Transcatheter implantation of a bovine valve in pulmonary position: a lamb study

BACKGROUND

Pulmonary regurgitation can lead to severe right ventricular dysfunction, which is a delicate postoperative problem in the long-term follow-up of patients who had surgery for congenital heart diseases. Clinical conditions of patients suffering from pulmonary valve incompetence are improved by valve replacement with a prosthetic valve. To date, the surgical approach is the only option to replace a pulmonary valve. We report the first experience of percutaneous pulmonary valve implantation.

METHODS AND RESULTS

A fresh bovine jugular vein containing a native valve was sutured into a vascular stent and then cross-linked with a 0.6% glutaraldehyde solution for 36 hours. After being hand-crimped onto a balloon catheter, the device was inserted percutaneously according to standard stent-placing techniques. The valved stent was finally deployed in the position of the native pulmonary valve of the lamb. Hemodynamic evaluation was carried out before and 2 months after implantation. Anatomic evaluation was finally performed. Percutaneous pulmonary valve replacement was successful in 5 lambs. No complications were noted. Early and late angiographic and hemodynamic studies confirmed a good position of the stents with a competent valve at the end of the protocol. One stent was slightly stenotic, with macroscopically visible calcifications.

CONCLUSIONS

Nonsurgical implantation of pulmonary valves is possible in the lamb. This new technique is similar to standard stent implantation. Thus, it should be feasible in humans, in whom it will lead to a significant reduction of reoperations in patients in need of pulmonary valve replacement.

Percutaneous endovascular stents: an experimental evaluation

Percutaneous, expanding, endovascular stents were constructed of stainless steel wire formed in a zig-zag pattern. Stents were placed for varying periods of time in the jugular vein, vena cava, and abdominal aorta in each of five adult dogs. The dilating force of the stents could be controlled by different wire size, number and angle of wire bends, and stent length. In addition, multiple stents could be placed one inside the other or one after the other, depending on the circumstance. The stents distended the vessels and increased their diameter. No flow defects, luminal narrowing, or occlusion were noted in any of the stented vessels, even after 6 months. Side branches bridged by the stents remained patent and showed no indication of narrowing. Stent wires became encased by a proliferation of the tunica intima where they contacted the vessel wall. Encasement was slower and less extensive in the abdominal aorta. No vascular erosion or clot formation was found to be associated with any of the stents.

Engineering of fibrin-based functional and implantable small-diameter blood vessels

We engineered implantable small-diameter blood vessels based on ovine smooth muscle and endothelial cells embedded in fibrin gels. Cylindrical tissue constructs remodeled the fibrin matrix and exhibited considerable reactivity in response to receptor- and nonreceptor-mediated vasoconstrictors and dilators. Aprotinin, a protease inhibitor of fibrinolysis, was added at varying concentrations and affected the development and functionality of tissue-engineered blood vessels (TEVs) in a concentration-dependent manner. Interestingly, at moderate concentrations, aprotinin increased mechanical strength but decreased vascular reactivity, indicating a possible relationship between matrix degradation/remodeling, vasoreactivity, and mechanical properties. TEVs developed considerable mechanical strength to withstand interpositional implantation in jugular veins of lambs. Implanted TEVs integrated well with the native vessel and demonstrated patency and similar blood flow rates as the native vessels. At 15 wk postimplantation, TEVs exhibited remarkable matrix remodeling with production of collagen and elastin fibers and orientation of smooth muscle cells perpendicular to the direction of blood flow. Implanted vessels gained significant mechanical strength and reactivity that were comparable to those of native veins. Our work demonstrates that fibrin-based TEVs hold significant promise for treatment of vascular disease and as a biological model for studying vascular development and pathophysiology.

