Intravascular Ultrasound Scanning Research Articles

Unexpected major role for venous stenting in deep reflux disease

Treatment of chronic venous insufficiency (CVI) has largely focused on reflux. Minimally-invasive techniques to address superficial and perforator reflux have evolved, but correction of deep reflux continues to be challenging. The advent of intravascular ultrasound (IVUS) scan and minimally invasive venous stent technology have renewed interest in the obstructive component in CVI pathophysiology. The aim of this study is to assess stent-related and clinical outcomes following treatment by iliac venous stenting alone in limbs with a combination of iliac vein obstruction and deep venous reflux. A total of 528 limbs in 504 patients, ranging in age from 15 to 87, underwent IVUS-guided iliac vein stent placement to correct obstruction over an 11-year period. The etiology of obstruction was nonthrombotic in 196 (37%), post-thrombotic in 285 (54%) limbs, and combined in 47 (9%). Clinical severity class of CEAP was C3 in 44%, C(4,5) in 27%, and C6 in 25% of stented limbs. Deep venous reflux was present in all limbs, associated with superficial and/or perforator reflux in 69%. Reflux was severe in 309/528 (59%) limbs (reflux multisegment score > or = 3) and 224/528 (42%) limbs had axial reflux. Venography and other functional tests had poor diagnostic sensitivity to detect obstruction, which was ultimately diagnosed by IVUS. The IVUS-guided iliac vein stenting was the only procedure performed and the associated reflux was left uncorrected. There was no mortality; morbidity was minor. Cumulative secondary stent patency was 88% at 5 years; no stent occlusions occurred in nonthrombotic limbs. Cumulative rates of limbs with healed active ulcers, freedom of ulcer recurrence in legs with healed ulcers (C5), and freedom from leg dermatitis at 5 years were 54%, 88%, and 81%, respectively. Cumulative rate of substantial improvement of pain and swelling at 5 years was 78% and 55%, respectively. Quality of life improved significantly. Reflux parameters did not deteriorate after stenting. Iliac venous stenting alone is sufficient to control symptoms in the majority of patients with combined outflow obstruction and deep reflux. Partial correction of the pathophysiology in limbs with multisystem or multilevel disease can provide substantial symptom relief. Percutaneous stent technology in concert with other minimally-invasive techniques to address superficial and/or perforator reflux offers such partial correction in limbs with advanced CVI and complex venous pathology. Open correction of obstruction or reflux is now required only infrequently as a "last resort".

Challenges in the diagnosis of blunt cardiac injuries

Blunt thoracic injuries (BTIs) are directly responsible for 20-25% of all deaths, worldwide. Involvement of heart in BTIs is largely underestimated and ignored, but reasonable estimate would be around 15%. This study was planned to emphasize on clinical-presentation and diagnosis of blunt cardiac injuries (BCIs). Clinical presentation of BCIs, varied from mild chest discomfort to haemodynamic shock secondary to rapid exsanguinations. Non-specific presentation with associated injuries diverts physician's attention and delayed appearance of clinical features makes diagnosis further difficult. Cardiac markers and ECG are not specific, but high sensitivity of 100% could be reached using combination of elevated cardiactroponin levels and alterations in ECG. Transoesophageal or transthoracic echocardiography, angiography, intravascular ultrasound and nuclear scan have proven to detect cardiac injuries in BTIs, but lack specificity. Patients with suspicious-ECG finding need cardiac-monitoring for at least 24 hours. Haemodynamically stable young (<55 years) subjects, without underlying cardiac diseases and with normal-ECG and cardiac marker, could be discharged safely.

Delivery of drug, or gene, to blood vessel wall using intravascular ultrasound and microbubbles.

