Intimal response of saphenous vein to intraluminal trauma by simulated angioscopic insertion

Influence of Angioscopic Vein Graft Preparation on Development of Neointimal Hyperplasia in an Organ Culture Model of Human Saphenous Vein

Purpose:

Angioscopy for in situ vein graft preparation has been criticized on the basis that the trauma of instrumentation may predispose to accelerated intimal hyperplasia, jeopardizing patency rates following infrainguinal revascularization. The aim of this study was to assess the effects of angioscopic preparation on endothelial integrity and smooth muscle cell (SMC) behavior in an established organ culture model of human saphenous vein (HSV).

Methods:

HSV was harvested from 12 patients during bypass surgery before and after angioscopic preparation. Endothelial integrity was evaluated by immunohistochemical staining with JC-70 and scanning electron microscopy (SEM); remaining segments of pre-and postangioscopy vein were maintained in culture for 14 days in medium supplemented with 30% fetal calf serum. Viability was confirmed by measurement of tissue adenosine triphosphate on day 14 and thickness of the neointima was measured by computerized image analysis of histologic sections. Monoclonal antibodies to proliferating cell nuclear antigen (PCNA) were used as an immunohistochemical marker for proliferating SMCs.

Results:

There was a significant reduction in the percentage staining by JC-70 (71.3% versus 20.4%) in pre- versus postangioscopy vein (p = 0.002 by Wilcoxon's rank test; n = 12). This was supported by SEM images. Despite this, there were no significant differences between the pre- and postangioscopy HSVs after 14 days of culture with respect to neointimal thickness (61 versus 56 μm) and staining with PCNA (4.80 versus 4.08 nuclei per 10 (μm), all according to Wilcoxon's rank test.

Conclusions:

Angioscopic vein graft preparation is associated with endothelial cell loss but does not induce additional neointimal hyperplasia in HSV in vitro. These results suggest that angioscopic manipulation does not alter SMC behavior.

Intravascular Imaging Methods for Venous Disorders

The purposes are to assess the problems associated with intravascular imaging methods such as angioscopy and intravascular ultrasound (IVUS) and to evaluate their efficacy through the results of our observations. A total of 54 limbs in 53 patients, 50 patients with chronic venous insufficiency and 3 patients with deep vein thrombosis, were diagnosed and operated on using angioscopy (Olympus OES, order made type) and IVUS (Endosonics, model 82700). The imaging catheters were inserted through a branch of the long saphenous vein and the valves and the intraluminal views were observed. By angioscopy, intraluminal views were clearly observed in 98% of all lesions. However, observation became more difficult in iliac veins compared to in femoral and in long saphenous veins (p < 0.01). Venous wall and thrombus were detected more by IVUS than by angioscopy (p < 0.01), but only 21 valves (24%) were visualized by IVUS among the 88 valves observed by angioscopy. The intravascular imaging method of angioscopy is more suitable for observing valves and intraluminal views compared with IVUS, whereas IVUS is more suitable for observing the cross-sectional venous wall.

Brachytherapy with iridium-192 HDR to prevent from restenosis in peripheral arteries. An update

The use of stents does not appreciably improve restenosis (usually resulting from intimal hyperplasia) as compared to percutaneous transluminal angioplasty (PTA) alone. The development of small-caliber probes for afterloading therapy in the biliary tract allowed us to use these for therapy in the vascular system. Using a special 9 F catheter, exact measurement of the length of the stented vascular segment and of the insertion length of the afterloading probe could be reproducibly performed. We used a Nucletron (Micro) Selectron HDR planning system version 10.10 for exact calculation, monitoring, and control of the afterloading procedure. Our source was iridium 192 (10 Ci) with a diameter of 1.1 mm. The program controls and monitors the insertion and removal of the iridium probe from the source into the special catheter through to the tip, and monitors the irradiation duration. The exposure time was around 200 seconds for a surface dose of 12 Gy. To date, a total of 40 patients have been treated with endovascular afterloading. All patients suffered from clinically relevant reocclusions or restenoses in stented vascular segments of the superficial femoral artery following successful PTA or laser treatment, within 6 to 8 months after the last therapy. In all patients it was possible to perform re-PTA treatment without remaining residual stenoses in the stented region. The additional time required as compared to PTA alone was approximately 45 minutes with most of this time spending for transportation between the cath lab and afterloading room. The follow-up period of the 40 patients ranged from 4 months to 71/2 years. In 33 patients, there was no deterioration of the clinical stage and no restenosis. One patient suffered from an acute thrombosis approximately 3 months after stent implantation, another patient had a stenosis 3 cm above the stented vascular segment 12 months after irradiation treatment. Follow-up examinations have revealed no evidence of nerve lesions following irradiation therapy. The tissue surrounding the artery showed no change following irradiation therapy, either in the CT, color-coded Doppler, endovascular ultrasonic scan or MRI. No complaints of discomfort were reported during or after irradiation. With the exceptions mentioned above, there was no evidence of any complications.