Arterial enlargement in response to high flow requires early expression of matrix metalloproteinases to degrade extracellular matrix

This study investigated the effects of high flow and shear stress on the expression of matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinase-2 (TIMP-2) during flow-induced arterial enlargement using a model of arteriovenous fistula (AVF) creation on the carotid artery with the corresponding jugular vein in Japanese white male rabbits. Flow increased 8-fold 7 days after AVF. Endothelial cells (EC) and smooth muscle cells (SMC) proliferated with internal elastic lamina (IEL) degradation in response to high flow and shear stress. Expression of MMP-2 mRNA peaked at 2 days (1700-fold) and maintained high level expression. MMP-9 mRNA gave a 10.8-fold increase within 2 days and decreased later. Their proteins were detected in EC and SMC. Membrane type-1-MMP (MT1-MMP) mRNA increased 121-fold at 3 days and maintained high expression. TGF-beta1 was increased after AVF. Two-peak up-regulation of Egr-1 mRNA was recognized at 1 and 5 days of AVF. These results suggest that high flow and shear stress can mediate EC and SMC to express MMP-2 and MMP-9, which degrade cell basement membranes and IEL to induce arterial enlargement. The disproportional increase in MT1-MMP and TIMP-2 might contribute to MMP-2 activation. Egr-1 and TGF-beta1 might play important roles in this process.

The jugular foramen: microsurgical anatomy and operative approaches

The jugular foramen, based on these studies of microsurgical anatomy, is divided into three compartments: two venous and a neural or intrajugular compartment. The venous compartments consist of a larger posterolateral venous channel, the sigmoid part, which receives the flow of the sigmoid sinus, and a smaller anteromedial venous channel, the petrosal part, which receives the drainage of the inferior petrosal sinus. The petrosal part forms a characteristic venous confluens by also receiving tributaries from the hypoglossal canal, petroclival fissure, and vertebral venous plexus. The petrosal part empties into the sigmoid part through an opening in the medial wall of the jugular bulb between the glossopharyngeal nerve anteriorly and the vagus and accessory nerves posteriorly. The intrajugular or neural part, through which the glossopharyngeal, vagus, and accessory nerves course, is located between the sigmoid and petrosal parts at the site of the intrajugular processes of the temporal and occipital bones, which are joined by a fibrous or osseous bridge. The glossopharyngeal, vagus, and accessory nerves penetrate the dura on the medial margin of the intrajugular process of the temporal bone to reach the medial wall of the internal jugular vein. The operative approaches, which access the foramen and adjacent areas and are demonstrated in a stepwise manner, are the postauricular transtemporal, retrosigmoid, extreme lateral transcondylar, and preauricular subtemporal-infratemporal approaches.

Genesis of a dural arteriovenous malformation in a rat model

A rat model was developed to determine the role of sinus thrombosis and elevated sinus pressures in the pathogenesis of dural arteriovenous malformations (AVMs). Five protocols were tested to compare various sinus pressures and thrombosis of a sinus: 1) Control I, sham operation (five animals); 2) Control II, occlusion of the right common carotid artery, the right external jugular vein, and the vein draining the left transverse sinus, as well as thrombosis of the sagittal sinus (10 animals); 3) arteriovenous fistula (AVF) I, anastomosis of the right common carotid artery to the external jugular vein causing retrograde flow through the transverse sinus (10 animals); 4) AVF II, anastomosis (as described in AVF I) and thrombosis of the sagittal sinus (12 animals); 5) AVF III, anastomosis (as described in AVF I) as well as thrombosis of the sagittal sinus and occlusion of the vein draining the transverse sinus on the left (12 animals). Mean arterial and sagittal sinus pressures were monitored and cerebral angiograms were obtained intraoperatively and again 90 days later. Afterward, the animals were sacrificed and their brains and dura were examined histologically. Formation of a fistula resulted in a significant (p < 0.05) threefold increase in sagittal sinus pressure in the AVF II group and a significant (p < 0.05) sixfold increase in the AVF III group. Seven dural AVMs (three in the AVF II group and four in the AVF III group) were demonstrated angiographically and histologically. The seven malformations were located adjacent to a thrombosed sagittal sinus. All lesions were within the dura and sinus wall with direct thrombus-sinus wall connections demonstrated in four of the malformations. The other three lesions displayed arteriovenous connections within the sinus wall and dura. These data suggest the importance of not only sinus thrombosis but also sinus hypertension in the development of a dural AVM.

