Effect of balloon angioplasty on femoral artery evaluated with intravascular ultrasound imaging

Patient-specific finite element simulation of peripheral artery percutaneous transluminal angioplasty to evaluate the procedure outcome without stent implantation

The purpose of this work is to present a patient-specific (PS) modeling approach for simulating percutaneous transluminal angioplasty (PTA) endovascular treatment and assessing the balloon sizing influence on short-term outcomes in peripheral arteries, i.e. without stent implantation. Two 3D PS stenosed femoral artery models, one with a dominant calcified atherosclerosis while the other with a lipidic plaque, were generated from pre-operative computed tomography angiography images. Elastoplastic constitutive laws were implemented within the plaque and artery models. Implicit finite element method (FEM) was used to simulate the balloon inflation and deflation for different sizings. Besides vessel strains, results were mainly evaluated in terms of the elastic recoil ratio (ERR) and lumen gain ratio (LGR) attained immediately after PTA. Higher LGR values were shown within the stenosed region of the lipidic patient. Simulated results also showed a direct and quantified correlation between balloon sizing and LGR and ERR for both patients after PTA, with a more significant influence on the lumen gain. The max principal strain values in the outer arterial wall increased at higher balloon sizes during inflation as well, with higher rates of increase when the plaque was calcified. Results show that our model could serve in finding a compromise for each stenosis type: maximizing the achieved lumen gain after PTA, but at the same time without damaging the arterial tissue. The proposed methodology can serve as a step toward a clinical decision support system to improve angioplasty balloon sizing selection prior to the surgery.

Influence of balloon design, plaque material composition, and balloon sizing on acute post angioplasty outcomes: An implicit finite element analysis

In this work we propose a generic modeling approach for simulating percutaneous transluminal angioplasty (PTA) endovascular treatment, and evaluating the influence of balloon design, plaque composition, and balloon sizing on acute post-procedural outcomes right after PTA, without stent implantation. Clinically-used PTA balloons were classified into two categories according to their compliance characteristics, and were modeled correspondingly. Self-defined elastoplastic constitutive laws were implemented within the plaque and artery models, after calibration based on experimental and clinical data. Finite element method (FEM) implicit solver was used to simulate balloon inflation and deflation. Besides balloon profile at max inflation, results are mainly assessed in terms of the elastic recoil ratio (ERR) and lumen gain ratio (LGR) obtained immediately after PTA. No variations in ERR nor LGR values were detected when the balloon design changed, despite the differences observed in their profile at max inflation. Moreover, LGR and ERR inversely varied with the augmentation of calcification level within the plaque (-11% vs. +4% respectively, from fully lipidic to fully calcified plaque). Furthermore, results showed a direct correlation between balloon sizing and LGR and ERR, with noticeably higher rates of change for LGR (+18% and +2% for LGR and ERR respectively for a calcified plaque and a balloon pressure increasing from 10 to 14 atm). However a larger LGR comes with a higher risk of arterial rupture. This proposed methodology opens the way for evaluation of angioplasty balloon selections towards clinical procedure optimization.

New Innovations and Devices in the Management of Chronic Limb-Threatening Ischemia

As the number of patients afflicted by chronic limb-threatening ischemia (CLTI) continues to grow, new solutions are necessary to provide effective, durable treatment options that will lead to improved outcomes. The diagnosis of CLTI remains mostly clinical, and endovascular revascularization remains mostly balloon-based. Multiple innovative techniques and technologies are in development or in early usage that may provide new solutions. This review categorizes areas of advancement, highlights recent developments in the management of CLTI and looks forward to novel devices that are currently under investigation.

Usefulness of the “Non-Slip Element” Percutaneous Transluminal Angioplasty Balloon in the Treatment of Femoropopliteal Arterial Lesions

Purpose: To evaluate a new scoring balloon, the non-slip element (NSE) percutaneous transluminal angioplasty (PTA) balloon, in the treatment of femoropopliteal lesions by comparing angiographic dissection patterns to those of a conventional balloon. Methods: This retrospective, single-center study included 71 symptomatic patients (mean age 77.4±8.8 years; 33 men) with de novo femoropopliteal lesions <20 cm long treated with balloon angioplasty between January 2017 and May 2018. Thirty-four patients were treated with 3 inflations of an NSE balloon and 37 patients were treated with a conventional balloon. Results: Severe dissections were fewer (8.8% vs 29.7%, p=0.027) and the total dissection length was shorter (11.5±12.8 vs 35.7±24.1 mm, p=0.027) in the NSE group. The bailout stenting rate was also lower in the NSE group (17.6% vs 40.5%, p=0.035). There were no significant differences between the groups regarding lesion length (70.3±50.4 vs 77.8±56.6 mm, p=0.28), inflation time (294±162 vs 353±179 seconds, p=0.08), or inflation pressure (10.6±5.0 vs 11.3±5.3 atm, p=0.31). Conclusion: Three NSE balloon inflations may reduce severe dissections induced by balloon angioplasty in femoropopliteal lesions.

A Novel Endoluminal Ultrasound Imaging Technique to Determine Urethral Luminal Cross-Sectional Area

INTRODUCTION AND OBJECTIVES

Retrograde urethrogram (RUG) and voiding cystourethrogram (VCUG) are currently the gold standard imaging technique for diagnosis of urethral stricture and determination of stricture location. However, RUG and VCUG have multiple limitations. These techniques require exposure to ionizing radiation, the quality is operator and patient dependent, there is a moderate degree of invasiveness with urethral catheterization, can have artifacts because of patient positioning that underestimates stricture length. The development of novel imaging modalities without ionizing radiation to accurately evaluate the presence, location, length, and lumen cross-sectional area (CSA) of the urethral stricture would be of great value. The objective of this study was to develop a novel endoluminal ultrasound (ELUS) imaging technique that permits the accurate quantitation of urethral stricture.

METHODS

Urethral strictures were created in rabbits (n = 5) by electrocautery and an ELUS technique was developed for subsequent luminal imaging. A 3.2F 40 MHz ultrasound (US) probe was introduced transurethrally and infused with US contrast agent. Images were recorded as the catheter was pulled back at a constant speed to acquire tomographic images. Lumen CSA over the entire urethral length was calculated using a custom methodology and validated in our laboratory.

RESULTS

Urethral luminal CSA over the entire length of urethra before and after experimental stricture development was quantified including the length of stenosis. Intra- and interobserver variability (r = 0.99 for both) was excellent.

CONCLUSIONS

Feasibility of ELUS as a quantitative technique to determine healthy urethral lumen and stricture CSA was demonstrated. The translational potential for a nonionizing imaging modality to better describe CSA, length, location, and uninvolved urethral CSA of the stricture is a significant improvement over current methodology.

Directional Atherectomy Followed by a Paclitaxel-Coated Balloon to Inhibit Restenosis and Maintain Vessel Patency: Twelve-Month Results of the DEFINITIVE AR Study

Background—

Studies assessing drug-coated balloons (DCB) for the treatment of femoropopliteal artery disease are encouraging. However, challenging lesions, such as severely calcified, remain difficult to treat with DCB alone. Vessel preparation with directional atherectomy (DA) potentially improves outcomes of DCB.

