Regional and Conducted Vascular Effects of Endovascular Ultrasound Catheters

Intra-vascular ultrasound catheters are used clinically to facilitate clot lysis. We hypothesized that these devices could also directly lower microvascular resistance and increase tissue perfusion through established shear-dependent pathways. In mice, either the proximal hind-limb muscles or the upstream femoral artery alone was exposed to an endovascular ultrasound catheter (2.3 MHz, 0.5-1.1 MPa) for 10 min. Quantitative microvascular perfusion imaging in the hind limbs exposed to the endovascular ultrasound system exhibited a more-than-twofold increase in flow (p < 0.01) compared with the contralateral control limb after exposure of either the muscle or the femoral artery alone. Using an in vivo optical imaging reporting system, an eight- to ninefold increase in tissue adenosine triphosphate (ATP) was detected in the region of insonification (p = 0.006). Ultrasound was found to produce an immediate release of ATP from ex vivo erythrocytes (p = 0.03). In situ electrochemical sensing revealed an immediate increase in nitric oxide with initiation of ultrasound which returned to baseline within 5 min of termination, as well as ultrasound-triggered nitric oxide (NO) release from erythrocytes. These data indicate that non-cavitating ultrasound produced by endovascular catheters can reduce vascular resistance and increase flow through recognized shear-dependent vasodilator pathways involving purinergic signaling and NO.

High dose-rate brachytherapy for the treatment of lower extremity in-stent restenosis

OBJECTIVE

Historically, edge stenosis and late thrombosis limited the effectiveness of adjunctive endovascular brachytherapy (EVBT) for in-stent restenosis (ISR) after percutaneous transluminal angioplasty (PTA) and stenting. We evaluated an updated protocol of PTA and EVBT for ISR among patients with lower extremity occlusive disease.

METHODS

This is a retrospective, single-center review of patients treated with PTA and EVBT for ISR in the iliac and femoropopliteal segments between 2004 and 2012. A dose of 20 Gy was given at a depth of 0.5 mm beyond the radius of the largest PTA balloon using iridium 192, with at least 2-cm-long margins of radiation coverage proximal and distal to the injured area. Stents were assessed for patency by duplex ultrasound imaging at 1, 3, 6, 9, 12, and 18 months and then yearly. The primary end point was freedom from ≥50% restenosis in the treated segment at 6 months, 1 year, and 2 years. Patency data were estimated using the Kaplan-Meier method. Secondary end points were early and late thrombotic occlusion.

RESULTS

Among 42 consecutive cases in 35 patients of EVBT for ISR in common or external iliac (9 [20.8%]) and superficial femoral or popliteal (33 [76.7%]) arteries, or both, 21 patients (50%) had claudication, asymptomatic hemodynamically significant stenoses were identified on duplex ultrasound imaging in 16 (38.1%), and 4 (9.8%) had critical limb ischemia. Mean treated length was 23.5 ± 12.3 cm over a mean duration of 16.1 ± 9.6 minutes. There was one technical failure (2.3%). Median post-EVBT follow-up time was 682 days (range, 1-2262 days). There were two (4.9%) and five (11.9%) cases of early and late thrombotic occlusions, respectively. There was one death, believed to be secondary to acute coronary syndrome. Primary, assisted primary, and secondary patency in the entire cohort was 75.2%, 89.1%, and 89.1%, respectively, at 1 year and 63.7%, 80.6%, and 85.6%, respectively, at 2 years.

CONCLUSIONS

This contemporary protocol of PTA and adjunctive EVBT for lower extremity ISR, which is updated from those used in prior trials and includes a surveillance strategy that identifies at-risk stents for reintervention before occlusion, may be a promising treatment for lower extremity ISR at institutions where a close collaboration between vascular surgeons and radiation oncologists is feasible.

Percutaneous Treatment of Superficial Femoral Artery Stenosis Secondary to Radiation Arteritis

Radiation arteritis is a rare cause of lower extremity peripheral arterial occlusive disease, and has been traditionally treated with open interventions. There have been only a few reported cases of endovascular interventions for this disease. Previous reports described endovascular treatment in the iliac and common femoral regions, but intervention in the superficial femoral artery have not been described. Described here is a case of acute lower extremity ischemia caused by remote radiation arteritis of the superficial femoral artery, which was successfully treated by percutaneous endovascular technique.

Trans-Stent B-Mode Ultrasound and Passive Cavitation Imaging

Angioplasty and stenting of a stenosed artery enable acute restoration of blood flow. However, restenosis or a lack of re-endothelization can subsequently occur depending on the stent type. Cavitation-mediated drug delivery is a potential therapy for these conditions, but requires that particular types of cavitation be induced by ultrasound insonation. Because of the heterogeneity of tissue and stochastic nature of cavitation, feedback mechanisms are needed to determine whether the sustained bubble activity is induced. The objective of this study was to determine the feasibility of passive cavitation imaging through a metal stent in a flow phantom and an animal model. In this study, an endovascular stent was deployed in a flow phantom and in porcine femoral arteries. Fluorophore-labeled echogenic liposomes, a theragnostic ultrasound contrast agent, were injected proximal to the stent. Cavitation images were obtained by passively recording and beamforming the acoustic emissions from echogenic liposomes insonified with a low-frequency (500 kHz) transducer. In vitro experiments revealed that the signal-to-noise ratio for detecting stable cavitation activity through the stent was greater than 8 dB. The stent did not significantly reduce the signal-to-noise ratio. Trans-stent cavitation activity was also detected in vivo via passive cavitation imaging when echogenic liposomes were insonified by the 500-kHz transducer. When stable cavitation was detected, delivery of the fluorophore into the arterial wall was observed. Increased echogenicity within the stent was also observed when echogenic liposomes were administered. Thus, both B-mode ultrasound imaging and cavitation imaging are feasible in the presence of an endovascular stent in vivo. Demonstration of this capability supports future studies to monitor restenosis with contrast-enhanced ultrasound and pursue image-guided ultrasound-mediated drug delivery to inhibit restenosis.

Far red/near infrared light treatment promotes femoral artery collateralization in the ischemic hindlimb

Nitric oxide (NO) is a crucial mediator of hindlimb collateralization and angiogenesis. Within tissues there are nitrosyl-heme proteins which have the potential to generate NO under conditions of hypoxia or low pH. Low level irradiation of blood and muscle with light in the far red/near infrared spectrum (670 nm, R/NIR) facilitates NO release. Therefore, we assessed the impact of red light exposure on the stimulation of femoral artery collateralization. Rabbits and mice underwent unilateral resection of the femoral artery and chronic R/NIR treatment. The direct NO scavenger carboxy-PTIO and the nitric oxide synthase (NOS) inhibitor L-NAME were also administered in the presence of R/NIR. DAF fluorescence assessed R/NIR changes in NO levels within endothelial cells. In vitro measures of R/NIR induced angiogenesis were assessed by endothelial cell proliferation and migration. R/NIR significantly increased collateral vessel number which could not be attenuated with L-NAME. R/NIR induced collateralization was abolished with c-PTIO. In vitro, NO production increased in endothelial cells with R/NIR exposure, and this finding was independent of NOS inhibition. Similarly R/NIR induced proliferation and tube formation in a NO dependent manner. Finally, nitrite supplementation accelerated R/NIR collateralization in wild type C57Bl/6 mice. In an eNOS deficient transgenic mouse model, R/NIR restores collateral development. In conclusion, R/NIR increases NO levels independent of NOS activity, and leads to the observed enhancement of hindlimb collateralization.