Embolic Events and Char Formation During Pulmonary Vein Isolation in Patients with Atrial Fibrillation: Impact of Different Anticoagulation Regimens and Importance of Intracardiac Echo Imaging

Thromboembolic events are important complications of pulmonary vein isolation (PVI) procedures, occurring in up to 2.8% of patients. In this study, we report the incidence of char formation and embolic events with different anticoagulation protocols prospectively changed to reduce such complication.

METHODS

A total of 785 patients (mean age: 54 years, 83.5% male) underwent catheter-based PVI for treatment of drug refractory, symptomatic atrial fibrillation (AF). PVI was performed utilizing different strategies including radiofrequency (RF) using temperature control energy delivery and RF using intracardiac echocardiography (ICE)-guided power titration. Patients were divided based on the anticoagulation protocol into three groups: in group 1 (194 patients), activation coagulation time (ACT) was maintained between 250 and 300 seconds; in group 2 (180 patients), ACT was maintained between 300 and 350 seconds plus the IV infusion of eptifibatide (135 microg/kg bolus + 0.5 microg/kg/min); and in group 3 (411 patients), ACT was maintained between 350 and 400 seconds.

RESULTS

Char formation was detected in 69 patients of group 1, 5 of group 2, and 8 of group 3. An embolic event was observed in 7 patients of group 1, 3 of group 2, and 2 of group 3 (P = 0.01; group 1 vs group 3). Higher degree of anticoagulation with heparin was associated with a reduced incidence of embolic events even after removing the patients undergoing ICE-guided ablation (P = 0.04).

CONCLUSION

More aggressive anticoagulation with heparin reduced periprocedural embolic events. The use of platelet inhibition does not have incremental beneficial effect. None of the anticoagulation protocol abolished char formation.

Jugular vein catheterization for repeated blood sampling in the unrestrained conscious rat

The ability to obtain repeated, low-stress blood samples from adult rats enables the design of complex experiments in which time course information or evaluation of repeated treatments is necessary. Furthermore, it reduces the number of animals necessary to acquire such information and, thus, facilitates compliance with the animal use 3Rs (reduction, refinement and replacement). To this end, a microsurgical technique to collect blood samples from the right atrium through a catheter (cannula) implanted into the right external jugular vein of adult rats is described. Rats tolerate this simple and efficient vascular access technique as evidenced by the absence of overt morbidity or abnormal behaviors. Blood is easily sampled while the rats reside in their home cages. Because the sample volume is replaced, repeated sampling is possible without compromising blood volume. Successful adoption of this procedure by other investigators will be aided by the photographic illustrations accompanying this detailed description of the procedure. Application of this technique to monitor temporal changes in plasma stress hormones during stressor paradigms as well as after behavioral and pharmacological challenges is discussed.

Further experience with peritoneo-venous shunt for ascites

A specially devised pressure-sensitive valve forms the basis for a new peritoneo-venous shunt operation which delivers ascitic fluid continuously into the venous system. It is effective in ascites attributed to different causes. The procedure is simple and brings a long lasting relief with recovery in strength and nutrition and improved kidney function. Hepatorenal syndrome in ascites is reversed.

