The EVS- Vascular Closure System by Angiolink

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Every year, millions of people worldwide undergo a femoral artery catheterization. The early discharge of these patients undergoing elective diagnostic and interventional procedures, such as angiography, percutaneous transluminal coronary angioplasty (PTCA), stenting, atherectomy, and catheter ablation, hinges on the lack of bleeding complications at the access site after the procedure sheath is removed from the femoral artery. The size of the access route, coupled with routine administration of anticoagulants, creates a strong need to stop bleeding at the puncture site as quickly as possible. However, hemostasis must be achieved without producing clotting in the vessels just treated in order to prevent a potentially fatal myocardial infarction or thrombosis.

Simple compression - the use of hand pressure, clamps, and/or sandbags - is currently the standard of care for managing femoral vascular access sites following interventional cases. Under this conventional technique, anticoagulation therapy is discontinued for up to four hours prior to vascular closure in order to permit the patientÔÇÖs clotting capability to return to a normal state. Throughout this period, the introducer sheath remains in place and the patient must remain immobilized to prevent bleeding. Upon sheath removal, direct compression is applied to prevent bleeding and formation of hematomas. While the patient lies flat, a nurse or technician holds direct manual pressure on the site for 20 to 60 minutes until thrombus forms to seal the access site. This monotonous and tiresome task often relies on trained hospital personnel to administer. Use of sandbags and other adjunctive mechanical compression devices like C-clamps may reduce the need for the nurse or other skilled individual to continuously hold initial manual pressure.There is the possibility for these compression devices to slip, necessitating close monitoring of the patient during this critical time to ensure correct compression of the access site. Additionally, these devices have failed to show measurable advantages over hand pressure and may increase patient discomfort.

Once hemostasis has been achieved, the patientÔÇÖs leg must remain motionless for a minimum of six and up to 24 hours (depending on the amount of anticoagulation drug therapy used and the particular procedure) in order to avoid dislodging of the clot, which can lead to internal or external bleeding. Because this restriction to the patient can lead to great discomfort - especially those suffering with back problems - this period is anything but bed rest.1

Since 1995 several vascular closure devices have been marketed in the US to address the comfort of the patient, hospital resources and staff. Widespread market acceptance of these devices has likely been hindered by several deficiencies associated with them which include;

  1. complex instructions for use associated with a significant learning curve;
  2. frequent requirements for bed rest following closure;
  3. complication rates similar to manual closure;
  4. an increased incidence of certain types of complications compared to manual closure (arterial occlusion and infection); and
  5. impaired or delayed ability to re-access the femoral artery.2-25

These devices either employ the use of collagen to create plugs of differing configurations, suturing devices with both braided and monofilament suture material, and collagen/thrombin slurries with various delivery systems.

Staple Mediated Closure

The EVS™ Vascular Closure System (see Figure 1) does not rely upon the formation of thrombus to achieve hemostasis nor does it rely on suturing. It is a mechanical closure device employing a very small staple. The staple is made from titanium alloy, one of the most biocompatible materials that can be implanted in the human body. Since titanium does not react within the human body, it is used to create artificial hips, pins for setting bones and for other biological implants.

Special design features built into the staple and its delivery system makes it truly unique from anything else. The staple is designed to penetrate into no more than two of the three layers that make up a vessel (see Figure 2H). An artery is made up of an outer layer of tissue called the adventitia, followed by the media (middle layer) and lastly the innermost layer - visible from the vessel lumen - called the intima. A thin layer of tissue called the femoral sheath acts as a conduit, encapsulating the femoral artery, vein, and nerve. The femoral sheath is also clasped by the staple, aiding in a secure closure. This level of control really makes the staple more of a clip because it does not penetrate all three layers of the vessel but rather purses the outer two layers.Vessel occlusion is avoided by not impinging on the intimal vessel layer. The EVS™ staple expands during its deployment which allows it to grasp a considerable amount of tissue (see Figures 2C and D). The staple expansion also allows this one system to close arteriotomies from 6Fr to 8Fr, negating the need to stock multiple sizes of the same product.

Before using the EVS™ Vascular Closure System, a guide-wire is reinserted through the existing procedure sheath. The procedure sheath is removed, leaving the guide-wire in place. The EVS™ introducer/dilator assembly is threaded over the guide-wire to the arterial access site. When the dilator enters the artery, a blood-marking port allows arterial blood to flow through it to the proximal end of the device, thereby communicating to the operator that correct positioning has been reached. The operator then activates a mechanism within the introducer to gently lock it onto the vessel and maintain control of the site (see Figures 2A and B) before the staple delivery. The wire and dilator are removed. The stapler is inserted through the introducer to the arteriotomy, after which the trigger is activated to deploy the staple (see Figures 2E-H).The staple expands to maximize the amount of sheath, adventitia and media (see Figure 2C and D) brought together to close the vessel. Simultaneously, the locking mechanisms release the vessel and allow the entire instrument to be removed. One to two minutes of digital pressure may be needed to control tract bleeding.

The artery may be re-accessed shortly after hemostasis has been achieved. The staple is radiopaque (see Figure 3) and can be used as a marker for future access.

Clinical Trial

The EVS™ Vascular Closure System was evaluated in a pivotal, prospective, multi-center, open-label, randomized study involving 362 patients. It was compared to manual compression methods following interventional and diagnostic cardiac and peripheral vascular procedures with 8Fr or smaller sheath sizes. Of the 362 randomized patients, 243 (67%) were randomized to the EVS™ Vascular Closure System and 119 (33%) were randomized to manual compression. Randomized EVS™ patients were approximately evenly divided between the procedure groups: 118 (49%) had interventional procedures and 125 (51%) had diagnostic procedures.

The effectiveness of the EVS™ Vascular Closure System was evaluated using two primary endpoints: time to hemostasis and time to ambulation. Time to hemostasis was defined as the time from staple delivery to the time total cessation of bleeding (including any oozing) was achieved. Time to ambulation was defined as the time from staple delivery to the time the patient stands at bedside and walks no less than 20 feet in total distance.

Use of EVS™ significantly reduced time to hemostasis and ambulation. The mean time to hemostasis was 4.4 minutes for randomized EVS™ patients, compared with 20.7 minutes for manual compression patients. The mean time to ambulation was 2.4 hours for randomized EVS™ patients compared with 6.0 hours for MC patients.

Patients who were randomized to the EVS™ device were asked to ambulate at pre set time intervals after the diagnostic/interventional procedure was complete. EVS™ patients without IIb/IIIa inhibitors were ambulated at one hour, while patients with IIb/IIIa inhibitors were ambulated at two hours.

The study was designed to detect a difference in the observed cumulative incidence of major complications at 30 days. Assuming a 3% cumulative major complication rate for manual compression, the study was designed to rule out a 5% higher major complication rate for the randomized EVS™ group. The sample size was adequate to rule out a 5% EVS™ disadvantage using a 95% upper confidence bound method.

The EVS™ device demonstrated safety. By day 30, a cumulative total of one (0.4%) major complication was reported for randomized patients who received EVS™ compared to three (2.5%) major complications in the manual compression patients.

Minor complication rates were similar between randomized EVS™ and manual compression patients (8.7% and 8.3%, respectively).

The majority of investigators reported that the use of the EVS™ was as easy or easier to use as other marketed devices, and that they had no difficulty or insignificant difficulty with the device set-up, operation, deployment, and function.

The EVS™ Vascular Closure System is pending FDA approval (PMA). Clearance is expected in the fourth quarter of 2004, at which time it will become available in the US. 

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