[The impact of microbubbles-mediated intermitten HIFU on bloodflow in femoral artery of rabbit]

This study sought to find out whether the femoral artery of rabbit could be occluded after microbubbles mediated intermitten ultrasound exposure. One hundred and eight rabbits were randomly divided into 3 groups subjected to 3 different factors, namely ultrasound, HIFU combined with Microbubble (the intermitten mode and the continuous mode). After exposure, HE staining was used for visual inspection of the histopathologic change of femoral artery. Electron microscope was used for observation of the ultramicrostructural change; digital subtraction radiography (DSA) was used for inspections of the change in blood flow. There were thrombi formed in the femoral artery and the blood flow was occluded; the endarterium of the femoral artery of rabbits was damaged, and there was cavitation observed in the intermitten exposure group. In the other two groups, there was no change in the the femoral artery of rabbits. Thrombus could be formed in the femoral artery, and blood flow was occluded after exposure to microbubbles-mediated intermitten HIFU.

[Spontaneous rupture of the femoral artery after radiotherapy: a case report]

Radiation-induced arteriopathy is a well-known disease whose incidence is not known and which usually arises chronically many years after radiation therapy. When it arises acutely, spontaneous rupture or, more rarely, thrombosis of the involved vessel may occur. Spontaneous rupture can occur within 4 to 32 weeks of radiotherapy, and usually affects the carotid artery involved in radiotherapy of the neck and head. Spontaneous rupture of the femoral artery is a very rare event and only a few cases have been reported in the literature. In this paper we report a case of spontaneous rupture of the left femoral superficial artery after adjuvant radiotherapy following surgery for a liposarcoma of the spermatic cord with multiple local recurrences, successfully treated with an extra-anatomic bypass through the obturator canal and rectal muscle flap.

[125Iodine-induced radiation damage in the femoral arteries of rabbits]

BACKGROUND & OBJECTIVE

What damages 125Iodine (125I) seed implantation will do to normal tissue is an observation topic in clinic. This study was to investigate the impact of 125I seed implantation to the femoral arteries of rabbits.

METHODS

A total of 30 healthy rabbits were divided into 3 groups. The femoral sheath in the hind leg at one side selected by random was opened and 10 125I seeds at 0.79-0.85 mCi were implanted near the femoral artery according to the treatment planning system (TPS) before operation. In control group, 10 seeds without radioactivity were implanted. After 2 weeks, 2 months and 4 months, the rabbits were killed, the vessel wall nearest to the seeds was taken out and its morphologic changes were observed by gross examination, light microscopy and electron microscopy.

RESULTS

In gross observation, the vessel segments of the legs with 125I seed implantation had no apparent abnormality. Under light microscope, a few exfoliative endothelial cells were observed. Under electron microscope, exfoliation of endothelial cells, degeneration of endothelial cells and smooth muscle cells were observed. The ratios of degenerative vessel endothelial cells to all vessel endothelial cells were 60%-70% in 2-week group, 50% in 2-month group and 30% in 4-month group; the ratios of degenerative vessel smooth muscle cells to all vessel smooth muscle cells in the 3 groups were 50%, 30% and 10%.

CONCLUSION

125I permanent implantation at 0.79-0.85 mCi mainly damages endothelial cells and smooth muscle cells of the normal vessels and this damnification is reversible.

Effects of percutaneous transluminal angioplasty and endovascular brachytherapy on vascular remodeling of human femoropopliteal artery: 2 years follow-up by noninvasive magnetic resonance imaging

OBJECTIVES

We aimed to assess in vivo the long-term effects of percutaneous transluminal angioplasty (PTA) and endovascular brachytherapy (EVBT) on vessel wall by serial MRI.

METHODS

Twenty patients with symptomatic stenosis of the femoropopliteal artery were randomly assigned to PTA (n=10) or PTA+EVBT (n=10, 14Gy by gamma-source). High-resolution MRI was performed prior, at 24-hours, 3-months, and 24-months after intervention. MRI data were analyzed by an independent, blinded observer.

RESULTS

The effects of both procedures on vessel wall at 24-hours and 3-months have been reported. Despite similar percent decrease in lumen area between 3- and 24-months in both groups (-8% for PTA and -11% for PTA+EVBT), at 24-months lumen area gain compared to baseline was +30% in PTA versus +82% in PTA+EVBT (p<0.05). Total vessel area, which was increased at 24-hours and 3-months, returned to pre-treatment value in both groups.

CONCLUSIONS

We demonstrated non-invasively that restenosis and inward remodeling after PTA are delayed by EVBT. At 24-months, patients treated with brachytherapy have larger lumen than those treated with PTA alone. The decrease in luminal and total vessel area between 3- and 24-months after EVBT indicates that the restenotic and remodeling process is not abolished but delayed with this therapy.

Adaptation of a photochemical method to initiate recurrent platelet-mediated thrombosis in small animals

Platelet-mediated thrombosis represents the initial precipitating event in the genesis of unstable angina, acute myocardial infarction, and stroke. As a result, there is considerable interest in the preclinical discovery and screening of new 'anti-platelet' therapies aimed at limiting the incidence and reoccurrence of arterial thrombosis-efforts that, to date, have largely required the use of large animal models of thrombotic occlusion. In the current report, we describe the successful development of a small-animal (rat) model of spontaneous and recurrent platelet-mediated arterial thrombosis achieved by the in vivo administration of a photoactive dye (rose bengal) followed by focal illumination with green laser light.

External Beam Irradiation and Restenosis Following Femoral Stenting: Long-Term Results of a Prospective Randomized Study

PURPOSE

To assess the long-term outcome of external beam irradiation (EBI) for the prevention of restenosis due to neointimal hyperplasia, following percutaneous transluminal angioplasty (PTA) and stenting of the superficial femoral artery.

METHODS

Sixty consecutive patients with peripheral arterial disease, who were treated with "bail-out" stent implantation in the superficial femoral artery due to suboptimal PTA, were included in this study. Patients were randomly allocated into two groups, receiving either external beam irradiation (6 MV photons, total dose 24 Gy in a hypofractionated schedule) plus antiplatelet therapy (EBI group) or antiplatelet therapy alone (control group).

RESULTS

No procedure-related complications occurred, and all patients of the EBI group received the full dose of 24 Gy. During the long-term follow-up, an overall statistically significant difference was demonstrated in favor of the EBI group patients, regarding both the in-stent (log-rank test, p = 0.0072) and the in-segment binary restenosis (log-rank test, p = 0.0103). The primary patency rates were also significantly better in the EBI group at specific time-points, such as in the first (74.2% vs 46.5%, p = 0.019), second (62.5% vs 33.8%, p = 0.020), and third (54.6% vs 29.0%, p = 0.039) year, respectively. Moreover, the overall clinically driven reintervention rate was significantly lower among patients of the irradiated group (log-rank test, p = 0.038).

