Douglas M. Cavaye

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.

Changes in arterial wall compliance after endovascular stenting

PURPOSE The response of arterial wall to endovascular stenting after angioplasty is not well understood. Additionally, changes in the elastic properties of stented vessels are unknown in situ. Vascular compliance was measured in normal canine iliac arteries (n = 11) before and after intravascular ultrasound-guided deployment of self-expandable metallic stents. METHODS Nine animals were restudied and killed 1, 2, and 4 weeks after initial deployment, and two dogs were studied at deployment only. An absolute induction angiometer was used to make in situ measurements of vessel compliance via catheter-based delivery. The angiometer consists of a wire loop probe, which conforms to the diameter of the vessel in which it is placed. Systolic/diastolic changes in loop diameter are translated into measureable changes of induced voltage. RESULTS Mean compliance of the artery before and immediately after stenting was 4.4 +/- 2.1 and 1.9 +/- 2.0 (x 10(-2) diameter %/mm Hg), respectively. As early as 1 week after deployment, stented arteries began to lose expansile properties, and some were noncompliant. At explantation diminished compliance was accompanied by a periadventitial fibrous reaction around stented vessels. A thin, unobstructing layer of neointimal hyperplasia covered the iliac stents at all intervals, and all vessels remained patent and free of thrombus. CONCLUSIONS The potential advantages provided by a flexible, radially compliant stent are lost within a relatively short time after implantation in nonatherosclerotic canine arteries.

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.

Endoscopic Surgery Training: Application of an in Vitro Trainer and in Vivo Swine Model

The development of endoscopic surgical procedures is changing general surgery, with many operations such as cholecystectomy, appendectomy, and hernia repair being performed using laparoscopic surgical techniques. Training and credentialing of surgeons are key issues for the safe and ethical introduction of these new procedures. This article reviews techniques employed at our institution for laparoscopic surgical training and certification including didactic instruction, an in-vitro model for learning instrumentation and hand-eye coordination, and in-vivo training using the porcine animal model.

Nd:YAG laser-welded canine arteriovenous anastomoses.

This preliminary report describes formation of femoral arterio‐venous fistulas (n = 10) in six dogs using a 1.32‐μm wavelength Nd:YAG laser welding technique. Stay sutures (6‐0 polypropylene) were placed at 5–7 mm intervals along the anastomoses for vessel apposition. Delivery of laser energy through a 400‐μm diameter fiber optic was controlled by a new computer‐based software system. At 3 mm distance above the anastomosis, energy fluences of 110–260 J/mm2/cm length of anastomosis were used for laser welding. One or two additional hemostatic sutures were required in seven of the ten anastomoses. Flow was maintained for 1–2 hours prior to tissue harvesting. No thrombosis or delayed anastomotic failures were observed after initial welding and repair. Histologic examination revealed good apposition and adherence between wall layers and a fibrinous coagulum at the intimal junctions. Mild thermal injury of the wall was present at some anastomoses. This early investigation suggests that a 1.32 μm Nd:YAG laser welding technique can successfully create large vessel arteriovenous fistulas in the canine.

Sequential Intraluminal Ultrasound Evaluation of Balloon Angioplasty of an Iliac Artery Lesion

This report describes intravascular ultrasound imaging of a localized 81% stenosis in the left common iliac artery of a 52-year-old woman. The lesion was dilated using an 8 mm balloon and was imaged pre- and post-dilatation using arteriography and a 5F, 30 Mhz intravascular ultrasound catheter. The same site was imaged again intraoperatively at two months following the initial procedure using an 8F, 20 Mhz intravascular ultrasound catheter when the patient had a femoropopliteal bypass for continuing ischemia. Intravascular ultrasound imaging allowed accurate, sequential, on-line calculation of the cross-sectional area and volume of the lesion both, acutely and following healing of the site. The morphology of the fractured arterial plaque was clearly defined, demonstrating distribution of calcification, and intraluminal flaps not apparent on arteriography. The case demonstrates the unique potential of intravascular ultrasound in assessing the immediate effect of interventions and evaluating the long-term healing.

Computerized Surgical Databases: Introduction to Design and Function

There has been an enormous increase in the variety and volume of information encountered in surgical practice, either as measurable clinical variables or laboratory research data over the last three decades. Despite its form and origin, this information remains the basis of both daily clinical decision making and analytical research. Inferences drawn from past experience will modify an individuals approach to disease and treatment. However, when the demands of information processing cannot be met, mischief begins and quality of care declines. Modern computers offer an extraordinarily powerful method of processing the large volumes of medical data that are acquired, and provide techniques for analysis that would have been impossible, and often inconceivable, without computers. The applications of computer technology to surgical data management range from such simple and repetitive tasks as practice administration and accounting to elegant statistical and image analysis. This paper outlines the utility of computerized data management in clinical surgery and surgical research, and describes techniques for designing and implementing a customized surgical database system.

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-cm 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% and 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.

Laser cytoreduction as part of multimodality therapy for squamous cell carcinoma of the anus: a case report

ABSTRACT The treatment of anal canal epidermoid cancer has changed dramatically during the last two decades, exemplified by the excellent results of primary chemoradiotherapy compared with traditional radical surgical resection. Despite this progress, the management of large (>5 cm) tumors remains controversial. We report a case of advanced (tumor size 8 cm, lymphatic metastases; Stage T4N2), moderately differentiated squamous cell carcinoma of the anal canal which was managed by CO2 laser ablation with followup combined chemoradiotherapy. The patient has remained well in the 12 months since initial treatment with excellent anal sphincter function and no evidence of distant metastases or residual disease on biopsy. We conclude that combined debulking and chemoradiotherapy should be considered in patients with locally advanced, unfavorable squamous cell cancer of the anal canal.