Automated calcium burden measurement in internal carotid artery plaque with CT: a hierarchical adaptive approach.

AIM: Calcium burden measurement in internal carotid artery (ICA) plaque could play an important role in assessing stroke risk and stenosis quantification in the ICA. We propose an automatic method for labelling calcified plaques in ICA in CT images. METHODS: Our approach builds upon the mean shift paradigm via an adaptive thresholding strategy. The data consists of single CT slices from 75 patients, with variety of plaque sizes and number of calcium regions. The manual measurements were carried out by a neuroradiologist for benchmarking. The calcium burden was measured as the area of the labelled plaque. Various metrics were employed to compare manual and automated measurements including correlation coefficient (CC), dice similarity (DS), Jacard Index (JI), polyline distance metric (PDM) and precision of merit (PoM). RESULTS: We found that our automated method of calcium area characterization performed accurately compared to manual measurements with CC=0.978, and PoM=0.915. The PDM, DS, and JI, also indicate a good performance with a mean DS=0.85 (SD=0.085), a mean JI=0.747 (SD=0.12), and a mean PDM=0.195 (SD=0.177). CONCLUSION: The proposed approach for calcium burden measurement, yields reasonably accurate labelling of calcified plaque when benchmarked against manual measurements. The approach is independent of the number and size of calcium regions, and the prototype design shows encouraging results to be adaptable to clinical practice.

Femoropopliteal in-stent restenosis: current treatment strategies.

Nitinol self-expanding stents are increasingly used to treat symptomatic peripheral arterial disease. Despite reduction in procedural complications and rates of stent fracture, femoropopliteal in-stent restenosis (FP-ISR) remains a common and important clinical problem. Due to heterogenous patient and angiographic characteristics, treatment of FP-ISR continues to evolve. Multiple modalities have been evaluated including standard balloon angioplasty, cutting or scoring balloon angioplasty, repeat stenting (nitinol stent vs. stent-graft vs. drug eluting stent), excisional or laser atherectomy, drug coated balloon angioplasty, and atherectomy followed by drug coated balloon angioplasty. This review highlights the clinical evidence for the currently available modalities in the treatment of FP-ISR. Future studies should utilize uniform classification schemes and assess similar outcomes to help determine the optimal approach for endovascular treatment of FP-ISR.

The role of stent-grafts for prevention and treatment of restenosis.

Restenosis rates in the superficial femoral artery remain high in patients treated with balloon angioplasty or bare metal stents. Stent-grafts represent an alternative endovascular treatment modality for these patients. In the US, the only FDA-approved stent-graft for femoral use is the Viabahn endoprosthesis (W.L. Gore, Flagstaff, AZ). The Viabahn is constructed of nitinol and ePTFE and has a proprietary heparin bioactive surface. Stent-grafts have the potential to reduce restenosis by impeding intimal hyperplasia and reducing tissue in-growth; however, the problem of edge restenosis has not been eliminated. Graft thrombosis remains an important mode of stent-graft failure. The Viabahn has been shown in observational studies and randomized trials to be an effective and safe treatment strategy compared to bare self-expanding stents and surgical prosthetic bypass grafts. Patient and appropriate lesion selection remain important in achieving long term patency. In this paper, we review the data surrounding the use of stent-grafts in the SFA to prevent and treat restenosis. Important technical considerations specific to the use of the Viabahn are also discussed.

Excimer laser assisted angioplasty for complex infrainguinal peripheral artery disease: a 2008 update.

Conventional percutaneous transluminal angioplasty (PTA) for complex or long segment infrainguinal occlusive arterial disease is limited by elastic recoil, dissection and restenosis, with high rates of intermediate and long term restenosis . Debulking with excimer laser has been advocated as a useful adjunctive strategy to improve procedural success and long term patency. This paper reviews the technological development of excimer laser, the studies supporting its use in infrainguinal arterial disease, effective and safe lasing techniques, its advantages, limitations and disadvantages. Case examples will be presented to illustrate its use in infrainguinal arterial disease. Although randomized controlled trials are lacking, existing registry and case series studies suggest efficacy of the excimer laser-assisted PTA for complex infrainguinal arterial disease, including patients with critical limb ischemia.