CONCLUSION

Our long-term follow-up analysis revealed that EBI following femoral artery PTA and stenting significantly reduces restenosis and reintervention rates, while improving primary patency.

Is radiation a risk factor for atherosclerosis? An echo-color Doppler study on Hodgkin and non-Hodgkin patients

AIMS AND BACKGROUND

The aim of the present paper was to study the role of irradiation in the atherosclerotic process in patients affected by Hodgkin and non-Hodgkin lymphoma.

METHODS

We studied 84 subjects, 42 with Hodgkin or non-Hodgkin disease and 42 controls. All 42 cases had been irradiated and were comparable in terms of risk factors for atherosclerosis. All 84 subjects underwent echo-color Doppler of the arterial axis (carotids, abdominal aorta, and femoral arteries), and the intima-media thickness was measured.

RESULTS

The irradiated cases had a greater intima-media thickness in the carotid district, even after dividing them according to age and sex; males were affected more than females. The irradiated patients were at greater risk of developing cardiovascular events than the controls.

CONCLUSIONS

An echo-color Doppler of the carotid district is advisable in all patients who have been submitted to radiotherapy, and the patients with a significantly greater than normal intima-media thickness need a strict follow-up, and antioxidant or antiaggregant therapy should be considered.

[Evaluation of hemodynamic changes by digital subtraction angiography after treatment of avascular osteonecrosis of femoral head with vascularized bone flaps]

OBJECTIVE

To evaluate the effect of digital subtraction angiography (DSA) in evaluation of the hemodynamic changes after treatment of avascular osteonecrosis of femoral head with vascularized bone flaps.

METHODS

Fifty-four patients, 33 males and 21 females, 33 hips being at the stage II and 21 hips being at the stage III, were treated with vascularized bone flaps, including iliac bone flaps pedicled with ascending branch of lateral femoral circumflex artery for 23 hips, greater trochanter bone flaps pedicled with gluteal muscle branch of ascending branch of lateral femoral circumflex artery for 13 hips, greater trochanter bone flaps pedicled with transverse branch of ascending branch of lateral femoral circumflex artery for 9 hips, and greater trochanter bone flaps pedicled with gluteal muscle branch and transverse branch of ascending branch of lateral femoral circumflex artery for 9 hips. Selective DSA was performed on all 54 patients pre-operatively and on 19 patients 6-24 months post-operatively.

RESULTS

DSA before operation demonstrated abnormal vascularization in all 54 patients. Six months after operation reconstruction of blood supply on the femoral head was seen in 48 cases. Six patients showed poor filling or failure of filling of the vessel pedicles in transplanted bone flaps 6 months post-operatively and DSA conducted 8 months postoperatively showed satisfactory filling in one of the 6 cases. The clinical success rate of this group was 91%, and the radiological success rate was 85%.

CONCLUSION

Selective DSA is effective in evaluation of the postoperative hemodynamic changes in the necrotic femoral head. Significant blood supply in the bone flap is the key point in the success of treatment of ONFH.

Endovascular gamma irradiation for the prevention restenosis after angioplasty of femoropopliteal de novo stenoses

The purpose of this study was to investigate the effectiveness and detect side effects of centered, overlapped endovascular gamma irradiation after angioplasty of de novo femoropopliteal stenoses. Thirty patients (age 65.3+/-9.2 years) with arterial occlusive disease were prospectively enrolled to receive endovascular gamma irradiation (192-iridium, 14 Gy centered at 2 mm vessel wall) immediately after percutaneous transluminal angioplasty (PTA) of femoropopliteal stenoses. Irradiation overlapped dilatation by 1-2 cm at each end. Follow-up involved angiography after 12 months; duplex sonography; and interviews before and after PTA and at 1, 6, and 12 months follow-up. PTA and centered endovascular irradiation were performed successfully in all patients. Three thromboembolic complications occurred during irradiation. Angiographic and clinical follow-up was possible in 28 patients. The angiographic degree of stenosis was 73.8%+/-16.3% before and 3.6%+/-23.5% after PTA and was 3.5%+/-43.7% at the 1-year follow-up. Restenosis (>50%) of the target lesion developed in three patients (10.7%) and edge stenoses (>30%) in nine patients (32.1%). An aneurysm of the irradiated segment in one patient was treated by stenting. The rate of retreatment was 17.9%. The vessel diameter after endovascular gamma irradiation and PTA of femoropopliteal stenoses remained stable. Restenosis, induction of edge stenoses, and aneurysm were reasons for reinterventions.

Effects of probucol versus aspirin and versus brachytherapy on restenosis after femoropopliteal angioplasty: the PAB randomized multicenter trial

PURPOSE

To evaluate the effect of probucol and/or of endovascular brachytherapy (EVBT) on restenosis after percutaneous transluminal angioplasty (PTA) of femoropopliteal arteries.

METHODS

A total of 335 patients (206 men; mean age 72+/-9 years) with intermittent claudication were randomized according to a 2x2 factorial design to 1 of the 4 groups: probucol, placebo, EVBT, and EVBT+probucol. Probucol (1 g/d) or placebo were given in double-blinded fashion 1 month before and for 6 months after PTA. Gamma irradiation (192Iridium, 14 Gy, 5-mm reference depth) was randomly applied in an unblinded manner from a noncentered endoluminal catheter. All patients received aspirin (100 mg/d). Primary endpoint was restenosis (>50% diameter reduction) detected by duplex ultrasound 6 months after PTA. Secondary endpoints included clinical and hemodynamic assessment.

RESULTS

Restenosis in patients undergoing EVBT was 17% (23/133) versus 35% (50/142) in patients without EVBT (p<0.001); in patients treated with probucol versus placebo, the rates were 23% (31/135) and 30% (43/140, p<0.001). Three quarters (77%, 102/133) of patients were free of claudication after EVBT therapy versus 61% (87/142) without EVBT (p<0.05). Need for target vessel revascularization was 6% (8/133) with EVBT versus 14% (20/142) without EVBT (p<0.01). Late thrombotic occlusions occurred in 4% (6/133), exclusively in patients treated with EVBT after stent implantation.

CONCLUSIONS

Endovascular brachytherapy significantly reduces restenosis, improves symptoms, and reduces reinterventions after PTA of femoropopliteal arteries. Probucol reduces restenosis but has no additive effect when combined with brachytherapy.