Atherosclerotic arteries are routinely treated using balloon angioplasty followed by stent placement. We developed a concept for a new therapy to prevent restenosis involving using ultrasound and microbubble‐based drug/gene carriers. A number of early in vitro and in vivo results are presented. In particular, data for delivery of antiproliferative gene via microbubbles ruptured via catheter‐based intravascular ultrasound (IVUS) at the site of vessel injury in vivo in a pig coronary artery are presented. Optimal design of a modified IVUS catheter is discussed. The proposed catheter includes a bubble port, an elongated single element transducer to provide radiation force to cause the bubbles to traverse to the vessel wall, and a bubble rupture transducer. The bubble rupture transducer is ideally coincident with an imaging IVUS scanning single element or annular phased array. These requirements provide the impetus to develop enhanced designs of both PZT based transducers and silicon micromachined transducers. In our initial pig study, transfection efficiency was measured using fluorescence microscopy and quantified as the percent of vessel perimeter cells expressing red fluorescent protein. We observed 23.3±6.0% transfection in the treated vessel whereas the control exhibited 3.6±2% transfection.

Late thrombosis of a thoracic aorta stent graft: Therapeutic management

The case of a 17-year-old adolescent boy with severe polytrauma is reported. Among other injuries, he presented with aortic rupture distal to the origin of the subclavian artery with no bleeding into the mediastinum. The lesion was repaired by placement of a Cook TX2 endovascular graft (Cook Incorporated, Bloomington, Ind). One year later, he was hospitalized with acute heart failure. Computed tomography angiography showed nearly complete stent graft occlusion and no evidence of altered integrity of the device. A right axillofemoral bypass was performed, allowing conversion to successful definitive repair consisting of an extra-anatomic bypass from the ascending aorta to the supraceliac abdominal aorta.

Dethrombosis of the Lower Extremity Arteries Using the Power-Pulse Spray Technique in Patients with Recent Onset Thrombotic Occlusions:Results of the DETHROMBOSIS Registry

To assess the presence of thrombus using intravascular ultrasound (IVUS) and evaluate the feasibility of combined thrombolysis [power-pulse spray (P-PS)] and rheolytic thrombectomy (RT) in patients with recent-onset limb ischemia (<6 months) due to total occlusion of at least 1 infrainguinal vessel. Seventeen patients (12 women; mean age 68.3+/-10.7 years) enrolled in a prospective registry underwent IVUS imaging at baseline, after treatment with P-PS using tissue plasminogen activator and RT (AngioJet), and prior to definitive treatment of the vessel. The primary safety endpoints were major bleeding, distal embolization, vascular access complications, and renal failure. Effectiveness outcomes were (1) procedural success with a residual stenosis <30%, (2) IVUS-documented resolution of the thrombus, and (3) the combined clinical endpoint of procedure-related death, stroke, unplanned amputation, and unplanned urgent revascularization of the treated limb. At baseline, the majority of patients (16, 94.1%) had a definite thrombus identified by IVUS; in the remaining patient (6.3%), thrombus was likely to be present according to the IVUS scan. By angiography, 2 (11.8%) patients had a definite grade 3 thrombus and 5 (29.4%) patients had a grade 1 thrombus (modified TIMI scale) at baseline. IVUS data were available pre and post P-PS/RT in 16 (94.1%) patients. In 10 (62.5%), the thrombus was partially resolved; in 5 (31.25%), there was no apparent change. The thrombus appeared to have completely resolved in only 1 (6.3%) patient. Embolization occurred in 3 (17.6%) patients with no adverse clinical sequelae. The combined clinical endpoint was met in 1 (5.9%) of 17 patients. After final definitive treatment of the vessel, acute procedural success was 100%, with no angiographic filling defects seen. Thrombus is present in most if not all patients with a recent history of limb ischemia who are found to have an occluded culprit vessel. The application of the P-PS/RT led to partial or complete thrombus resolution in about two thirds of the patients treated. The overall safety outcome was favorable, but large studies are needed to test the effectiveness of the P-PS/RT technique prior to routine use.