Methods and Results—

DEFINITIVE AR study (Directional Atherectomy Followed by a Paclitaxel-Coated Balloon to Inhibit Restenosis and Maintain Vessel Patency—A Pilot Study of Anti-Restenosis Treatment) was a multicenter randomized trial designed to estimate the effect of DA before DCB to facilitate the development of future end point-driven randomized studies. One hundred two patients with claudication or rest pain were randomly assigned 1:1 to DA+DCB (n=48) or DCB alone (n=54), and 19 additional patients with severely calcified lesions were treated with DA+DCB. Mean lesion length was 11.2±4.0 cm for DA+DCB and 9.7±4.1 cm for DCB (P=0.05). Predilation rate was 16.7% for DA+DCB versus 74.1% for DCB; postdilation rate was 6.3% for DA+DCB versus 33.3% for DCB. Technical success was superior for DA+DCB (89.6% versus 64.2%; P=0.004). Overall bail-out stenting rate was 3.7%, and rate of flow-limiting dissections was 19% for DCB and 2% for DA+DCB (P=0.01). One-year primary outcome of angiographic percent diameter stenosis was 33.6±17.7% for DA+DCB versus 36.4±17.6% for DCB (P=0.48), and clinically driven target lesion revascularization was 7.3% for DA+DCB and 8.0% for DCB (P=0.90). Duplex ultrasound patency was 84.6% for DA+DCB, 81.3% for DCB (P=0.78), and 68.8% for calcified lesions. Freedom from major adverse events at 1 year was 89.3% for DA+DCB and 90.0% for DCB (P=0.86).

Conclusions—

DA+DCB treatment was effective and safe, but the study was not powered to show significant differences between the 2 methods of revascularization in 1-year follow-up. An adequately powered randomized trial is warranted.

Clinical Trial Registration—

http://www.clinicaltrials.gov. Unique Identifier: NCT01366482.

Computational Modeling and Comparative Tissue Damage Analysis of Angioplasty and Orbital Atherectomy Interventional Procedures

This research was directed toward quantitatively characterizing the effects of arterial mechanical treatment procedures on the stress and strain energy states of the artery wall. Finite element simulations of percutaneous transluminal angioplasty (PTA) and orbital atherectomy (OA) were performed on arterial lesion models with various extents and types of plaque. Stress fields in the artery were calculated and strain energy density was used as an explicit description of potential damage to the artery. The research also included numerical simulations of changes in arterial compliance due to orbital atherectomy. The angioplasty simulations show that the damage energy fields in the media and adventitia are predominant in regions of the lesion that are not protected by a layer of calcification. In addition, it was observed that softening the plaque components leads to a lower peak stress and therefore lesser damage energy in the media and adventitia under the action of a semicompliant balloon. Orbital atherectomy simulations revealed that the major portion of strain energy dissipated is concentrated in the plaque components in contact with the spinning tool. The damage and peak stress fields in the media and adventitia components of the vessel were significantly less. This observation suggests less mechanically induced trauma during a localized procedure like orbital atherectomy. Artery compliance was calculated pre- and post-treatment and an increase was observed after the orbital atherectomy procedure. The localized plaque disruption produced in atherectomy suggests that the undesirable stress states in angioplasty can be mitigated by a combination of procedures such as atherectomy followed by angioplasty.

Infrainguinal Atherectomy Using the Transluminal Endarterectomy Catheter: Patency Rates and Clinical Success for 144 Procedures

Purpose:

To determine if atherectomy using the transluminal endarterectomy catheter (TEC) is an effective endoluminal therapy for infrainguinal occlusive disease.

Methods:

Three surgeons used the TEC for 144 infrainguinal atherectomy procedures in 133 patients. The indications were severe claudication in 83, critical ischemia in 56, and graft stenosis in 5 limbs. The pathology was stenosis in 36 and occlusion in 105 limbs. Balloon dilation was also performed in 109 and stenting in 17 limbs.

Results:

There was initial technical and anatomic success in 124 (86%) procedures. There were 67 technically successful procedures at mean follow-up of 19 months, although 3 of these limbs with gangrene and extensive distal disease required major amputation. There were 26 failures due to stenosis leading to further intervention and 51 due to occlusion. Twenty of these cases were managed conservatively, 21 were treated with repeat endovascular intervention, 31 with bypass grafting, and 5 with amputation. Repeat intervention in 52 limbs resulted in 36 with patent arteries, 10that are occluded, and 6that required amputation. Thirteen of the 14 amputations were for limbs with critical ischemia, but 1 was in a patient with claudication. Life-table analysis showed that the primary patency rate was 51%, the assisted primary patency rate was 61%, and the secondary patency rate was 75% at 15 months. The clinical success rate was 49%, and the salvage rate for limbs with critical ischemia was 78% at 12 months. Univariate log-rank testing showed no significant differences according to the clinical presentation or pathology, but results were worse for lesions > 5 cm long due to more frequent immediate failures. However, multivariate Cox regression analysis showed that results were significantly worse for critical ischemia than for claudication, stenosis compared to occlusions, for limbs with poor runoff, for operations performed by percutaneous rather than an open approach, and for those performed more recently.

Conclusions:

TEC atherectomy may have a place in selected patients, but the optimal circumstances for its use and long-term efficacy require further study.

Intravascular Ultrasound Guidance for Peripheral Vascular Interventions

Intravascular ultrasound (IVUS) imaging during peripheral endovascular interventions adds important information regarding the distribution of disease by providing controlled measurements of the cross-sectional area of the vessel lumen and wall prior to and following procedures. IVUS is useful in determining the mechanism and efficacy of balloon angioplasty, in guiding atherectomy devices, and in assuring appropriate placement of intravascular stents. The incorporation of an IVUS element into catheter-based interventional devices may improve the immediate and long-term results of endovascular interventions by decreasing complications from dissection and perforation of the arterial wall. Combined IVUS-stent prototype catheters are being developed to enable imaging and deployment simultaneously. Similar devices are being explored to enhance expedient, precise delivery of endoluminal grafts. Future studies of endovascular techniques should include IVUS, when possible, to accurately quantitate the initial efficacy of devices and to determine the nature and distribution of recurrent lesions.

Femoropopliteal Venous Bypass Studied with Intravascular Ultrasound: A Case Report

Purpose:

To describe the ability of intravascular ultrasound (IVUS) to document the status of the greater saphenous vein during bypass surgery, the long-term changes in the bypass, and the effects of balloon angioplasty on vein graft stenoses.

Methods:

An 80-year-old female underwent in situ femoropopliteal venous bypass grafting. Vein graft stenosis developed 6 months later, necessitating balloon angioplasty. The angioplasty failed, and a polytetrafluoroethylene (e-PTFE) interposition graft was placed. Ten months after bypass surgery, balloon angioplasty was performed for new stenoses. This procedure also failed, and the venous bypass and interposition graft were removed and replaced by an e-PTFE graft. IVUS images obtained during the first surgery were compared with those obtained 10 months later. Histologic sections were used to confirm the IVUS findings.

Results:

IVUS detected a distinct narrowed venous segment, pre-existent intimal thickening, and disrupted valves. Over the follow-up period, both the pre-existent intimal thickening and the narrowed segment evolved into stenoses, necessitating treatment. Luminal gain after balloon angioplasty of graft stenosis was associated with vascular damage.

Conclusions:

This report shows that IVUS has the ability to document long-term venous bypass alterations and to demonstrate the effect of balloon angioplasty on venous bypass stenoses.

Intravascular Ultrasound in Endovascular Stent-Grafts for Peripheral Aneurysm: A Clinical Study

Purpose:

To evaluate the potential diagnostic information of intraprocedural intravascular ultrasound (IVUS) in patients undergoing endovascular stent-grafting for peripheral aneurysm.

Methods:

IVUS was used in 17 patients preprocedurally to measure the diameter of the proximal and distal neck and the length of the aneurysm. Balloon and stent-graft sizes were selected based on these measurements. Following stent-graft deployment, angiography and IVUS were used to document stent apposition and the configuration and diameter of the stent-graft.

Results:

Stent-graft insertion was considered successful in 8 patients based on angiography and IVUS images. In 9 others, both imaging modalities showed inadequate results, necessitating 12 additional procedures: balloon angioplasty for stent-graft stenosis (2) and inadequate stent-graft apposition (1); an additional stent-graft (4); an extra stent (1); thrombectomy (2); and conversion (2) for inadequate stent-graft position and a graft rupture. In these patients, intraprocedural IVUS was superior to angiography in contributing vital information to aid in the selection of the additional interventions.

Conclusions:

During management of peripheral aneurysms with endovascular stent-grafts, IVUS monitoring was a useful adjunct when the initial procedure was unsatisfactory and/or when intraprocedural angiographic studies were inconclusive.

