The value of intraoperative intravascular ultrasound for determining stent graft size (excluding abdominal aortic aneurysm) with a modular system

Diagnostic approach to peripheral arterial disease

This article discusses diagnostic imaging techniques used in the evaluation and management of patients with peripheral arterial disease (PAD). Along with a complete vascular examination, noninvasive physiologic testing is used for the initial evaluation of patients with suspected PAD. Duplex ultrasonography provides information on the degree of stenosis or occlusion within a vessel and allows assessment of the vessel wall and plaque morphology. Angiographic imaging techniques should be reserved for determining the optimal endovascular or surgical approach for patients requiring revascularization. Together, all available diagnostic modalities contribute to successful evaluation and management of patients with PAD.

Intravascular ultrasound measurement of the aortic lumen

Intravascular ultrasound (IVUS) has been successfully used to guide the implantation of stents in the thoracic aorta. However, its accuracy in measuring the diameter of the aortic lumen has not been clearly established. Thirteen patients with thoracic aortic disease underwent IVUS, and lumen diameter measurements were compared with those obtained by CT or magnetic resonance imaging. A total of 31 comparable measurements were obtained. The correlation was good (r=0.98; P< .001), with IVUS tending to give a larger minimum diameter than CT (systematic error, 0.59+/-1.8 mm; P=.077). Given that the aorta is often not circular, the diameter obtained by IVUS was also compared to the mean diameter obtained by CT, and it was found that these two measurements were more closely related (P=.425), except in aortic segments with significant eccentricity (i.e., >10%). In conclusion, IVUS was a reliable tool for measuring the diameter of the aorta, particularly in concentric segments where stents are normally placed. Consequently, IVUS could supplement conventional imaging techniques.

Endovascular Thoracic Aortic Aneurysm Repair without Angiography

Objective

Intravascular ultrasound (IVUS) generates high definition circumferential cross-sectional images and provides real-time readout of vascular dimensions, including visualization of vessel branches. We have used it as an alternative to angiography in the endovascular thoracic aneurysm repair work-up.

Methods

Out of consecutive 203 patients with descending thoracic aortic aneurysm, 89 (43.8%) received endovascular treatment [mean age, 68 ± 8 years; range, 29–82; male, 79 (88.7%); female, 10 (11.3%)] without using angiography during the endovascular procedure. IVUS (6 F, 12.5 MHz probe or 10 F 9 MHz) coupled with fluoroscopy for the placement of radiopaque markers was used for target site identification, landing zone measurement, device positioning, and assessment of endovascular repair.

Results

Hospital mortality was 4/89 (4.5%). Number of devices implanted in each patient was 1.2 (range, 1–3). X-ray exposure time was 12 ± 8 minutes. Median procedure time was 63 ± 20 minutes. Conversion to open surgery was necessary in one patient (1.1%) because of aortic dissection. In nine patients (10.1%) left subclavian artery was covered because of a short neck. Two patients (2.2%) had vascular access lesions and required surgical repair. One patient developed paraplegia (1.1%). Early endoleak was observed in eight patients (8.9%) and 4 (4.5%) required additional procedures (proximal or distal extensions). Late conversion was necessary in one patient (1.1%).

Conclusions

IVUS provides all information necessary for device selection, target site identification as well as safe and correct deployment of thoracic endoprostheses and makes periprocedural angiography unnecessary, thus avoiding the risk of renal failure because of contrast medium.

The future of imaging in the management of abdominal aortic aneurysm

The development of endovascular techniques depends on the concomitant development of imaging techniques. Imaging with ultrasonography (US), computed tomography (CT) and magnetic resonance imaging (MR) is evolving at rapid pace. Angiography has largely been replaced by these techniques as a diagnostic tool in the clinical setting. New methods, e.g., rotational angiography and intravascular ultrasound, will play an important role in endovascular treatment of vascular disease. It is necessary to have easy access to ultrasonography, CT and MR images in future hybrid angiographic/surgical suites and the operator must be able to do advanced immediate reconstructions in a sterile environment. The combined use of advanced imaging, open and endovascular techniques will further improve the treatment of vascular disease in the future.