Arterial enlargement, tortuosity, and intimal thickening in response to sequential exposure to high and low wall shear stress

We investigated the effects of sequential and prolonged exposure to high and low wall shear stress on arterial remodeling using a rabbit arteriovenous fistula (AVF) model. Blood flow was increased by approximately 17-fold to 20-fold when the AVF was open, and returned to normal when the AVF was occluded. Repeated opening and closing of the AVF resulted in sequential exposure of the artery to high and low wall shear stress. High flow and high wall shear stress induced arterial dilatation, elongation, and tortuosity, without intimal thickening. The common carotid artery was elongated 37% after 4 weeks of high flow, and was shortened 10% after 6 weeks of normal flow. Subsequent cycles of high flow induced less elongation, with less shortening after return to normal flow. Enlargement of the distal segment was more dramatic than in the proximal segment, despite exposure to the same volume of flow and the same initial high wall shear stress after creation of the AVF. The distal carotid segment enlarged more than did the proximal segment during each exposure to high flow. In segments of carotid artery exposed to low wall shear stress (<5 dynes/cm(2)) intimal thickening developed. These changes were maximal in the distal carotid segment, just before the AVF. Each cycle of low wall shear stress induced intimal thickening accompanied by medial hyperplasia. Intimal thickening was inhibited during periods of high flow when wall shear stress was high. Three cycles of flow alteration induced three layers of intimal thickening in the distal arterial segment, two layers of intimal thickening in the middle segment, and one layer of intimal thickening in the proximal segment. Long-term exposure to low wall shear stress induced severe intimal thickening and medial hyperplasia in different segments. Thus the response of the carotid artery afferent to an AVF varies along the length of the artery, with maximum enlargement, elongation, and tortuosity in the distal segment, just proximal to the AVF. Similarly, intimal thickening in response to low wall shear stress is maximal in the distal carotid artery. It appears that intimal thickening is related to local levels of low wall shear stress, and occurs when wall shear stress chronically falls to less than 5 dynes/cm(2).

The radial forearm free flap in orofacial reconstruction. Personal experience in 120 consecutive cases

120 cases of orofacial cancer underwent ablative surgery to cure their disease. The resultant defects were reconstructed using free radial fascio-cutaneous forearm flaps with microvascular anastomosis. The cases were consecutive and both ablation and reconstruction were performed by the same operator.

Internal jugular vein versus external jugular vein anastamosis: Implications for successful free tissue transfer

BACKGROUND

Microvascular free flaps are becoming the reconstructive option of choice for many head and neck defects. Many previous studies have examined factors predicting free flap survival. No study has compared differences in free flap survival when anastomosed to the internal or external jugular systems.

METHODS

Retrospective review of all free flaps performed at an academic medical center by a single head and neck microvascular surgeon during the period July 1995 to December 1999. Flaps were closely monitored postoperatively and taken back to the operating room urgently for arterial insufficiency or venous congestion.

RESULTS

On hundred fifty-six free flaps were performed during this time period. Sixty-five free flaps were anastomosed to the external jugular (EJ) vein and 86 to the IJ system (62 to the proximal common facial vein, 17 end-side on the IJ, and 7 to other branches). Five had either two venous anastomoses or were anastomosed to other veins and were excluded from statistical analysis. Six (4%) vascular thromboses occurred; 5 were venous and 1 arterial. Success by group was 99% for IJ anastomosis (1 arterial thrombosis) and 92% for EJ anastomosis (5 venous thromboses, p =.03). Urgent anastomotic revision and reperfusion salvaged 5 of the 6 flaps (overall success 99%).

CONCLUSIONS

Although the overall success rate (96% success with 99% success with salvage) is comparable to other large series, microvascular free flaps anastomosed to the external jugular vein failed at a significantly higher rate than those anastomosed to the IJ system. This suggests that the IJ system should be used as a recipient vessel when feasible.