High prevalence of nonthrombotic iliac vein lesions in chronic venous disease: A permissive role in pathogenicity

Nonthrombotic iliac vein lesions (NIVL), such as webs and spurs described by May and Thurner, are commonly found in the asymptomatic general population. However, the clinical syndrome, variously known as May-Thurner syndrome, Cockett syndrome, or iliac vein compression syndrome, is thought to be a relatively rare contributor of chronic venous disease (CVD), predominantly affecting the left lower extremity of young women. The present study describes the much broader disease profile that has emerged with the use of intravascular ultrasound (IVUS) scanning for diagnosis and analyzes stent placement outcome in two specific NIVL subsets that may offer clues to their pathogenic role. Among 4026 patients with CVD symptoms spanning the range of CEAP clinical classes, IVUS examinations were selectively done in severely symptomatic patients for indications as described. Iliac vein obstructive lesions were found in 938 limbs of 879 patients; 53% of the limbs had NIVL, 40% were post-thrombotic, and 7% were a combination. Stents were placed in 332 limbs in 319 patients in two NIVL subsets. The subsets, one with and one without associated distal limb reflux, were compared. Reflux was left untreated in the first subset. The median age was 54 years (range, 18 to 90 years). The female-male ratio was 4:1 and the left-right ratio was 3:1. NIVL lesions in the iliac vein occurred at the iliac artery crossing (proximal lesion) and also at the hypogastric artery crossing (distal lesion), a new IVUS finding. Venography was only 66% sensitive, with 34% of venograms appearing "normal." IVUS had a diagnostic sensitivity of >90%. The cumulative results observed at 2.5 years after stent placement in the NIVL subsets with reflux and without reflux, respectively, were complete relief of pain 82% and 77%, complete relief of swelling 47% and 53%, complete stasis ulcer healing 67% and 76%, and overall clinical relief outcome 75% and 79%. These results are nearly identical between the two subsets even though distal reflux remained uncorrected in the NIVL plus reflux subset. NIVL has high prevalence and a broad demographic spectrum in patients with CVD. Similar lesions in the asymptomatic general population may be permissive of future development of CVD. Stent placement alone, without correction of associated reflux, often provides relief.

Adaptive-Outward and Maladaptive-Inward Arterial Remodeling Measured by Intravascular Ultrasound in Hyperhomocysteinemia and Diabetes

Coronary artery remodeling implies structural changes in the vessel wall in response to various pathophysiologic conditions. However, the classification of remodeling is unclear. We hypothesized that the adaptive, positive-outward remodeling is a reactive and compensatory response to the stress. The maladaptive negative-inward constrictive remodeling is a passive atherosclerotic condition in which the vessel becomes stiffer. Patients with atherosclerotic lesions underwent intravascular ultrasound (IVUS) scans. The size of the vessels distal to and proximal to plaques were analyzed by IVUS. Diabetes was created in mice by an intraperitoneal injection of alloxan (65 mg/kg). To reduce remodeling, mice received ciglitazone, an agonist of peroxisome proliferators activated receptor-gamma (PPARgamma) in drinking water. After 8 weeks, atherosclerotic vessels were analyzed for collagen and elastin. IVUS data suggest an adaptive coronary arterial remodeling was a positive compensatory response to various pathologic stimuli; for example, with the deposition of atherosclerotic plaque, coronary arterial segments enlarged to maintain luminal area. This phenomenon was commonly observed during the initial phases of the development of atherosclerosis. However, negative coronary artery remodeling, or a decrease in vessel area with the formation of atherosclerotic plaque, was maladaptive and was associated with smoking, hypertension, hyperhomocysteinemia, diabetes mellitus, and also after percutaneous coronary interventions (restenosis). In diabetic mice, there was increased collagen and decreased elastin contents; however, treatment with ciglitazone ameliorated the decrease in elastin contents. Global enlargement of the coronary vascular tree occurs during pressure and volume overload associated with ventricular hypertrophic states such as athletic conditioning, hypertensive heart disease, and dilated cardiomyopathy. On the other hand, maladaptive coronary arterial remodeling occurs in patients with severe deconditioning, diabetes mellitus, after coronary artery bypass surgery, and in some instances, postintervention.