Effective dose for patients undergoing coronary and femoral intravascular radiotherapy involving an HDR 192Ir source

Effective dose equivalent (EDE), and effective dose (ED) for coronary and femoral Intravascular brachytherapy (IVBT) procedures involving a 370 GBq (10 Ci) HDR 192Ir gamma source are tabulated. MIRD stylised models and the MCNP Monte Carlo code were used for the calculations. For coronary irradiation, the normalised EDE is 0.18 mSv (GBq min)(-1) and the ED is 0.056 mSv (GBq min)(-1). For femoral IVBT, the normalised EDE is 0.01629 mSv (GBq min)(-1) and the ED is 0.01195 mSv (GBq min)(-1). Although the medical benefits to a patient undergoing IVBT are often significant and justified, patient doses are high compared with dose limits for radiation protection purposes. As IVBT is becoming a routine procedure, data in this paper could be useful to manage the procedures efficiently.

Effects of Percutaneous Transluminal Angioplasty and Endovascular Brachytherapy on Vascular Remodeling of Human Femoropopliteal Artery by Noninvasive Magnetic Resonance Imaging

Background— Percutaneous transluminal angioplasty (PTA) of severely stenotic peripheral vascular lesions is hampered by a higher restenosis rate. The effects of PTA on vascular wall as well as the effects of the antirestenotic properties of endovascular brachytherapy (EVBT) remain unclear. MRI allows in vivo noninvasive assessment of the vascular effects of such treatment strategies. We sought to elucidate the vascular effect of PTA and PTA+EVBT by serial MRI.

Methods and Results— Twenty symptomatic patients with severe stenosis of the femoropopliteal artery were randomly assigned to PTA (n=10) or PTA+EVBT (n=10; 14 Gy by γ-irradiation source) and imaged by high-resolution MRI before and 24 hours and 3 months after intervention. An independent observer blinded to the procedure analyzed the MRI data. At 24 hours, cross-sectional MRI revealed that lumen area (86% and 67%) and total vessel area (47% and 34%) increased similarly in the PTA and PTA+EVBT groups, respectively. All patients showed severe splitting of the atherosclerotic plaque, resulting in an irregularly shaped lumen. At 3 months, MRI revealed a significant difference in lumen area change between the PTA and PTA+EVBT groups (40% and 106%, respectively; P =0.026) and in the total vessel area (14% and 39%, respectively; P =0.018). At 3 months, plaque disruption was still present in 50% of the patients treated with PTA+EVBT.

Conclusions— After PTA, there is deep disruption of the atherosclerotic plaques and an extensive remodeling process of the arterial wall. Luminal loss after PTA is partially due to inward vessel remodeling. Brachytherapy prevents inward remodeling and induces an increase in lumen area but partially prevents healing of disrupted vessel surface.

Radiation-induced femoral arteritis

Radiation arteritis is currently an uncommon sequalae of external beam radiation, however because of the increasing use of radiotherapy in the management of neoplastic conditions its recognition is increasingly important. We present two cases of debilitating femoral occlusive disease, secondary to radiation exposure, at a long period post irradiation and review the pathophysiolgy and management options for this condition.

Optimal parameters for arterial repair using light-activated surgical adhesives

The clinical acceptance of laser-tissue repair techniques is dependent on the reproducibility of viable repairs. Reproducibility is dependent on two factors: (i) the choice of materials to be used as the adhesive; and (ii) obtaining temperatures high enough to cause protein denaturation at the vital tissue interface without causing excessive thermal damage to the surrounding tissue. The use of a polymer scaffold as a carrier for the protein solder provides for uniform application of the solder to the tissue, thus allowing for pre-selection of optimal laser parameters. The scaffold also facilitates precise tissue alignment and ease of clinical application. In addition, the scaffold can be doped with various pharmaceuticals such as hemostatic and thrombogenic agents to aid wound healing. An ex vivo study was performed to correlate solder and tissue temperature with the tensile strength of arterial repairs formed using scaffold-enhanced light-activated surgical adhesives. Previous studies by our group using solid protein solder without the scaffold indicate that a solder/tissue, interface temperature of 65 degrees C is optimal. Using this parameter as a benchmark, laser irradiance was varied and temperatures were recorded at the surface and at the tissue interface of scaffold-enhanced protein solder using an infrared temperature monitoring system, designed by the researchers, and a type-K thermocouple, respectively.

Endovascular brachytherapy after percutaneous transluminal angioplasty of recurrent femoropopliteal obstructions

PURPOSE

To test the preventive effect of endovascular brachytherapy (EVBT) on restenosis following secondary angioplasty in patients with presumed neointimal restenosis in the femoropopliteal segment.

METHODS

From March 1997 through May 2000, 100 patients (58 men; mean age 70 years, range 45-87) with postangioplasty femoropopliteal segment restenoses were enrolled and randomized to treatment with repeat angioplasty and EVBT (n=51) or to angioplasty alone (n=49) as control. The groups were similar with regard to demographics and lesion characteristics. High-dose-rate EVBT was performed with (192)Ir irradiation without a centering device (12 Gy for a reference vessel radius of 3 mm and a 2-mm reference depth). Primary endpoint in the 1-year follow-up was recurrent obstruction >50% documented by duplex ultrasound; the secondary endpoint was clinical improvement.

RESULTS

Only 44 (86%) of 51 patients received adequate EVBT due to technical failure, so the 7 failures were included with the controls in the per-protocol adherence analysis. At 1 year, the patients receiving EVBT had a restenosis rate of 23% (10/44), which differed significantly (p<0.028) from the 42% (23/56) rate in controls. Clinical results tended to be better with EVBT, but differences did not achieve statistical significance.

CONCLUSIONS

EVBT without a centering device reduced restenosis significantly in patients with recurrent stenosis after angioplasty, which confirms previous results in primary long-segment femoropopliteal obstructions.

Late acute thrombotic occlusion after endovascular brachytherapy and stenting of femoropopliteal arteries

OBJECTIVES

The aim of this article is to underline the importance of this complication after endovascular brachytherapy (EVBT) and intravascular stenting of the femoropopliteal arteries occurring in a running randomized trial.

BACKGROUND

Endovascular brachytherapy has been proposed as a promising treatment modality to reduce restenosis after angioplasty. However, the phenomenon of late acute thrombotic occlusion (LATO) in patients receiving EVBT after stenting is of major concern.

METHODS

In an ongoing prospective multicenter trial, patients were randomized to undergo EVBT (iridium 192; 14 Gy at a depth of the radius of the vessel +2 mm) after percutaneous recanalization of femoropopliteal obstructions. Of the 204 patients who completed the six months follow-up, 94 were randomized to EVBT.

RESULTS

Late acute thrombotic occlusion occurred exclusively in 6 of 22 patients (27%) receiving EVBT after intravascular stenting and always in concomitance with reduction of antithrombotic drug prevention (clopidogrel). Conversely, none of the 13 patients with stents and without EVBT (0%; p < 0.05) and none of the 72 patients (0%; p < 0.01) undergoing EVBT after simple balloon angioplasty presented LATO.

CONCLUSIONS

Late thrombotic occlusion occurs not only in patients undergoing EVBT after percutaneous coronary recanalization but also after stenting of the femoropopliteal arteries and may compromise the benefits of endovascular radiation. The fact that all our cases with LATO occurred concomitantly with stopping clopidogrel may indicate a possible rebound mechanism. An intensive and prolonged antithrombotic prevention is probably indicated in these patients.

