82%. sICH occurred in two patients treated with IVRTPA alone (1.1%). The median door-to-needle interval was 30 min. Fifty (17%) non-EST eligible AIS patients presenting within 4.5 h without absolute contraindications did not receive IVRTPA mainly due to mild or regressive symptoms. Most of these untreated IVRTPA eligible patients (82%) were discharged with a good clinical outcome (modified Rankin Scale ≤ 2).

CONCLUSIONS

Intravenous recombinant tissue plasminogen activator remains the most frequently applied reperfusion therapy in AIS patients presenting within 4.5 h of onset in a tertiary stroke centre. An effective thrombolysis rate of over 80% can be achieved without increased rates of sICH.

Clinical Impact of Ventilation Duration in Patients with Stroke Undergoing Interventional Treatment under General Anesthesia: The Shorter the Better?

BACKGROUND AND PURPOSE

Whether general anesthesia for neurothrombectomy in patients with ischemic stroke has a negative impact on clinical outcome is currently under discussion. We investigated the impact of early extubation and ventilation duration in a cohort that underwent thrombectomy under general anesthesia.

MATERIALS AND METHODS

We analyzed 103 consecutive patients from a prospective stroke registry. They met the following criteria: CTA-proved large-vessel occlusion in the anterior circulation, ASPECTS above 6 on presenting cranial CT, revascularization by thrombectomy with the patient under general anesthesia within 6 hours after onset of symptoms, and available functional outcome (mRS) 90 days after onset.

RESULTS

The mean ventilation time was 128.07 ± 265.51 hours (median, 18.5 hours; range, 1-1244.7 hours). Prolonged ventilation was associated with pneumonia during hospitalization and unfavorable functional outcome (mRS ≥3) and death at follow-up (Mann-Whitney U test; P ≤ .001). According to receiver operating characteristic analysis, a cutoff after 24 hours predicted unfavorable functional outcome with a sensitivity and specificity of 60% and 78%, respectively. Our results imply that delayed extubation was not associated with a less favorable clinical outcome compared with immediate extubation after the procedure.

CONCLUSIONS

Short ventilation times are associated with a lower pneumonia rate and more favorable clinical outcome. Cautious interpretation of our data implies that whether patients are extubated immediately after the procedure is irrelevant for clinical outcome as long as ventilation does not exceed 24 hours.

[Reconstruction of the aortic bifurcation: endovascular aortic repair (EVAR) and alternatives]

CLINICAL ISSUE

Diseases of the aortic bifurcation, whether stenotic or dilating, are mostly a manifestation of arteriosclerosis. If only stenosis is present aortic bifurcation disease is equivalent to a certain form of peripheral arterial occlusive disease (PAOD) characterized by the specific anatomical location. Aneurysmal disease and PAOD of the aortic bifurcation may occur together and men older than 60 years are particularly affected. The main symptom of aortic bifurcation PAOD is bilateral claudication whereas aneurysmal disease of the aortic bifurcation is frequently asymptomatic.

STANDARD TREATMENT

Therapy of stenotic and aneurysmal disease of the aortic bifurcation depends on the degree of the disease. Simple lesions, such as isolated stenoses of the aortic bifurcation or unilateral occlusions of the common iliac artery extending to the aortic bifurcation have been treated endoluminally for many years. Current standard treatment of complex aortic bifurcation disease is open surgery with implantation of an aortobifemoral bypass graft. However, recent developments in less invasive endoluminal methods have shifted the indications more towards endoluminal therapy. This development is mirrored by the international TransAtlantic Inter-Society Consensus (TASC) II recommendations from 2007 and even more clearly by the current national S3 guidelines on PAOD (http://www.degir.de/site/leitlinien). It is stated that in complex aortic bifurcation disease, such as bilateral occlusions of the common iliac arteries (TASC C lesions) or diffuse aortobiiliac stenoses and occlusions (TASC D lesions), endoluminal therapy may be considered as an alternative to open surgery. Therapy of aneurysmal disease of the aortic bifurcation depends on the pathoanatomical conditions. Prerequisite for endoluminal therapy is a sufficient landing zone for the prostheses. If this prerequisite is fulfilled endoluminal therapy is very likely comparable to open surgery with regard to technical and clinical success. Long-term results are still lacking.

DIAGNOSTIC WORK-UP

For the decision on the type of therapy and the sizing of the prostheses, thin-slice (≤ 3 mm slice thickness) computed tomography angiography (CTA) of the abdominal aorta and the iliac arteries including multiplanar reconstruction in the sagittal and coronal plane are sufficient. The inguinal arteries have to be included in the CTA volume.

PERFORMANCE

Compared to open surgery, endoluminal therapy of stenotic and aneurysmal disease of the aortic bifurcation has the advantage of reduced invasiveness. Hence patient recovery and hospital stay may be shorter.

ACHIEVEMENTS

Therapy of stenotic and aneurysmal disease of the aortic bifurcation is changing. Standard treatment of complex aortic bifurcation disease, which is open surgery is extended by the possibilities of endoluminal methods. Due to improvements in current endoluminal systems and development of new techniques, the importance of endoluminal therapy will further increase.

