George E. Kopchok

Intravascular Ultrasound Imaging

The application of ultrasound in medical diagnosis has increased considerably due to the miniaturization of ultrasonic transducers and overall compatibility and ease of use. Current intravascular ultrasound (IVUS) catheters provide real-time, high-resolution, cross-sectional, sectional imaging in vessels with dimensional accuracy. IVUS can delineate wall morphology, lesion consistency and length, as well as the exact location of visceral or aortic branch orifices. Concomitant rapid expansion of minimally invasive endovascular therapies continues to add new roles for IVUS. In addition to diagnostic information, IVUS can assist clinicians in choosing appropriate endovascular devices and appropriate deployment sites and guidance. IVUS also allows real-time post-procedural assessment of efficacy on intervention. Further acceptance and implementation relies on effectiveness of IVUS in improving outcomes and minimizing peri- and post-procedural complications, as compared to alternative imaging modalities. This chapter reviews the design and function of available IVUS catheters, imaging techniques, and therapeutic utility in peripheral endovascular interventions.

Volume regression of abdominal aortic aneurysms and its relation to successful endoluminal exclusion

OBJECTIVES Evaluating the success of endoluminal repair of abdominal aortic aneurysms (AAAs) is frequently based on diameter measurements and determining the presence of endoleaks. The use of three-dimensional volumetric data and observation of morphologic changes in the aneurysm and device have been proposed to be more appropriate for postdeployment surveillance. The purpose of this study was to analyze the long-term volumetric and morphologic data of 161 patients who underwent endovascular AAA exclusion and to assess the utility of volume measurements for determining successful AAA repair. METHODS Patients with spiral computed tomography scans obtained preoperatively, within the first postoperative month, at 6 months, and annually thereafter, were included in this analysis. Computerized interactive three-dimensional reconstruction of each AAA scan was performed. Total aneurysm sac volume was measured at each time interval (mean preoperative volume 169.0 +/- 78.5 mL), and the significance of volume changes was determined by mixed linear modeling, a form of repeated measures analysis, to account for longitudinal data clustered at the individual level. Sixty-two patients (38%) developed endoleaks at some time during follow-up-15 type I leaks, 45 type II leaks, and 2 type III leaks. The patients with type I and type III leaks were treated with cuffs, and the type II leaks were treated either with observation, side-branch embolization, or required open conversion. RESULTS Aneurysm sac volume increased slightly at 1-month follow-up (+3.3%), and then decreased steadily to -12.9% at 5 years (P <.0001). This effect remained unchanged after controlling for the three device types used in our study population. Patients who did not exhibit an endoleak (n = 99) showed a significant decrease in aneurysm volume across the entire follow-up duration when compared with those who did exhibit an endoleak (n = 62) (P <.0001). The presence of a 10% or greater decrease in volume at 6 months demonstrated a sensitivity of 64%, a specificity of 95%, a positive predictive value of 95%, a negative predictive value of 62%, and an accuracy of 75% for predicting primary clinical success defined by successful deployment of the device; freedom from aneurysm- or procedure-related death; freedom from endoleak, rupture, migration, or device malfunction; or conversion to open repair. CONCLUSIONS Volumetric analysis may be used to predict successful endoluminal exclusion of AAAs. Volume regression appears to be device-independent and should be expected in most clinically successful cases. The presence of volume increases in the first 6 months is suspicious for an endoleak that is pressurizing the aneurysm sac and heralds the need for closer evaluation and possible intervention. A volume decrease of 10% or greater at 6 months and continuing regression over time is associated with successful endovascular repair.

Stent-graft migration following endovascular repair of aneurysms with large proximal necks: anatomical risk factors and long-term sequelae.

Purpose: To evaluate the outcome of aortic endografts deployed in large infrarenal necks and to identify any association of preoperative aneurysm characteristics and postoperative morphological changes with the incidence of neck dilatation and device migration in this patient subset. Methods: The records of 47 patients (41 men; mean age 74, range 55–84) with large aortic neck diameters treated with Talent stent-grafts from 1998 to 2001 were reviewed. Patients with anatomical criteria that precluded aneurysm exclusion with currently available devices were preferentially selected. Mean baseline aneurysm morphology included 27.6-mm (range 18–33.4) suprarenal and 28.1-mm (range 24–34) infrarenal neck diameters; the infrarenal neck length was 26 ± 16 mm with angulation of 37° ± 18°. Computed tomographic (CT) angiograms up to 3 years were analyzed using specialized interactive software; migration was defined as >1-cm change in the distance from the lower renal artery to the top of the device. Pre- and postoperative morphological characteristics of the aneurysm were compared between patients with and without migration. Results: Of the 45 patients successfully treated, 40 had complete CT data for analysis. During a mean 17-month follow-up, 7 (17.5%) of the 40 devices exhibited distal migration. Six patients required secondary procedures; 5 were in the migration cohort. No preoperative anatomical characteristic or degree of neck dilatation over time was predictive of stent-graft migration. Aneurysm sac regression was significant at 1 (–0.09 ± 4.90 mm) and 2 (–1.48 ± 2.56 mm) years in endografts without migration (p<0.001). Distal endograft migration >1 cm predicted the need for secondary interventions (p<0.001), with 83% sensitivity and 94% specificity. Conclusions: Endovascular repair is successful in patients with large infrarenal necks and complex neck morphology. Changes in aneurysm remodeling over time were similar to reported observations in patients with more favorable neck criteria. Although no anatomical factor associated with migration could be identified from this analysis, distal displacement >1 cm correlated with the need for a secondary intervention.