Intravascular Ultrasound in Lower Extremity Peripheral Vascular Interventions

Purpose: To examine the impact of intravascular ultrasound (IVUS) utilization during lower limb endovascular interventions as regards postprocedural complications and amputation. Methods: The study cohort was derived from the Healthcare Cost and Utilization Project Nationwide Inpatient Sample database between the years 2006 and 2011. Peripheral endovascular interventions were identified using appropriate ICD-9 procedure codes. Two-level hierarchical multivariate mixed models were created. The co-primary outcomes were in-hospital mortality and amputation; the secondary outcome was postprocedural complications. Model results are given as the odds ratio (OR) and 95% confidence interval (CI). Hospitalization costs were also assessed. Results: Overall, among the 92,714 patients extracted from the database during the observation period, IVUS was used in 1299 (1.4%) patients. IVUS utilization during lower extremity peripheral vascular procedures was independently predictive of a lower rate of postprocedural complications (OR 0.80, 95% CI 0.66 to 0.99, p=0.037) as well as lower amputation rates (OR 0.59, 95% CI 0.45 to 0.77, p<0.001) without any significant impact on in-hospital mortality. Multivariate analysis also revealed IVUS utilization to be predictive of a nonsignificant increase in hospitalization costs ($1333, 95% CI −$167 to +$2833, p=0.082). Conclusion: IVUS use during lower limb endovascular interventions is predictive of lower postprocedural complication and amputation rates with a nonsignificant increase in hospitalization costs.

Simulation of human atherosclerotic femoral plaque tissue: the influence of plaque material model on numerical results

Background

Due to the limited number of experimental studies that mechanically characterise human atherosclerotic plaque tissue from the femoral arteries, a recent trend has emerged in current literature whereby one set of material data based on aortic plaque tissue is employed to numerically represent diseased femoral artery tissue. This study aims to generate novel vessel-appropriate material models for femoral plaque tissue and assess the influence of using material models based on experimental data generated from aortic plaque testing to represent diseased femoral arterial tissue.

Methods

Novel material models based on experimental data generated from testing of atherosclerotic femoral artery tissue are developed and a computational analysis of the revascularisation of a quarter model idealised diseased femoral artery from a 90% diameter stenosis to a 10% diameter stenosis is performed using these novel material models. The simulation is also performed using material models based on experimental data obtained from aortic plaque testing in order to examine the effect of employing vessel appropriate material models versus those currently employed in literature to represent femoral plaque tissue.

Results

Simulations that employ material models based on atherosclerotic aortic tissue exhibit much higher maximum principal stresses within the plaque than simulations that employ material models based on atherosclerotic femoral tissue. Specifically, employing a material model based on calcified aortic tissue, instead of one based on heavily calcified femoral tissue, to represent diseased femoral arterial vessels results in a 487 fold increase in maximum principal stress within the plaque at a depth of 0.8 mm from the lumen.

Conclusions

Large differences are induced on numerical results as a consequence of employing material models based on aortic plaque, in place of material models based on femoral plaque, to represent a diseased femoral vessel. Due to these large discrepancies, future studies should seek to employ vessel-appropriate material models to simulate the response of diseased femoral tissue in order to obtain the most accurate numerical results.

Mechanical, biological and structural characterization of human atherosclerotic femoral plaque tissue

The failure of endovascular treatments of peripheral arterial disease represents a critical clinical issue. Specialized data are required to tailor such procedures to account for the mechanical response of the diseased femoral arterial tissue to medical device deployment. The purpose of this study is to characterize the mechanical response of atherosclerotic femoral arterial tissue to large deformation, the conditions typical of angioplasty and stenting, and also to determine the mechanically induced failure properties and to relate this behaviour to biological content and structural composition using uniaxial testing, Fourier transform infrared spectroscopy and scanning electron microscopy. Mechanical and biological characterization of 20 plaque samples obtained from femoral endarterectomy identified three distinct classifications. "Lightly calcified" samples display linear mechanical responses and fail at relatively high stretch. "Moderately calcified" samples undergo an increase in stiffness and ultimate strength coupled with a decrease in ductility. Structural characterization reveals calcified nodules within this group that may be acting to reinforce the tissue matrix, thus increasing the stiffness and ultimate strength. "Heavily calcified" samples account for the majority of samples tested and exhibit significantly reduced ultimate strength and ductility compared to the preceding groups. Structural characterization of this group reveals large areas of calcified tissue dominating the failure cross-sections of the samples. The frequency and structural dominance of these features solely within this group offers an explanation as to the reduced ultimate strength and ductility and highlights the need for modern peripheral endovascular devices to account for this behaviour during novel medical device design.

A prospective evaluation of using IVUS during percutaneous superficial femoral artery interventions

BACKGROUND

The outcomes of endovascular interventions of the superficial femoral artery (SFA) are variable. Completion angiography is typically performed to confirm satisfactory outcomes after SFA angioplasty and/or stenting. However, two-dimensional angiography may not accurately reflect the extent of residual stenosis. We sought to determine whether intravascular ultrasound (IVUS) can help with residual disease assessment and procedure outcome.

METHODS

Patients with anticipated SFA disease were prospectively recruited to the study. Patients with primary SFA disease on diagnostic angiography were included. After SFA endovascular intervention with angioplasty and/or stenting, a completion angiogram was performed to confirm satisfactory results before IVUS evaluation. IVUS-detected maximal residual stenosis, maximal residual lesion volume, and number of nonconsecutive posttreatment SFA segments with >50% residual stenosis were evaluated. Periprocedural ankle-brachial indexes (ABIs), Short Form 36 (SF-36) surveys, and Walking Impairment Questionnaires were also collected.

RESULTS

Fifty-nine patients were prospectively enrolled. Thirty-three received angioplasty only, and 26 received angioplasty and stenting. All patients were men, mean age was 67 years, and major comorbidities included coronary artery disease (53%), active smoking (56%), hypertension (88%), and diabetes (68%). The angioplasty-only cohort had more nonconsecutive areas of >50% residual stenosis (P = 0.004), greater residual stenosis (P = 0.03), and smaller minimal lumen diameters after treatment (P = 0.01) than the angioplasty and stenting cohort. However, there was no significant difference in ABI between the 2 groups and no difference in ABI improvement after intervention. Sixty-four percent of all patients demonstrated a >0.2 increase in postintervention ABI. Improvement in ABI at 1 month after procedure significantly correlated with postintervention SF-36 survey physical scores (r = 0.435, P = 0.007).

CONCLUSIONS

IVUS evaluation provides more-accurate intraprocedural insight on the extent of residual stenosis after SFA interventions. Future studies are warranted to determine whether IVUS-guided postangioplasty and/or stenting can impact long-term interventional outcome.

Comparison of orbital atherectomy plus balloon angioplasty vs. balloon angioplasty alone in patients with critical limb ischemia: results of the CALCIUM 360 randomized pilot trial

PURPOSE

To evaluate the role of orbital atherectomy in calcified infrapopliteal arteries in patients with critical limb ischemia compared to balloon angioplasty (BA) alone.

METHODS

A randomized multicenter study was undertaken to evaluate short and 1-year outcomes in 50 patients (32 men; mean age 71 years, range 40-90) with confirmed calcified lesions using 1∶1 randomization to the Diamondback 360° Orbital Atherectomy System followed by BA vs. BA alone. All patients had severe (≥50% stenosis) peripheral artery disease (Rutherford classification 4-6) in the popliteal, tibial, and/or peroneal arteries. The primary endpoint was defined as restoration of a normal lumen (residual stenosis ≤30%) with no bailout stenting or dissection types C through F. Scheduled follow-up visits were conducted according to a common protocol at 1, 6, and 12 months.