PRACTICAL RECOMMENDATIONS

Good quality of the preinterventional CTA is important for planning the intervention. In order for a radiologist to offer endoluminal therapy, besides knowledge of interventional skills a close cooperation with clinical colleagues, in particular vascular surgeons is mandatory.

[Local lysis with alteplase for the treatment of acute embolic leg ischemia following the use of the duett closure device: preliminary results]

PURPOSE

To analyze retrospectively the result of the alteplase lysis therapy of embolic complications following the use of the Duett closure device.

METHODS AND MATERIALS

For 3.5 years, the Duett closure device was used in 1,398 angiographies to close the femoral puncture site. The Duett device consists of a balloon and a liquid procoagulant containing collagen and thrombin, which is injected into the puncture tract under endovascular balloon protection of the arterial puncture site. In 9 patients (0.64 %), the procoagulant was incidentally injected into the femoral artery causing acute leg ischemia. Eight patients received local lysis therapy with alteplase via a contralateral femoral access. One patient underwent surgery. On average, 21 mg alteplase (4 - 35 mg) were administered within 14 h (4 - 21 h). The course of the lysis was followed angiographically and clinically. All patients were interviewed by telephone 23 months (4 - 35 months) later.

RESULTS

In 3 patients, lysis was complete. In 5 patients, only little thrombotic material remained. In all patients, symptoms of ischemia resolved completely within the first hours after initiation of lysis. In 5 cases, bleeding occurred at the puncture site closed with the Duett device during lysis, including development of a false aneurysm in 2 cases. Complications led to premature termination (n = 2) or interruption of the lysis (n = 3). All complications were treated conservatively. Clinically, long-term sequelae were paresthesia and hypoesthesia in the lower leg and foot in 2 patients treated with lysis, and in the patient who underwent surgery.

CONCLUSION

Very rarely occurring embolic complications after use of the Duett closure device can be effectively treated with alteplase lysis. A high rate of complications is to be expected at the puncture site closed with the Duett device.

[A novel hirudin coating of vascular endoprostheses: experimental results]

PURPOSE

Does hirudin coating improve the patency of iliac artery endoprostheses in comparison to non-hirudin-coated endoprostheses?

MATERIALS AND METHODS

Nitinol stents and stentgrafts covered with polytetrafluoroethylene (PTFE) were coated with the polymer polyamino-p-xylylene-co-poly-p-xylylene using chemical vapor deposition (CVD) technique. Hirudin was covalently bound to the surface of the endoprostheses via the amino-group. External factors (mounting of the prosthesis, sterilization, storage time and temperature, release) affecting the hirudin activity were evaluated in vitro. Five types of prostheses were compared in vivo: (1) plain and (2) CVD- and hirudin-coated stents; (3) plain, (4) CVD-coated, and (5) CVD- and hirudin-coated PTFE-stentgrafts. In 20 sheep, 16 protheses of each type were inserted in arteries pretreated with a Fogarty maneuver. The animals were followed for either 1 (n = 10) or 6 (n = 10) months. Immediately after implantation and after 1, 3, and 6 months, intravascular ultrasound (IVUS) and angiography were performed. The vascular specimens were analyzed histologically.

RESULTS

Within 10 weeks, the hirudin activity of coated stents dropped 60 % due to external factors; the activity of coated PTFE stentgrafts dropped 20 %. After 1, 3, and 6 months, IVUS and histology revealed a significantly reduced patency of the hirudin-coated stentgrafts compared to the other prostheses. Only IVUS showed a significantly reduced patency of hirudin coated stents after 1 and 3 months compared to plain and CVD-coated PTFE-stentgrafts. The reduced patency was caused by neointimal hyperplasia.

CONCLUSIONS

In an experimental setting, hirudin coating did not improve the patency of vascular endoprostheses.

[Selective CT mesentericography in the diagnostics of obscure overt intestinal bleeding: preliminary results]

AIM

To evaluate intra-arterial CT mesentericography (CTM) in the diagnostics of severe obscure overt intestinal bleeding in comparison with conventional mesentericography (MG) and surgery.

METHODS

In 8 patients (23 - 82 years, mean 59 years), CTM was performed via the catheter left in the superior mesenteric artery after MG to detect the source of bleeding. Early and late-phase spiral CT scans were acquired after administration of contrast medium. Active bleeding was considered to be present if extravasation of contrast medium into the bowel was found. The results of MG and CTM were compared with the results of surgery.

RESULTS

With MG active bleeding was found in one patient, with CTM in five patients. In three patients, both MG and CTM were negative. Six patients underwent surgery. Five cases of bleeding detected with CTM were confirmed by surgery. In one case, bleeding found with CTM was not confirmed by surgery. One patient underwent surgery although all imaging procedures were negative. The source of bleeding remained unknown. Surgically, the site of bleeding was located in the jejunum in 3 patients (jejunitis, jejunal ulcers, carcinoid), one patient had a diverticulum in the ascending colon. The colonic bleeding site was correctly localized with CTM, whereas the small bowel bleeding could only roughly be assigned to the proximal or distal jejunum or jejunoileal transition area.

CONCLUSION

Preliminary results indicate that selective CTM is superior to MG in the evaluation of severe obscure overt intestinal bleeding.

