Goetz M. Richter

The transjugular intrahepatic portosystemic stent-shunt (TIPSS): results of a pilot study.

The new concept of TIPSS (Transjugular Intrahepatic Portosystemic Stent-Shunt) using the Palmaz iliac stent was successfully accomplished in 9 patients with severe portal hypertension (7 alcoholic, 2 postinfectious liver cirrhosis) and histories of multiple life-threatening upper GI bleeding. All patients were considered noncandidates for surgical portal decompression. An intrahepatic central connection was made transjugularly between the right hepatic vein and the right portal vein in 8 patients and the left portal vein in 1. The portosystemic gradient dropped from an average of 29±7.2 mmHg to 17.8±2.9 mmHg immediately after, and to 15.7±2.8 mmHg at the latest follow-up control after the procedure. Seven patients survived the procedure and progressed to Childs A stage during the observation period of 1–10 months (mean 5 months). One patient died as a direct complication from the procedure, and another patient 11 days after the procedure from a severe nosocomial infection. In none of the surviving patients has bleeding from varices recurred or encephalopathic coma developed. In one patient the shunt diameter was moderately increased by a routine PTA catheter to further decrease the portosystemic gradient (23 to 14 mmHg) 3 months after the primary procedure. Autopsy in the two patients who died demonstrated open stent-shunts with early neoendothelial incorporation.

Angioplasty and stenting of completely occluded iliac arteries

Percutaneous angioplasty and placement of balloon-expandable intraluminal stents were performed in 12 iliac occlusions in 12 patients. Indications were limb salvage in seven and claudication in five. After successful stenting, ankle-brachial indexes improved by 0.15 or more in 11 of 12 patients (mean increase, 0.40), transstenotic pressure gradients decreased to less than 5 mm Hg (mean, 0.58 mm Hg) in all patients, and improvement in clinical grade was seen in all patients. At follow-up at 1-14 months (median, 6 months), ankle-brachial indexes were stable (mean, 0.95), and clinical grades were unchanged in all patients. Complications occurred in two patients; both experienced distal embolization, and one, who was receiving corticosteroid therapy, also suffered stent thrombosis. Local surgical embolectomy was successful in both patients, and the thrombosed stent was recanalized with urokinase. This early experience suggests that stenting may play an important role in the management of iliac occlusions, especially in poor surgical candidates.

Relationship between blood flow, thrombus, and neointima in stents

PURPOSE To establish a relationship between flow, acute thrombus formation, and late intimal hyperplasia in arterial stents. MATERIALS AND METHODS To compare short-term stent patency in the canine femoral artery with normal flow to that in the opposite femoral artery with restricted flow, 24 dogs were subdivided in four groups: groups 1 (no intravenous heparin) and 2 (intravenous heparin) had unilateral flow restriction by surgically created stenosis, downstream of a Palmaz stent. Group 3 (no intravenous heparin) and 4 (intravenous heparin) had sham surgical exposure of the corresponding arterial segment, without flow restriction. Thrombocyte activity over the stent segment was evaluated for 3 hours after stent placement with nuclear scanning, after administration of indium-111-labeled platelets. To evaluate long-term stent patency in relationship to arterial flow, 14 additional dogs were subjected to long-term observation. Matched, symmetrically implanted femoral stents with normal and restricted flow, were explanted at 1, 12, and 24 weeks for histologic analysis and comparative measurement of neointimal thickness. Angiographic studies were performed before and after nuclear scanning in the short-term study group and before explant in the long-term animal group. RESULTS In the short-term, groups 2 and 4 showed neither increased platelet uptake nor angiographically demonstrable thrombus. Group 1 had increased platelet uptake and occlusive or subocclusive angiographic thrombus. Group 3 had increased platelet uptake and angiographic thrombus in one instance. In the long-term, stents with flow restriction had significantly greater neointimal formation in comparison with unrestricted stents. Histologic studies suggested that the stent neointima resulted from progressive replacement of stent thrombus. CONCLUSION Regardless of flow condition, intravenous heparinization is necessary to prevent thrombus formation in the stent lumen. Within the experimental parameters of this study, low flow and absent heparinization consistently lead to stent thrombosis. Stent implantation under low flow is associated with increased neointima formation. It is not known whether this is preventable by antithrombotic medication.

