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

Continuous Piezoelectric Pulse-Sensor Monitoring of Peripheral Vascular Reconstructions

Postoperative assessment of vascular surgical reconstructive procedures is most commonly performed by means of Doppler flowmetry or manual pulse palpation. Because these techniques are intermittent and can be subjective, the authors have investigated the application of a piezoelectric pulse sensor in monitoring distal pulses continuously in patients undergoing limb revascularization. By placing a piezoelectric sensor on the skin overlying an artery, systolic displacement of the underlying vessel wall and tissue is converted into a graphically displayed real-time waveform. Hardcopies of the waveforms (n = 90) were obtained at hourly postoperative intervals from a total of 10 patients undergoing vascular surgery for occlusive disease. In all cases, continuous monitoring confirmed ongoing patency of the reconstructions, despite impalpable distal pulses in 60% of the patients. The amplitudes of the waveforms increased (mean = 18%, range = 6% to 33%) during the first eight postoperative hours. Because of the small size and sensitivity of the sensor, this technique was especially useful in patients with foot lesions requiring occlusive dressings, or where sequential stenoses prevented accurate assessment of postoperative circulation by manual palpation or Doppler examination. The authors conclude that continuous postoperative piezoelectric pulse monitoring allows accurate, continuous assessment of limb revascularization and alleviates the subjective, time-consuming observations by physicians and ancillary personnel

In-vivo intravascular ultrasound in human ileo-femoral vessels

This study evaluates the ability of intravascular ultrasound (IUS) to image normal and mildly diseased human ileo-femoral vessels during angioplasty or vascular bypass procedures. Five Fr. and 8Fr. rotating A scan IUS catheters were used to obtain 43 images in 4 superficial femoral arteries, and 5 iliac arteries in 8 vascular surgery patients. Luminal cross sectional (LCS) areas measured by IUS were compared to LCS areas calculated by uniplanar angiography (ANGIO) at the same location in the vessel. The correlation between the areas (IUS vs ANGIO) for all images was significant (n = 43, r = 0.90, P<0.05). Mean LCS area calculated from ANGIO (33.7 +/- 21 mm ) was greater than LCS area measured by IUS (30.6 +/- 19.5 mm ) with n = 43; P = 0.02. In addition to providing accurate luminal determinations, IUS images displayed transmural morphology, the location of the atherosclerotic lesions and the thickness of the vessel wall. We conclude that IUS imaging provides accurate, novel information regarding human vessel wall anatomy and luminal dimensions. This technology may play a significant role in future diagnostic and interventional therapies

Intravascular Ultrasonography

Intravascular ultrasonography is developing rapidly as a method for defining the transmural anatomy of vascular structures, with diagnostic and therapeutic applications. The ultrasound technology not only has unique diagnostic capabilities by defining the distribution and character of lesions, but also provides accurate control information regarding efficacy of angioplasty methods. An exciting recent development is the three-dimensional reconstruction of two-dimensional images which permits global examination of luminal and transmural vessel morphology. This technology may enable improved guidance of intraluminal devices to enhance lesion removal without damaging adjacent normal wall structure and appropriate device selection by differentiating specific plaque characteristics

Laser-Fused Biologic Vascular Graft Anastomoses

Tissue fusion using laser energy is a promising new technology that may improve the healing of anastomoses. This study evaluated the feasibility of using argon laser energy to fuse vascular tissue and biologic vascular prostheses (St. Jude Medical, Inc.) in a canine arteriovenous (A-V) fistula model. Five animals had 4-cm length, 3-mm internal diameter grafts (n;eq 10) placed bilaterally as side-to-side A-V interpositions from the femoral artery to femoral vein. One A-V graft was placed using argon laser energy with the vessel edges aligned by 6-0 polypropylene traction sutures at 3 to 4 mm intervals. The contralateral graft was sutured using running 6-0 polypropylene suture. Anastomoses were successfully fashioned in all animals except for episodes of delayed bleeding at two laser-fused segments (15 min and 2 hrs) and one segment in a suture control (6 days). The implants were removed to evaluate the integrity and healing of the anastomoses at 2 hrs, 8 days, and at 7, 9, and 11 weeks. In all instances, there was no evidence of anastomotic dehissance or enlargement. Histologic examination of the anastomoses revealed coapted vessel and prosthetic edges in laser-fused specimens and a limited foreign-body response to the permanent sutures in the suture controls. In the longer term specimens there was marked intimal proliferation at the venous anastomosis in all implants, with recent bilateral occlusions of the 7 and 11 week implants at the venous connection. We conclude that laser fusion of biologic vascular prostheses to autogenous vessel is possible with healing and no evidence of anastomotic dehissance. The technique may provide a method to limit development of anastomotic stenosis by eliminating the foreign body reaction. In addition, the canine arteriovenous model used in these experiments develops aggressive intimal lesions at the venous anastomosis within weeks and may be used to evaluate the effect of anastomotic technique on the development of this lesion