[Endovascular Ir-192 HDR brachytherapy for avoidance of intimal hyperplasia in peripheral vessels after PTA and stent implantation. A 6-year experience]

BACKGROUND

The percutaneous transluminal angioplasty (PTA) is the "golden standard" in the therapy of vessel occlusions due to arteriosclerotic plaques. In spite of all improvements of the technique and the equipment with and without stent implantation there is still a restenosis rate of 40%.

PATIENTS AND METHODS

Endovascular brachytherapy with an iridium-192 HDR source was performed in cases of a restenosis due to intimal hyperplasia which occurred within 6 months after a former PTA. After PTA and stent implantation a 9-French ReKa catheter was positioned with the tip 2 cm below the stent. This catheter served a centering device and as a guide for the 5-French applicator. After determination of the isodose and individual planning a dose of 12 Gy to 3 mm source distance was applied. After this procedure the patient received heparin for 72 hours followed by marcumar.

RESULTS

From May 1990 until June 1996 28 patients (21 male, 7 female) were treated after PTA and stent implantation with endovascular brachytherapy. All patients had clinical relevant restenosis or reocclusion of the arteria femoralis. The follow-up time ranges from 2 to 71 months. Twenty-seven patients had a reasonable follow-up time longer than 6 months. Twenty-five patients could be followed: 4 patients had no or only minimal flow in the treated area, 2 patients moved with an unknown address, 1 patient died without any follow-up examination. No side effects of the radiation appeared.

CONCLUSION

Regarding the small number of patients endovascular brachytherapy with iridium 192 HDR seems to be a save and useful adjuvant treatment form to avoid intimal hyperplasia after PTA.

192IR endovascular brachytherapy for avoidance of intimal hyperplasia after percutaneous transluminal angioplasty and stent implantation in peripheral vessels: 6 years of experience

PURPOSE

Percutaneous transluminal angioplasty (PTA) with or without stent implantation is the accepted standard in the therapy of occlusive arterial disease. Despite improvements in the technique and medical equipment, there is still a restenosis rate of up to 40%. A high-dose-rate afterloading technique to avoid vascular stenosis or occlusion after PTA and subsequent stent implantation caused by intimal hyperplasia is presented with long-term results.

METHODS AND MATERIALS

Intravascular brachytherapy with a 10-Ci 192Ir source was performed in cases of recurrent vascular occlusion or stenosis which appeared within 6 months after a previous PTA. After recanalization by PTA and stent implantation, a 9-Fr ReKa catheter was positioned within the stent to center the applicator with its tip 2 cm below the stent. This catheter served as a guide for a 5-Fr flexible applicator. After this procedure the isodose was calculated and a 12-Gy to 3-mm source distance was applied. The procedure was followed by 72 h of heparinization.

RESULTS

From May 1990 to June 1996, 28 patients (21 male and seven female) were treated with endovascular brachytherapy. All patients had a clinically relevant restenosis or reocclusion of the arteria femoralis. Follow-up time ranged from 1 to 71 months. Twenty-eight patients had a sufficient follow-up time; 25 of these patients were examined. Twenty-one patients had treated vessel segments; four patients had no flow in the treated area. Two patients moved away with unknown addresses, and one patient died without any follow-up examination. Radiation-associated side effects were not notable.