Excimer laser assisted angioplasty for the treatment of critical limb ischemia.

Two decades after the clinical introduction of percutaneous transluminal angioplasty (PTA), controversy still exists about the role of PTA for the treatment of occlusive disease in the femoropopliteal and infragenicular arteries. For the patient with critical limb ischemia (CLI), where diffuse disease and long occlusions are the rule, the results with PTA have not been optimal. Surgical revascularization has long been considered the gold standard for this patient population, but this procedure is associated with significant morbidity and mortality and up to 37% of patients may be poor surgical candidates. With advances in laser catheter design and refinement of recanalization techniques, improved results have been seen with laser assisted angioplasty of complex peripheral arterial disease. There has been renewed interest in excimer laser angioplasty for the treatment of patients with long total occlusions and diffuse disease who otherwise would have limited options for treatment. Excimer laser assisted angioplasty has been shown to be a successful approach to the treatment of long occlusions in the superficial femoral artery. Data from the recently completed Laser Angioplasty for Critical Limb Ischemia Phase 2 Trial (LACI) suggest that this is a viable treatment strategy for patients with CLI who are otherwise not good candidates for bypass surgery.

Mechanism of lumen enlargement with direct stenting versus predilatation stenting: influence of remodelling and plaque characteristics assessed by volumetric intracoronary ultrasound.

OBJECTIVE: To compare the effects of arterial remodelling and plaque characteristics on the mechanisms of direct stenting and predilatation stenting. Direct stenting has become routine in some laboratories and differs technically from predilatation stenting. METHODS: Pre- and post-interventional volumetric intravascular ultrasound (IVUS) was undertaken in 30 patients with direct stenting and in 30 with predilatation stenting of non-calcified native coronary lesions, using the same stent design and stent length. Lumen, vessel (external elastic membrane (EEM)), and plaque (plaque + media) volumes were calculated. Remodelling was determined by comparing the EEM area at the centre of the lesion with the EEM areas at proximal and distal reference sites. Plaque eccentricity was defined as the thinnest plaque diameter to the thickest plaque diameter ratio. Plaque composition was characterised as soft, mixed, or dense. RESULTS: All volumetric IVUS changes were similar in the two groups. Pre-intervention remodelling remained uninfluenced after direct stenting, but was neutralised after predilatation stenting. Eccentric lesions responded to intervention by a greater luminal gain owing to greater vessel expansion in direct stenting. Plaque composition influenced luminal gain in direct stenting, the gain being greatest in the softest plaques; in predilatation stenting, luminal gain was equivalent but vessel expansion was greater for "dense" plaque and plaque reduction greater for "soft" plaque. CONCLUSIONS: In non-calcified lesions, the mechanisms of lumen enlargement after direct or predilatation stenting are significantly influenced by atherosclerotic remodelling, plaque eccentricity, and plaque composition.

Intravascular radiation therapy after balloon angioplasty of narrowed femoropopliteal arteries to prevent restenosis: results of the PARIS feasibility clinical trial.

PURPOSE: To conduct a feasibility study to assess the feasibility, safety, and outcome of endoluminal gamma radiation therapy after balloon angioplasty of superficial femoral artery (SFA) lesions. MATERIALS AND METHODS: Forty patients with claudication were enrolled in the study and underwent percutaneous transluminal angioplasty (PTA) of SFA lesions with a mean lesion length of 9.8 cm +/- 3.0 and a mean reference vessel diameter of 5.2 mm +/- 3.1. After successful PTA, a segmented centering balloon catheter was positioned to cover the PTA site. The patients were then transported to the radiation oncology suite and treated with a microSelectron HDR afterloader with use of an Ir-192 source with a prescribed dose of 14 Gy, 2 mm into the vessel wall. Ankle-brachial index (ABI) and Rutherford score were evaluated at 1, 6, and 12 months after the procedure and angiographic follow-up was conducted at 6 months. RESULTS: Radiation was delivered successfully to 35 of 40 patients. There were no procedural complications. Exercise and rest ABI were higher at 1 year (0.72 +/- 0.26 and 0.89 +/- 0.18, respectively) compared to baseline (0.51 +/- 0.25 and 0.67 +/- 0.17, respectively). Maximum walking time on a treadmill increased from 3.41 min +/- 2.41 to 4.43 min +/- 2.49 at 30 days and was 4.04 min +/- 2.8 at 12 months. The angiographic binary restenosis rate at 6 months was 17.2% and the clinical restenosis rate at 12 months was 13.3%. There were no angiographic or clinical adverse events related to the radiation therapy. CONCLUSIONS: Intraarterial radiation after PTA of SFA lesions with use of high-dose rate gamma radiation is feasible and safe. The angiographic and clinical improvements are sustainable at 1 year and represent a potent antirestenotic therapy for the treatment of narrowed peripheral arteries.