Routine intravascular ultrasound scanning guidance of coronary stenting is not associated with improved clinical outcomes

Routine intravascular ultrasound scanning guidance of coronary stenting is not associated with improved clinical outcomes

Routine intravascular ultrasound scanning guidance of coronary stenting is not associated with improved clinical outcomes

Purpose The purpose of the current study was to determine whether there is any incremental benefit to routine intravascular ultrasound (IVUS) guidance of percutaneous coronary intervention. Methods and results We compared the outcome of 796 patients who underwent an IVUS study (IVUS group) during the index stent procedure with 8274 patients who did not have an IVUS study (angiography group). The primary end point was the composite end point of death, myocardial infarction, or ischemia-driven target vessel revascularization within 9 months of the index stent procedure. There were statistically significant differences in multiple procedural characteristics. Most importantly, those patients who underwent an IVUS study had a larger postprocedural minimal lumen diameter and smaller postprocedural percent diameter stenosis. However, there was no significant difference between the IVUS group and the angiography group with respect to the primary end point (RR 1.10, 95% CI 0.91, 1.32) or any of the individual clinical end points. Adjustment for multiple clinical and procedural characteristics did not significantly alter these findings. Conclusions These data suggest that the routine performance of IVUS during stent placement influences the performance of the procedure, as judged by differences in procedural characteristics, but does not improve clinical outcome at 9 months.

Oral rapamycin to prevent human coronary stent restenosis: A pilot study

Background Recent human trials with rapamycin-eluting stents have shown very low restenosis rates. However, the high costs of these devices preclude their use in routine angioplasty, especially when considering multiple stenting. We evaluated whether orally administered rapamycin inhibits in-stent neointimal growth in patients with unstable angina. Methods We enrolled 15 patients successfully treated with the implantation of a single stent in a single de novo lesion in native coronary arteries. Correct stent expansion and apposition were corroborated with intravascular ultrasound scanning in all patients. Patients received aspirin, clopidogrel, and atorvastatin for 6 months. Rapamycin was administered in a loading dose of 5 mg, followed by 2 mg/day for 4 weeks. Results The reference diameter was 3.4 ± 0.4 mm, lesion length was 11.2 ± 2 mm, lesion type B1 was 36%, and lesion type B2 was 64%. After the procedure, in-stent minimal lumen diameter and diameter stenosis (DS) were 3.3 ± 0.4 mm and 0.3% ± 7.5%, respectively. At 10 days, plasma levels of rapamycin were 7.95 ± 2.6 ng/mL. At 6 months, angiographic determinations demonstrated an in-stent minimal lumen diameter of 2 ± 1 mm, an in-stent DS of 41.3% ± 28.0%, and an in-stent late loss of 1.4 ± 1.1 mm. Binary restenosis (>50% DS) was present in 6 of 15 patients (40%). Target lesion revascularization (coronary artery bypass grafting) was performed in 2 of 15 patients (13.3%). There were no serious adverse events during the 6-month period of follow-up, but 1 patient had severe heartburn caused by esophagitis, and another patient had herpes zoster at the end of the protocol. Conclusions Oral rapamycin was well tolerated, but did not suppress in-stent neointimal growth in this small group of patients.

Percutaneous bypass: subintimal recanalization of peripheral occlusive disease with IVUS guided luminal re-entry