[Low-grade malignant peripheral nerve sheath tumor of the neck soft tissues]

BACKGROUND

Malignant Peripheral Nerve Sheath Tumours (MPNST) either grow sporadically, after radiation or chemotherapy respectively. In many cases they are associated with Neurofibromatosis I. Because of the multiform histologic picture they are often difficult to differentiate from other soft tissue tumours.

PATIENT

We present the case of a sporadic MPNST which developed from the vagus nerve of a 39-year-old patient following radiation of the neck 7 years before. After complete excision there has been no recurrence up to now.

RESULTS AND CONCLUSIONS

Sporadic MPNST of the head and neck are comparatively rare. With regard to the strong association with Neurofibromatosis I and the difficult differential diagnosis to other soft tissue tumours the emphasis should be put on excluding further manifestations of Neurofibromatosis I and of secondary tumours.

[Changes in the region and the proximal aneurysm neck after endovascular repair of infrarenal aortic aneurysms]

PURPOSE

To analyze short and mid-term changes of the proximal aneurysm neck and to evaluate renal function after endovascular repair of infrarenal abdominal aortic aneurysms.

MATERIALS AND METHODS

24 of 29 patients, who were treated endoluminally with the bifurcated Vanguard Stent graft between 1997 and 1999 underwent spiral CT follow-up after 1, 3, 6 and every 12 months. Mean follow-up period was 10.5 months (3-32 months). Follow-up included spiral CT scanning. The aortic diameter as well as cross-sectional area were measured. Stent graft position and renal perfusion were checked by spiral CT. Serum creatinine levels were determined preoperatively and during follow-up.

RESULTS

Supra- and infrarenal aortic sizes remained stable. No correlation to the distance between the stent-graft and the renal arteries was observed. Caudal migration of the stent-graft with an average of 6.5 (3-15) mm occurred in 13 patients. Cranial migration was observed in 3 patients. Uncovered stent wires partially overlapped at least one renal artery in 18 patients. No renal infarction occurred. No significant increase of the serum creatinine level was found.

CONCLUSION

The risk of proximal endoleakage due to post-interventional dilatation of the aorta abdominalis seems to be low. Insufficient stent graft fixation requires a wide distance between the proximal end of the stent graft and the aneurysm. In the mid-term uncovered stent wires overlapping the renal arteries had no relevant influence on renal function.

Recanalization of thrombosed dialysis access with use of a rotating mini-pigtail catheter: follow-up study

PURPOSE

To evaluate the feasibility, efficacy, and safety of mechanical thrombectomy of occluded dialysis access with use of a rotating mini-pigtail catheter.

MATERIALS AND METHODS

Thrombus was fragmented by mechanical action of the rotating pigtail tip (5-mm diameter), while the guide wire exited a sidehole at the pigtail curvature and served as a fixed rotation axis. Twenty-six procedures were performed in 22 patients (12 men, 10 women; mean age, 55.5 years). Native fistulas were treated in 15 instances, polytetrafluoroethylene (PTFE) grafts were treated in 11 instances. Average occlusion time was 20 hours +/- 13 (range, 5-46 hours), average occlusion length was 25.6 cm +/- 10.1 (range, 6-45 cm). Thrombus fragmentation was followed by balloon angioplasty of underlying stenoses.

RESULTS

In all 26 procedures, the dialysis access was successfully declotted with subsequent dialysis using the access (clinical success rate, 100%). Handling of the mini-pigtail catheter was simple and rapid, regardless of whether a graft or a native fistula was treated. Average duration of the intervention was 118 minutes +/- 30. Mean primary patency was 165 days +/- 167. Primary patency rate was 82% at 30 days, 65% at 3 months, and 47% at 6 months. There was no evidence of complications due to the thrombus fragmentation procedure.

CONCLUSION

The results suggest that declotting of occluded dialysis grafts and fistulas with the mini-pigtail catheter is as effective and safe as other more established percutaneous therapies. It may serve as an easy-to-handle, low-budget alternative to current thrombectomy devices.

[Endoluminal vascular prostheses]

Endoluminal vascular prostheses that can be implanted by percutaneous routes represent the most recent development in vascular interventional radiology. Various commercially available types of prosthesis are presented and the construction principles and applications are described. At present secure indications for the implantation of endoluminal prostheses are limited to the elimination of aneurysms and arteriovenous fistulae of the large vessels near the trunk in sections that do not cross a joint. The wide use in peripheral occlusive diseases cannot yet be recommended because confirmed data are not available.

[Temporary implantation of a metal stent in Vater's ampulla. Evaluation of early changes of the bile ducts in an animal study]

PURPOSE

Evaluation of temporary stent implantation in the papilla of vater and the subsequent alterations of the bile ducts in a controlled animal study.

MATERIAL AND METHODS

In seven domestic pigs the papilla of vater was stented with a nitinolelastalloy-strecker stent over a period of three days. The microscopic and macroscopic changes of the biliary tract and the serologic parameters were judged.

RESULTS

In three cases a slight widening of the peripheric bile ducts was found. With the exception of a mild elevation of lactate dehydrogenase the serological parameters remained normal. The explantation of the stent two possible in six cases. A thickening of the outer layers of the bile ducts and a low to middle grade injury of the mucosa were found histologically.