Healing basis and surgical techniques for complete revascularization of the left ventricle using only the internal mammary arteries

Long-term follow-up data from several leading centers concerning patients undergoing coronary artery bypass clearly demonstrate the superiority of the internal mammary artery (IMA) with patency rates of 83 to 94% at 7 to 12 years compared with the saphenous vein and its patency rates of 41 to 53%. Our experimental studies provide a biological basis for understanding this difference. Thin-walled arterial autografts undergo no histological change after being implanted in the arterial system, while venous autografts undergo major changes with an initial scattered loss of endothelium and marked thickening due to a proliferative reaction. The challenge to the cardiac surgeon is to revascularize the entire left ventricle with the IMAs. We have found this possible in most patients with advanced three-vessel disease by using both IMAs either as in situ grafts or free grafts with as many sequential anastomoses as necessary to achieve full revascularization. Our use of the term in situ refers to the graft's origin from the subclavian artery as opposed to a free IMA graft arising from another site.

Management of Penetrating Neck Injuries: A New Paradigm for Civilian Trauma

PURPOSE

Improvements in imaging technology, particularly computed tomographic angiography (CTA), have altered the management of patients with penetrating neck injuries. Although some centers still advocate routine exploration for all zone 2 neck injuries penetrating the platysma, many civilian centers in the United States have adopted a policy of selective exploration based on clinical and radiographic examination. The purpose of this retrospective study is to evaluate our 5-year experience with the management of penetrating neck injuries, to further elucidate the role of CTA in clinical decision-making, and to assess treatment outcome.

PATIENTS AND METHODS

One hundred thirty-four consecutive patients were identified from the Legacy Emanuel Trauma Registry as having sustained penetrating neck injuries from 2000 to 2005. Using data collected from the Trauma Registry, as well as individual chart notes and electronic records, variables were collected and evaluated including age, gender, mechanism of injury, number of associated injuries, and the Injury Severity Score, Glasgow Coma Scale on admission, initial hematocrit, airway management techniques, diagnostic and therapeutic modalities, missed injuries, length of hospital stay, disposition, and outcome. Descriptive statistics were used to describe demographics, treatment, and outcome.

RESULTS

One hundred twenty patients met the inclusion criteria, 55 of which had only superficial injuries that did not penetrate the platysma. The primary study group consisted of 65 patients who sustained more significant injuries that violated the platysma including deep, complex, and/or avulsive wounds, vascular injuries, injuries to the aerodigestive tract, musculoskeletal system, cranial nerves, or thyroid gland. The overall mortality rate for the 65 patients with injuries penetrating the platysma was 3.0% (n = 2). Complications occurred in 7 of the surviving 63 patients (10.7%): 2 patients with zone 3 internal carotid artery injuries developed hemispheric ischemic infarcts and hemiplagia; as well as other complications including: infection (n = 2); deep venous thrombosis (n = 1); aspiration pneumonia (n = 1); and hematoma (n = 1). All surviving patients except the 2 stroke patients eventually healed uneventfully without significant functional deficit. The use of CTA as a guide to clinical decision-making led to a significant decrease in the number of neck explorations performed and a virtual elimination of negative neck explorations.

CONCLUSION

The management of stable patients with neck injuries that penetrate the platysma has evolved at our institution into selective surgical intervention based on clinical examination and CTA and has resulted in minimal morbidity and mortality.

Functional tissue-engineered blood vessels from bone marrow progenitor cells

OBJECTIVE

Stem cells have significant potential for development of cell-based therapeutics for cardiovascular tissue regeneration.

METHODS

We developed a novel method for isolating smooth muscle cells (SMC) from ovine bone marrow using a tissue-specific promoter and fluorescence-activated cell sorting.

RESULTS

As compared to vascular SMC, bone marrow-derived smooth muscle progenitor cells (BM-SMPC) exhibited similar morphology, showed higher proliferation potential and expressed several SMC markers including alpha-actin, calponin, myosin heavy chain, smoothelin, caldesmon and SM22. When embedded in fibrin hydrogels, BM-SMPC contracted the matrix and displayed receptor- and non-receptor-mediated contractility, indicating that BM-SMPC can generate force in response to vasoreactive agonists. We also prepared tissue-engineered blood vessels from BM-SMPC and BM-derived endothelial cells and implanted them into the jugular veins of lambs. As early as five weeks post-implantation, grafted tissues displayed a confluent endothelial layer overlaying the medial layer in which BM-SMPC were aligned circumferentially and synthesized significant amounts of collagen. In contrast to previous results with vascular SMC, BM-SMPC synthesized high amounts of elastin that was organized in a fibrillar network very similar to that of native vessels.

