An endovascular model of carotid stenosis for the evaluation of thrombolysis and angioplasty

The role of simulation in the development of endovascular surgical skills

Endovascular trainees in the National Health Service still largely rely on the apprentice-apprenticeship model from the late 19th century. As the scope for endovascular therapy increases, due to the rapid innovation, evolution and refinement of technology, so too do patients' therapeutic options. This climate has also opened the door for more novel training adjuncts, to address the gaps that exist in our current endovascular training curriculum. The aim of this paper is to present a succinct overview of endovascular simulation, synthesizing the trials and research behind this rapidly evolving training as well as highlighting areas where further research is required. The authors searched MEDLINE and EMBASE for relevant manuscripts on all aspects of endovascular simulation training. A comprehensive Google search was also undertaken to look for any relevant information on endovascular training courses available and any unpublished work that had been presented at relevant scientific meetings. Papers were categorized into the four models: synthetic, animal, virtual reality and human cadaver, and separate searches for evidence of skill transfer were also undertaken. Authors of novel research projects were contacted for further details of unpublished work and permission granted to report such findings in this manuscript.

Rheolytic pharmacomechanical thrombectomy in experimental chronic deep vein thrombosis: effect of L-arginine on thrombogenicity and endothelial vasomotor function

PURPOSE

Endovascular removal of intravascular thrombus using the AngioJet rheolytic thrombectomy (RT) system has been shown to be clinically effective. This system also permits the concomitant infusion of thrombolytic agent followed by thrombectomy, thus creating a novel strategy known as pharmacomechanical thrombectomy (PMT). Although these interventions have gained wide clinical application, little is known regarding the vessel wall response following thrombectomy therapy. The aims of this study were to assess the effect of thrombectomy interventions on endothelial function in a porcine model of deep venous thrombosis (DVT) and to evaluate the effect of nitric oxide (NO) precursor L-arginine on endothelial function following thrombectomy therapy.

METHODS

Deep vein thrombosis was created in bilateral iliac veins by deploying a self-expanding stent-graft incorporating an intraluminal stenosis from a groin approach. Five pigs underwent sham operation. Following 14 days of DVT, animals were randomized to three groups: the first group received RT treatment (RT group, n = 5); the second group received pharmacomechanical thrombectomy (PMT) with tissue plasminogen activator (alteplase 10 mg; PMT group, n = 5); and the third group received PMT with tPA plus intravenous L-arginine (20 mmol/l) (arginine group, n = 5). Iliac vein patency was evaluated by venography and intravascular ultrasound at 1 week. Nitric oxide level was determined by a chemiluminescent assay of the nitrite/nitrate metabolites (NO(x)). Thrombogenicity was evaluated by radiolabeled platelet and fibrin deposition. Veins were harvested and evaluated with light microscopy and scanning electron microscopy (SEM). Endothelial function was evaluated using organ chamber analysis.

RESULTS

The luminal areas in the sham, RT, PMT, and arginine groups were 34 +/- 10 mm(2), 21 +/- 13 mm(2), 35 +/- 18 mm(2), and 37 +/- 16 mm(2), respectively. All iliac veins remained patent at 2 weeks. No difference in endothelial cell structure was observed between the three treatment groups by means of light microscopic or SEM examination. A decrease in platelet deposition occurred in the arginine group compared to the RT and PMT groups (P < 0.05). The arginine group also showed a greater endothelium-dependent relaxation compared to the RT or PMT groups in response to A23187, bradykinin, and ADP (P < 0.05). Local NO(x) level was higher in the arginine group than in the RT or PMT group (2.6 +/- 0.6 micromol/l versus 0.3 +/- 0.1 micromol/l and 0.3 +/- 0.2 micromol/l; P < 0.01).

CONCLUSIONS

AngioJet RT and PMT interventions resulted in similar attenuated endothelium-dependent vasoreactivity and morphologic effect. L-Arginine supplementation preserves endothelial vasoreactivity and reduces platelet deposition following PMT in iliac DVT. Additionally, L-arginine enhances NO production at sites of venous thrombosis. The NO precursor L-arginine may have a therapeutic potential in preserving endothelial function following mechanical thrombectomy.

L-arginine improves endothelial vasoreactivity and reduces thrombogenicity after thrombolysis in experimental deep venous thrombosis

PURPOSE

Nitric oxide (NO) is important in regulation of platelet aggregation, endothelial function, and intravascular thrombosis. The purposes of this study were to assess the effect of thrombolysis on endothelial function in a porcine model of deep venous thrombosis (DVT) and to evaluate the effect of NO precursor l-arginine on endothelial function after thrombolytic therapy.

METHODS

DVT was created in bilateral iliac veins by deploying a self-expanding stent-graft that incorporated an intraluminal stenosis, from a groin approach. Five pigs underwent sham operation. After 7 days of DVT, animals were randomized to three groups: saline pulse-spray (saline group, n = 5), thrombolytic pulse-spray with tissue plasminogen activator (alteplase, 8 mg; t-PA group, n = 5), and thrombolytic pulse-spray plus intravenous l-arginine (20 mmol/L; arginine group, n = 5). At 2 weeks iliac vein patency was evaluated at venography and intravascular ultrasound scanning. NO level was determined with a chemiluminescent assay of the nitrite and nitrate metabolites (NO(x)). Thrombogenicity was evaluated with radiolabeled platelet and fibrin deposition. Veins were harvested and evaluated with light microscopy and scanning electron microscopy. Endothelial function was evaluated with organ chamber analysis.

RESULTS

All iliac veins remained patent at 2 weeks. The luminal areas in the sham, saline, t-PA, and arginine groups were 53 +/- 23 mm(2), 14 +/- 11 mm(2), 34 +/- 19 mm(2), and 42 +/- 21 mm(2), respectively. No difference in endothelial cell structure was observed between the three treatment groups at light microscopy or scanning electron microscopy. Although no difference in fibrin deposition was noted among the three treatment groups, decreased platelet deposition occurred in the arginine group compared with the saline or t-PA groups (P <.05). The arginine group showed greater endothelial-dependent relaxation compared with the t-PA or saline groups (73% +/- 23% vs 49% +/- 18% and 32% +/- 21%; P <.05). Local NO(x) level in the arginine group was correspondingly higher compared with the saline or t-PA groups (1.8 +/- 0.3 micromol/L vs 0.3 +/- 0.05 micromol/L and 0.2 +/- 0.04 micromol/L; P <.05).

CONCLUSIONS

NO precursor l-arginine supplementation enhances NO production at sites of venous thrombosis. Moreover, l-arginine preserves endothelial vasoreactivity and reduces platelet deposition after thrombolysis in iliac DVT. These data suggest that l-arginine may preserve endothelial function after thrombolysis and may reduce the likelihood of postthrombotic syndrome.