RESULTS

Procedural success was 93.1% (27/29 lesions) for atherectomy + BA patients and 82.4% (28/34 lesions) for BA alone (p = 0.27). Bailout stenting was needed in 2 (6.9%) of the 29 atherectomy + BA lesions and in 5 (14.3%) of the 35 BA-treated lesions (p = 0.44). At 1 year, there were no amputations in either group related to the index procedure. Estimates for freedom from target vessel revascularization and all-cause mortality were 93.3% and 100% in the atherectomy + BA group vs. 80.0% (p = 0.14) and 68.4% (p = 0.01) in the BA group, respectively. Proportional hazard models evaluating survival time vs. status of residual stenosis determined a hazard ratio for major adverse events of 5.6 for patients with an acute post-procedure residual stenosis >30% (p = 0.01).

CONCLUSION

Debulking with orbital atherectomy appeared to increase the chance of reaching a desirable angioplasty result, with less acute need for bailout stenting and a higher procedure success. A negative association between procedure success and risk of serious adverse outcomes should encourage larger confirmatory studies.

Comparison of angiography, duplex sonography and intravascular ultrasound for the graduation of femoropopliteal stenoses before and after balloon angioplasty

The graduation of femoropopliteal stenoses by either digital subtraction angiography (DSA) or duplex sonography remains challenging, particularly after percutaneous transluminal angioplasty (PTA). More accurate assessment of stenosis might be achieved with intravascular ultrasound (IVUS). We investigated the relationship between DSA, IVUS and duplex before and after 32 femoropopliteal PTAs. Over the whole range of stenoses, peak systolic velocity (PSV) and peak velocity ratio (PVR) correlated better with DSA-stenosis (R(2) = .72 and 0.74, respectively, p < 0.01) than with IVUS-stenosis (R(2) = 0.58 and 0.50, p < 0.01). Within the subgroup of preinterventional (51 to 99%) stenoses, PVR was significantly correlated only with DSA-stenosis (R(2) = 0.60, p < 0.01). Severe dissection after PTA was associated with a disproportionate rise in PSV and large discrepancies between IVUS and DSA. Unexpectedly, our data show that intrastenotic flow acceleration assessed by duplex sonography correlates better with DSA- than with IVUS-stenosis. The concordance between duplex sonography, DSA and IVUS was particularly weak in postinterventional measurements, casting some doubt on the reliability of these methods for the assessment of residual stenosis after femoropopliteal PTA.

Applications of Intravascular Ultrasound in the Treatment of Peripheral Occlusive Disease

Intravascular ultrasound (IVUS) has emerged as a useful and often necessary adjunct in a rising number of catheter-based peripheral interventions. IVUS catheters enable luminal and transmural cross-sectional imaging of peripheral vessels with high dimensional accuracy and provide detailed information about lesion morphology. IVUS is able to guide the optimal choice of appropriate angioplasty technique, guide the delivery of endovascular devices, and assess the immediate outcome of an intervention. In this review we discuss the role of IVUS for peripheral occlusive diseases, specifically the application of IVUS technology during percutaneous transluminal angioplasty (PTA), intravascular stent placement, crossing total occlusions, and venous obstructive disease.

Basics of intravascular ultrasound: An essential tool for the endovascular surgeon

The concept of catheter-based ultrasound imaging was first introduced in the early 1970s. Since its inception, intravascular ultrasound (IVUS) technology has become more user-friendly because of improvements in both the catheters and computer-driven imaging platforms. IVUS catheters enable luminal and transmural cross-sectional imaging of coronary and peripheral blood vessels with high-dimensional accuracy and detailed information about lesion morphology. With the advent of endovascular techniques in both the coronary and peripheral vasculature, IVUS has emerged as a useful and necessary adjunct. In addition to providing diagnostic information, IVUS enables optimal choice of appropriate angioplasty technique, endovascular device guidance, and controlled assessment of the efficacy of interventions. In this review we discuss the design and function of available IVUS catheters, imaging techniques and interpretation, and the present and future clinical utility in peripheral endovascular interventions.

Mechanisms of acute lumen gain following cutting balloon angioplasty in calcified and noncalcified lesions: an intravascular ultrasound study

Several studies have shown that mechanisms for lumen enlargement following conventional balloon angioplasty (BA) consist of plaque reduction and vessel expansion. To assess the mechanisms of lumen enlargement after Cutting Balloon (CB) angioplasty, intravascular ultrasound images were analyzed in 180 lesions (89 CB and 91 BA). External elastic membrane (EEM) cross-sectional area (CSA), lumen CSA, and plaque plus media (P+M) CSA were measured before and after angioplasty. In the CB group, lower balloon pressure was utilized (P < 0.0001). DeltaP+M CSA was significantly larger (P = 0.02) and deltalumen CSA showed a trend toward being larger (P = 0.07) compared to BA group. For noncalcified lesions, CB resulted in a larger deltaP+M CSA (P < 0.05) and a smaller deltaEEM CSA (P = 0.10) than BA. For calcified lesions, deltalumen CSA was significantly larger in the CB group (P < 0.05) without significant differences in deltaEEM CSA and deltaP+M CSA. Dissections complicated with calcified lesions were associated with larger deltalumen CSA for the CB group. In conclusion, for noncalcified lesions, CB achieves similar luminal dimensions with larger plaque reduction and less vessel expansion compared to BA. On the other hand, for calcified lesions, the CB achieves larger lumen gain, especially in lesions with evidence of dissections.

Is coronary stent deployment and remodeling affected by predilatation? An intravascular ultrasound randomized study Stenting with or without predilation: an IVUS study

In this intravascular ultrasound (IVUS) randomized trial we compared a strategy of direct stenting (DS) without predilation (n = 30) vs. conventional stenting with predilation (SWP) (n = 30) in patients with suitable type A or B non-calcified lesions in native vessels > or = 3 mm. Optimal deployment was achieved using angiographic criteria without interactive IVUS. The goal of our study was to determine whether stent expansion and coronary remodeling were similar. Maximal pressure inflation was comparable in the two groups (11.4 +/- 2.2 vs. 11.8 +/- 1.9 atm; NS). Stent deployment was obtained in all patients with complete apposition to the vessel wall. DS and SWP resulted in comparable lumen enlargement (5.4 +/- 2.5 vs. 5.5 +/- 2.1 mm2) with an identical mechanism: 66% of lumen enlargement was due to increased enlarged elastic membrane (EEM)-cross sectional area (CSA) (delta = 3.7 +/- 2.1 mm2 and delta = 2.4 +/- 6.8 mm2, respectively, p < 0.49) and 34% was due to a reduced P + M-CSA (delta = 0.02 +/- 6.9 mm2 and delta = 1.2 +/- 6.3 mm2, respectively, p < 0.50). We conclude that at the same maximal pressure inflation the mechanisms of stent expansion are similar in both DS and SWP groups. In this observational study, the IVUS data showed clearly under-expansion of stents in both groups in comparison with previously published CSA values (minimum stent CSA of 7.5 mm2).

Mechanics of the human femoral adventitia including the high-pressure response

Adventitial mechanics were studied on the basis of adventitial tube tests and associated stress analyses utilizing a thin-walled model. Inflation tests of 11 nonstenotic human femoral arteries (79.3 +/- 8.2 yr, means +/- SD) were performed during autopsy. Adventitial tubes were separated anatomically and underwent cyclic, quasistatic extension-inflation tests using physiological pressures and high pressures up to 100 kPa. Associated circumferential and axial stretches were typically <20%, indicating "adventitiosclerosis." Adventitias behaved nearly elastically for both loading domains, demonstrating high tensile strengths (>1 MPa). The anisotropic and strongly nonlinear mechanical responses were represented appropriately by two-dimensional Fung-type stored-energy functions. At physiological pressure (13.3 kPa), adventitias carry ~25% of the pressure load in situ, whereas their circumferential and axial stresses were similar to the total wall stresses (~50 kPa in both directions), supporting a "uniform stress hypothesis." At higher pressures, they became the mechanically predominant layer, carrying >50% of the pressure load. These significant load-carrying capabilities depended strongly on circumferential and axial in-vessel prestretches (mean values: 0.95 and 1.08). On the basis of these results, the mechanical role of the adventitia at physiological and hypertensive states and during balloon angioplasty was characterized.