Angioplasty of chronic total occlusions (CTOs) has lower technical success rates with longer procedure times and poorer outcomes. Subintimal recanalization remains limited by the lack of controlled re-entry into the true lumen of the target vessel. We report our experience using a commercially available catheter-based system equipped with an intravascular ultrasound scanner to achieve controlled true lumen re-entry in patients with peripheral CTOs. In a 4-month period, 6 patients with lower extremity (LE) ischemia from CTOs were treated. Occluded segments were crossed subintimally, and controlled re-entry was secured using the CrossPoint TransAccess catheter. This 6.2 F dual-lumen catheter contains an integrated 64-element phased array intravascular ultrasound scanner enabling targeting of structures. Intravascular ultrasound-guided luminal re-entry was achieved by advancing a 24-gauge needle to a desired length and delivering a 0.014” guide wire into the target lumen. The occluded segments were balloon dilated and stented using self-expanding nitinol stents. Effective luminal re-entry and re-establishment of antegrade flow occurred in all 6 patients. Time to recanalization ranged from 5 to 10 minutes. All patients were free of ischemic symptoms at 1 to 5 month follow-up. There were no procedure-related complications. Our preliminary results demonstrate the feasibility of using this catheter system for subintimal recanalization with controlled re-entry in CTOs. This approach can improve the technical success rate, reduce the time of the procedure, and minimize potential complications.

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

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. 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. 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). 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.

Pioglitazone reduces neointimal tissue proliferation after coronary stent implantation in patients with type 2 diabetes mellitus: an intravascular ultrasound scanning study

Background It has been reported that pioglitazone reduces neointimal hyperplasia after balloon-induced vascular injury in an experimental model. Methods To determine whether pioglitazone reduces neointimal tissue proliferation after coronary stent implantation in patients with type 2 diabetes mellitus, we studied 44 stented lesions in 44 patients with diabetes mellitus who underwent successful coronary stent implantation. Study patients were randomized into 2 groups: the pioglitazone group (23 patients with 23 lesions) and the control group (21 patients with 21 lesions). All patients underwent serial quantitative coronary angiography and serial intravascular ultrasound scanning studies. With a motorized pullback system, multiple image slices within the stent were obtained at every 1 mm. The stent area and lumen area were measured, and the neointimal area was calculated. Measurements were averaged over the number of selected image slices. The neointimal index was calculated as the averaged neointimal area divided by the averaged stent area multiplied by 100 (%). Results After 6 months of treatment, angiographic in-stent restenosis (17% vs 43%, respectively, P = .0994) and target lesion revascularization (13% vs 38%, respectively, P = .0835) were less frequent in the pioglitazone group than the control group; however, these differences did not reach significance. The intravascular ultrasound scanning study demonstrated that the neointimal index in the pioglitazone group was significantly smaller than that in the control group (28% ± 9% vs 48% ± 15%, respectively, P <.0001). Conclusion A serial intravascular ultrasound scanning assessment demonstrated that pioglitazone reduces neointimal tissue proliferation after coronary stent implantation in patients with type 2 diabetes mellitus.

Automated three-dimensional assessment of coronary artery anatomy with intravascular ultrasound scanning

BackgroundAngiography allows the definition of advanced, severe stages of coronary artery disease, but early atherosclerotic lesions, which do not lead to luminal stenosis, are not identified reliably. In contrast, intravascular ultrasound scanning allows the precise characterization and quantification of a wide range of atherosclerotic lesions, independent of the severity of luminal stenosis. MethodsThree-dimensional (3-D) reconstruction of entire coronary segments is possible with the integration of sequential 2-dimensional tomographic images and allows volumetric analysis of coronary arteries. ResultsAutomated systems able to recognize lumen and vessel borders and to display 3-D images are becoming available. ConclusionThese systems have the potential for on-line 3-D image reconstruction for clinical decision-making and fast routine volumetric analysis in research studies. This review describes 3-D intravascular ultrasound scanning acquisition, analysis, and processing, and the associated technical challenges.