Advances in vascular imaging

Advances in vascular surgery have mirrored advances in diagnostic imaging. Indeed, the endovascular revolution has been made possible largely by advances in computed tomography, magnetic resonance imaging, and vascular ultrasound. As technology allows better noninvasive vascular diagnosis, conventional angiography, once the gold standard for the diagnosis of vascular disease, is now reserved largely for intervention. This article discusses the current state of vascular imaging. Specific emphasis is placed on the comparative clinical utility of different imaging modalities in the detection and management of vascular disease.

Intravascular Ultrasound Use in the Treatment of Thoracoabdominal Dissections, Aneurysms, and Transections

Intravascular ultrasound (IVUS) has become an important adjunct in the endovascular treatment of thoracoabdominal aortic pathology. In this article, we hope to describe and define the expanding role of IVUS as a tool for the vascular surgeon in the treatment of thoracoabdominal aortic dissections, aneurysms, and transections. IVUS is of particular benefit in the treatment of aortic dissections and aortic transections.

Endovascular Treatment of Ruptured Abdominal Aortic Aneurysms:A Shift of the Paradigm?

PURPOSE

To compare endovascular aneurysm repair (EVAR) of ruptured abdominal aortic aneurysms (rAAA) to the results with open surgery.

METHODS

Between May 2001 and January 2004, 50 patients were diagnosed with rAAA. Fifteen (30%) patients (14 men; median age 73 years, range 58-85) underwent EVAR, while 26 (52%) patients (23 men; median age 75 years, range 60-84) had open surgery. Nine (18%) patients (5 men; median age 86 years, range 77-91) were not operated upon. Circulatory shock was defined as systolic blood pressure<80 mmHg. Mortality was defined as death within 30 days after operation; in cases where hospital stay exceeded 30 days, in-hospital mortality was registered. Five risk factors (age>76 years, loss of consciousness, hemoglobin<90 g/L, creatinine>190 micromol/L, and electrocardiographic ischemia) were analyzed.

RESULTS

In the EVAR group, 93% (14/15) of the aneurysms were excluded from the bloodstream; there were 2 (13%) conversions: 1 intraoperatively for stent-graft migration and another owing to dissection prior to hospital discharge. Mortality after open surgery was 46% (12/26) versus 13% (2/15) in the EVAR group (p>0.05). Univariate analysis without considering variables other than mortality resulted in OR 5.4 (95% CI 0.9 to 58; p=0.07). Considering risk factors and shock, multivariate analysis resulted in OR 6.5 (95% CI 0.8 to 96; p=0.08). In the EVAR group, 60% (9/15) had complications; in the group with open surgery, the complication rate was 85% (22/26; p=0.13).

CONCLUSIONS

It is possible to treat rAAA with EVAR. Hypotensive patients can, at least initially, be operated under local anesthesia to stabilize blood pressure utilizing a percutaneously inserted occlusion balloon. There was a trend in our study for reduced mortality and morbidity with EVAR, but further studies are required to conclude whether EVAR significantly increases survival and reduces complications.

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.

Value of intravascular ultrasound for endovascular stent-graft placement in aortic dissection and aneurysm

BACKGROUND

Endovascular stent-graft placement is a new concept for the treatment of aortic dissection and aneurysm. Intravascular ultrasound (IVUS) with established diagnostic features may be instrumental in guiding endovascular procedures.

METHODS

We performed IVUS and digital angiography before, during, and after implantation of 47 stent grafts in 40 patients with Stanford type B dissection (26 patients, 28 stent grafts), thoracic aneurysm (9 patients, 11 stent grafts), and abdominal aneurysm (5 patients, 8 stent grafts).

RESULTS

IVUS could clearly identify the aortic anatomy and differentiate between true and false lumen in all cases of dissection. In four patients with type B dissection extending from the thoracic to the abdominal aorta the true lumen was exclusively identified by IVUS, and thus, essential for safe execution of the procedure. In another patient stent-graft placement in the aorta was optimized by covering a second entry detected by IVUS, but undetected by angiography. The site of stent implantation, the true and false lumen, as well as entry and reentry were always identified in both thoracic and abdominal aorta. In comparison with angiography, IVUS information led to additional balloon molding due to incomplete stent apposition in seven cases.