CONCLUSION

Intraluminal brachytherapy with 192Ir is a safe and useful procedure to avoid endovascular hyperplasia after transluminal percutaneous angioplasty.

Angioscopically-assisted in situ saphenous vein bypass for infrainguinal revascularisation

OBJECTIVES AND STUDY DESIGN

The diagnostic capability of angioscopy for endoluminal evaluation is established and its superiority over arteriography for completion studies has been confirmed. The therapeutic use of angioscopy in vein graft preparation is more controversial. The aim of this prospective study was to establish whether angioscopic vein preparation confers real benefits over existing techniques.

METHODS

Forty-seven patients were randomised to either full angioscopic (ANG) vein preparation (23 patients) or conventional (CON) in situ grafting (19 patients). All patients underwent completion studies with arteriography and angioscopy and postoperatively, entered a Duplex graft surveillance programme.

RESULTS

There was a significant difference in the incidence of wound morbidity: 26% in the ANG group as against 63% in the CON group (Fisher's exact test: p = 0.043), but no significant differences with respect to duration of operation, duration of vein graft preparation, length of hospital stay and both 30 day and 12 month secondary cumulative patencies (log rank test: p > 0.5). Completion angioscopy detected eight persistent valve cusps in six patients, all missed at arteriography, but failed to detect arteriovenous fistulae.

CONCLUSIONS

Angioscopic preparation reduces wound morbidity and complements arteriography for detecting intraoperative defects. A large, prospective, randomised trial is now warranted to fully evaluate the potential therapeutic role of angioscopy with respect to current vascular practice.

Angioscopy in vascular surgery: the state of the art

Although angioscopy is considered by many vascular surgeons to be a valuable clinical tool, others view it as expensive and unnecessary. To better define the appropriate role for angioscopy in vascular surgery, a critical review of the recent literature was undertaken. Angioscopy allows more complete valvulotomies with fewer endothelial injuries when preparing autogenous veins to be used as arterial conduits, and results in more complete thromboembolectomy of native arteries and grafts. Angioscopy can replace completion arteriography in infrainguinal arterial reconstructions with an equivalent clinical outcome. Angioscopy may be useful in the assessment of carotid endarterectomy, femoral vein valve repair, and pulmonary embolectomy. It has been useful in various research applications. The rate of complications is less than 1%. Angioscopy is of benefit in preparing veins to be used as arterial conduits and in performing thromboembolectomy. In some circumstances it can replace intraoperative arteriography. Other applications await further validation. The risks of angioscopy are acceptably low.

Angioscopy

Endoscopy of the vascular system has evolved over recent years from an experimental procedure to a sophisticated diagnostic and therapeutic technique for surgical or percutaneous interventions of the peripheral vascular system. Particularly in procedures involving remote instrumentation of arteries, the angioscope provides a method of controlled guidance and a monitor of the effects of the various instruments on the vessel wall and allows immediate assessment of results. Angioscopic examination reveals the extent of intimal injury after angioplasty, in situ vein preparation, trauma, and thrombectomy and gives insights into the mechanisms and effects of endovascular devices.

Technique and results of vascular endoscopy in arterial and venous reconstructions

In an effort to maximize results, vascular endoscopy was used in our institution to monitor arterial and venous reconstructions. Since 1982, angioscopy was applied as a control method in 182 venous thrombectomies to treat iliofemoral thrombosis and 114 aortoiliac thromboendarterectomies. Of the cases with venous thrombectomy reviewed, 50% were incomplete by endoscopic evidence; of these, in 80% the remaining clots could be partly or completely removed. Additionally, in six patients a venous spur was found. Of 114 attempted aortoiliac thromboendarterectomies, only 91 could be completed. In the remainder, endoscopic evidence of persistent intimal flaps forced us to bypass the affected segments. With further miniaturization of the angioscopes, the method was also applied to check vessel repair on small-caliber arteries. In an initial study with 220 femorodistal bypasses we were unable to find a statistically significant difference of primary patency in grafts that were endoscopically controlled or not. In the learning phase with the in situ technique, we identified competent valve remnants in 40%, but this rate could be reduced to 12.7% with growing experience in valvulotomy. We conclude from our data that angioscopy is very helpful in assessing the morphological integrity of aortoiliac thromboendarterectomies and venous thrombectomies. The actual value in infrainguinal arterial reconstructions still remains to be proven.

