The ideal guidance imaging system for endovascular interventions.

Endovascular interventions enable a minimally invasive approach to a variety of cardiovascular lesions. Small catheter-based delivery systems have rapidly evolved, diversifying endovascular therapeutic options. Coronary and peripheral vascular occlusive lesions may be amenable to angioplasty dilatation, intravascular stenting and ablation with mechanical atherectomy devices or lasers. New experimental transluminally placed endovascular stented grafts (TPEGs) have demonstrated feasibility for treating aneurysmal arteries, arteriovenous fistulas, and atherosclerotic occlusions. Improvements in imaging systems have provided better resolution of lesions, have improved patient selection and interventional strategy, and are invaluable for precise performance of procedures. The ideal guidance system should provide realtime imaging by a combination of complimentary modalities. These include cinefluoroscopy and contrast angiography, catheter-based intravascular ultrasound and angioscopy.

Comparison of the utility of CT scans and intravascular ultrasound in endovascular aortic grafting.

Using CT scans and intravascular ultrasound (IVUS), aortic, aneurysm neck, and endoluminal graft cross-sectional dimensions were compared in a canine model before and after placement of endoluminal grafts in normal aortas (n = 10) and in artificially constructed abdominal aortic aneurysms (n = 15). Measurement of diameters (n = 83) revealed an average difference or bias between imaging modalities of 0.17 +/- 0.92 mm. Measurements obtained using IVUS were slightly larger than CT values (8.84 +/- 1.0 vs. 8.65 +/- 1.1, p < 0.03) but correlated very well by linear regression analysis (r = 0.948, p < 0.02). Analysis of cross-sectional area (n = 44) revealed an average difference or bias of 7.21 +/- 7.76 mm2 between the two modalities. Again IVUS measurements were larger than CT measurements (65.0 +/- 16.5 vs. 57.9 +/- 11.9, p < 0.001) and linear regression analysis showed less correlation (r = 0.897, p < 0.001). Qualitative assessment of the graft and stent characteristics was more precise using IVUS. Graft folding, stent-aorta interfaces, and thrombus formation were easily identified by IVUS, whereas these more subtle characteristics were missed by CT scanning and arteriography. These studies demonstrate that IVUS measurements were slightly larger than CT values; however, both modalities demonstrate small bias and good correlation. Qualitative analysis of the aneurysmal aorta and endoluminal graft using IVUS is comparable to and in some respects more detailed than measurements from CT scanning and arteriography.

Anterior patch aortic aneurysm model for the study of endoluminal grafts.

Endovascular graft repair for aortic aneurysms has led to concerns regarding the healing characteristics of the graft within a thrombus-lined aneurysm and the effect that collateral flow may have on the endoluminal prosthesis and the aneurysm. An anterior aortic patch aneurysm model that preserved collateral arteries was examined and modified to address these issues. In canines (n = 30) a Dacron knitted patch (n = 27) or a rectus fascia patch (n = 3) was sutured into a 3.5-cm anterior aorotomy. Dacron patch aneurysm diameter was an average of 21.8 +/- 2.2 mm (mean canine normal aortic diameter 9.06 +/- 0.79 mm). Canines underwent angiogram, computed tomography, and/or intravascular ultrasound from 1 to 11 weeks later, at which time an endoluminal prosthesis was deployed and followed 30 to 60 days until harvest. Aneurysms accumulated minimal thrombus through the initial 11 weeks. Significant stenosis (mean 21.2% +/- 19%) occurred at aneurysm necks in association with a patch imbrication suture technique (n = 11). Following modification (n = 16), this decreased to a mean of 3.6 +/- 9.7%. Collateral lumbar artery patency was 95% at the time of imaging prior to graft placement. Following successful graft implantation, 16 of 18 aneurysms were filled with thrombus and in most cases the collateral circulation occluded. One of three fascial patch aneurysms ruptured 21 days after creation. This model more accurately depicts abdominal aortic aneurysms with the inherent thrombus and collateral flow that is important when studying aspects of endovascular aortic graft repair.

The role of cinefluoroscopy and intravascular ultrasonography in evaluating the deployment of experimental endovascular prostheses.

PURPOSE: This study compares the utility of cineangiography and real-time intravascular ultrasonography (IVUS) in achieving successful deployment of endovascular prostheses. METHODS: Five types of 5 cm long, 8 mm internal diameter polyester vascular grafts were secured in the infrarenal aorta of mongrel dogs by 18 mm long Palmaz balloon expandable vascular stents sutured to each end of the prostheses. The endovascular prostheses were delivered by crimping the stents at the ends of the grafts onto a 10 mm outside diameter, 8 cm long polyethylene balloon-dilation catheter. Real-time IVUS of the procedure was provided by a 0.035-inch, 20 MHz imaging element passed through the guide wire lumen in the balloon catheter. Two prostheses of each type were implanted, with one removed at 30 days and the other at 60 days for analysis. RESULTS: At implantation, both angiography and IVUS provided information regarding the choice of site for placement of the device and sizing of the aortic lumen. Real-time IVUS enhanced the information obtained by cineangiography by displaying tomographic views of the vessel anatomy, enabling determination of cross-sectional areas, assessing full stent expansion, and providing information regarding surface topography along the length of the prostheses. Several critical observations were apparent only on IVUS, including incomplete initial stent expansion during two procedures evidenced by pulsation of the aortic wall independent of the stent and movement of unstented segments of thin-walled grafts. Some of these observations led to further interventions at the time of deployment. At death, a comparison of cineangiography, IVUS, and ultrafast computed tomography outlined lumenal continuity and areas of irregularity, thrombus, or narrowing, with IVUS being more sensitive than cineangiography or computed tomography for determining most parameters. CONCLUSIONS: We conclude that IVUS is a promising alternative method for precise placement of intravascular grafts.

Gallstone pancreatitis. The role of preoperative endoscopic retrograde cholangiopancreatography.

OBJECTIVES: To evaluate the efficacy of endoscopic retrograde cholangiopancreatography (ERCP) and laparoscopic cholecystectomy in patients with gallstone pancreatitis and to determine criteria predictive of common bile duct stones (CBDS). DESIGN: Retrospective chart review. PATIENTS: Seventy-one consecutive patients with gallstone pancreatitis. MAIN OUTCOME MEASURES: Identification and endoscopic management of CBDS, complications, and mortality. RESULTS: Preoperatively, ERCP revealed CBDS in seven of 22 patients and postoperatively, in five of six patients. All stones were successfully removed. Laboratory values and common bile duct dilatation on admission did not predict CBDS. Persistent hyperamylasemia (> 150 U/L) and persistent hyperbilirubinemia (> 29.07 mumol/L [1.7 mg/dL]) were associated with CBDS on ERCP or intraoperative cholangiography. All five patients with cholangitis underwent ERCP, and CBDS were found and removed in four. There were no deaths and there was a 7% complication rate. CONCLUSIONS: Gallstone pancreatitis can be effectively managed by selective ERCP, endoscopic sphincterotomy, and laparoscopic cholecystectomy. Preoperative ERCP can be restricted to patients with cholangitis, persistent hyperbilirubinemia, or persistent hyperamylasemia.

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 quantitative the initial efficacy of devices and to determine the nature and distribution of recurrent lesions.