Intravascular ultrasound-guided renal artery stenting.

PURPOSE: To evaluate the clinical outcomes of patients undergoing renal artery stenting with intravascular ultrasound (IVUS) guidance and compare measurements between IVUS and angiography. METHODS: One hundred thirty-one patients (71 women; mean age 71 +/- 8 years) underwent IVUS-guided Palmaz stent implantation in 153 stenotic renal arteries at a single center. The indications for stenting were uncontrolled hypertension (102, 77.9%), renal insufficiency (10, 7.6%), and both conditions (19, 14.5%). The majority of lesions were ostial (114, 74.5%); the remainder occupied the proximal renal artery (39, 25.5%). The mean lesion length and diameter stenosis were 6.5 +/- 3.0 mm and 74% +/- 10%, respectively, as measured by angiography. Data were recorded in a prespecified database; angiographic and IVUS images were analyzed at dedicated core laboratories and compared. RESULTS: Angiographic success was achieved in all patients, but IVUS indicated the need for additional intervention in 36 (23.5%) cases. There was strong correlation between the angiographic and IVUS measurements of lesion length (r = 0.60, p < 0.0001) and pre-/postprocedural minimal luminal diameter (r = 0.72 and 0.63, respectively; p < 0.0001). The mean contrast volume was 74 +/- 18 mL per case. In-hospital renal failure occurred in 8 (6.1%) patients; 2 (1.5%) required transient hemodialysis. At a mean 15-month follow-up, patients were treated with fewer antihypertensive medications (p = 0.05), and systolic and diastolic arterial blood pressures had decreased (p = 0.001); no significant change was noted in serum creatinine. CONCLUSIONS: IVUS-guided stenting facilitates safe renal artery revascularization. IVUS imaging may complement angiography in certain cases, which should be studied further in prospective studies with iodinated or noniodinated contrast agents.

Intravascular ultrasound assessment of the stenoses location and morphology in the left main coronary artery in relation to anatomic left main length.

Eighty-seven left main stenoses were evaluated by angiography and intravascular ultrasound. Intravascular ultrasound analysis included left main length (bifurcation to ostium), stenosis location, stenosis length, stenosis external elastic membrane, lumen, plaque & media cross-sectional area (CSA), plaque burden (plaque & media/external elastic membrane CSA), calcium arc, calcium length, eccentricity, and remodeling index (stenosis/reference external elastic membrane CSA). Long anatomic left main arteries (length > or =10 mm, n = 43) were compared with short anatomic left main arteries (length <10 mm, n = 44) regarding stenosis location. Ostial (proximal third of left main artery) (n = 32) and nonostial (midthird and distal third) stenoses (n = 55) were compared regarding stenosis morphology. Short anatomic left main arteries developed stenoses more frequently near the ostium (ostium 55%, bifurcation 38%). Conversely, long anatomic left main arteries developed stenoses more frequently near the bifurcation (ostium 18%, bifurcation 77%, p = 0.001). Ostial left main stenoses were more common in women (44% vs 20%, p = 0.02), had larger lumen area (6.2 +/- 2.2 vs 4.6 +/- 2.3 mm(2), p = 0.002), less plaque burden (62 +/- 15% vs 80 +/- 9%, p <0.0001), less calcification (arc = 78 +/- 65 degrees vs 195 +/- 101 degrees, p <0.0001), and more negative remodeling (remodeling index = 0.87 +/- 0.19 vs 1.01 +/- 0.21, p = 0.005) than nonostial left main stenoses. Most ostial left main stenoses were categorized as eccentric (97% vs 76%, p = 0.01). Short and long left main arteries develop stenoses at different locations. Stenosis morphology was significantly different in these 2 locations.