Angioscopy: a new light on peripheral vascular disease

Although fibre-optic imaging has been used in a number of medical specialties for several years, it has only recently begun to develop in the area of peripheral vascular disease. This review considers the historical development of angioscopy, its current role in peripheral vascular surgery and, finally, its potential for the future.

The natural history of intimal flaps caused by angioscopy

This study tried to determine the natural history of angioscopy-induced arterial intimal flaps as assessed by video angioscopy, light and transmission electron microscopy. Eight mongrel dogs were anesthetized and bilateral femoral and carotid arteries surgically exposed. A 3.0 mm American Edwards angioscope was inserted into each artery and passed vigorously until an intimal flap was visualized by angioscopy. The location of intimal flaps was externally marked with 6-0 polypropylene adventitial sutures. Animals were then recovered and follow-up angioscopy performed at one, two, three, and four week intervals. Following repeat angioscopy, all animals were sacrificed and vessels perfusion-fixed in situ with 2.5% glutaraldehyde in 0.1 M sodium cacodylate. A total of 37 intimal injuries were created (immediate, n = 10; one week, n = 8; two weeks, n = 4; three weeks, n = 8; four weeks, n = 7). No arterial thrombosis occurred following intimal flap formation. Only one of 37 (2.7%) lesions progressed to a hemodynamically significant stenosis. Histology of immediate lesions demonstrated deep intimal fractures extending into the tunica media. Complete healing of intimal flaps was observed by follow-up angioscopy in zero of eight lesions by one week, zero of four lesions by two weeks, one of eight lesions by three weeks, and four of seven lesions by four weeks (p = 0.02). Light and electron microscopy confirmed the angioscopic intimal fractures and regrowth of denuded endothelium.

CONCLUSION

follow-up angioscopy and microscopy one month after angioscopy-induced arterial intimal trauma demonstrated a significant trend towards complete endothelial healing.

Angioscopic valvulotomy: evaluation of a new miniaturized prototype

This study compares valvulotomy performed by a new experimental instrument delivered through the angioscope with the standard technique used in the in situ arterial bypass procedure. Eighteen mongrel dogs (approximately 20 kg) were anesthetized and both femoral veins were exposed from the groin to the knee. A 2.5-mm-external-diameter angioscope was passed through the medial saphenous vein to just below the proximal superficial femoral vein valve. Under direct vision, an experimental valvulotome passed through one of the angioscope ports cut the valve leaflets. In the contralateral limb, a Mills valvulotome was inserted in the same fashion and blindly cut the valve. Operative time was recorded and difficulties were noted. Bilateral ascending lower limb venography, animal sacrifice, and removal of the vein segment containing the area of previous valvulotomy for gross and histologic study were performed immediately (n = 3), and at 2 (n = 3), 7 (n = 3), 21 (n = 4), and 42 (n = 5) days after valvulotomy. In each case, both techniques had cut the valve leaflets by visual and histologic evaluation. It took significantly longer to perform the operative procedure with the angioscope (8.0 +/- 3.7 min) than with the Mills valvulotome (0.8 +/- 0.4 min) (P less than or equal to .001, Student's ttest). There was no difference in the patency of the venous system by venographic study but evaluation for a histologically normal venous system was more common with the Mills technique. The angioscopic technique demonstrated 8 of 18 samples to be histologically normal versus 14 of 18 by the Mills technique (P less than or equal to .05, chi-square test). Both techniques are effective in valve leaflet incision. The new angioscope device is more technically demanding (e.g., operative time) and may be more traumatic (e.g., histologic study). However, a gross estimation of luminal damage (venography) does not find the angioscopic method more thrombogenic. The new angioscopically directed device for venous valvulotomy does function effectively. However, adaptation to the in situ bypass technique to replace present angioscopic methods or blind valvulotomy methods requires an appraisal of just what degree of intraluminal trauma is permissible before the risks outweigh the possible benefits.