Patient outcomes and thoracic aortic volume and morphologic changes following thoracic endovascular aortic repair in patients with complicated chronic type B aortic dissection.

OBJECTIVE True and false lumen changes and patient outcomes following thoracic endovascular aortic repair (TEVAR) for patients with stable type B dissection have been described by the The Investigation of Stent Grafts in Aortic Dissection (INSTEAD) trial. However, these changes have not been described in TEVAR patients treated for complications of chronic dissection. METHODS A single-institution study was conducted of 73 prospectively evaluated patients treated for complications of chronic type B dissection from 2002 to 2010. Spiral computed tomography reconstructions using M2S (Medical Media Systems, West Lebanon, NH) were analyzed for sequential changes in aortic volume and diameter during patient follow-up. Changes in aortic volume and diameter were tabulated as a percent change from preoperative values. Patient outcomes were determined by sequential evaluations postprocedure. RESULTS TEVAR was successfully performed in 72 out of the 73 patients (99%). Indications for intervention were aortic enlargement (n = 62), failure of medical management (n = 7), and perforation (n = 4). The 30-day all-cause mortality rate was 14%; events were due to retrograde dissection (n = 4), cardiac-related (n = 4), and rupture (n = 2). Eleven out of the 72 patients (15%) required a secondary procedure for endoleak (n = 7) and persistent distal perfusion of the false lumen (n = 4). Mean percentage expansion of the thoracic true lumen was noted during the follow-up period: 38%, 46%, 71%, and 114% at 1-, 3-, 6-, and 12-month follow-up, respectively. Concomitant regression of the thoracic false lumen of -65%, -68%, -84%, and -84% was observed at the same intervals, respectively. Patients with an initial extension of the thoracic dissection into the infrarenal aorta (n = 46) had an increase in mean percentage change of aortic diameter and volume to 21% and 17% at 1 year, respectively. By contrast, in the patient group without infrarenal dissection (n = 14), the infrarenal aortic diameter and volume remained relatively unchanged at 3% and -0.9%, respectively, at 1-year postintervention. CONCLUSIONS TEVAR is a potential treatment option for patients experiencing complications of chronic type B dissection. During follow-up, there is a predictable expansion of the thoracic true lumen and regression of the thoracic false lumen. These findings correlate with those of the INSTEAD trial, which demonstrated false lumen regression and true lumen expansion in a cohort of patients with stable type B dissection. However, many patients with extension of thoracic dissection into the infrarenal aorta demonstrate continued aortic dilation and, on occasion, the need for secondary intervention for persistent distal perfusion. Further analysis is needed in this subgroup of patients so as to better determine potential predictors and the clinical significance of post-TEVAR infrarenal expansion. Moreover, further investigations may support a role for secondary endovascular intervention in remedying persistent infrarenal aortic expansion after TEVAR for chronic dissection.

Intravascular Ultrasound: The Ultimate Tool for Abdominal Aortic Aneurysm Assessment and Endovascular Graft Delivery

Intravascular ultrasound (IVUS) imaging is a relatively new, rapidly evolving technology that enables precise catheter-based assessment of the dimensions and morphology of vascular structures and lesions. In extensive preclinical laboratory developmental studies and in clinical cases of endograft deployment for treatment of abdominal aortic aneurysms, we have found IVUS invaluable for determining key parameters of aortic morphology before and during interventions and for assessing the accuracy of deployment after device placement. By combining the IVUS data with information obtained from angiography, magnetic resonance imaging, and computed tomography (axial and three-dimensional reconstructions), we have been able to size devices and choose optimal fixation sites to prevent endoleaks and maintain luminal patency acutely and in the long term.