CONCLUSIONS

As an adjunctive imaging modality IVUS is likely to improve stent-graft placement in aortic type B dissection, especially in patients with abdominal extension.

Endoluminal AAA repair using intravascular ultrasound for graft planning and deployment: a 2-year community-based experience

PURPOSE

To examine the effectiveness of intravascular ultrasound (IVUS) and digital subtraction angiography (DSA) for preoperative planning and intraoperative deployment of stent-grafts to treat abdominal aortic aneurysms.

METHODS

One hundred seventy patients (143 men; mean age 73.6+/-7.2 years, range 51-89) underwent successful DSA and IVUS to determine suitability for stent-graft repair. Patients subsequently received the AneuRx (n=157) or Ancure (n=13) device; intraprocedural IVUS was used to survey the proximal endograft for proper apposition to the aortic wall.

RESULTS

Reliable preoperative IVUS measurements were obtained in all patients. Plaque morphology was assessed in 140 (82.3%) aortic necks; in 36 (25.7%), preoperative IVUS showed high-grade atherosclerotic plaque in the nonaneurysmal abdominal aortic neck. The procedure was successful in 168 (98.8%) cases (1 [0.6%] acute conversion and 1 access failure). There were 2 (1.2%) periprocedural deaths related to bowel ischemia. Four (2.3%) patients developed graft occlusion/kinking and 2 (1.2%) developed renal failure requiring dialysis within 30 days. Multivariate logistic regression analysis revealed that female gender (p=0.0247), a short nonaneurysmal aortic neck (p=0.0185), and presence of high-grade atherosclerotic plaque (p=0.0185) correlated with major acute complications. Over a mean 10.4-month follow-up (range 1-25), 11 patients died of unrelated causes; there was no known AAA rupture or device failure. The Kaplan-Meier estimate of survival at 1 year was 91.0%+/-2.8%. Sixteen (9.4%) patients underwent 17 secondary procedures for endoleak or graft limb occlusion at a mean 5.4 months after stent-graft repair (freedom from secondary intervention at 1 year 86.5%+/-3.2%).

CONCLUSIONS

Our findings suggest that IVUS may identify patients at increased risk of major adverse complications following endovascular repair. The combination of IVUS and DSA for endoluminal stent-graft planning and placement provides excellent short- and mid-term patient outcomes.

Prediction of aortoiliac stent graft length: comparison of a semiautomated computed tomography angiography method and calibrated aortography

OBJECTIVE

The aim of this study is to compare multislice computed tomography (MSCT) in combination with a newly developed semiautomated software program with calibrated aortography in patients who are scheduled for endovascular aortic stent graft placement.

METHODS

From November 2000 until December 2001, seven patients with an abdominal aortic aneurysm (AAA) underwent both calibrated aortography and MSCT for preoperative endovascular stent graft planning. Both studies were performed within 14 days. Further, length measurements were performed with a semiautomated computerized tomographic angiography (CTA) calibration method and a conventional calibrated aortography technique using three differently configured tubes with variable tortuosity. The AAA length measurements of the semiautomated CTA calibration method and the calibrated aortography were compared.

RESULTS

Statistical analysis included linear regression analysis and revealed a probability value of 0.000381 and an r2 value of 0.93. Using phantoms, it is proven by the authors that the accuracy of the semiautomated CTA calibration method increases with increasing tortuosity when compared with the conventional calibrated aortography technique.

CONCLUSIONS

Our preliminary results show that the semiautomated CTA calibration method has a potentially advantageous role in preoperative stent graft planning regarding the aortic length measurements and seems to be more accurate than calibrated aortography, especially in extremely tortuous vessels. Further studies have to be performed, however.

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

PURPOSE

The purpose of this retrospective review was to assess the accuracy of aortic measurements with intravascular ultrasound scan (IVUS) compared with computed tomographic (CT) scan and to assess the role of IVUS in the performance of endovascular repair of abdominal aortic aneurysms (AAAs).

METHODS

Seventy-eight patients undergoing repair of AAA with the AneuRx stent graft (Medtronic AVE, Inc, Santa Rosa, Calif) underwent measurement with CT scan and IVUS. The initial selection of stent graft size was made on the basis of the CT scan measurements, but the final decision for size was made on the basis of the IVUS measurements. Standard measurements of a phantom tube obtained with IVUS, CT scan, and digital caliper were also compared.