Angioscopic evaluation of intravascular morphology after coronary endarterectomy

Coronary endarterectomy in diffuse coronary disease is attended by an increased incidence of perioperative myocardial infarction and vein graft occlusion, which have been partially attributed to the presence of occlusive or thrombogenic intraluminal flaps in the main vessel or its smaller branches. To define the nature and incidence of these features we studied 15 endarterectomized right coronary arteries in 15 patients (12 men, 3 women; age, 55 +/- 7 years [mean +/- standard deviation]) undergoing a coronary operation for multivessel disease. After endarterectomy and distal graft anastomosis, angioscopy was performed using a 1.8-mm Olympus angioscope during graft perfusion with crystalloid solution. The endarterectomy cores were 66 +/- 30 mm in length with 11 major bifurcations and two trifurcations providing 30 major endpoints. At 22 of 30 major endpoints the distal end of the core was smooth and tapered. There were 17 minor side-branch endpoints. Angioscopy revealed the presence of wispish intraluminal fronds and medial bruising in all (100%) arteries. Twenty-nine of the 30 intraluminal endpoints could be visualized. Major intraluminal flaps were seen at the eight nontapered endpoints and six of the 21 smooth tapered endpoints that were visualized. Fifteen minor side branches could be identified angioscopically: a flap was seen at only one side-branch origin. The average examination time was 3.2 +/- 1.1 minutes (7.7% +/- 2.7% of cross-clamp time), and examination required 200 to 250 mL of perfusate. This technique enables immediate and accurate postinterventional assessment of intravascular morphology with minimal prolongation of ischemic time and has shown that small side branches are not compromised by endarterectomy.(ABSTRACT TRUNCATED AT 250 WORDS)

Simulated blood flow and the effects on prostacyclin production in the dog femoral artery

Effects of blood flow on the production of prostacyclin (PGI2) were examined in the canine femoral artery perfused ex vivo. Each artery was perfused in situ with medium 199, under conditions of simulated blood flow. To simulate the normal and abnormal blood flow waveforms at the same mean flow rate, we developed a flow apparatus capable of making various waveforms by changing the duration when the electromagnetic valve in the circuit was open. Group I (n = 7) was exposed to a steep acceleration waveform followed by a steep deceleration, as the normal flow waveform; group II (n = 7) was exposed to a gentle sloping waveform in the deceleration phase, as the abnormal flow waveform. PGI2 was measured as 6-ketoprostaglandin F1 alpha. PGI2 production was estimated as the cumulative production for the first 5 minutes (acute response) and as the production rate after the first 30 minutes (stable production rate). Under conditions of normal flow, the acute response was 5.87 +/- 2.16 ng/cm2/5 min, whereas under conditions of abnormal flow, the rate was 2.20 +/- 0.27 ng/cm2/5 min (p less than 0.01). Stable production rates were 82.5 and 37.5 pg/cm2/min, respectively (p less than 0.05). Both the acute response and the stable production rate of PGI2 production were greater under conditions of simulated normal flow as compared with findings in the case of an abnormal flow. Our working hypothesis is that the decreased production of PGI2, as well as a deterioration in the implanted graft, under conditions of abnormal blood flow leads to a loss of late patency of the reconstructed arteries.

Angioscopy. New developments in vascular surgery

Angioscopy is not a new procedure, but it is one that has undergone recent changes as the effects of technological improvement are adapted to the surgical environment. Recent advances allow the use of angioscopy to change the way some surgeries are performed and has altered others to a great degree. If the procedure is done infrequently, it can take several months and more than a few cases to master the procedure and setup. Having a small team of six vascular nurses for four full-time vascular surgeons has helped speed this process in our institution. In some institutions, the role of the nurse described in this article is performed by the surgical resident or fellow. As we gained experience, breakdown time was reduced and setup was more efficient.