Endovascular brachytherapy in peripheral arteries

Increasing knowledge about the pathophysiology of the process leading to restenosis has given the rationale to investigate the potential role of radiation in the prevention of restenosis. Compared to the rapidly increasing experience in the coronary circulation, there is until now only a limited number of studies concerning the use of brachytherapy (BT) in the peripheral circulation. The-Vienna 2-Trial was the first randomized study to demonstrate the efficacy of endovascular BT for prophylaxis of restenosis after femoropopliteal percutaneous transluminal angioplasty. The cumulative patency rates at 12 months of follow-up were 63.6% in the PTA + BT-group and 35.3% in the PTA-group (p < 0.005), and the significant improvement in patency was also maintained after two years. The results of two ongoing randomized, double-blinded multicenter trials (PARIS; Vienna 3) have to be awaited before definitive recommendations can be given. The rather high incidence of late thrombotic occlusion after long-segment femoropopliteal stenting and endovascular BT requires optimization of the antithrombotic regimen.

Synergism between radiotherapy and vascular risk factors in the accelerated development of atherosclerosis: a report of three cases

Radiotherapy is commonly used in the management of testicular tumors. However, to date the risk of radiation-induced vascular occlusive disease in men following radiotherapy for testicular cancer has not been regarded as a major factor in their long-term care. Several animal studies have shown the importance of established vascular risk factors such as hypercholesterolemia and hypertension in the pathogenesis of radiation-induced atherosclerosis. This report presents three cases of premature chronic iliofemoral arterial disease presenting 5,13, and 16 years following exposure to therapeutic irradiation for the treatment of testicular cancer. The patients were in the age group of 40-45 years and all demonstrated associated known atherosclerotic risk factors. The patients had received radiotherapy in the dose of 3,500-4,000 rads in a standard "dog-leg" fashion to the ipsilateral aortoiliac lymphatic chain. Our results showed that young men treated with radiotherapy for testicular cancer may be targeted from the outset for atherosclerotic risk factor reduction to minimize the risk of development of late chronic occlusive arterial disease. It may be that a cohort of men so treated with historical regimes of radiotherapy and now entering middle age should be screened for arterial disease and risk factor reduction.

Gamma radiation induces positive vascular remodeling after balloon angioplasty: a prospective, randomized intravascular ultrasound scan study

BACKGROUND

Endovascular brachytherapy (EBT) has been shown to prevent restenosis after percutaneous transluminal coronary angioplasty (PTA) in both animal and clinical studies. However, as yet, the effect of EBT on peripheral arteries is unknown.

OBJECTIVE

This intravascular ultrasound scan (IVUS) study evaluates the effect of EBT on the extent of plaque growth and vascular remodeling after PTA of the femoropopliteal artery.

METHODS

Twenty-four patients with obstructive disease of the femoropopliteal artery underwent standard PTA. Patients were randomized to receive no additional therapy or additional EBT (192-Iridium) after PTA. IVUS investigation was performed after PTA and at 6-month follow-up. A comparison was made between patients without EBT (n = 16) and with EBT (n = 8) in the change in lumen, vessel, and plaque area and plaque dissections seen with IVUS at 6-month follow-up.

RESULTS

At follow-up, IVUS revealed a significant difference in lumen area change between patients without and with EBT (-9% and +23%, respectively; P =.03). This difference was the result of a significant difference in vessel area change (+2% and +19%, respectively; P =.05). In both groups of patients, a similar increase in plaque area (+12% and +16%, respectively; P =.80) was encountered. Plaque dissections encountered immediately after PTA were absent at follow-up in patients without EBT, whereas in four of the eight patients with EBT, a persistent dissection was encountered.

CONCLUSION

This randomized IVUS study showed that gamma-radiation after PTA has a positive effect on lumen dimensions at 6-month follow-up by inducing positive vascular remodeling (ie, vascular dilatation); gamma-radiation seemed not to affect plaque growth. In addition, gamma-radiation has an effect on the healing process of dissections after PTA.

PhotoPoint photodynamic therapy inhibits intimal hyperplasia in arteriovenous access grafts

PURPOSE

To evaluate the ability of PhotoPoint photodynamic therapy (PDT) to suppress venous anastomotic intimal hyperplasia (IH) in a canine prosthetic arteriovenous graft (AVG) model.

METHODS AND MATERIALS

Bilateral femoral AVGs were placed in 12 mongrel dogs. PhotoPoint PDT was optimized by treating venous anastomoses with a fixed dose of photosensitizer (MV6401) followed by varying light doses. Veins were evaluated at 3 days for cell depletion. Other venous anastomoses received the optimal PhotoPoint PDT dose following graft placement and were harvested 1 month later. Histological sections of venous anastomoses were analyzed for intimal thickness, fibrosis, inflammation, necrosis and thrombosis.

RESULTS

PhotoPoint PDT resulted in a significant reduction of venous anastomotic intimal thickness. In addition, PhotoPoint PDT tended to reduce the development of fibrosis. All veins were patent at harvest, and there was no evidence of PhotoPoint PDT-related pathologies.

CONCLUSIONS

PhotoPoint PDT significantly inhibited the development of venous anastomotic IH. These results suggest that PhotoPoint PDT is feasible and may increase patency rates of synthetic hemodialysis AVGs in the clinic.

Endovascular irradiation impairs vascular functional responses in noninjured pig coronary arteries

PURPOSE

To assess the effects of endovascular irradiation on vascular structure and function in pig coronary arteries in the absence of vascular injury.

METHODS AND MATERIALS

Vasomotor responses to contractions of KCl and prostaglandin F2alpha (PGF2alpha), relaxations to endothelium-dependent (substance P, A23187) and -independent (sodium nitroprusside, SNP) agents; endothelial morphology and superoxide anion (02*-) production were investigated in control (naive), sham and irradiated (20 Gy, 32P) arteries 1 month after irradiation.

RESULTS

Contractions to KCl and PGF2alpha in the presence of L-NAME were significantly decreased, relaxations to substance P and A23187 were abolished and SNP-induced relaxation was potentiated in irradiated arteries compared to naive and sham-treated vessels. Scanning electron microscopy (SEM) revealed enlarged endothelial cells (ECs) exhibiting surface microvilli. O2*- production was significantly increased in irradiated vessels (437.0 +/- 37.3 vs. 126.0 +/- 11.6 RLU/s/mg tissue, P < .01).

CONCLUSIONS

One month after brachytherapy, normal pig coronary arteries showed abnormal vascular reactivity, altered endothelial morphology and increased production of O2*-. Lack of relaxation to substance P and A23187 reflects ionizing radiation-mediated damage to ECs, whereas potentiation of relaxation to SNP suggests additional deleterious effects on medial smooth muscle cells (SMCs). Increased O2*- production might have contributed to endothelial dysfunction by scavenging nitric oxide (NO).