Transient contrast encephalopathy after carotid artery stenting.

PURPOSE: To report an unusual case of transient contrast encephalopathy arising after carotid artery stenting. CASE REPORT: An 82-year-old right-handed man with a recent history of transient ischemic events was admitted to the hospital for evaluation of carotid artery disease. During cerebral angiography, which identified a 90% right internal carotid artery stenosis, the patient received 25 mL of an ionic, low-osmolar contrast agent (ioxaglate) in each carotid artery. The following day he underwent successful carotid stenting, during which 180 mL of ioxaglate were used. He developed rapidly worsening confusion and left hemiparesis on the table. Noncontrast computed tomography showed marked cortical enhancement and edema of the right cerebral hemisphere in the distribution of the right anterior and middle cerebral arteries. The patient improved rapidly and by day 2 was completely recovered; magnetic resonance imaging documented no cortical edema and normal sulci. One month after the procedure, he was well, with patent carotid arteries. CONCLUSIONS: Transient neurotoxicity after carotid interventions must be differentiated from massive cerebral infarction and hyperperfusion syndrome, but the prognosis is excellent. However, subsequent contrast studies in a patient with this complication should be undertaken with extreme caution.

Excimer laser-assisted recanalization of long, chronic superficial femoral artery occlusions.

PURPOSE: To examine the safety and efficacy of excimer laser-assisted angioplasty (ELA) for recanalization of superficial femoral artery (SFA) occlusions. METHODS: Data were analyzed from 318 consecutive patients (207 men; mean age 64.2 +/- 10.7 years, range 33-91) who underwent ELA of 411 SFAs with chronic occlusions averaging 19.4 +/- 6.0 cm in length. More than 75% of patients had severe claudication (category 3). Critical lower limb ischemia with rest pain or minor tissue loss was present in 6 and 15 patients, respectively. The mean ankle brachial index (ABI) before and after exercise was 0.62 +/- 0.15 and 0.40 +/- 0.18, respectively. RESULTS: The initial attempt (crossover approach 89.7%, antegrade 6.6%, transpopliteal 3.6%) to cross the occlusion with an excimer laser catheter was successful in 342 (83.2%) of 411 limbs. A secondary attempt performed in 44 of 69 failed cases was successful in 30 limbs, increasing the technical success rate to 90.5% (372/411). Complications included acute reocclusion (4, 1.0%), perforation (9, 2.2%), and distal thrombosis/embolization (16, 3.9%). Postprocedurally, 219 (68.8%) patients were asymptomatic; mild (category 1) or moderate (category 2) claudication remained in 53 (16.6%) and 26 (8.2%) patients, respectively. The primary patency at 1 year was 33.6%. In the majority of patients, reocclusion was treatable on an outpatient basis. The 1-year assisted primary and secondary patency rates were 65.1% and 75.9%, respectively. CONCLUSIONS: Long SFA occlusions can be recanalized safely and successfully by ELA. However, to maintain patency and quality of life, intensive surveillance using objective testing followed by prompt repeat intervention are mandatory.

Carotid artery stenting in patients with high-risk anatomy for carotid endarterectomy.

PURPOSE: To report the results of carotid artery stenting (CAS) in patients considered to have high-risk anatomical characteristics for carotid endarterectomy. METHODS: CAS was performed in 39 carotid arteries of 37 consecutive patients (26 men; mean age 72 +/- 8 years, range 56-88) who met the criteria for high-risk surgical anatomy: previous ipsilateral carotid endarterectomy (20/39, 51.3%), common carotid bifurcation above the mandibular angle (5/39, 12.8%), contralateral carotid artery occlusion (15/39, 38.5%), or previous radiation therapy to the neck (1/39, 2.6%). Palmaz, Integra, or Wallstents were deployed via a percutaneous femoral artery access. Independent neurological evaluation was performed at specified time points, and a dedicated committee adjudicated all clinical events. RESULTS: Procedural success was 100%, with no major in-hospital complications. Neurological events were rare. Only 1 (2.6%) transient ischemic attack occurred prior to discharge; at 30 days, 1 (2.6%) additional minor stroke had been observed, giving a 2.6% cumulative 30-day "death plus any stroke" rate. Over a mean 11 +/- 6-month follow-up, 2 (5.4%) patients died of nonneurological causes, but there were no strokes. CONCLUSIONS: CAS is a viable endovascular revascularization technique that can be performed safely and effectively in patients with high-risk anatomy for carotid endarterectomy.