In vivo human comparison of intravascular ultrasonography and angiography

This study evaluates the in vivo correlation of intravascular ultrasonography and uniplanar angiography in determining the luminal dimensions of normal and moderately atherosclerotic human arteries. Five French and 8F rotating A scan intravascular ultrasound catheters were used to obtain 48 images in four superficial femoral arteries, five iliac arteries, and one aorta in eight patients undergoing vascular surgery. Cross-sectional areas measured by intravascular ultrasonography were compared to cross-sectional areas calculated by uniplanar angiography of the same location in the vessel. Maximum and minimum luminal diameters were also measured from intravascular ultrasound images. An ellipticity index was defined as the maximum/minimum diameter ratio (max/min) and ranged from 1.0 to 1.8 (mean, 1.2). Comparison of the cross-sectional areas measured from intravascular ultrasound images and those calculated from uniplanar angiography showed no significant difference at any level of ellipticity studied. However, when the values of cross-sectional areas were analyzed in groups corresponding to the diameter of the vessel, that is, aortic, iliac, and femoral, the values for the iliac arteries calculated from uniplanar angiography were significantly greater by 9.8% +/- 0.7% (n = 29, p = 0.03) when compared to those measured by intravascular ultrasonography. In addition to providing accurate luminal determinations, intravascular ultrasound images displayed transmural morphology, the location and character of the atherosclerotic lesions, and the thickness of the vessel wall. We conclude that intravascular ultrasound imaging provides accurate, novel information regarding human vessels and that this technology may play a significant role in future diagnostic and interventional therapies.

Initial human evaluation of argon laser—assisted vascular anastomoses

Forearm Brescia-Cimino arteriovenous fistulas were chosen for the initial clinical evaluation of argon laser-assisted anastomosis of human vessels. Ten patients with chronic renal failure had side-to-side radial artery/cephalic vein fistulas fused by laser. Incisions 1.2 to 1.5 cm in length were made in adjacent segments of artery and vein and were aligned for application of laser energy by four 6-0 polypropylene sutures. The sutures divided each fistula into four segments that were 5.0 to 6.5 mm long. Each segment was sealed satisfactorily in 75 to 100 seconds by use of 0.5 W, 1130 to 1520 joule/cm2 argon laser energy fluence. Seven (17.5%) of 40 bonds required an additional 7-0 biodegradable suture to close small gaps that did not fuse adequately. Serial prospective follow-up studies of the patients by physical examination and duplex scanning for periods of 12 to 20 months (15.4 +/- 2.8, n = 7) postoperatively have shown uniformly patent, compliant anastomoses with no evidence of hematomas, false aneurysms, or luminal narrowing. Histologic examination of two patent fistulas that were excised during revision procedures at 4 and 5 months postoperatively showed healing of the entire circumference of the anastomosis similar to that noted in extensive preclinical canine studies. We conclude from these preliminary results that argon laser vascular tissue fusion is possible in humans when reliable primary sealing of vascular anastomoses is achieved, and that healing occurs without aneurysmal dilatation during follow-up of up to 20 months.

Preliminary clinical outcome and imaging criterion for endovascular prosthesis development in high-risk patients who have aortoiliac and traumatic arterial lesions

PURPOSE This report reviews our preliminary experience of prospective treatment of arterial lesions with endoluminal grafts in a Food and Drug Administration (FDA)-approved, investigator-sponsored Investigation Device Exemptions study. The utility and accuracy of various imaging methods, including angiography, cinefluoroscopy, computed tomography (CT), intravascular ultrasonography (IVUS), and duplex scanning, in performing the procedures was also assessed. METHODS Thirty-one patients were evaluated; 17 patients were treated, including 11 with abdominal aortic aneurysms, one with an aortic occlusive lesion, two with iliac artery aneurysms, and three with traumatic arteriovenous fistulas. Twelve of the 14 patients who had aorta and iliac artery lesions were high-risk. The mean follow-up of patients treated was 9 months (range, 6 to 15 months). RESULTS Aortoaortic endoluminal interposition procedures were not successful for treating abdominal aortic aneurysms early in the study (n = 3). Aortoiliac endoluminal bypass, contralateral iliac artery occlusion, and femorofemoral bypass procedures were successful in seven of eight subsequent cases (88%), with no incidence of endoleaks at either the proximal or distal fixation sites using the deployment methods described in this report. The 30-day operative mortality rate on follow-up evaluations for patients who underwent aortoiliac procedures was 14% (two of 14). Other major complications included transient renal failure in three patients that required short-term (two to eight times) dialysis, one arterial perforation and one dissection, and one prolonged intubation. No myocardial infarctions or strokes occurred. After major complications or identification of limitations in the study, the protocol was modified with the approval of the FDA to help avoid the recurrence of the same problems. There were no deaths or complications in the trauma cases. CONCLUSIONS Contrast-enhanced CT (axial images and spiral reconstructions) was the most accurate method to determine candidacy for aortoiliac procedures and to choose the site for deployment of the devices. Angiographic scans were misleading in several patients regarding the critical determinants of patient candidacy and device deployment, particularly regarding the presence of a distal aortic neck. Cinefluoroscopy was used in all patient and was particularly useful for determining the continuity of vascular structures and the anatomy of branch arteries and for enabling precise positioning of stent devices. Determination of fixation sites and assessing dimensional information by cinefluoroscopy and angiography were limited by inaccuracies produced by image magnification, parallax, and uniplanar views. IVUS was used to determine the morphologic features of vascular structures (i.e., calcium, thrombus), to perform real-time observation of the expansion of devices, and to assure firm fixation of balloon-expanded stents before the procedures were completed. Duplex scanning was very helpful in assessing and identifying precisely the location of arteriovenous fistulas before intervention and provided assessment at follow-up intervals. Three-dimensional reconstruction imaging technologies such as spiral CT were particularly helpful for assessing the morphologic features of vascular anatomy before the intervention and at follow-up intervals, whereas 3-D IVUS provided a similar real-time perspective during the procedure.