Hemodialysis access assessment with intravascular ultrasound

Reliable identification and treatment of specific hemodialysis access complications may improve access patency and result in significant cost reduction. Angiography is the gold standard for the evaluation of vascular access; however, it has significant limitations. Intravascular ultrasound (IVUS) is a relatively new technique capable of detecting subtle vascular abnormalities. To investigate the safety, feasibility, and accuracy of IVUS imaging to detect hemodialysis access complications, including stenoses, graft deterioration, and thrombus, we performed 31 IVUS imaging studies in 22 hemodialysis patients. Nineteen studies were performed in the dialysis unit, and 12 studies in the angiography suite. The IVUS catheter was inserted into the graft through the access used for hemodialysis. Findings of 21 studies (17 patients) imaged on the same day by both angiography and IVUS were compared. Grafts and vessels were successfully imaged using IVUS in 29 of 31 studies. There were no adverse effects caused by IVUS. Angiography assessed 17 of 54 vessel segments as normal versus 9 of 54 segments by IVUS (P < 0.001). Angiography detected lesions in 25 segments as opposed to 33 segments by IVUS (P < 0.001). A thrombus was detected in 32 of 54 vessel segments by IVUS, but in only 1 of 54 segments by angiography (P < 0.001). In conclusion, IVUS imaging is feasible and safe to assess hemodialysis access in the angiographic suite and dialysis unit. IVUS detected more vascular abnormalities than angiography. IVUS may be a useful independent imaging and screening modality in the assessment of dialysis access complications, which may help increase graft patency and reduce cost.

Quantification of elastic recoil after balloon angioplasty in the iliac arteries

PURPOSE

Elastic recoil of the arterial wall has been shown to be responsible for a significant loss of luminal area after balloon angioplasty in the coronary arteries, but it has not been well studied in the peripheral arteries. Because elastic recoil depends on the presence of elastin in the arterial wall, and the amount of elastin varies by artery and proximity to the aorta, the importance of this response to angioplasty may be different in peripheral arteries. The purpose of this study is to document the degree of elastic recoil in the iliac arteries, and analyze variables that might influence the results.

MATERIALS AND METHODS

A series of 19 patients with 25 iliac artery stenoses underwent balloon angioplasty followed by placement of a Palmaz stent with the same-sized angioplasty balloon. The minimum luminal diameter of the lesion was measured before treatment, immediately after balloon angioplasty, and again after stent placement. The arterial diameter after stent placement was defined as the diameter of the inflated balloon. The degree of recoil was correlated with nine variables: patient age and sex, lesion location and length, lesion severity (as percent stenosis), the balloon:artery ratio, and three factors related to lesion morphology--complex versus simple, eccentric versus concentric, and calcified versus noncalcified.

RESULTS

Elastic recoil averaged 36% +/- 11% and ranged from 19% to 54% in this series of patients. The only variable that significantly influenced the degree of elastic recoil was the balloon:artery ratio (P =.039), which was directly related.

CONCLUSION

Elastic recoil is a significant limitation of balloon angioplasty in the iliac arteries. This study illustrates the importance of techniques that limit recoil, such as vascular stents, in angioplasty of the iliac arteries.

Mechanisms of angioplasty and stent restenosis: implications for design of rational therapy

Restenosis after angioplasty or stenting remains the major limitation of both procedures. A vast array of drug therapies has been used to prevent restenosis, but they have proven to be predominantly unsuccessful. Recent trends in drug therapy have attempted to refine the molecular and biological targets of therapy, based on the assumption that a single biological process or molecule is critical to restenosis. In contrast, both stenting and brachytherapy, which are highly nonspecific, can successfully reduce restenosis after angioplasty or stenting, respectively. This review examines the biology of both angioplasty and stent stenosis, focussing on human studies. We also review the landmark human trials that have definitively proven successful therapies, such as stenting and brachytherapy. We suggest that the successful trials of stenting and brachytherapy and the failure of other treatments have highlighted the shortcomings of conventional animal models of arterial intervention, and gaps in our knowledge of human disease. In contrast to arguments advocating gene therapy, these studies suggest that the most likely successful drug therapy will have a wide therapeutic range, targeting as many of the components or biological processes contributing to restenosis as possible.

Treatment of stable angina

Severe atherosclerotic narrowing of one or more coronary arteries is responsible for myocardial ischemia and angina pectoris in most patients with stable angina pectoris. The coronary arteries of patients with stable angina also contain many nonobstructive plaques, which are prone to fissures or rupture resulting in presentation of acute coronary syndromes (unstable angina, myocardial infarction, sudden ischemic death). In addition to symptomatic relief of symptoms and an increase in angina-free walking time with antianginal drugs or revascularization procedures, the recent emphasis of treatment has been to reduce adverse clinical outcomes (coronary death and myocardial infarction). The role of smoking cessation, aspirin, treatment of elevated lipids, and treatment of high blood pressure in all patients and of beta-blockers and angiotensin-converting enzyme inhibitors in patients with diminished systolic left ventricular systolic function in reducing adverse outcomes has been well established. What is unknown, however, is whether any anti-anginal drugs (beta-blockers, long-acting nitrates, calcium channel blockers) effect adverse outcomes in patients with stable angina pectoris. Recent trials evaluated the usefulness of suppression of ambulatory ischemia in patients with stable angina pectoris, but it remains to be established whether suppression of ambulatory myocardial ischemia with antianginal agents or revascularization therapy is superior to pharmacologic therapy targeting symptom relief. Patients who have refractory angina despite optimal medical treatment and are not candidates for revascularization procedures may be candidates for newer techniques of transmyocardial revascularization, enhanced external counterpulsation, spinal cord stimulation, or sympathectomy. The usefulness of these techniques, however, needs to be confirmed in large randomized clinical trials.

Endovascular stent-grafts for aneurysms of the femoral and popliteal arteries

Our objective was to investigate the preliminary use of endovascular stent-grafts for the treatment of femoropopliteal artery aneurysm. Ten patients with an aneurysm of the femoropopliteal artery referred for endovascular treatment were investigated. The series consisted of patients with a true aneurysm of the superficial femoral artery (n = 2); a true aneurysm of the popliteal artery (n = 4); an aneurysmal dilatation of a Biograft bypass (n = 2); a false aneurysm of the superficial femoral aneurysm (n = 1); and a false aneurysm of a composite bypass (n = 1). In 8 of the 10 patients the stent-graft was composed of one or more Palmaz stents sutured to an ePTFE tube graft; in the other 2 patients a venous covering was used in combination with Palmaz stents. The procedure was guided by angiography and intravascular ultrasound. The results of our investigation showed that endovascular stent-grafting of aneurysms of the femoropopliteal artery is a feasible but experimental technique that should be restricted to a selected group of patients.

Plaque area increase and vascular remodeling contribute to lumen area change after percutaneous transluminal angioplasty of the femoropopliteal artery: an intravascular ultrasound study

OBJECTIVE

The aim of the study was to assess the change in lumen area (LA), plaque area (PLA), and vessel area (VA) after percutaneous transluminal angioplasty (PTA) of the femoropopliteal artery.

METHODS

This was a prospective study. Twenty patients were studied with intravascular ultrasound (IVUS) immediately after PTA and at follow-up examination. Multiple corresponding IVUS cross-sections were analyzed at the segments that were dilated by PTA (ie, treated sites; n = 168), including the most stenotic site (n = 20) and the nondilated segments (ie, reference sites; n = 77).