Percutaneous arterial aortoiliac intervention.

Historically reconstructive vascular surgery, has been a cornerstone of treatment for symptomatic obliterative aortoiliac disease. Surgical results include a reported aortobifemoral bypass 5-year patency rate from 85% to 90% and a 10-year patency rate of 70% to 75%. Operative mortality for aortoiliac reconstruction ranges from 1.6% to 3.3%, with an aggregated systemic morbidity of 8.3%. Clinical indications for surgical intervention are well-established and are limited primarily to severe claudication and limb-threatening ischemia. Broader application of surgical intervention is not recommended because of significant morbidity and mortality associated with the procedure. As balloon angioplasty and endovascular stenting technologies evolve, they are proving to be an effective modality for the treatment of aortoiliac disease. These lower risk procedures have allowed expansion of traditional indications for intervention. Treatment is recommended presently for patients with clinical symptoms that impact lifestyle and professional requirements. Less conventional indications include allowing access for coronary intervention or for placement of an intra-aortic balloon pump, or improving inflow prior to a distal surgical bypass procedure. Results of aortoiliac percutaneous interventions are difficult to compare with surgical data since methods and technology continue to improve and evolve, and randomized studies are limited. It is clear that as long as outcomes of percutaneous interventions are predictable and secondary patency rates acceptable, the low complication rates of a percutaneous intervention are clearly preferable to a riskier surgical alternative.

The management of acute limb ischemia: techniques for dealing with thrombus.

Acute limb ischemia (ALI) has long been a major clinical problem, producing significant risks for limb loss and death. It is most commonly caused by arterial thrombosis in the setting of underlying atherosclerotic peripheral vascular disease or by arterial embolism, usually of cardiac origin. Over the past several decades, preferred treatment options for ALI have alternated between medical and surgical approaches. More recently, direct intra-arterial thrombolysis became the standard of care after several randomized trials demonstrated the benefit of this approach as compared with acute surgical intervention. Despite all of the experience with direct intra-arterial thrombolysis for the treatment of ALI, the optimal thrombolytic approach not been clearly established. Current investigation is directed at identifying the ideal thrombolytic agent for this purpose and the appropriate dosing regimen. In addition, there is interest in the newer mechanical thrombectomy devices and the use of platelet glycoprotein IIb/IIIa inhibitors to speed the time to reperfusion of the acutely ischemic limb.

Postprocedural hypotension after carotid artery stent placement: predictors and short- and long-term clinical outcomes.

PURPOSE: To describe the predictors of persistent hypotension after carotid artery stent (CAS) placement and define the clinical outcome of patients with this hemodynamic disturbance. MATERIALS AND METHODS: One hundred forty CAS procedures were performed in 133 consecutive patients. Post-CAS hypotension-defined as a greater than 40 mm Hg decrease in arterial pressure without evidence of hypovolemia, with a systolic pressure lower than 90 mm Hg at the end of CAS and lasting at least 1 hour-was observed in 25 patients (group 1); 108 patients did not have hypotension (group 2). RESULTS: Post-CAS hypotension developed in 33.9% of cases after balloon-expandable stent placement versus in 13.6% of cases after self-expanding stent placement (P =.04). In-hospital minor ipsilateral strokes occurred in 16% of cases in group 1 versus in 3% of cases in group 2 (P =.03). There was one (0.9%) major stroke (transient) and three (2.6%) transient ischemic attacks, all of which occurred in group 2 (not significant vs group 1 for both conditions). At 10 months +/- 4 (SD) of follow-up, there was greater total mortality in group 1 than in group 2 (20% vs 4%, P =.02), whereas neurologic events did not differ significantly between the groups. CONCLUSION: Hypotension due to carotid sinus stimulation is frequent after CAS with balloon-expandable stents. This phenomenon correlates with increased in-hospital complications and long-term risk of death.