Quantitative IVUS blood flow: validation in vitro, in animals and in patients

In recent years, a new method to measure transverse blood flow based on the decorrelation of the radiofrequency (RF) signals of intravascular ultrasound (IVUS) rotating single-element scanners was introduced. We report here in vitro, animal and patient testing to evaluate the correlation-based method using an IVUS array catheter. A new correlation-based method to dynamically correct the correlation coefficients for noise is implemented. The decorrelation due to noise was estimated from the correlation coefficients from flowing blood obtained at increasing time lags. First, blood flow experiments were carried out with different catheters in a tissue-mimicking flow phantom with an inner diameter ranging from 3.0 to 5.0 mm. A calibrated electromagnetic flow meter (EMF, range: 0 to 250 cc/min) was used as a reference. Good linear relationships were found between the IVUS-derived flow and the calibrated EMF (all R 2> 0.96). The catheter position within the flow phantom and the size of the ring-down were theoretically analyzed. These elements, and noise in the RF signals, have an important influence on the IVUS blood flow measurements reflected by the offset and the slope of the linear relationships. By placing the IVUS catheter outside the flow phantom, parabolic blood flow profiles were also measured. Second, IVUS blood flow measurements were performed in the carotid artery of two Yorkshire pigs, which showed linear relationships (all R 2> 0.85) between the IVUS-derived flow and the calibrated EMF. Experimentally, the offset was lower than 3 mL/min and the slope was close to 1. Third, IVUS blood flow measurements were performed in coronary arteries in patients. Preliminary results for the coronary flow reserve (CFR = high flow/baseline flow) in patients using the decorrelation method of RF signals of an array IVUS scanner were comparable with CFR based on Doppler measurements. (E-mail: a.vandersteen@erasmusmc.nl)

Intravascular ultrasound aids in the performance of endovascular repair of abdominal aortic aneurysm.

The purpose of this retrospective review was to assess the accuracy of aortic measurements with intravascular ultrasound scan (IVUS) compared with computed tomographic (CT) scan and to assess the role of IVUS in the performance of endovascular repair of abdominal aortic aneurysms (AAAs). Seventy-eight patients undergoing repair of AAA with the AneuRx stent graft (Medtronic AVE, Inc, Santa Rosa, Calif) underwent measurement with CT scan and IVUS. The initial selection of stent graft size was made on the basis of the CT scan measurements, but the final decision for size was made on the basis of the IVUS measurements. Standard measurements of a phantom tube obtained with IVUS, CT scan, and digital caliper were also compared. IVUS measurements of the phantom standard agreed closely with CT scan measurements. However, stent graft size initially selected with CT measurement was altered in 28% of cases on the basis of intraoperative IVUS measurements. No type I endoleaks were encountered in our series, and no aortic cuffs were necessary for endoleak repair. IVUS accurately measures the aorta for selection of stent grafts for endovascular repair of AAA and may prevent type I endoleaks and remedial procedures for their repair.

Doppler colour flow imaging and flow quantification with a novel forward-viewing intravascular ultrasound system

The aim of this work was to investigate the potential of a novel forward-viewing intravascular ultrasound (IVUS) system for flow quantification and colour flow imaging combined with B-mode imaging. A stiff 3.8-mm diameter catheter was used to scan a 72° sector ahead of its tip. Operating at 30 MHz, the catheter was integrated with an IVUS scanner and a radiofrequency (RF) data-acquisition system. RF data were software processed for producing B-mode images and deriving velocity estimates. Steady flow in the range of 45 to 146 mL/min toward the catheter, was used in wall-less tissue-mimicking phantoms simulating healthy lumen (8-mm diameter), 30% diameter symmetrical stenosis and 37% diameter eccentric stenosis. The system provided colour flow images and good estimation of peak velocity and volumetric flows (within 1% to 9% and 16% to 48%, respectively, of calculated values) at 5 to 7 mm distal to the catheter. A sector forward-viewing IVUS imaging/Doppler system is suitable for combined anatomical and functional assessment of stenosed vessels. (E-mail: N.McDicken@ed.ac.uk)

Recanalization of totally occluded iliac and adjacent venous segments.