External beam irradiation in angioplasted arteries of hypercholesterolemic rabbits. The dose and time effect

PURPOSE

To study the dose and time effect of external beam irradiation on the morphometry of both angioplasted and nonangioplasted arteries in a hypercholesterolemic rabbit model.

METHODS AND MATERIALS

Eight groups of rabbit femoral arteries were studied: arteries (a) with no intervention, (b) irradiated with a 12-Gy 6 MV X-ray dose, (c) with a 18-Gy, (d) treated with balloon angioplasty, (e) dosed with 12-Gy half an hour post-angioplasty, (f) dosed with 18-Gy half an hour post-angioplasty, (g) dosed with 12-Gy 48 h post angioplasty, (g) dosed with 18-Gy 48 h post angioplasty.

RESULTS

External irradiation at either 12 or 18 Gy was not found to change vessel morphometry in noninjured arteries. The 12-Gy dose given soon after angioplasty further increased percentage stenosis (63% on the average), despite the preservation of the lumen cross-sectional area. Positive remodeling was not observed in arteries given 18-Gy half an hour post angioplasty to counterbalance the increased neointimal formation. Therefore, this treatment resulted in a drastic reduction in lumen area and in enhancement of percentage stenosis (84% on the average). On the contrary, the delayed irradiation of the angioplasted arteries at either 12 or 18 Gy was not found to influence any of the studied morphometric parameters 5 weeks after angioplasty.

CONCLUSIONS

Uniform external beam irradiation up to 18 Gy was well tolerated by intact femoral arteries. Prompt 12- or 18-Gy irradiations accentuated percentage stenosis. However the lumen cross-sectional area was preserved only at the lower dose point. Delayed irradiation at any dose did not influence the restenosis process.

Inhibition of experimental vasospasm by pretreatment with ultraviolet light irradiation in a rat femoral artery model

OBJECTIVE

Chronic cerebral vasospasm is resistant to conventional treatments despite recent advances in treatment modalities. We studied the preventive effect of ultraviolet (UV) irradiation on development of vasospasm and its mechanism in a rat femoral artery model.

METHODS

The rat femoral artery model for vasospasm was used in this investigation (n = 108). The femoral arteries were divided into four groups: empty and no irradiation (control), UV irradiation (UV group), blood placement (VS group), and blood placement after UV irradiation (VS + UV group). Luminal area was measured, and smooth muscle cell counts in the medial layer of the vessel wall were obtained. An immunohistochemical study was performed with cross sections of fixed femoral arteries at 12 hours and 1, 3, 5, 7, and 49 days after blood placement. The rings of femoral arteries on Day 7 were subjected to pharmacological study.

RESULTS

Pretreatment with UV irradiation (VS + UV group) resulted not only in significant inhibition of chronic vasospasm but also in a significant decrease in smooth muscle cells compared with the VS group on Days 5 and 7. The UV-treated arteries (UV and VS + UV groups) exhibited a significant number of Bax- and Bcl-2-positive cells on Days 5 and 7, but few CPP-32 positive cells were observed at the same time points. In the pharmacological study, contractile response to KCI or phenylephrine was reduced significantly in the UV-treated arteries.

CONCLUSION

These results imply that UV irradiation prevents chronic vasospasm and suggest that UV-induced cell death plays an important role in the preventive effect without causing complications during the chronic period.

[Radiation-induced aorto-ilio-femoral arterial arteritis. Mediocrity of the long-term results after conventional surgery]

OBJECTIVES

To assess long-term outcome after surgical cure of radiation-induced aorto-ilio-femoral arterial occlusion and to deduce therapeutic indications.

PATIENTS AND METHODS

Over a 20-year period, 15 patients were treated for occlusion of the aorto-ilio-femoral vessels 4 to 28 years after receiving radiotherapy. Primary treatment was medical (n=1), balloon dilatation (n=5), anatomic revascularization (n=5), and extra-anatomic bypass (n=4). Mean follow-up was 6.8 years.

RESULTS

Among the 5 balloon dilatations, there was one failure requiring right axillofemoral bypass that was followed shortly by fatal septic shock; the 4 others have remained patent at 2 to 15 years, one having required stent dilatation at 6 months. Among the 5 patients who had anatomic revascularization, excepting on patient who died shortly after surgery from her cancer, all have required revision; 2 patients died of infection at 9 and 10 years; the two others are alive at 5 and 18 years. Among the 4 patients with extra-anatomic bypass (one aortothoracic-bifemoral bypass, two axillofemoral bypasses and one cross-over bypass), 2 died with prosthetic sepsis at 3 and 7 years and 2 others have had a bypass replacement. Overall, at last follow-up, half of the operated patients have died from infection (n=5) or cancer (n=2).

DISCUSSION

In reports in the literature, revision and infection after conventional surgery is frequent. There is less risk with the endovascular approach, but it can be only applied for short occlusions.

CONCLUSION

Excepting easily accessible occlusions with an apparent minimal risk for percutaneous balloon dilatation, irradiated arteries should be operated on only in case of severe ischemia. Patients with claudication should be treated conservatively because of the high risk of complications for prosthesis implantation with irradiated arteries.

Endovascular brachytherapy for prophylaxis of restenosis after femoropopliteal angioplasty : results of a prospective randomized study

BACKGROUND

Inasmuch as endovascular brachytherapy (BT) has gained recent interest because of its inhibitory effect on mechanisms leading to restenosis after percutaneous transluminal angioplasty (PTA), we performed this randomized study to determine its efficacy for prophylaxis of restenosis after femoropopliteal PTA.

METHODS AND RESULTS

One hundred thirteen patients (63 men, 50 women; mean age 71 years) with de novo or recurrent femoropopliteal lesions were included in this randomized trial comparing the restenosis rate after PTA plus BT (57 patients, PTA+BT group) versus PTA (56 patients, PTA group) without stent implantation. The mean treated length was 16.7 cm (PTA+BT group) versus 14.8 cm (PTA group). In patients randomized to PTA plus BT, a dose of 12 Gy was applied by an (192)Ir source 3 mm from the source axis. Follow-up examinations included measurement of the ankle-brachial index, color-flow duplex sonography, and angiography. The primary end point of the study was patency after 6 months. The overall recurrence rate after 6 months was 15 (28.3%) of 53 in the PTA+BT group versus 29 (53.7%) of 54 in the PTA group (chi(2) test, P<0.05). The cumulative patency rates at 12 months of follow-up were 63.6% in the PTA+BT group and 35.3% in the PTA group (log-rank test, P<0.005).

CONCLUSIONS

This is the first randomized study to demonstrate the efficacy of endovascular BT for prophylaxis of restenosis after femoropopliteal PTA. The value of this approach should now be improved by modification of the BT procedure and by combination with stent implantation.

Vascular brachytherapy: update on clinical trials

The ultimate test for any emerging technology to become a standard of care depends on the outcome of the clinical trials. In the field of vascular brachytherapy, we are currently in the midst of multi-center, randomized clinical trials, and at the same time, data is being collected regarding long-term outcome of patients that enrolled early on in the pilot trials. These reports have recently reached three years of clinical and angiographic information on patients who were treated with intracoronary radiation for the prevention of restenosis. These data may give a clue to potential side effects and to the ultimate question: will dose radiation therapy be a standard of care for prevention of restenosis?