Eccentric Iliac Artery Stenosis: A Canine Model for Angioplasty

A canine model was developed to induce eccentric iliac artery stenosis. Lesions were induced by exposing the medial aspect of the right and left common iliac arteries in four animals to direct argon laser energy (LA). A 2.5-mm diameter side-firing laser probe was used to deliver 10 W of power in 5-s intervals. Twenty-five pulses were delivered over a 5-ctn length of artery with an approximate spot size of 0.8 mm2. Selected arteries (n = 2, LA + Ca) were injected in the same laser injury site with calcium chloride (10% solution). Injections were accurately accomplished using an angioscopically guided guidewire/needle device. In all cases, the internal elastic lamina was broken with focal disruptions of the media. At 9 and 14 days, the LA (n = 3) and LA + Ca vessels (n = 1) had minimal stenoses (< 5% area reduction). These vessels contained edematous media with replacement of necrotic smooth muscle by fibrous tissue. At 23 days, the LA (n = 1) and LA + Ca (n = 1) vessels contained 22% und 33% luminal reductions, respectively, with moderate neointimal proliferation and no evidence of calcification. At 56 days the LA vessels (n = 2) contained 30 and 42% luminal area stenoses with marked neointimal hyperplasia. This preliminary data suggests that controlled arterial wall injury with LA irradiation can induce eccentric fibrointimal lesions in a canine model

Intraluminal Ultrasound Assessment of Vascular Stent Deployment

This study assessed the utility of intraluminal ultrasound imaging during deployment of a self-expanding vascular stent and quantitated changes in arterial morphology produced by the stent. Cross-sectional images of arterial lumens (n = 50) were obtained before stenting, in-vitro (n = 35) from formalin-preserved human superficial femoral arteries and in-vivo (n = 15) from canine iliac arteries containing laser-induced eccentric stenoses. Comparison of ultrasound-derived vessel dimensions (minimum and maximum diameter and cross-sectional area) with histological morphometric analysis of corresponding vessel sites showed good correlation by linear regression analysis (r = 0.930–0.987, p = 0.001–0.005). Following stent placement, 23 intraluminal ultrasound images were obtained from the stented vessel sites (in-vitro n = 15, in-vivo n = 8) and were compared to prestented cross-sectional areas. In the in-vitro vessels there was a small increase (p = 0.023) in area, but there was no change in the in-vivo arteries (p = 0.6). To assess the effect of stenting on luminal shape (ellipticity), minimum/ maximum diameter ratios were compared before and after stent deployment. There was an increase in this ratio in the in-vitro vessels (p = 0.001) but no change in the in-vivo arteries (p = 0.2). We conclude that intraluminal ultrasound produces clear and accurate images of the location, shape and degree of arterial pathology, ensuring good stent: vessel size matching and immediate quantitative assessment of the effects of arterial stent placement

A Canine Iliac Artery Occlusion Model

This report describes an occlusive canine iliac artery model for use in experimental angioplasty procedures. Lesions were induced by overdistending and breaking the internal elastic lamina of the artery and implanting a 2-cm long occlusive collagen plug. The collagen plug diameter was varied to fit the iliac artery and caused immediate bilateral iliac occlusions. Histology of the lesions at 9 and 14 days (n= 2) showed that the lumen was filled with a mixture of fresh thrombus and collagen pad material (more collagen than thrombus) with focal disruptions of the internal elastic lamina. At 36 days (n= 2) the lumen was obliterated with a mixture of organizing thrombus and collagen pad material (more organizing thrombus than collagen). At 60 (n= 4) and 80 (n=8) days the collagen pad had been completely replaced with organizing thrombus consisting of collagen fibers and hemosiderinladen macrophages with persistent focal disruptions of the internal elastic lamina. These initial data demonstrate the ability to create fibrotic arterial occlusions in as short a time as 60 days and to provide a practical model to study methods for treating localized peripheral vascular occlusive disease