CONCLUSION

A temporary stent implantation in the papilla of vater is feasible. The mucosal injuries caused by the temporary stent placement may be fully repairable. The method seems to be suitable for prolonged dilatation of benign stenoses.

Suramin inhibits proliferation of human arterial smooth muscle cells in vitro: potential drug for prevention of restenosis by local drug delivery

PURPOSE

Suramin is known to inhibit proliferation of various tumor cells. This study was performed to investigate the effect of suramin on proliferating human arterial smooth muscle cells (HASMC) and thus to examine its suitability for the prevention of restenosis.

METHOD

Proliferation of HASMC was stimulated with human whole blood serum (HWBS), as well as with platelet-derived growth factor (PDGF) and basic fibroblast growth factor (bFGF). Proliferation was assessed by measuring DNA synthesis and cell viability was assessed by measuring mitochondrial activity.

RESULTS

Suramin exerted a strong attenuating effect on the proliferation stimulators HWBS, PDGF, and bFGF. A suramin concentration of 0.5 mmol/L, which is approximately twice the dosage used for systemic application, was sufficient for complete neutralization of proliferation stimulation by 10% HWBS added to the cell culture medium.

CONCLUSION

The authors' data demonstrate a strong proliferation inhibiting effect of suramin on HASMC in vitro. Because it is known to interact not only with one but with a multitude of relevant growth factors, these results make suramin a most interesting substance for local application for prevention of hyperplastic neointima formation.

Comparison of two stent-grafts with different porosity: in vivo studies in a sheep model

PURPOSE

To compare two stent-grafts with a polyurethane-carbonate (PUC) polymer lining of different pore size and water permeability in the iliac arteries of sheep.

MATERIALS AND METHODS

Two stent-grafts with an inner PUC-lining of normal and low water permeability (normal, 1,200 mL/min/cm2; low, 280 mL/min/cm2; pressure gradient, 20 mm Hg) were implanted in each of 16 sheep. Hoop strength was two times higher in low-permeable than in normal-permeable stent-grafts. Patency was monitored with use of angiography and intravascular ultrasound (IVUS) after 1, 3, and 6 months. The sheep were killed after 1 or 6 months. Specimens were studied histologically. IVUS and histologic data were analyzed statistically.

RESULTS

IVUS measurements showed a wider patent lumen of the low- compared to the normal-permeable prostheses at all time points (P < .03). This is likely due to the greater hoop strength of the low-permeable stent-graft. After 1 month, both types of prostheses demonstrated complete transprosthetic tissue penetration and were covered with neointima and endothelium. The neointimal area was greater in low- than in normal-permeable stent-grafts (1 month, P < .005; 6 months, P < .03).

CONCLUSIONS

Presumably, the higher permeability of the normal-permeable stent-grafts led to the reduced neointimal area by improving transprosthetic capillary ingrowth and endothelialization.

Percutaneous treatment of thrombosed primary arteriovenous hemodialysis access fistulae

BACKGROUND

We reviewed the efficacy of percutaneous intervention in acute thrombotic occlusion of native arteriovenous (AV) fistulae for hemodialysis.

METHODS

Eight-one percutaneous procedures were performed in 54 patients presenting with a clotted native dialysis fistula. There were 60 cases of a long-segment thrombosis of the fistula. In 20 cases, a small thrombus usually caused by an underlying severe stenosis was observed. A proximal arterial occlusion was seen in one case. Treatment depended on clot size and included balloon dilation (N = 20), mechanical thrombectomy with various devices (N = 58), as well as pharmacomechanical thrombolysis (N = 3).

RESULTS

Full restoration of flow was established in 72 cases (88.9%). Early reobstruction within 14 days occurred in eight cases (11.1%). Primary patency rates after a 1-, 3-, 6-, and 12-month period were 74, 63, 52, and 27%, respectively. Overall fistula patency was 75% after 3 months, 65% after 6 months, 51% after 12 months, and 22% after 24 months.

CONCLUSIONS

Acute thrombotic occlusion of native AV fistulae is a major complication of hemodialysis. The results of treatment are believed to be less successful than thrombosis treatment in synthetic grafts. Our results, however, indicate the efficacy of percutaneous treatment in native fistulae, and demonstrate comparable technical results and patency rates.

Magnetic resonance angiography of nonferromagnetic iliac artery stents and stent-grafts: A comparative study in sheep

PURPOSE

To compare nonferromagnetic iliac artery prostheses in their suitability for patency monitoring with magnetic resonance angiography (MRA) using conventional angiography as a reference.

METHODS

In experiment 1, three Memotherm stents were inserted into the iliac arteries of each of six sheep: two "tandem" stents on one side and a single stent on the other side. In experiment 2, four prostheses (normal and low-porosity Corvita stent-grafts, Memotherm, ZA-stent) were inserted in each of 11 sheep. Patency was monitored before and 1, 3, and 6 months after insertion with 3D phase-contrast and two 2D time-of-flight sequences (TOF-1: TR/TE = 18/6.9, TOF-2: 13/2.5) with and without contrast at 1.5 T. On 206 coronal MIP images (72 pre-, 134 post-stenting), three readers analyzed 824 iliac segments (206 x 4) for patency and artifacts.