The purpose of this study was to report our experience with percutaneous recanalization of totally occluded iliac veins and inferior vena cava. Recanalization of the iliac vein was performed in 38 limbs. In nine limbs, recanalization of the inferior vena cava was also necessary (two with filter). In 28 of 38 limbs, the stent was extended below the groin crease into the common femoral vein segment. Large-caliber (14 or 16 mm for iliac vein) flexible self-expanding stents were used. Stents were routinely extended for a short distance into the inferior vena cava to forestall development of iliocaval stenosis. Intravascular ultrasound scan was a valuable tool in the procedure. The median length of the recanalized segment was long (22 cm), and multiple stents (median, n = 3) were necessary in most patients. Forty-five percent of the patients had coagulation abnormalities. No morbidity or mortality was seen. Actuarial primary, primary assisted, and secondary patency rates of the stents at 24 months were 49%, 62%, and 76%, respectively. Median pain level decreased significantly (level 4 to level 0; P <.0001) after stent placement, and more than two thirds of the patients became totally pain free after the procedure. Swelling also improved significantly, and a third of the patients became totally free of any swelling after stent placement. Sixty-six percent of cases with stasis ulcers/dermatitis (n = 14) were resolved (actuarial, 1 year), although uncorrected reflux persisted in many of these limbs. Percutaneous recanalization of the occluded iliac vein with stent placement appears to be successful in the short term, with good patency, significant symptom resolution, and minimal morbidity.

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 γ-radiation after PTA has a positive effect on lumen dimensions at 6-month follow-up by inducing positive vascular remodeling (ie, vascular dilatation); γ-radiation seemed not to affect plaque growth. In addition, γ-radiation has an effect on the healing process of dissections after PTA. (J Vasc Surg 2002;36:318-24.)

Effect of endovascular stent strut geometry on vascular injury, myointimal hyperplasia, and restenosis

Purpose: Early restenosis and the development of myointimal hyperplasia in stented blood vessels have been attributed to deep vascular injury with fracture of the internal elastic lamina (IEL). The purpose of this study was the evaluation of the vascular wall response to superficial injury (without IEL rupture) after balloon angioplasty and intravascular stent placement in porcine arteries and the determination of the effect of stent strut geometry on the degree of vessel injury and early restenosis. Methods: Balloon-expandable stainless-steel stents were placed into the iliac arteries of 10 Sinclair miniature swine that had been fed an atherogenic diet. A Palmaz stent, with rectangular struts and smooth corners, was randomly assigned to one iliac artery (group 1), and a novel stent, which was designed and manufactured in the laboratory with thicker struts and sharper corners specifically to induce large wall stress concentrations, was placed in the contralateral iliac artery (group 2). Intravascular ultrasound scan was used in all deployments to ensure accurate balloon sizing and to avoid stent overexpansion and deep vascular injury. At 90 days after implantation, the animals were killed, the stented vessels harvested, and histomorphometric analysis performed. Results: Deployment of novel stents in group 2 resulted in a statistically higher incidence rate of deep vascular injury (fracture of the IEL) compared with group 1, despite identical balloon size used for deployment (with Student t test, P < .05). Vessels with deep injury showed a 10-fold increase in myointimal thickening compared with those vessels in which the IEL remained intact. A statistically higher restenosis rate was observed for group 2 (33.5% ± 19.90%) compared with group 1 (20.39% ± 14.70%). For both stent designs, there was a trend toward lower degrees of restenosis within the mid-portion of the stent. For superficially injured arteries in both groups, no correlation was observed between the amount of vessel wall/medial layer compression and the development of restenosis from myointimal hyperplasia. Conclusion: Maintenance of an intact IEL is an important factor in the prevention of myointimal hyperplasia and restenosis in stented porcine iliac arteries. The alteration of stent strut height and geometry does not significantly affect restenosis and the development of myointimal hyperplasia in vessels with superficial injury. Superficial injury elicits a response that is independent of stent strut geometry and vessel wall compression. Stent strut profile may, however, increase local vessel wall stress concentrations, leading to IEL rupture and an exaggerated response to injury. (J Vasc Surg 2002;36:143-9.)