The goal of all aortic valve replacement (AVR) therapies is to decrease left ventricular load and increase coronary perfusion without producing additional regurgitation.  Traditional AVR surgery attains this goal by directly replacing the stenotic aortic valve. In an aortic valve bypass procedure, outflow resistance is reduced by creating a second outflow channel connected to the aorta.  By forming a parallel outflow tract, the outflow resistance acting on the ventricle is effectively reduced without replacing the native aortic valve.  The native valve is left intact and operational.  Since pressure within the large diameter aorta is largely independent of the attachment point of the graft, normal coronary and carotid flow is maintained.

Clinical History
The concept of using an apex to aorta valved conduit to bypass a stenotic aortic valve was first conceived by Nobel laureate Alexis Carrel in 1910 and first performed clinically by Sir John Templeton in 1962.  Although Templeton’s initial series of human implants proved feasibility of the valved conduit device, the procedure did not gain popularity with surgeons because precisely at that point in the evolution of surgical techniques the heart-lung machine was perfected.  This led surgeons to select direct aortic valve removal and replacement over Templeton’s indirect valve bypass procedure.

Even though direct valve replacement rapidly became the standard, the valved conduit procedure continues to be used in special circumstances by doctors throughout the world.  Although there are no commercially available devices approved for aortic valve therapy, there is a substantial body of published literature reporting on the use of surgeon constructed “back table” valved conduit devices used in both “on pump” and “off pump” operations.  The results document that the procedure provides clinical relief with minimal complications.

Product Description
The AvA™ Aortic Valve Bypass Graft System is a minimally invasive alternative to traditional aortic valve replacement therapy.  The patent pending implantable device is composed of two polyester grafts, a titanium valve housing, and an associated cutting tool.  Requiring only a small incision between the ribs to expose the beating heart, the device is implanted by a surgeon using the system’s innovative cutting tool to bloodlessly connect one of the custom designed grafts into the left ventricle of the beating heart and the other graft to the descending aorta.  The surgeon then inserts a commercially available prosthetic heart valve into the titanium valve housing to form an alternative pathway for blood to flow out of the heart.   The native valve is left intact and functioning, although the primary blood flow is through the implanted AvA device. In preliminary lab tests, the improvement in heart function created by the valve bypass is the same as that obtained with a traditional valve replacement.  The valve bypass procedure does not require the patient to undertake the life threatening risks and potential serious side effects associated with the use of a heart-lung machine.

Implantation Steps
A small incision is made between the ribs at the 5th intercostal space.  The aortic graft, with cutting tool inside, is then placed on the descending aorta adventitia and firmly sutured into place.  The surgeon activates the cutting tool to excise a circular piece of tissue to form the anastomosis.  This is done without any cross or partial clamping of the aorta.  The tool (with cut aortic wall securely adhered to it) is removed and the graft is immediately clamped.  The surgeon performs a similar technique to insert the apical graft into the ventricle except simultaneous to cutting, the apical graft’s rigid connector is advanced into the ventricle thereby allowing a near bloodless insertion.  After suturing the graft to the heart wall, the tool is removed and the graft is clamped.  The surgeon then selects a bioprosthetic heart valve to insert into the graft housings.  No suturing is necessary to install the heart valve.  The valve’s sewing cuff is used as a sealing gasket.  Once inserted, the grafts are de-aired and the clamps are removed to create the apex to aorta outflow path.

With the help of Master communications group, we recently produced an animation of the implant procedure.  Click play to watch this 1 minute, 20 second animation, or download the Flash animation file.