Application of low-intensity ultraviolet irradiation to the treatment for pharmacological vasoconstriction via a percutaneous transluminal approach

We applied low-power ultraviolet (UV) laser irradiation via a thin flexible optical fiber to an in vivo model of vasospasm using an intravascular transluminal approach. The surgically exposed left femoral arteries of a rabbit were constricted by norepinephrine. A quartz fiber of 400 microm in diameter was introduced into the artery via the right common carotid artery through a 2.5F catheter. The femoral artery lumen was then irradiated with a helium-cadmium laser (wavelength 325 nm, output power 8 mW) through the fiber for 30 s. The UV irradiation increased the mean luminal diameter by 85% in comparison to the precontracted state, while the increase was only 45% in a sham operation. A histopathologic examination revealed no thermal damage and an intact internal elastic lamina. These results suggest that intravascular transluminal irradiation with a low-power UV laser may thus have potentially clinical applications to reverse acute arterial vasospasm.

Radiation-related arterial disease

Arterial occlusive disease has been recognized in association with radiation arteriopathy and, rarely, with spontaneous arterial disruption. This association results from the greater role of radiation therapy in the current management of malignant diseases coupled with longer patient survival and the lengthy latency period between radiation and clinical manifestations of radiation arteriopathy. Experience with six patients having radiation-associated arterial disease was retrospectively reviewed. There were four men and two women, with a mean age of 51 years (range, 36-74). Arteries exposed to radiation include two carotids, three subclavians, one coronary, and one femoral. The time from radiation therapy until clinical arterial disease was a mean of 14.3 years (range, 4-30). Operative repairs with polytetrafluoroethylene and saphenous vein bypass grafts were performed in four patients, stent placement in one patient, and one patient had spontaneous carotid disruption that ultimately was treated with ligation. In conclusion, elective bypass can be performed safely and successfully for arterial occlusive disease in a previously irradiated artery. In contrast, life-threatening arterial disruption secondary to radiation arteriopathy usually requires concomitant exposure to a source of bacterial contamination, and ligation may be the best choice to prevent recurrent hemorrhage.

External beam irradiation following balloon angioplasty in an atherosclerotic rabbit model

PURPOSE

To study the effect of external beam irradiation on the morphometry of both angioplasted and nonangioplasted arteries in a hypercholesterolemic rabbit model.

METHODS AND MATERIALS

Four groups of rabbit femoral arteries were studied: arteries (a) with no intervention, (b) irradiated with a 12-Gy x-ray dose, (c) treated with balloon angioplasty, and (d) dosed with 12 Gy 30 min after balloon angioplasty.

RESULTS

External irradiation did not change vessel morphometry in nonangioplasted arteries. On the contrary, it induced neointimal formation and decreased luminal area, without causing any vessel remodeling in arteries treated with balloon angioplasty.

CONCLUSION

External irradiation at 12 Gy given 30 min after angioplasty in the studied model accentuated the neointimal response to vascular injury, without causing any vessel remodeling.

Tolerance of normal rabbit femoral arteries to single high dose external beam irradiation

PURPOSE

We gave high single doses of external radiation to normal vessels to produce vascular injury and establish the dose tolerance in an animal model. We also performed immunohistochemical staining for macrophages and smooth muscle cells to assess qualitative changes in their populations.

METHODS

Following direct bilateral inguinal cutdown in New Zealand white rabbits, single doses of 15, 20 and 30 Gy were delivered to one vessel. At predetermined time intervals following treatment, the animals underwent angiography and were sacrificed. Both systems were harvested and analyzed, and their luminal and medial areas compared.

RESULTS

No statistically significant differences were found between any treatment vessel and its contralateral control at any time point. In addition, no alterations in subintimal or medial content of macrophages or smooth muscle cells were observed.

CONCLUSIONS

Our data suggest that single radiation doses as high as 30 Gy appear to be well tolerated in the normal, uninjured rabbit vessel over a 6-month follow-up. However, the use of a diseased vessel model and longer follow-up times need to be studied to provide a better clinical understanding of the basic radiobiology of this technique.

Possible mechanisms of vascular relaxation induced by pulsed-UV laser

This study was designed to examine the mechanism of vasorelaxation induced by pulsed-UV laser. Luminal diameters of rat femoral arteries were measured prior to and following krypton-fluoride excimer laser irradiation of 248 nm in wavelength. The diameter was enlarged to 1.3 times the preirradiated size at 1 or 10 Hz irradiation when the fluence was over 2.0 mJ/pulse/mm2, while the diameter reached 1.8 times at 100 Hz with a fluence of 0.8 mJ/pulse/mm2. Vasorelaxation by the 100 Hz irradiation was inhibited when the artery was pretreated with methylene blue but was enhanced with superoxide dismutase. Pathological analysis revealed an ablation crater and vacuole formation in the vessel at 1 or 10 Hz irradiation, but these changes were not remarkable in the 100 Hz-exposed sample. These findings suggest that vasorelaxation induced by the pulsed UV irradiation at 1 or 10 Hz results from structural alteration of vascular smooth muscle by the ablation crater or vacuolization. On the other hand, a possible mechanism of vasorelaxation at the 100 Hz irradiation is partially related to nitric oxide.

Brachytherapy for prophylaxis of restenosis after long-segment femoropopliteal angioplasty: pilot study

PURPOSE

To evaluate in a pilot study the feasibility and efficacy of endovascular brachytherapy for prophylaxis of restenosis after femoropopliteal percutaneous transluminal angioplasty (PTA) without stent implantation in a group of patients with a high risk of restenosis.

MATERIALS AND METHODS

Ten patients (six women, four men; mean age, 68 years) with long-segment (mean length, 16 cm; range, 9-22 cm) restenosis underwent PTA followed by endovascular irradiation with high-dose-rate afterloading of an iridium-192 rod. A dose of 12 Gy was targeted to the inner intimal layer of the vessel. Follow-up examinations until 12 months after PTA included measurement of the ankle-brachial index, color duplex ultrasonography (US) with calculation of the peak velocity ratio, and intraarterial angiography when recurrence was suspected.

RESULTS

Irradiation was technically feasible in all patients without complications. In six patients, the dilated and irradiated segment remained widely patent at color US, with corresponding excellent hemodynamic and clinical results after 12 months. In four patients, clinical and laboratory findings indicated recurrence and arteriography demonstrated restenosis with a diameter reduction of 60%, 70%, 80%, or 90%.

CONCLUSION

Considering the negative selection of patients with a high risk of restenosis, the results of our pilot study are promising concerning the possibility of reduction of restenosis by means of endovascular brachytherapy after long-segment femoropopliteal PTA without stent implantation. The value of this approach should now be determined definitively in randomized trials.