Arterial Distribution Characteristics of Embozene Particles and Comparison with Other Spherical Embolic Agents in the Porcine Acute Embolization Model

PURPOSE To determine the arterial distribution pattern of the embolic agent Embozene within the porcine kidney and compare it with those of other spherical embolic agents. MATERIALS AND METHODS Embozene, Embosphere, Bead Block, and Contour SE in size classes of 100-300 microm, 500-700 microm, and 700-900 microm and Embozene and Embosphere in the size class of 40-120 microm were used for total arterial occlusion in minipig kidneys. Organs were evaluated microscopically regarding vascular distribution of the different embolic agents and particle sizes. RESULTS The following variations of arterial distribution were identified. In the 40-120-microm size class, Embosphere particles penetrated significantly deeper compared with Embozene (P = .04). In the 100-300-microm size class, Bead Block showed a significantly deeper distribution as microscopy identified particles in arteries much smaller than their nominal size. In the 500-700-microm size class, Embosphere and Contour SE showed a deeper distribution. The most uniform arterial distribution was observed in the 700-900 microm size class,. However, few Embosphere and Contour SE particles were found in arcuate arteries, also indicating a distal distribution. CONCLUSIONS Throughout the four most-used size classes, from very small (40-120 microm) to large (700-900 microm), the distribution characteristics of the four tested materials vary substantially. Particularly, small Embosphere particles and small Bead Block particles showed a more distal distribution, as did medium-sized Embosphere and Contour SE particles. In the largest investigated size class, the distribution was more uniform. In general, the Embozene particles are very uniform in size, and they seem to reach vessels closely corresponding to their nominal size.

Inflammation and Recanalization of Four Different Spherical Embolization Agents in the Porcine Kidney Model

PURPOSE To evaluate the pattern of recanalization and specific inflammatory reaction after superselective embolization with four commercially available spherical embolic agents of different sizes in the mini pig kidney model. MATERIALS AND METHODS In 40 mini pigs, the lower poles of both kidneys were superselectively embolized with Embozene, Embosphere, Bead Block, and Contour SE particles in sizes of 40-120 mircom (Embozene, Embosphere) and 100-300 microm, 500-700 microm, and 700-900 microm (Embozene, Embosphere, Bead Block, Contour SE). After a follow-up time of 4 or 12 weeks, recanalization was determined with angiography. Pathologic and histologic evaluation of the kidneys was performed, and the Banff 97 classification was used to evaluate the extent of vessel wall inflammation. Macroscopically visible ischemic changes were evaluated by using a specific ischemia score. RESULTS After embolization with Embozene microspheres, larger Embosphere particles, and Bead Block and Contour SE particles, the absence of inflammation or a low inflammation score was observed. Significantly elevated inflammation scores were evident with small Embosphere particles after 4 weeks (mean score, 1.21 +/- 1.0). Distinct recanalization occurred with Contour SE particles (100% recanalization with 100-300-microm particles at 12 weeks, 500-700-microm particles at 4 and 12 weeks, and 700-900-microm particles at 4 weeks). Ischemia scores were highest in the target area in all specimens. Mildly elevated ischemia scores in nontarget tissue areas were indicative of minor nontarget embolization. CONCLUSIONS Except for small Embosphere particles at 4 weeks, the absence of inflammatory reaction to the embolization procedure or only low inflammatory changes were observed with all embolic agents, particle sizes, and follow-up intervals. Recanalization was evident with all embolic agents; however, it was pronounced with Contour SE particles.

Expulsion of dominant submucosal fibroids after uterine artery embolization

PURPOSE Purpose of this study was to evaluate the frequency, probability, and factors associated with expulsion of submucosal fibroids after uterine artery embolization (UAE) in addition to the technical and clinical results at 1-year follow-up. MATERIALS AND METHODS We determined the preinterventional volume of each dominant submucosal fibroid using the commonly used ellipsoid formula and a 3D volumetry in the MRI to define a threshold value in milliliters that indicates the probability for a fibroid expulsion. Assessment of fibroid expulsion was done by MRI at 3-month intervals for a year. Assessment of clinical mid term success was achieved by applying questionnaires at 1-year follow-up. RESULTS Technical success was observed in all 20 patients (mean age of 41.4+/-5.6 years; range: 29.2-51.1 years). Two (10%) minor and one (5%) major complications occurred. 10/20 dominant submucosal fibroids were completely expelled during the follow-up. Using 3D MRI volumetry the preinterventional mean volume of the later expelled fibroids was 56.8+/-57.0 ml (range 2.3-198.0 ml) and the mean volume of non-expelled fibroids was 123.8+/-147.3 ml (range 24.0-531.8 ml). This difference was statistically significant, but weak (p=0.0494). Fibroids with a volume equal or less than the threshold value (66.0 ml) were 73% likely to be expelled and fibroids larger than 66.0 ml were 78% likely not to be expelled. All 20 patients demonstrated a significant reduction in the fibroid related symptoms. CONCLUSION In our study the complication rate was low despite increased rates of fibroid expulsion (50%); simultaneously the rate of treatment satisfaction was very high. Patients with a dominant submucosal fibroid under 66.0 ml should be informed about the probability of fibroid expulsion and the accompanying symptoms.