CONCLUSIONS

Our results suggest that BM-SMPC may be useful in studying SMC differentiation and have high potential for development of cell therapies for the treatment of cardiovascular disease.

Stroke after internal jugular venous cannulation

OBJECTIVE

To alert clinicians to the stroke risk associated with carotid artery injury secondary to attempted internal jugular venous (IJV) cannulation.

METHODS

Case reports and review of the literature.

RESULTS

Four patients developed a stroke following carotid artery (CA) injury during attempted IJV cannulation using the landmark technique. In all cases the arterial puncture was detected immediately and firm pressure applied for several minutes. In three cases there was evidence of intimal injury and thrombus formation. Two strokes were delayed by more than 24 h. One patient died. A review of studies describing 4487 IJV line insertion attempts using the landmark technique reveals that 5.9% of attempts are associated with CA injury.

CONCLUSION

Cannulation of the IJV using visible and palpable landmarks is associated with a risk of stroke. Arterial injury and stroke should be mentioned when consent is obtained for cannulation. Consideration should be given to a reduction of the arterial injury risk by using ultrasound guidance during line insertion.

Mandatory vs selective exploration for penetrating neck trauma. A prospective assessment

To determine the optimal management of patients with penetrating wounds to zone II of the neck, we performed a prospective evaluation of 120 consecutive patients with such injuries, correlating the results of clinical and diagnostic examinations with operative findings. Seven patients presenting with life-threatening hemorrhage from the neck wound were operated on immediately; the remaining 113 patients underwent arteriography, laryngotracheoscopy, esophagoscopy, and esophagography, followed by neck exploration. Forty-eight major injuries were identified in 35 neck explorations. Five patients were identified with clinical and diagnostic findings that were considered normal preoperatively; however, at operation six major injuries were found in these patients. This study indicates that potentially lethal injuries to major vascular and visceral structures in the neck may go undetected if selective exploration criteria are used in the decision to explore penetrating wounds to zone II of the neck.

Comparison of endovenous radiofrequency versus 810 nm diode laser occlusion of large veins in an animal model

BACKGROUND

Endovenous occlusion using radiofrequency (RF) energy has been shown to be effective for the elimination of sapheno-femoral reflux and subsequent elimination of varicose veins. Recently, endovenous laser occlusion has been introduced with initial clinical reports indicating effective treatment for varicose veins. However, in our practice we note increased peri-operative hematoma and tenderness with the laser. Little is known regarding the mechanism of action of this new laser vein therapy.

OBJECTIVE

To better understand the mechanism of action of endovenous laser vs. the endovenous RF procedure in the jugular vein of the goat model.

METHODS

A bilateral comparison was performed using 810 nm diode laser transmitted by a bare-tipped optical fiber vs. the RF delivery by engineered electrodes with a temperature feedback loop using a thermocouple (Closure procedure) in three goat jugular veins. Immediate and one-week results were studied radiographically and histologically. Temperature measurements during laser treatment were performed by using an array of up to five thermocouples, spaced 2 mm apart, placed adjacent to a laser fiber tip during goat jugular vein treatment.

RESULTS

Immediate findings showed that 100% of the laser-treated veins showed perforations by histologic examination and immediate contrast fluoroscopy. The RF-treated side showed immediate constriction with maintenance of contrast material within the vein lumen and no perforations. The difference in acute vein shrinkage was also dramatic as laser treatments resulted in vein shrinkage of 26%, while RF-treated veins showed a 77% acute reduction in diameter. At one week, extravasated blood that leaked into the surrounding tissue of laser treated veins acutely, continued to occupy space and impinge on surrounding structures including nerves. For the laser treatment, the highest average temperature was 729 degrees C (peak temperature 1334 degrees C) observed flush with the laser fiber tip, while the temperature feedback mechanism of the RF method maintains temperatures at the electrodes of 85 degrees C.