RESULTS

At follow-up examination, both the PLA increase (13%) and the VA decrease (9%) resulted in a significant LA decrease (43%) at the most stenotic sites (P =.001). At the treated sites, the LA decrease (15%) was smaller and was caused by the PLA increase (15%). At the reference sites, the PLA increase (15%) and the VA increase (6%) resulted in a slight LA decrease (3%). An analysis of the IVUS cross-sections that were grouped according to LA change (difference >/=10%) revealed a similar PLA increase in all the groups: the type of vascular remodeling (VA decrease, no change, or increase) determined the LA change. At the treated sites, the LA change and the VA change correlated closely (r = 0.77, P <.001). At the treated sites, significantly more PLA increase was seen in the IVUS cross-sections that showed hard lesion or media rupture (P <.05). No relationship was found between the presence of dissection and the quantitative changes.

CONCLUSION

At the most stenotic sites, lumen narrowing was caused by plaque increase and vessel shrinkage. Both the treated sites and the reference sites showed a significant PLA increase: the type of vascular remodeling determined the LA change at follow-up examination. The extent of the PLA increase was significantly larger in the IVUS cross-sections that showed hard lesion or media rupture.

In-vitro validation, with histology, of intravascular ultrasound in renal arteries

OBJECTIVE

To investigate the feasibility of using intravascular ultrasound to characterize normal and diseased renal arteries.

MATERIALS AND METHODS

Forty-four renal artery specimens from 21 humans, removed at autopsy, were studied with intravascular ultrasound in vitro. From each vascular specimen, two to four sets of corresponding intravascular ultrasound images and histologic sections were subjected to qualitative analysis. The renal arterial wall was considered normal by intravascular ultrasound when the wall thickness (intima and media) was 0.5 mm or less. On intravascular ultrasound imaging, a distinction was made between bright lesions with or without peripheral shadowing (i.e. calcification). Histological sections were examined and fibromuscular lesions were scored with or without calcifications. Quantitative analysis of a multitude of intravascular ultrasound cross-sections (interval 5 mm) included assessment of the lumen area, vessel area, plaque area and percentage area obstructed. The target site (smallest lumen area) was compared with a reference site (largest lumen area before the first major side branch).

RESULTS

Of the 130 corresponding intravascular ultrasound images and histologic sections analysed, 55 were normal and 75 presented a bright lesion on ultrasound; in 31 lesions, peripheral shadowing was involved. The sensitivity of the intravascular ultrasound in detecting calcifications was 87%, and the specificity was 89%. Lumen area reduction at the target site was associated with vessel and plaque area enlargement in eight specimens, with plaque area enlargement in 12 specimens and with a vessel area reduction in 21 specimens.

CONCLUSIONS

Intravascular ultrasound is a reliable technique for distinguishing renal arteries with or without a lesion. Both plaque development and local vessel narrowing may result in renal artery stenosis.

Intravascular ultrasound imaging before and after balloon angioplasty for pulmonary artery stenosis

Previous reports regarding intravascular ultrasound (IVUS) imaging of the pulmonary arteries in children and its application to balloon pulmonary angioplasty are limited. This study was designed to compare findings of IVUS imaging and those of angiography of the pulmonary artery before and after the balloon angioplasty procedure. Thirty patients had significant pulmonary artery stenosis and underwent balloon angioplasty. In all, of 34 branch pulmonary arteries were dilated. All patients underwent both angiography and IVUS imaging at the time of balloon angioplasty. The mean age at balloon angioplasty was 5.7 +/- 4.0 yr. One echo-dense layer on IVUS was detected in 9% of the 34 stenotic vessels, and a two- or three-layered vascular wall pattern in 91%. The thickness of intima-medial layer (inner and middle layers) was greater than normal in 91% of stenotic vessels. After balloon angioplasty, intimal flaps and aneurysm were observed at 29 and 28 locations, respectively. Of these locations, the intimal flaps were detected by angiography in 44% and by IVUS in 100%; the aneurysm was detected by angiography in 61% and by IVUS in 93%. Media rupture was observed at 26 locations, and the change was detected only by IVUS. The present study suggests that intimal and medial changes in the pulmonary artery can be detected more precisely by IVUS than by angiography.

Effect and outcome of balloon angioplasty and stenting of the iliac arteries evaluated by intravascular ultrasound

OBJECTIVES

To document the mechanism of percutaneous transluminal angioplasty (PTA) and stenting of the iliac arteries, and to relate the effect to patency.

MATERIALS AND METHODS

Thirty-seven stenotic iliac arteries were examined by intravascular ultrasound (IVUS) and arteriography before and after PTA, and after stent deployment (n = 16). The patients were followed prospectively by duplex scanning at 3, 6, 12, 18 and 24 months after the intervention.

RESULTS

The effect of PTA was established by both compression and stretching with the major contribution arising from stretching. There were differences in the effect of PTA dependent on plaque morphology: in homogeneous eccentric lesions, stretching contributed significantly more than compression to the luminal gain, while stretching and compression contributed equally in concentric or heterogeneous plaques. Stenting of the arteries had no effect on the free luminal area as measured by IVUS. The primary 1-year patency rate was 72%. The patency was related to the free luminal area and diameter and the heterogenicity of the plaque as evaluated by IVUS. The arteriographic measurements did not have any predictive value.

CONCLUSION

IVUS was able to document the effect of PTA and stenting in the iliac arteries, and predict the outcome. The luminal gain and reduction in degree of stenosis seemed to be accomplished primarily by stretching of the arteries and to a lesser extent by plaque compression. Stenting did not change the IVUS measurements. Patency was related to the size of the free lumen and the heterogenicity of the plaque.

Stent placement for treatment of renal artery stenosis guided by intravascular ultrasound

PURPOSE

To study the impact of intravascular ultrasound (IVUS) during renal artery stent placement.

MATERIALS AND METHODS

Patients (n = 22) with atherosclerotic renal artery stenosis were studied with IVUS after predilation and after angiographically successful stent deployment (diameter stenosis < 10%). After predilation, IVUS was used to assess whether the balloon size selected angiographically was correct (discrepancy balloon-reference lumen diameter < 20%). After stent placement, IVUS images were assessed for (i) complete stent-vessel wall apposition; (ii) complete stent expansion (discrepancy stent-reference lumen diameter < 20%), and (iii) complete lesion covering by the stent. Modification based on IVUS included selection of a larger balloon, additional dilation, and placement of a second stent. Clinical outcome was based on blood pressure, amount of antihypertensive drugs, and glomerular filtration rate during follow-up of 3 months.

RESULTS

Stent placement and ultrasound imaging were completed successfully in 18 patients. After predilation, IVUS warranted the use of a larger balloon in five patients. After stent placement, incomplete stent apposition (n = 1), discrepancy between stent and reference lumen diameter (n = 3), and lesion distal to the stent (n = 2) seen on IVUS were treated with additional dilation in five patients and with a second stent in one patient. A larger balloon was used in three patients. Mean blood pressure and amount of antihypertensive drugs decreased (P < .05).

CONCLUSIONS

In a number of patients, IVUS monitoring during renal artery stent placement resulted in additional lumen enlargement not considered necessary at angiography.

Comparison of angiography and intravascular ultrasound before and after balloon angioplasty of the femoropopliteal artery

PURPOSE

To compare angiographic and intravascular ultrasound (IVUS) data before and after balloon angioplasty (PTA) of the femoropopliteal artery.

METHODS

Qualitative and quantitative analyses were performed on corresponding angiographic and IVUS levels obtained from 135 patients.

RESULTS

IVUS detected more lesions, calcified lesions, and vascular damage than angiography. Sensitivity of angiography was good for the presence of a lesion (84%), moderate for eccentric lesions (53%) and for vascular damage (52%), and poor for calcified lesions (30%). The increase in angiographic diameter stenosis was associated with a decrease in lumen area and increase in percentage area stenosis on IVUS.

CONCLUSIONS

Angiography is less sensitive than IVUS for detecting lesion eccentricity, calcified lesions, and vascular damage. Presence of a lesion and amount of plaque were underestimated angiographically. Only before PTA was good agreement found between angiographic diameter stenosis and lumen size on IVUS.