A new polymer concept for coating of vascular stents using PTFEP (poly(bis(trifluoroethoxy)phosphazene) to reduce thrombogenicity and late in-stent stenosis

Objectives:We sought to evaluate the new polymer PTFEP (poly(bis(trifluoroethoxy)phosphazene) for (1) its ability to reduce thrombogenicity and late in-stent stenosis and (2) its effect on endothelialization in a rabbit iliac artery model. Materials and Methods:Nanocoated (∼50 nm) and bare stainless-steel stents were implanted bilaterally in the iliac arteries of 30 New Zealand White rabbits (1, 4, 8, 12, and 16 weeks follow-up) and evaluated by angiography, light, and scanning electron microscopy. Results:Bilateral stent placement was successful in 27 of 30 rabbits. Thrombus depositions occurred in none of the 27 coated but in 4 of the 27 bare stents (P = 0.037). A normal angiogram was obtained in 18 of 22 coated stents at risk for restenosis (follow-up ≥4 weeks) but only in 13 of 22 bare stents (P = 0.023). Marked restenosis (luminal loss >30%) was found in 6 bare stents (P = 0.011) but not in any coated stents. The neointima was 47.7–73.9 μm on coated and 66.9–115.2 μm on bare stents (statistically significant at 4, 8, and 16 weeks). Scanning electron microscopy detected full endothelialization in all stents from 4 weeks on (22 stents in both groups). Conclusion:PTFEP nanocoating successfully showed thromboresistance and reduced late in-stent stenosis. Endothelialization was equal in both stent types. Studies in more human-like models and human feasibility studies in human arteries are encouraged.

Prolonged survival following palliative renal tumor embolization by capillary occlusion

Nine patients with renal cell carcinoma and severe hematuria were palliatively treated with a new type of angioocclusion: The concept of capillary embolization. The so-called occlusion gel Ethibloc was used as embolizing agent. Each patient was followed up until death or for at least 4 years. All patients had a stage T3 or T4 tumor, 3 patients had metastases to multiple organs, 3 had lung metastases, and 3 were free of metastatic disease. In all cases, very high volumes (14–40 ml) of the embolizing agent were necessary to achieve total occlusion of the entire arterial compartment. Patients without metastatic disease had a mean survival time of 6 years and 4 months, all of them without signs of malignant disease. Patients with metastases had a mean survival time of 3 years. Compared with the natural history of renal cell carcinoma treated otherwise, this represents a substantial prolongation of survival time. Contrary to other angioocclusive treatment modalities, the concept of capillary occlusion with Ethibloc seem to achieve total tumor destruction.

The efficacy of nanoscale poly[bis(trifluoroethoxy) phosphazene] (PTFEP) coatings in reducing thrombogenicity and late in-stent stenosis in a porcine coronary artery model.

Objectives:Previous experimental studies have demonstrated that poly[bis(trifluoroethoxy)phosphazene] (PTFEP) nanocoated stents have antithrombotic characteristics, reduce in-stent stenosis, prevent wall inflammation, and do not hamper endothelialization. This study was designed to validate these findings in a porcine coronary artery model. Materials and Methods:PTFEP-coated (n = 15) and bare stents (n= 13) were implanted in coronary arteries of 18 mini-pigs (4- and 12-week follow-up). Primary study endpoints were thrombogenicity and in-stent stenosis, secondary study endpoints were inflammatory response and re-endothelialization evaluated by quantitative angiography and light microscopy. Results:No thrombus deposition occurred on any stent. At 4 weeks follow-up, the bare stents (n = 4) had a significantly smaller neointimal area (1.93 vs. 3.20 mm2, P = 0.009). At 12 weeks, PTFEP-coated stents (n = 11) had significantly superior results in almost all parameters: neointimal area (2.25 vs. 2.65 mm2, P = 0.034), neointimal height (204.46 vs. 299.41 &mgr;m, P = 0.048), percentage stenosis (38.25 vs. 50.42%, P = 0.019), and inflammation score (0.12 vs. 0.30, P = 0.029). Complete re-endothelialization was seen in both stent types at both intervals. Conclusion:At long-term follow-up, the superior results of PTFEP-coated stents were characterized by a noteworthy reduction of neointimal growth and inflammatory response.

The value of preoperative lytic therapy in limb-threatening acute ischemia from popliteal artery aneurysm

In a retrospective study, we analyzed our experiences in 24 patients with acute ischemia from popliteal artery aneurysms over a period of 27 years and evaluated the value of a preoperative lytic therapy as an adjunct to surgical revascularization, compared to surgery alone. Preoperative urokinase therapy revealed a satisfactory improvement of the runoff in all cases. Follow-up angiography showed complete lysis in 6 and incomplete lysis in 3 of 9 patients. In contrast, in patients treated by surgery alone, postoperative angiography showed residual clots in all cases. The overall amputation rate was 25% (6/24) in 24 popliteal aneurysms with acute ischemia, including four patients with primary amputation for irreversible gangrene. Bypass grafting alone resulted in an early amputation rate of 9% (1/11) and occlusive complications of 45% (5/11) compared to no limb loss and no bypass complication in patients who underwent combined surgery and preoperative lysis (0/9). Our results underline the value of preoperative lytic therapy as an important factor in the management of acute ischemia in popliteal artery aneurysms.