Julio C. Palmaz

Transfemoral Intraluminal Graft Implantation for Abdominal Aortic Aneurysms

This study reports on animal experimentation and initial clinical trials exploring the feasibility of exclusion of an abdominal aortic aneurysm by placement of an intraluminal, stent-anchored, Dacron prosthetic graft using retrograde cannulation of the common femoral artery under local or regional anesthesia. Experiments showed that when a balloon-expandable stent was sutured to the partially overlapping ends of a tubular, knitted Dacron graft, friction seals were created which fixed the ends of the graft to the vessel wall. This excludes the aneurysm from circulation and allows normal flow through the graft lumen. Initial treatment in five patients with serious co-morbidities is described. Each patient had an individually tailored balloon diameter and diameter and length of their Dacron graft. Standard stents were used and the diameter of the stent-graft was determined by sonography, computed tomography, and arteriography. In three of them a cephalic stent was used without a distal stent. In two other patients both ends of the Dacron tubular stent were attached to stents using a one-third stent overlap. In these latter two, once the proximal neck of the aneurysm was reached, the sheath was withdrawn and the cephalic balloon inflated with a saline/contrast solution. The catheter was gently removed caudally towards the arterial entry site in the groin to keep tension on the graft, and the second balloon inflated so as to deploy the second stent. Four of the five patients had heparin reversal at the end of the procedure. We are encouraged by this early experience, but believe that further developments and more clinical trials are needed before this technique becomes widely used.

Balloon-expandable intracoronary stents in the adult dog.

We studied the acute and chronic biological reaction to balloon-expandable intracoronary stents in the adult dog. Twenty stainless steel stents were placed, by standard angioplasty techniques, into the left anterior descending, left main, or circumflex coronary arteries of 20 dogs. Angiography was performed at 1, 3, 6, and 12 months and animals were killed in groups of three at 1, 3, 8, and 32 weeks, for gross, light, and electronmicroscopic analysis. All dogs survived, all stents were patent, and there was no evidence of myocardial infarction, spasm, rupture, or aneurysm formation during follow-up (longest 18 months; average, 12 months). The stent was initially covered by a thin layer of thrombus that was replaced later by neointimal muscular proliferation that reached its maximal thickness by 8 weeks (p less than .01). This neointima gradually thinned as it became more sclerotic and less cellular. The stents were covered completely by immature endothelium by 1 week without loss of side branches. We conclude that balloon-expandable intraluminal stents can be safely placed percutaneously into normal canine coronary arteries. Because of rapid endothelialization high patency rates can be expected, thus offering promise for clinical applications in man.

Stenting of the iliac arteries with the palmaz stent: Experience from a multicenter trial

Balloon-expandable, intraluminal stenting of the iliac arteries with the Palmaz stent was the subject of a multicenter study for 4 years. A total of 486 patients underwent 587 procedures. Four hundred and five patients had unilateral and 81 had bilateral iliac stent placements. Follow-up ranged from 1 to 48 months (mean 13.3±11 months). Sustained clinical benefit of the treated patients was obtained in 90.9% at 1 year, 84.1% at 2 years, and 68.6% at 43 months. Angiographic patency rate was 92%. Diabetes mellitus and poor runoff had significant negative influence on the clinical outcome. The 10% incidence of procedural complications was not altered by operator experience.

Implantation of balloon-expandable intravascular grafts by catheterization in pulmonary arteries and systemic veins.

The purpose of this investigation was to evaluate the efficacy and safety of implanting expandable intravascular stents in pulmonary arteries and systemic veins. Twenty-seven balloon-expandable grafts were placed in 13 mongrel dogs under anesthesia. A long sheath was introduced over a wire and catheter or dilator into the pulmonary artery or target vein. A collapsed stainless steel expandable mesh stent was placed over the balloon of an angioplasty catheter. The catheter with the mounted stent was advanced through the sheath. The stent expanded to the diameter of the balloon as the balloon was inflated, and remained expanded as the balloon was deflated. The stent was expanded further with a larger balloon in 11 instances. Eleven stents were placed successfully in pulmonary arteries (out of thirteen attempted), and 11 of 14 were installed in tributaries of the precava or postcava. Three inadvertent embolizations of the devices occurred. All three devices that embolized lodged in the pulmonary arteries and did not obstruct flow. Seven dogs were recatheterized at intervals ranging from 56 to 278 days. Twelve stents were patent and nonobstructive, and two were malpositioned, one of which was obstructed. Three animals were killed 2 months (two dogs) and 9 months (one dog) after the implantations. The stents (four in the pulmonary arteries and two in veins) were completely covered with neointima and were patent, without thrombosis. These stents hold promise for definitive dilation of congenital or postoperative vessel stenoses.

Influence of Surface Topography on Endothelialization of Intravascular Metallic Material

PURPOSE To determine whether grooves on a metal surface help endothelialization and, furthermore, what groove size is more likely to promote the fastest endothelialization in an in vitro model. Hypothetically, a microscopic pattern of parallel grooves disposed in the direction of flow, on the inner surface of stents, increases endothelial cell migration rates, resulting in decreased time to total coverage of the prosthetic surface. MATERIALS AND METHODS Square, flat pieces of nitinol were placed level on a monolayer, confluent culture of endothelial cells. The metal pieces were treated to produce parallel grooves on the surface of 1, 3, 15, and 22 microm to be compared to polished, smooth controls. Microscopy images were obtained by digital capture and processed for analysis of migration distance and cell count, density, shape, and alignment. RESULTS Grooved surfaces promoted increased rate of migration of endothelial cells, up to 64.6% when compared to smooth, control surfaces. Larger grooves resulted in greater migration rates. The cells aligned with the grooves, elongated, and become more numerous on grooved surfaces, particularly with large grooves. CONCLUSION A pattern of microscopic parallel grooves more than doubles the migration rate of endothelial cells over metallic surfaces ordinarily used for endovascular stents. Future research in this area is aimed at demonstrating the potential effect of grooved endovascular stent surfaces on faster endothelialization times.