Intravascular ultrasound predictors of restenosis after balloon angioplasty of the femoropopliteal artery

OBJECTIVES

To determine intravascular ultrasound parameters related to restenosis following percutaneous transluminal balloon angioplasty (PTA) of the femoropopliteal artery.

DESIGN

Prospective study.

MATERIALS AND METHODS

Patients were studies with intravascular ultrasound before and after angiographic successful PTA (n = 114). Intravascular ultrasound cross-sections obtained with 1 cm interval in the dilated segment were analysed. A distinction was made between anatomic (duplex scanning) and clinical (Rutherford criteria) restenosis assessed within 1 month and at 6 months after PTA.

RESULTS

Intravascular ultrasound predictors of 1 month anatomic outcome were lumen area stenosis after PTA, lumen area increase, plaque area decrease, and area stenosis decrease; predictor of 6 months anatomic outcome was area stenosis after PTA. Multivariate analysis revealed that area stenosis after PTA was the only independent predictor of both 1 and 6 months anatomic outcome. Intravascular ultrasound predictors of 1 month clinical outcome were the presence of hard lesion and the mean arc of hard lesion. Multivariate analysis revealed that the mean arc of hard lesion was the only independent predictor of 1 month clinical outcome. No predictors for 6 months clinical outcome were found.

CONCLUSIONS

Intravascular ultrasound can elucidate parameters predictive of restonosis after PTA. The strongest intravascular ultrasound parameter predictive of anatomic restenosis was a large area stenosis after PTA.

Elastic response of human iliac arteries in-vitro to balloon angioplasty using high-resolution CT

Previous angioplasty studies have used angiography and intravascular ultrasound to obtain vascular dimensions. These imaging methods do not always provide reliable measurements due to limitations in image orientation and resolution. In this study, high-resolution (0.1 x 0.1 x 0.5 mm) transverse CT slices were obtained from human common-iliac arteries in vitro to study their elastic response pre- and post-angioplasty. Seven iliacs from five patients were imaged over the physiological pressure range both pre- and post-angioplasty. Contrast was obtained with humidified air surrounding the artery. Angioplasty was done with 10 or 12 mm diameter Medi-Tech balloon catheters with a balloon pressure of 300 kPa held for 30 s. Lumen circumference, c, measured from the images, was plotted against pressure, P, and curve fitting showed c = A(1 - e(-KP)) + B where A, K, and B are fitting parameters. Six lesions appeared soft and were compressed, while one was calcified and partially lifted off the wall. Normalized changes in parameters B and K were much higher post-angioplasty in the calcified lesion, and were over 3 standard deviations from the means of the normalized changes in the six compressed lesions. Balloon/stenosed lumen diameter ratios greater than 1.2 produced a lumen area increase of 38.6 +/- 4.1%(S.D.)(n = 3); ratios less than 1.2 produced an increase of 4.4 +/- 5.1%(S.D.)(n = 4). There was no correlation between area increase and balloon/normal lumen diameter ratio (the value used clinically). Arteries with lesions containing stiffer plaques that tear from the artery wall during angioplasty appear more distensible over the physiological pressure range post-angioplasty.

CT angiography in vascular intervention for steno-occlusive diseases: role of multiplanar reconstruction and source images

The aim of this study was to assess the efficacy of CT angiography for steno-occlusive diseases before and after interventional procedures, focusing on the role of multiplanar reconstruction (MPR) and source images. 17 patients with 20 steno-occlusive lesions underwent CT angiography before and after interventional procedures. For each lesion, the percentage stenosis obtained on CT angiography was compared with that on conventional angiography. In addition, MPR and source images were evaluated for the presence of wall thickening and calcification before interventional procedures, and the presence of dissection and luminal shape after interventional procedures. These findings were compared with those of conventional angiography. Although the percentage stenosis depicted on CT angiography correlated well with that on conventional angiography, MPR and source images clearly demonstrated the effect of intervention and the residual stenosis. MPR and source images clearly depicted wall thickening, wall calcification, the presence of dissection and the luminal shape. CT angiography provides useful information before intervention, while MPR and source images are of value in evaluating arterial wall abnormalities and morphological changes associated with interventional procedures.

Intravascular ultrasound in endovascular stent-grafts for peripheral aneurysm: a clinical study

PURPOSE

To evaluate the potential diagnostic information of intraprocedural intravascular ultrasound (IVUS) in patients undergoing endovascular stent-grafting for peripheral aneurysm.

METHODS

IVUS was used in 17 patients preprocedurally to measure the diameter of the proximal and distal neck and the length of the aneurysm. Balloon and stent-graft sizes were selected based on these measurements. Following stent-graft deployment, angiography and IVUS were used to document stent apposition and the configuration and diameter of the stent-graft.

RESULTS

Stent-graft insertion was considered successful in 8 patients based on angiography and IVUS images. In 9 others, both imaging modalities showed inadequate results, necessitating 12 additional procedures: balloon angioplasty for stent-graft stenosis (2) and inadequate stent-graft apposition (1); an additional stent-graft (4); an extra stent (1); thrombectomy (2); and conversion (2) for inadequate stent-graft position and a graft rupture. In these patients, intraprocedural IVUS was superiorto angiography in contributing vital information to aid in the selection of the additional interventions.

CONCLUSIONS

During management of peripheral aneurysms with endovascular stent-grafts, IVUS monitoring was a useful adjunct when the initial procedure was unsatisfactory and/ or when intraprocedural angiographic studies were inconclusive.

Reliability and reproducibility of automated contour analysis in intravascular ultrasound images of femoropopliteal arteries

An automated contour analysis system was previously developed to increase reproducibility and facilitate quantitative analyses of intravascular ultrasound (IVUS) images. The aim of this study was to compare measurements by this automated system with those obtained by conventional manual tracing, and to determine the intra- and interobserver variability of the automated system. IVUS images obtained in the femoropopliteal artery (n = 12) were analyzed with both systems. Area measurements by the automated system agreed well with the results obtained by manual tracing, displaying low coefficients of variation (8.5 to 15.7%) and high correlation coefficients (r = 0.92 to 0.98). Intra- and interobserver comparison of lumen area, vessel area, plaque area and percentage area stenosis showed low coefficients of variation (6.0 to 15.3% and 5.7 to 14.0%, respectively) and high correlation coefficients (both: r = 0.93 to 0.99). These data indicate that the automated analysis system is a reliable tool for the quantitative assessment of vessel dimensions in IVUS images obtained during clinical examination of peripheral arteries.

Failure of intravascular ultrasound to predict dissection after balloon angioplasty by using plaque characteristics

Intravascular ultrasound (IVUS) is more sensitive than angiography in the assessment of plaque characteristics before intervention and vascular damage after balloon angioplasty. On the basis of IVUS data, this finding may improve clinical treatment by reducing the incidence of severe dissections after balloon angioplasty. We therefore studied the relation between plaque characteristics and dissections after balloon angioplasty. First, an in vitro study on atherosclerotic arteries (n = 42) was performed in which IVUS images were compared with histologic sections to validate the IVUS technique; second, the in vitro findings were compared with IVUS findings obtained in vivo (n = 73). Dissections were observed in 37 histologic sections and visualized on IVUS in 22 (59%) of the corresponding ultrasonic cross-sections; in vivo dissections were demonstrated by IVUS in 46 (63%) cases. Dissections were generally seen at the thinnest region of the plaque on both histologic sections (92%) and IVUS cross-sections (in vitro 83%; in vivo 93%). No significant relation was found between pre-interventional plaque characteristics such as composition features and eccentricity and the incidence, location, and extent of postinterventional dissections. Thus IVUS is able to identify dissections after balloon angioplasty, generally occurring at the site of the thinnest plaque diameter. However, neither the incidence nor the severity of these dissections was related to any of the preinterventional plaque characteristics.