Argon laser-welded arteriovenous anastomoses

This study compared the healing of laser-welded and sutured canine femoral arteriovenous anastomoses. Arteriovenous fistulas 2 cm in length were created bilaterally in the femoral vessels of 10 dogs and were studied at 1 (n = 2), 2 (n = 2), 4 (n = 3), and 8 (n = 3) weeks. In each animal, one anastomosis (control) was closed with running 6-0 polypropylene sutures, and the contralateral anastomosis (experimental) was sealed with an argon laser (0.5 watt, 4 minutes of exposure, 1830 J/cm2/1 cm length of anastomosis). At removal all experimental anastomoses were patent without hematomas, aneurysms, or luminal narrowing. Histologic examination at 4 weeks revealed that laser-welded anastomoses had less inflammatory response and almost normal collagen and elastin reorientation. At 8 weeks sutured anastomoses had significant intimal hyperplasia whereas laser repairs had normal luminal architecture. Tensile strength and collagen production, measured by the synthesis of hydroxyproline and the steady-state levels of type I and type III procollagen messenger ribonucleic acids, at the anastomoses and in adjacent vein and artery specimens were similar in sutured and laser-welded repairs at 2, 4, and 8 weeks. We conclude that argon laser welding of anastomoses is an acceptable alternative to suture techniques, with the advantage of improved healing without foreign body response and possible diminished intimal hyperplasia at the anastomotic line.

Modular bifurcation endoprosthesis for treatment of abdominal aortic aneurysms.

OBJECTIVE The authors analyzed a single groups experience treating abdominal aortic aneurysms (AAAs) with a new self-expanding, modular, bifurcated device. SUMMARY BACKGROUND DATA Successful exclusion of AAAs by prototype devices has led to several controlled clinical trials evaluating prostheses designed and manufactured specifically for this application. METHODS Sixteen patients (15 males, 1 female) of American Society of Anesthesiologists grade 2 through 4 and average age of 72 years had AAAs (average 57-mm diameter) treated as part of a phase I Food and Drug Administration-approved trial. RESULTS All patients were treated successfully with no surgical conversions. No endoleaks or aneurysm enlargement was noted either predischarge by contrast computed tomography or on follow-up at 1 month by duplex ultrasound examination. At 6 months, 12 of 13 patients who were observed for this interval had no endoleaks, whereas one patient (patient 3) showed a small area of extravasation that appeared to arise from the device in an area that was traumatized at the time of deployment. One procedure-related mortality (6%) occurred in a patient who died of septic complications secondary to a gangrenous gallbladder diagnosed 1 day after the procedure. There were no device-related mortalities. Complications included two iliac artery dissections, two groin wound infections, and two transient elevations of serum creatinine. Other significant variables including median procedure length (5 hours), intensive care unit stay (1 day), hospitalization postprocedure (4.5 days), and blood loss (1100 mL) all decreased as the study progressed. Blood replacement in all but three patients was accomplished by autotransfusion or banked-autologous blood replacement. At 6-month follow-up in 13 patients, the maximum diameter of the aneurysm decreased by an average of 5.6 mm (range, 0-15 mm), and the maximal cross-sectional area decreased an average of 20.3% (range, 0-72%). CONCLUSIONS This study suggests that endovascular prosthesis exclusion of AAAs using a self-expanding modular device may be effective in many patients who are otherwise surgical candidates for repair if further clinical studies confirm these observations.