RESULTS

There was no difference in the number of artifacts between tandem and single iliac Memotherm stents. The ZA-stent induced significantly fewer artifacts than the other prostheses (p < 0.00001). With MRA, patency of the ZA-stent was correctly diagnosed in 88% of cases, which was almost comparable to nonstented iliac segments (95%), patency of the Memotherm stent in 59%, and of the Corvita stent-grafts in 57% and 55%. The TOF-2 sequence with contrast yielded the best images.

CONCLUSION

MRA compatibility of nonferromagnetic prostheses depends strongly on the design of the device. MRA may be used to monitor the patency of iliac ZA-stents, whereas iliac Memotherm stents and Corvita stent-grafts appear to be less suited for follow-up with MRA.

[The Perflex stent, a new balloon-expandable vascular stent: the initial clinical results]

PURPOSE

Clinical evaluation of a newly developed balloon-expandable vascular stent.

METHOD

Participating in a multi-center study our clinic enrolled 12 patients with 15 iliac artery stenoses (Fontaine IIa-III) that were treated with the new stent. Three patients had bilateral stenoses. The mean ankle-brachial index (ABI) at rest was 0.76 +/- 0.25 (+/- 1 standard deviation), the mean ABI after exercise was 0.47 +/- 0.20. Indication for stent insertion was a residual trans-lesion pressure gradient > or = 10 mmHg after balloon angioplasty. Follow-up included clinical examination, measurements of the ABI at rest and after exercise, and colour duplex ultrasound (CDS) on the day of hospital dismissal and 1, 6 and 12 months after stent insertion.

RESULTS

16 stents were placed successfully. One stenosis was treated with two stents. Acute complications did not occur. The Fontaine stage increased by at least one stage in all patients. The ABI at rest rose to 0.91 +/- 0.26, the ABI after exercise to 0.86 +/- 0.29. During follow-up one stent occlusion, one stenosis proximal to a stent, and CDS-findings suggesting restenosis in two further stents were observed.

CONCLUSIONS

It appears that the Perflex stent may be used in the iliac arteries with a success rate similar to other stents. However, this preliminary result has to be confirmed in a larger series and after a longer follow-up.

[Stent placement with real time MRI guidance: initial animal experiment experiences]

PURPOSE

The aim of this study was to test the feasibility of iliac artery stent placement under MR guidance with real-time MR radial scanning in an animal model.

MATERIALS AND METHODS

The experiments were performed on three pigs in a 1.5 T scanner. Radial scanning with a gradient echo technique (TR 8.4 ms, TE 3.6 ms, flip angle 10 degrees) was used. A dedicated backprojector performed the reconstruction of the raw data in real-time. The resulting MR-images were displayed on LCD screens beside the magnet. The sliding window reconstruction technique allowed image acquisition at a frame rate of 16 images per second. MR-compatible self-expanding stents with a diameter of 8 mm and a length of 3 cm were placed into the left iliac artery. Their positions were verified by digital subtraction angiography (DSA) and compared to MRI.

RESULTS

All stents were successfully placed. Stent positions as monitored by real-time MR were identical to those seen on DSA images. The time needed for exact positioning of the scan plane ranged from 15 to 30 minutes. Stent placement itself took 8 minutes on average.

CONCLUSION

Radial scanning applied together with the sliding window reconstruction technique allows placement of stents in iliac arteries under real-time MR control.

[Novel endoluminal stents for the treatment of arterial fistulas and perforations]

PURPOSE

To evaluate the use of polycarbonate-polyurethane (Corethane) stented grafts for the treatment of arteriovenous fistulas and arterial perforations.

MATERIALS AND METHODS

4 patients at the age of 34 to 81 underwent percutaneous insertion of corethane endoluminal grafts. Two patients had an arterial fistula--one iliaco-iliac, one brachio-brachial. Two patients underwent treatment to seal arterial perforations that occurred in the external iliac artery in one and in a femoral venous bypass in another.

RESULTS

In all cases the communication or leakage was sealed by the endograft in place but had to be combined with a detachable balloon in om case. In three patients, a longer follow-up became available, one patient died three weeks after treatment from unrelated causes. While two stent grafts remained open for 15 and 24 months, one patient experienced stent graft occlusion three months after treatment.

CONCLUSIONS

Corethane stent grafts are helpful to seal short-neck arteriovenous fistulas and arterial perforations even under emergency conditions.

[Dose and contrast medium reduction in intravenous digital subtraction angiography by bolus sequence]

PURPOSE

This study evaluates the dose area product, the amount of contrast media and the examination quality of the bolus chasing technique compared to the single-step technique in intravenous digital subtraction angiography.

MATERIAL AND METHODS

15 examinations each with bolus chasing and single-step technique were compared. The dose area product and the volume of contrast media were recorded. The examination quality was scored by two examiners.

RESULTS

With bolus chasing the volume of the administered contrast media could be decreased on average by 114 ml (43%). The difference between the dose area product of bolus chasing (722 dGy/cm2) and single-step technique (1910 dGy/cm2) was significant. No significant difference in examination quality was found.