The transjugular intrahepatic portosystemic stent-shunt (TIPSS): results of a pilot study.

The new concept of TIPSS (Transjugular Intrahepatic Portosystemic Stent-Shunt) using the Palmaz iliac stent was successfully accomplished in 9 patients with severe portal hypertension (7 alcoholic, 2 postinfectious liver cirrhosis) and histories of multiple life-threatening upper GI bleeding. All patients were considered noncandidates for surgical portal decompression. An intrahepatic central connection was made transjugularly between the right hepatic vein and the right portal vein in 8 patients and the left portal vein in 1. The portosystemic gradient dropped from an average of 29±7.2 mmHg to 17.8±2.9 mmHg immediately after, and to 15.7±2.8 mmHg at the latest follow-up control after the procedure. Seven patients survived the procedure and progressed to Childs A stage during the observation period of 1–10 months (mean 5 months). One patient died as a direct complication from the procedure, and another patient 11 days after the procedure from a severe nosocomial infection. In none of the surviving patients has bleeding from varices recurred or encephalopathic coma developed. In one patient the shunt diameter was moderately increased by a routine PTA catheter to further decrease the portosystemic gradient (23 to 14 mmHg) 3 months after the primary procedure. Autopsy in the two patients who died demonstrated open stent-shunts with early neoendothelial incorporation.

Fibrinogen: Structure, Function, and Surface Interactions

Fibrinogen plays a central role in the mechanism of coagulation and thrombosis and is partially involved in the development of postintervention restenosis. Because of therapeutic implications, it is convenient for the vascular interventionalist to revisit its structure, function, and relationships within the vascular environment. This review focuses on the molecular structure, mechanisms of polymerization and lysis, and fibrinogen interaction with the platelet alpha(IIb)beta(3) [corrected] integrin. It also addresses the less understood interaction of fibrinogen with artificial surfaces. Glycoprotein IIb-IIIa blockers, targeted to interfere with fibrinogen-platelet interactions, widely used in clinical practice, are discussed, and trials of new drugs are also summarized.

Iliac Artery Stent Placement with the Palmaz Stent: Follow-up Study

PURPOSE The long-term efficacy of iliac artery stent placement with the Palmaz stent was evaluated for treatment of limb ischemia. PATIENTS AND METHODS Iliac stent implantation for limb ischemia was performed on 108 limbs in 83 patients. Eighty patients (96.4%) were followed up clinically from 1 to 70 months (mean, 25.8 months), and 30 patients (37.5%) were followed up with angiography from 1 to 48 months (mean, 10.4 months). Patients were classified into six categories by using an ischemic ranking profile. Clinical success was defined as a minimum one-category improvement from preprocedure ranking. RESULTS The clinical success rate was 98.9% immediately after the procedure and 86.2% at 48 months. Long-term success was statistically more common in patients with higher preprocedure and lower postprocedure ischemic ranking, and in patients without diabetes. Arteriography demonstrated a primary patency rate of 87.5% at latest follow-up, with five occlusions (12.5%) and only two (5.0%) restenoses. Average stenosis was 17.8% at 6 months and 24.7% at 2 years. Stent restenosis was statistically more common with a higher postprocedure pressure gradient. The complication rate was 9.7%, and 30-day mortality was 1.2%. CONCLUSION Long-term clinical and angiographic follow-up demonstrates iliac artery stent placement with the Palmaz stent is safe and efficacious for treatment of limb ischemia.

Angioplasty and stenting of completely occluded iliac arteries

Percutaneous angioplasty and placement of balloon-expandable intraluminal stents were performed in 12 iliac occlusions in 12 patients. Indications were limb salvage in seven and claudication in five. After successful stenting, ankle-brachial indexes improved by 0.15 or more in 11 of 12 patients (mean increase, 0.40), transstenotic pressure gradients decreased to less than 5 mm Hg (mean, 0.58 mm Hg) in all patients, and improvement in clinical grade was seen in all patients. At follow-up at 1-14 months (median, 6 months), ankle-brachial indexes were stable (mean, 0.95), and clinical grades were unchanged in all patients. Complications occurred in two patients; both experienced distal embolization, and one, who was receiving corticosteroid therapy, also suffered stent thrombosis. Local surgical embolectomy was successful in both patients, and the thrombosed stent was recanalized with urokinase. This early experience suggests that stenting may play an important role in the management of iliac occlusions, especially in poor surgical candidates.

Intravascular stenting: from basic research to clinical application

Although the use of intravascular stents is approaching widespread clinical use, several questions remain regarding their safety and efficacy. Several factors have direct bearing on the immediate and long-term results of intravascular stenting. The technical results of stenting are dependent on the mechanical characteristics of the device and long-term patency is closely related to thrombogenicity and endothelialization. Although stents are used most frequently for the treatment of atherosclerotic disease there is no clear understanding of how they influence the atheromatous lesion.