CONCLUSION

Vein perforations, extremely high intravascular temperatures, failure to cause significant collagen shrinkage, and intact endothelium in an animal model justify a closer look at the human clinical application of the 810 nm endovenous laser technique. Extravasated blood impinging on adjacent structures may theoretically lead to increased peri-operative hematoma and tenderness. Further study and clinical investigation is warranted.

Percutaneous bioprosthetic venous valve: a long-term study in sheep

A long-term evaluation of a new percutaneously placed bioprosthetic, bicuspid venous valve (BVV) consisting of a square stent and small intestinal submucosa (SIS) covering was performed in 12 sheep. Of 26 BVVs placed into the jugular veins, 25 exhibited good valve function on immediate venography and 22 on venograms obtained before the sheep were killed. Gross and histologic examination results demonstrated incorporation of remodeled and endothelialized SIS BVVs into the vein wall. Slight to moderate leaflet thickening was found mostly at their bases. Percutaneously placed SIS BVV is a promising one-way, competent valve that resists venous back-pressure while allowing forward flow.

Complications after peritoneovenous shunting for ascites

The results and complications in our first 23 consecutive patients receiving the peritoneovenous shunt for intractiable hepatic ascites are presented. A good initial diuretic effect was obtained in 20 of the 23 patients, with reversal of hepatorenal failure in 3 of 5 patients. The postoperative complication rate was high (74 percent). Infection, coagulopathy and complication of the underlying liver disease contributed to a mortality rate of 26 percent. Late complications were related to the primary liver disease. The 6 month survival rate was 58 percent and the 1 hear survival rate 52 percent with five patients followed up for more than 2 years. Because of the significant morbidity and mortality associated with the peritoneovenous shunt, we recommend it only for patients with massive intractable hepatic ascites whose condition is refractory to maximal medical therapy.

Experimental study of thrombogenicity and foreign body reaction induced by heparin-coated coronary stents

BACKGROUND

Results of recent randomized clinical trials have revealed a significant reduction in angiographic restenosis rate when adjunctive stenting was performed after conventional coronary balloon angioplasty. The thrombogenicity of metal stents, however, remains a concern. In the present study, we compare the thrombogenicity of heparin-coated coronary stents with that of bare metallic coronary stents.

METHODS AND RESULTS

Thrombogenicity of metallic coronary stents (four heparin-coated and eight bare stents) was studied in a rat arteriovenous shunt model with the use of 125I-labeled fibrinogen and 51Cr-labeled platelets. Total clot weight after 30-minute follow-up was significantly lower in the heparin-coated stents compared with the bare stents (8.1 +/- 3.7 versus 25.8 +/- 4.6 mg; P < .001). Relative 125I and 51Cr activities in the stents were significantly higher in the bare stents than in the heparin-coated stents (125I, 1.03 +/- 0.43 versus 0.18 +/- 0.04, P = .003; 51Cr, 17.5 +/- 6.8 versus 4.4 +/- 1.0, P = .004). Subsequently, heparin-coated and bare stents were randomly implanted in the right coronary artery of 20 domestic pigs. Angiographic parameters were similar between both groups at baseline and after 6-week follow-up. Morphometry also did not show a significant difference in lumen area (bare, 1.03 +/- 0.83 mm2; heparin-coated, 1.12 +/- 0.73 mm2; P = NS) or neointimal hyperplasia (bare, 1.01 +/- 0.81 mm2; heparin-coated, 1.21 +/- 0.57 mm2; P = NS).

CONCLUSIONS

Heparin coating of metallic coronary stents decreases their thrombogenicity but does not improve late vessel patency and neointimal hyperplasia at follow-up in a porcine coronary model.