CONCLUSIONS

The intravenous bolus chasing technique is a practicable method. Compared to the single-step technique it allows a remarkable dose reduction and a low consumption of contrast media without restriction of examination quality.

Single and tandem stents in sheep iliac arteries: is there a difference in patency?

PURPOSE

To compare patency and neointima formation of single and tandem arterial stents.

METHODS

In each of six sheep, two Memotherm nitinol stents (tandem stents) were inserted into the external iliac artery on one side and a single stent into the artery on the opposite side. The size of the iliac lumen was assessed in the proximal, middle, and distal segments of the stents by intravascular ultrasound (IVUS) before, immediately after, and 1 month after implantation when the sheep were killed. Neointimal thickness was determined in the proximal, middle, and distal segments of each stent by light microscopy.

RESULTS

All stents remained patent. There was no significant difference in lumen and neointimal thickness between single and tandem stents. Cranial tandem stents showed a significantly wider lumen and smaller neointimal thickness than caudal tandem stents. In the proximal and distal segments, the lumen of the stents was significantly smaller and the neointimal thickness greater than in the middle segment; differences in neointimal thickness were significant only between the proximal and the middle segment.

CONCLUSION

In an experimental setting, tandem stents did not interfere with one another with regard to patency and neointima formation when compared with a single contralateral stent. Neointimal thickening after stent insertion seems to be inversely related to the original arterial diameter.

Determination of stent stenosis: an in vivo experimental comparison of intravascular ultrasound and angiography with histology

PURPOSE

To compare intravascular ultrasound (IVUS) and angiography with histology in determining the degree of stent stenosis in an in vivo experiment.

METHODS

In 16 sheep, a total of 64 stents were implanted into the external iliac arteries. Two stents were inserted on either side. Patency was followed by angiography and IVUS. Four types of stent were used: two Dacron-covered (Cragg Endopro and heparinized Cragg Endopro) and two noncovered (Cragg and Memotherm stents). Eight animals were killed after 1 month, eight others after 6 months. Histological sections were prepared from the stented vessels. Measurements of the patent and total stent diameters determined by IVUS, angiography, and histology were compared.

RESULTS

Correlation between IVUS and angiography was 0.75, between IVUS and histology 0.77, and between angiography and histology 0.85. A mean stent stenosis of 17 +/- 11% (range 0-51%) was found on angiography, of 10 +/- 11% (0-46%) on IVUS, and of 20 +/- 11% (4%-49%) on histology. In comparison with histology, IVUS underestimated the degree of stenosis by 10 +/- 8%, and angiography underestimated it by 3 +/- 6%. Resolution of IVUS was calculated to be about 0.35 mm and that of angiography to be about 0.15 mm.

CONCLUSION

Under experimental conditions, IVUS was not superior to angiography in determining the degree of stent stenosis in long-segment stenoses of iliac artery stents, when measurements were correlated with histology. Angiography is sufficient for following the patency of iliac artery stents.

Stent placement on fresh venous thrombosis

PURPOSE

To report on the efficacy of fixing fresh venous thrombus to the venous wall by stent placement.

METHODS

Seven patients underwent stenting to treat acute venous thrombosis. In two patients, the hemodialysis fistula was thrombosed with the thrombus extending into the brachial veins. In three patients, the hemodialysis fistula was patent but massive swelling of the ipsilateral arm was caused by proximal venous thrombosis. Two patients presented with iliac venous thrombosis within stented pelvic veins. Stent placement was preceded by other mechanical thrombectomy methods in all cases.

RESULTS

Attachment of thrombus to the venous wall was successful in all cases treated. Acute rethrombosis did not occur. Follow-up patency in dialysis patients was 7.2 +/- 2.1 months. One patient had rethrombosis of the dialysis graft 3 months after primary treatment. Three patients developed restenosis within a mean period of 7.7 months. One shunt remained patent for 10 months with no event of reobstruction during follow-up. In both patients with iliac stent placement, the vein remained patent over a follow-up period of 8 and 12 months respectively.

CONCLUSION

Stenting fresh venous thrombus can achieve immediate venous patency. It may be used as an alternative approach when all other percutaneous methods fail. Frequent restenosis within stented veins limits its use to very selected cases.

Perigraft inflammation due to Dacron-covered stent-grafts in sheep iliac arteries: correlation of MR imaging and histopathologic findings

PURPOSE

To evaluate with magnetic resonance (MR) imaging the inflammatory perigraft response after implantation of Dacron-covered and noncovered arterial endovascular prostheses in sheep.

MATERIALS AND METHODS

Four prosthesis types--two Dacron-covered nitinol stent-grafts (plain and heparin-coated) and two noncovered nitinol stents (Memotherm and Cragg)--were each inserted into the external iliac arteries of eight sheep. MR imaging before and after gadolinium enhancement was performed 5-8 days and 1 month after implantation (before the animals were killed). Macroscopic and microscopic examinations of the vessels were performed, and findings were correlated with those on MR images.