Influence of coronary atherosclerotic remodeling on the mechanism of balloon angioplasty

OBJECTIVES

Intracoronary ultrasonography was used to assess coronary arteries before and after balloon percutaneous transluminal coronary angioplasty (PTCA) to determine whether the mode of coronary atherosclerotic remodeling affects the mechanism of balloon dilation.

BACKGROUND

Coronary arteries may enlarge or shrink in response to atherosclerotic plaque development. The effect of coronary remodeling on the mechanism of balloon PTCA has not yet been studied.

METHODS

Forty-one patients with 47 native de novo coronary artery lesions were studied with a 30 MHz intracoronary ultrasound catheter before and after balloon PTCA. Images were analyzed at the lesion site and the adjacent reference segments. At each site the lumen, vessel, and plaque area and the percent area stenosis were measured. Lesions were separated into two groups based on relative vessel area (lesion vessel area/reference vessel area). A relative vessel area >1.0 defines adaptive enlargement (group 1, n = 25), whereas a relative vessel area < or =1.0 reflects coronary shrinkage (group 2, n = 22). Regression analysis examined whether elastic recoil and the PTCA balloon/vessel area ratio correlated.

RESULTS

After balloon PTCA was performed, both the enlargement and shrinkage groups had similar gains in luminal area (2.3 +/- 1.8 mm2 [mean +/- SD] vs 2.8 +/- 1.7 mm2, p = 0.32), reduction in percent stenosis (-19.2% +/- 11.5% vs -14.4 +/- 12.7, p = 0.18), and final lumen area (4.9 +/- 1.7 mm2 vs 4.7 +/- 1.9 mm2, p = 0.73). However, the mechanism of luminal enlargement was different in each group. Reduction in plaque area was significantly greater in the enlargement group (group 1, -2.0 +/- 1.7 mm2 vs group 2, 0.04 +/- 2.2 mm2; p = 0.001), whereas increased vessel area was more important in the shrinkage group (group 1, 0.8 +/- 1.5 mm2 vs group 2, 2.4 +/- 2.3 mm2; p = 0.009). Positive correlation was seen between elastic recoil and the balloon/vessel area ratio in lesions with vessel enlargement (r = 0.80, p < 0.0001). No such correlation was observed in shrinkage vessels (r = 0.28, p = 0.21 ).

CONCLUSIONS

The acute luminal gain after balloon PTCA is similar regardless of the type of coronary remodeling. However, the mode of remodeling affects the mechanism of balloon dilation such that enlargement vessels exhibit plaque compression, whereas shrinkage arteries demonstrate vessel stretch. The post-PTCA elastic recoil correlates linearly to the balloon/vessel area ratio in arteries that have undergone adaptive enlargement.

Arterial remodeling after balloon angioplasty of the coronary artery: an intravascular ultrasound study. PICTURE Investigators. PostTreatment IntraCoronary Transluminal Ultrasound Result Evaluation

OBJECTIVE

Before balloon dilation, failure of compensatory enlargement and even arterial shrinkage are frequently observed at the lesion site in response to plaque accumulation. Balloon angioplasty may be regarded as artificial remodeling to enlarge the artery. The prevalence of the different types of arterial wall remodeling after applied stretch by balloon angioplasty is unknown.

METHODS AND RESULTS

In 181 patients an intravascular ultrasound study was performed after coronary balloon angioplasty (n = 200 lesions). The vessel area was measured at a proximal and distal reference site and at the lesion site. Subsequently, the relative vessel area [(Vessel area lesion site)/Vessel area reference site) x 100] was calculated. Lesions were classified in three groups on the basis of their relative vessel areas: > or =105%, <105% but >95%, and < or =95%. A relative vessel area > or =105%, indicating enlargement compared with the reference site, was observed in 84 (44%) lesions. A relative vessel area <105% but >95% was observed in 43 (22%) lesions. A relative vessel area < or =95%, indicating "shrinkage" compared with the reference site, was observed in 66 (34%) lesions.

CONCLUSIONS

After balloon angioplasty, the vessel area was found to be smaller compared with the reference site in 34% of the lesions. This small vessel area at the lesion site compared with a reference site may be a reflection of insufficient stretch by balloon angioplasty.

Automated lumen definition from 30 MHz intravascular ultrasound images

One prerequisite for standard clinical use of intravascular ultrasound imaging is rapid evaluation of the data. The main quantities to be extracted from the data are the size and the shape of the lumen. Until now, no accurate, robust and reproducible method to obtain the lumen boundaries from intravascular ultrasound images has been described. In this study, 21 different (semi-)automated binary-segmentation methods for determining the lumen are compared with manual segmentation to find an alternative for the laborious and subjective procedure of manual editing. After a preprocessing step in which the catheter area is filled with lumen-like grey values, all approaches consist of two steps: (i) smoothing the images with different filtering methods and (ii) extracting the lumen by an object definition method. The combination of different filtering methods and object definition methods results in a total of 21 methods and 80 experiments. The results are compared with a reference image, obtained from manual editing, by use of four different quality parameters--two based on squared distances and two based on Mahalanobis distances. The evaluation has been carried out on 15 images, of which seven are obtained before balloon dilation and eight after balloon dilation. While for the post-dilation images no definite conclusions can be drawn, an automated contour model applied to images smoothed with a large kernel appears to be a good alternative to manual contouring. For pre-dilation images a fully automated active contour model, initialized by thresholding, preceded by filtering with a small-scale median filter is the best alternative for manual delineation. The results of this method are even better than manual segmentation, i.e. they are consistently closer to the reference image than the average distance of all individual manual segmentations.

Effect of balloon angioplasty in femoropopliteal arteries assessed by intravascular ultrasound

OBJECTIVE

To study the effects of balloon angioplasty (PTA) of the femoropopliteal artery with intravascular ultrasound (IVUS).

MATERIALS AND METHODS

Corresponding IVUS cross-sections (n = 1033) obtained before and after PTA from 115 procedures were analysed. Vascular damage including plaque rupture, dissection and media rupture was assessed. Free lumen area (FLA), media-bounded area (MBA) and plaque area (PLA) were measured.

RESULTS

After PTA vascular damage was seen at the target site in 83 (72%) arteries: plaque rupture in 30 (26%), dissection in 66 (57%) and media rupture in 20 (17%) arteries. The FLA increased from 5.4 +/- 3.4 mm2 to 14.1 +/- 5.0 mm2 (p < 0.001), MBA increased from 26.9 +/- 10.0 mm2 to 32.9 +/- 10.7 mm2 (p < 0.001) and PLA decreased from 21.6 +/- 8.5 mm2 to 18.8 +/- 8.0 mm2 (p < 0.001). The increase in MBA accounted for 68% of lumen gain. The frequency of vascular damage and the relative contribution of MBA increase and PLA decrease to luminal gain were not different in procedures with balloon diameter < or = 5 mm and > or = 6 mm.

CONCLUSIONS

Vascular damage is common following PTA. Lumen gain is mainly due to vessel expansion and, to a lesser extent, to a decrease in plaque area.

Prediction of outcome after femoropopliteal balloon angioplasty by intravascular ultrasound

OBJECTIVE

To evaluate intravascular ultrasound (IVUS) as a control procedure after femoropopliteal percutaneous transluminal angioplasty (PTA), and compare it with arteriography.

DESIGN

Descriptive study.

MATERIAL

Arteriographic and intravascular ultrasound data obtained from 18 patients (20 limbs) undergoing PTA of the superficial femoral or popliteal artery. The degree of stenosis, the diameter and area of the lumen and the morphological changes in the plaque were related to the short-term patency of the intervention, as evaluated by duplex scan and ankle branchial index.

RESULTS

Fifteen arteries remained patent. Two occlusions and two stenoses developed during the first 3 months after the intervention and one occlusion occurred after 1 year. The following IVUS parameters were related to a favourable patency: presence of calcification; dissection or plaque rupture and residual stenosis of less than 70%. The arteriographically determined diameter reduction did not show predictive value.

CONCLUSION

This study shows that in contrast to arteriography, IVUS revealed parameters predictive for patency following PTA.