Treatment of symptomatic cervical carotid dissections with endovascular stents.

OBJECTIVE: Symptomatic dissections of the cervical carotid artery (CCA) can be spontaneous or secondary to trauma and may be associated with pseudoaneurysms. Surgical treatment is often difficult or unavailable. We report the successful use of endovascular stents in the treatment of symptomatic dissection of the CCA. METHODS: Five consecutive patients with symptomatic CCA dissection were seen at our institution. There were four female patients and one male patient, ranging in age from 19 to 56 years. One dissection was spontaneous. The others were secondary to a gunshot wound (one patient), blunt neck trauma (two patients), and endovascular treatment of atherosclerotic carotid bifurcation disease (one patient). Balloon-expandable and self-expanding stents were placed via a transfemoral approach. RESULTS: Success in restoring the carotid lumen with two to five stents in each patient was angiographically demonstrated. There were no procedure-related complications. All patients experienced significant clinical improvement within the first 24 hours and complete long-term recovery. CONCLUSION: Symptomatic dissections of the CCA can be successfully treated by using endovascular stents.

Intra-arterial reteplase for the treatment of acute limb ischemia.

The removal of urokinase from the market has created a dilemma for interventionists and vascular surgeons treating patients with acute limb threatening ischemia due to arterial thrombosis or embolization. Reteplase is a newer, fibrin-specific thrombolytic agent with properties that make it an attractive alternative to urokinase. We report two cases of successful treatment of acute, limb threatening ischemia with intra-arterial Reteplase therapy.

Progressive vascular remodeling and reduced neointimal formation after placement of a thermoelastic self-expanding nitinol stent in an experimental model.

Despite the improvements afforded by intracoronary stenting, restenosis remains a significant problem. The optimal physical properties of a stent have not been defined. We compared the vascular response to a thermoelastic self-expanding nitinol stent with a balloon-expandable tubular slotted stainless steel stent in normal porcine coronary arteries. Twenty-two stents (11 nitinol and 11 tubular slotted) were implanted in 11 miniature swine. The nitinol stents were deployed using the intrinsic thermal properties of the metal, without adjunctive balloon dilation. The tubular slotted stents were implanted using a noncompliant balloon with a mean inflation pressure of 12 atm. Intravascular ultrasound (IVUS) and histology were used to evaluate the vascular response to the stents. The mean cross-sectional area (CSA) of the nitinol stents (mm2) as measured by IVUS increased from 8.13 +/- 1.09 at implant to 9.10 +/- 0.99 after 28 days (P = 0.038), while the mean CSA of the tubular slotted stents was unchanged (7.84 +/- 1.39 mm2 vs. 7.10 +/- 1.07 mm2, P = 0.25). On histology at 3 days, the tubular slotted stents had more inflammatory cells adjacent to the stent wires (5.7 +/- 1.5 cells/0.1 mm2) than the nitinol (3.9 +/- 1.3 cells/0.1 mm2, P = 0.016). The tubular slotted also had increased thrombus thickness (83 +/- 85 microm) than the nitinol stents (43 +/- 25 microm, P = 0.0014). After 28 days, the vessel injury score was similar for the nitinol (0.6 +/- 0.3) and the tubular slotted (0.5 +/- 0.1, P = 0.73) designs. The mean neointimal area (0.97 +/- 0.46 mm2 vs. 1.96 +/- 0.34 mm2, P = 0.002) and percent area stenosis (15 +/- 7 vs. 33 +/- 7, P = 0.003) were significantly lower in the nitinol than in the tubular slotted stents, respectively. We conclude that a thermoelastic nitinol stent exerts a more favorable effect on vascular remodeling, with less neointimal formation, than a balloon-expandable design. Progressive intrinsic stent expansion after implant does not appear to stimulate neointimal formation and, therefore, may provide a mechanical solution to prevent in-stent restenosis.