RESULTS

Severe inflammatory perigraft responses to the heparin-coated Dacron-covered stent-grafts were found; MR images demonstrated contrast enhancement and edema. Macroscopic examination showed marked vascular wall thickening and adhesions around the Dacron fabric; microscopic examination showed a pronounced inflammatory foreign-body response. There was a moderate inflammatory response to the plain Dacron-covered stent-grafts and almost no response to noncovered stents.

CONCLUSION

In sheep, MR imaging findings of perigraft soft-tissue edema and contrast enhancement correlated well with histopathologic findings of severe perigraft inflammation due to heparin-coated Dacron-covered stent-grafts.

Color-coded duplex sonography of experimentally induced multilevel stenosis. Evaluation of poststenotic Doppler spectrum

RATIONALE AND OBJECTIVES

The authors evaluated the influence of a proximal arterial stenosis on the poststenotic doppler spectrum of a second, distal stenosis and determined duplex parameters, which permitted description of the severity of the distal stenosis.

METHODS

Moderate (ie, 50%) and severe (ie, 90%) stenoses of the distal aorta and the distal iliac arteries of 10 pigs were created surgically and characterized by angiography. All possible combinations of moderate and severe stenoses were examined. The Doppler spectrum was depicted in the distal iliac and distal femoral arteries of both limbs and analyzed by use of maximum and minimum flow velocity (Vmax, Vmin), acceleration index (modified Handa index), acceleration time, and pulsatility index.

RESULTS

In cases of moderate as well as severe proximal stenosis, acceleration index, acceleration time, and pulsatility index of the poststenotic curve of the distal stenosis were significantly reduced (P < 0.05). Independent of the severity of the proximal stenosis, differentiation of moderate as well as severe distal stenosis was possible (P < 0.05) with these parameters.

CONCLUSIONS

Despite interference of spectral curves in proximal and distal stenosis, duplex sonography enabled the differentiation of experimental aortic iliac multilevel stenosis.

[Sutureless vascular end-to-side anastomosis: an in-vivo test of a percutaneous concept in the animal model]

PURPOSE

To test a percutaneous concept for creation of a sutureless terminolateral vascular anastomosis in vivo.

MATERIAL AND METHOD

By creating sideholes into the middle portion of a stent and a stent graft, both implants could be arranged in a Y-shaped configuration. An arteriovenous shunt was created in 3 sheep between the left carotid artery and the left external jugular vein. A stent graft was partially inserted into the venous lumen. Axial venous patency was restored by placing a stent through the sidehole into the graft lumen from an upstream puncture site. Graft patency was maintained by placing the sidehole of the stent at the bridging point between stent graft and stent with no stent struts crossing. Arterial end-to-end anastomosis was performed by retrograde placement of a stent graft into the arterial lumen. Both anastomoses were connected by a silicone tube.

RESULTS

In all cases, a venous end-to-side anastomosis was created that was blood-tight and safely secured into the vascular lumen.

CONCLUSION

Y-shaped configuration of stent and stent grafts through sideholes allows creation of sutureless end-to-side anastomoses in vivo.

Iliac arteries: plain and heparin-coated Dacron-covered stent-grafts compared with noncovered metal stents--an experimental study

PURPOSE

To compare lumen patency, neointimal thickening, and local inflammatory reaction with noncovered metal stents and plain and heparin-coated Dacron-covered stent-grafts.

MATERIALS AND METHODS

In each of 16 sheep, four prostheses were placed in the iliac arteries: a plain and a heparin-coated Dacron-covered Cragg stent-graft, a noncovered Cragg stent, and a noncovered Memotherm nitinol stent. Two prostheses were inserted in the iliac artery on each side. Patency was monitored with angiography and intravascular ultrasound (US). Eight animals were killed at 1-month follow-up, and the other eight at 6 month follow-up. Neointimal thickening and inflammatory foreign-body reaction to the prostheses were determined macroscopically and with light microscopy.

RESULTS

More than 50% stenosis developed in 10 heparin-coated and three plain Dacron-covered stent-grafts but not in the noncovered stents. Two heparin-coated and one plain Dacron-covered stent-graft occluded completely. Neointimal thickening and inflammatory reaction were severe with the heparin-coated Dacron-covered stent-grafts, were less with the plain Dacron-covered stent-grafts, and were least with the noncovered stents.

CONCLUSION

Neointimal thickening and inflammatory reaction significantly increased with covered compared with noncovered prostheses in the iliac arteries in sheep and were worst with heparin-coated Dacron-covered stent-grafts. If possible, use of noncovered stents should thus be preferred to use of Dacron-covered stent-grafts.

A simple trick to facilitate bleeding control after percutaneous hemodialysis fistula and graft interventions

A simple technique of performing a circular subcutaneous suture that helps to stop bleeding after cannulation of hemodialysis grafts and fistulas following percutaneous revision is described.

Experimental impeller fragmentation of iliocaval thrombosis under tulip filter protection: preliminary results

PURPOSE

To assess the efficacy of catheter fragmentation of massive caval thrombosis and of filter protection against procedure-related pulmonary embolism.

METHODS

In 10 sheep, a self-expanding tulip-shaped filter made from Wallstent mesh (diameter 25 mm) was introduced from the right jugular approach into the proximal inferior vena cava. Experimentally induced massive iliocaval thrombosis was fragmented by an impeller catheter (expanded diameter 14 mm), which was advanced coaxially through the sheath of the expanded filter. Post-procedural cavography and pulmonary angiography were performed to document the extent of caval recanalization and pulmonary embolism.