Simple look-up table of optimized dwell time intervals using a high-dose-rate remote afterloader for endovascular irradiation

PURPOSE

This article's objective is to develop a simple methodology deliver a uniform radiation dose to the wall of a narrow peripheral artery for preventing restenosis using a high-dose-rate (HDR) 192Ir remote afterloader.

METHODS AND MATERIALS

Based upon published two-dimensional data such as anisotropy factors of an HDR 192Ir source calculated from the Monte-Carlo method, arterial wall doses at a close range from an HDR source may be easily calculated using the special formula suggested in Task Group Report No. 43 published by the American Association of Physicists in Medicine. An optimization procedure was used to calculate the optimized dwell times for delivering a uniform dose along arterial walls for various arterial diameters and lengths of lesions.

RESULTS

Based on lengths of the stenosis and diameters of arteries or angioplasty balloons, a set of simple look-up tables for optimal dwell time intervals of endovascular radiation treatment have been developed for the MicroSelectron HDR remote afterloader.

CONCLUSION

Doses for endovascular irradiation have been accurately calculated with anisotropy factors. For delivering uniform doses along the arterial wall, a set of look-up tables listed for optimal dwell times is available for the HDR remote afterloader.

Antithrombotic effects in a rat model of aspirin-insensitive arterial thrombosis of desethyl KBT-3022, the main active metabolite of a new antiplatelet agent, KBT-3022

The antithrombotic effect of desethyl KBT-3022, which is the main active metabolite of the new antiplatelet agent, KBT-3022 (ethyl 2-[4,5-bis(4-methoxyphenyl)thiazol-2-yl] pyrrol-1-ylacetate; a cyclooxygenase inhibitor), was determined using a photochemically induced arterial thrombosis model in the rat femoral artery. Pretreatment with desethyl KBT-3022 (0.1, 0.3 and 1 mg/kg, i.v.) prolonged the time required to achieve thrombotic occlusion in the femoral artery and inhibited collagen-induced platelet aggregation in whole blood ex vivo, each in a dose-dependent manner. In all 6 rats used, particularly at the highest dose (1 mg/kg, i.v.) tested, cyclic variations in blood flow were hardly ever observed and complete cessation of blood flow did not occur during the 30-min observation time. BM-13505 (1, 3 and 10 mg/kg, i.v.), a thromboxane A2 receptor antagonist, also prolonged the time to occlusion, but cyclic variations in blood flow did occur. On the other hand, aspirin (10 and 30 mg/kg, i.v.) had little effect in terms of preventing thrombosis, although it inhibited collagen-induced platelet aggregation to the same extent as did desethyl KBT-3022. Desethyl KBT-3022 inhibited the thrombin-induced aggregation of washed platelets in a concentration-dependent manner (1-40 microM), whereas aspirin and BM-13505 did not. These findings suggest that the potent antithrombotic effect of desethyl KBT-3022 may be attributable in part to its additional ability to inhibit thrombin-induced platelet aggregation. Accordingly, thromboxane A2 and thrombin may be important thrombotic mediators in this rat model.

Five year follow-up after brachytherapy for restenosis in peripheral arteries

Restenosis in peripheral vessels caused by intimal hyperplasia after stent implantation, PTA, atherectomy or laser treatment ranged up to 40%. In order to avoid the hyperplastic reaction with restenosis we treated our patients with prophylactic endovascular afterloading therapy after failure of PTA in case of recurrent stenosis. We had 30 patients with up to 4 recurrent stenoses between 4 and 7 months due to intimal hyperplasia in the stented area. To minimize the reocclusion rate we performed an irradiation with 12 Gy surface dose in one session using the endovascular afterloading method with 192 Iridium HDR following re-PTA in the stented vessel segment. The longest follow up is 68 months. The histological analyses of tissue years after irradiation showed a thinner, more compact cellular layer of the myofibroblasts with less myxoid degeneration between the cells compared to intimal hyperplasia and plaques in not irradiated vessel segments. The follow up showed a significant effect of endovascular radiotherapy. The histological findings after irradiation were a diminished growth in the cellular population of the analysed vessel wall compared to not irradiated vessel wall segments of the same patient. These findings may be explained by a reduced migration and mitosis rate of myofibroblastic cells after irradiation. The method may be an interesting alternative to stent implantation alone. Even vessel segments like the Hunter's channel will be patent for a long time follow up. Because of the steep decay in the dose using the endovascular irradiation method with 192 iridium HDR, the method can be used with minimal risk for the surrounding tissue.

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.

Spectro-temporal studies of Xe-Cl excimer laser-induced arterial wall fluorescence

We report on spectro-temporal fluorescence studies of cadaver femoral arterial walls at different stages in the progression of atherosclerosis. After excitation with a Xe-Cl excimer pulse, the time course of the fluorescence spectrum was recorded over time, and time-resolved multispectral analysis was performed. Then, under the assumption of linearity, we derived a linear spectro-temporal kernel (a weighting function) which describes the temporal behavior of the fluorescence process independently of the pulse width of the photoexcitation. The data analysis revealed both static and dynamic fluorescence characteristics which exhibited a good correlation with histological findings.

[Effect of laser biostimulation on leg blood flow in the course of arteriosclerosis]

Blood flow pattern (maximum moment velocity, mean velocity, artery diameter and minute flow) in the superficial femoral artery and in the foot artery was evaluated in 30 patients, subjected to laser biostimulation for symptoms of atherosclerotic ischemia of the lower limbs. The blood flow examination was performed before the treatment and immediately afterwards (20 procedures) and 6 months following the therapy. It was found that laser biostimulation had a favorable effect on the blood flow pattern, particularly in the initial stage of ischemia (Io), and may be a useful method of medical treatment in atherosclerotic ischemia of the lower limbs.

Characterization of pulsed-dye laser-mediated vasodilatation in a rabbit femoral artery model of vasoconstriction

Vasoconstriction is a clinical problem associated with invasive vascular procedures, microvascular reconstruction and subarachnoid hemorrhage. We sought to characterize the ability of pulsed-dye laser irradiation to reverse and prevent vasoconstriction in an anesthetized rabbit model of surgically and pharmacologically induced vasoconstriction. Five groups of experiments were performed to study the effect of pulsed-dye laser irradiation delivered through a 320 microns core ball-tip fiber into the femoral artery. The studies demonstrated that pulsed-dye irradiation can reproducibly cause vascular dilatation. The zone of vasodilatation propagated equally proximal and distal to the site of irradiation within the vessel. When saline was infused into the vessel to replace flowing blood during delivery of laser irradiation, no significant vasodilatation occurred. After laser irradiation reversed surgical and pharmacologic vasoconstriction, the vessel was resistant to further pharmacologic vasoconstriction. This resistance to pharmacologic vasoconstriction did not occur if the vessel was pharmacologically predilated before delivery of laser irradiation. Pathologic analysis of the vessels revealed endothelial damage and mild to moderate medial necrosis, most significant at the site of energy delivery. These studies provide characterization of pulsed-dye laser-mediated vasodilatation in an in vivo model. Delivery of pulsed-dye laser energy has potential clinical application and warrants further investigation.