RESULTS

IVUS measurements of the phantom standard agreed closely with CT scan measurements. However, stent graft size initially selected with CT measurement was altered in 28% of cases on the basis of intraoperative IVUS measurements. No type I endoleaks were encountered in our series, and no aortic cuffs were necessary for endoleak repair.

CONCLUSION

IVUS accurately measures the aorta for selection of stent grafts for endovascular repair of AAA and may prevent type I endoleaks and remedial procedures for their repair.

The endovascular management of ruptured abdominal aortic aneurysms

Endovascular aneurysm repair (EVAR) is a controversial technique, which remains the subject of a number of prospective randomised trials. Although questions remain regarding its long-term durability objective evidence exists which demonstrates its reduced physiological impact compared with conventional open repair. If this technique could be used in patients with ruptured abdominal aortic aneurysm (AAA) it may reduce the high peri-operative mortality. A review of the literature identified a limited experience with EVAR of ruptured AAA. Only a small number of case series with selected patients exist. The majority of patients were haemodynamically stable. However, the selective use of aortic occlusion balloons allowed successful endovascular management in a small number of unstable cases. All investigators had access to an "off the shelf" endovascular stent-graft (EVG). Per-operative mortality ranged from 9 to 45% and may reflect increasing experience and patient selection. A number of patients who underwent successful EVAR were turned down for open repair. A number of important lessons have been learned from these studies but questions remain regarding patient suitability and staffing issues. If these difficulties can be surmounted then the technique may offer an alternative to open repair.

Endovascular aortic aneurysm repair in patients with renal dysfunction or severe contrast allergy: utility of imaging modalities without iodinated contrast

Contrast-enhanced imaging studies are required for preoperative evaluation in patients undergoing endovascular aortic aneurysm repair; however, the use of iodinated contrast agents may not be suitable in patients with renal dysfunction or severe contrast allergy. The objective of this study was to evaluate the utility of imaging modalities without iodinated contrast in patients undergoing endovascular aortic aneurysm repair. A total of 297 patients underwent endo vascular repair of abdominal aortic aneurysms during a 6-year period ending in August 2001. Among them, 20 patients (6.2%), who underwent imaging studies without iodinated contrast because of either renal dysfunction or severe contrast allergy formed the basis of this study. Multiple non-iodinated contrast imaging studies were used, including gadolinium-enhanced magnetic resonance angiography (MRA), non-contrast computed tomography (CT), gadolinium or carbon dioxide (CO2) aortography, and intravascular ultrasound (IVUS). Hospital records were reviewed to evaluate the imaging study, renal function, perioperative morbidity, and clinical outcome of endo vascular aortic aneurysm repair. From the results of our study we concluded that endovascular aortic aneurysm repair can be performed safely in patients with renal dysfunction or severe contrast allergy utilizing non-iodinated contrast-based imaging modalities. IVUS is a useful intraoperative imaging modality, and postoperative endoleak surveillance can be performed using duplex ultrasound scanning to avoid risk of iodinated contrast exposure.

Using three-dimensional rotational angiography for sizing of covered stents

OBJECTIVE

The purpose of our study was to determine the value of three-dimensional (3D) rotational angiography in the assessment of patients to be treated with covered stents for peripheral arterial aneurysms.

CONCLUSION

Our preliminary experience suggests that 3D rotational angiography appears to be a valid tool in the pre- and perprocedural assessment of patients treated endovascularly for arterial aneurysms.

Imaging of abdominal aortic aneurysm before and after endoluminal stent-graft repair

Imaging is an essential component of endoluminal aneurysm repair. Detailed imaging with computed tomography, magnetic resonance imaging and angiography, alone or in combination, is required for the initial assessment and planning. Careful, lifelong follow-up is essential since complications of endoluminal repair may take months or years to appear. Follow-up imaging requires a combination of plain film radiography, colour Doppler ultrasound and helical computed tomography. Magnetic resonance imaging may be valuable for the follow-up of non ferro-magnetic endografts and intra-arterial angiography will be required for specific cases.