RESULTS

In all cases, impeller fragmentation cleared the inferior vena cava and the iliac veins of thrombi completely. Fragments washed downstream were trapped in the filter. In two of the first cases, parts of the clots caused pulmonary embolism before the filter was in place. Further events were avoided by a modification of the experimental setup. Except for some small peripheral perfusion defects in two cases, pulmonary angiograms did not show any incidence of pulmonary embolism.

CONCLUSION

Our preliminary results suggest that impeller fragmentation of iliocaval thrombi under tulip filter protection is effective and does not cause significant pulmonary embolism.

Neointimal hyperplasia in low-profile Nitinol stents, Palmaz stents, and Wallstents: a comparative experimental study

PURPOSE

To compare neointima formation following insertion of low-profile Nitinol stents, Palmaz stents, and Wallstents.

METHODS

Nitinol stents, Palmaz stents, and Wallstents similar in size were transfemorally inserted into the iliac arteries of 12 sheep. Four stents per sheep were deployed; the position of the stents was varied so that each type of stent was placed in each position (right or left, proximal or distal) with equal frequency. Stent patency was followed by angiography. Six sheep were euthanized after 1 month, and the remaining six after 6 months. Iliac arteries were removed en bloc and prepared for histological examination. Neointimal and medial thickness were measured by light microscopy, and measurements were analyzed statistically.

RESULTS

Mean neointimal thickness both over (NO) and between (NB) the stent struts was greater in Wallstents (NO = 0.341 mm, NB = 0.368 mm) than in the Nitinol (NO = 0.260 mm, NB = 0.220 mm) and Palmaz stents (NO = 0.199 mm, NB = 0. 204 mm), but differences were not significant (p > 0.05). Medial atrophy in the area between the stent struts was greater in Wallstents compared with Nitinol and Palmaz stents (p < 0.007 and p < 0.02, respectively); in the area under the stent struts there was a significant difference only between Palmaz stents and Wallstents (p < 0.02).

CONCLUSION

Under defined experimental conditions, none of the three types of stent appears to be preferable to the others regarding neointima formation in the short- to mid-term follow-up period.

Iliocaval stenosis and iliac venous thrombosis in retroperitoneal fibrosis: percutaneous treatment by use of hydrodynamic thrombectomy and stenting

A case of bilateral iliac stenosis and caval stenosis due to retroperitoneal fibrosis was treated by caval stenting and iliac balloon angioplasty, but was complicated by subsequent iliac thrombosis. Venous thrombectomy was successfully achieved by hydrodynamic thrombectomy, and iliac patency was stabilized by bilateral stent insertion.

Aortic and iliac stenoses: follow-up results of stent placement after insufficient balloon angioplasty in 118 cases

PURPOSE

To demonstrate follow-up results of stent placement in aortic and iliac stenoses.

MATERIALS AND METHODS

A total of 109 patients with 118 aortoiliac stenoses underwent placement of self-expanding stents. Mean length of the stenotic segments was 3 cm +/- 2 (standard deviation). Mean ankle-arm index at rest was 0.58 +/- 0.2. A total of 101 patients were followed up angiographically or clinically.

RESULTS

A mean of 1.2 stents +/- 0.5 were inserted per case. Clinical stage improved in 112 cases; it improved two or more stages in 89 cases. Mean ankle-arm index improved to 0.92 +/- 0.17. Total and major complication rates were 6.8% and 3.4%, respectively. Subacute occlusion occurred in four patients. Late stent obstruction occurred after a mean of 27 months (range, 16-48 months) in 10 cases. Primary patency was 95% after 1 year and 88% after 2 years; 4-year patency was 82%. Secondary patency was 96% after 1 year and 93% after 2 years. Three- and 4-year secondary patency were both 91%.

CONCLUSION

Placement of self-expanding stents in iliac stenoses is technically safe and offers sufficient follow-up patency.

Late reobstruction in iliac arterial stents: percutaneous treatment

PURPOSE

To retrospectively analyze in a nonrandomized fashion the efficacy of percutaneous reintervention in obstructed iliac stents.

MATERIALS AND METHODS

In 21 symptomatic patients with iliac lesions, 26 reinterventions (16 for stent occlusion and 10 for stent stenosis) were performed. Restenoses were treated with balloon dilation and either atherectomy or stent placement. Reocclusions were treated with atherectomy or aspiration thrombectomy and then recanalization with balloon dilation and selective stent placement.

RESULTS

Balloon angioplasty for stent stenosis was effective in all but one patient. Recanalization was successful in 14 of 16 patients with stent occlusion. The mean period of patency after reintervention was 18 months +/- 15. Cumulative stent stenosis patency after reintervention was 87% after 1 year. Stent occlusion patency was 57%. Recurrent stent obstruction occurred in eight of 24 (33%) patients with successful primary interventions.

CONCLUSION

Percutaneous reintervention for both stent stenosis and occlusion is feasible with a moderate complication rate and may be attempted before surgery.