The Thoratec VAD System includes three major components: Blood pump, Cannulae, and Dual Drive Console or TLC-IIR Portable Driver. This system provides partial or total circulatory assistance when the natural heart, with conventional therapy, is unable to maintain adequate circulation to perfuse vital organs. To accomplish support, blood flows from the natural heart to the VAD, which then pumps pulsatile blood flow back to the body.

The VAD pumps are prosthetic ventricles consisting of a smooth, seamless pumping chamber enclosed in a rigid polysulfone case. The blood sac is manufactured from ThoralonR. Thoralon is composed of:

• A base polymer, which provides enhanced strength, flexibility, and durability.
• A Surface Modifying Additive (SMA)

Thoralon works exceptionally well because of its excellent:

• Blood and tissue compatibility
• Thromboresistance
• Long-term fatigue characteristics
• In vivo stability
  

Two mechanical tilting disc valves maintain unidirectional flow through the blood pump. A sensor detects when the VAD is full of blood and automatically signals the console to eject blood from the pump. In clinical practice, an effective stroke volume of 65 milliliters (ml) is possible with rates ranging from 20 to 110 beats per minute (bpm) and flow outputs ranging from 1.3 to 7.2 liters/minute (L/min).

The Thoratec VAD System

Is the only system that offers circulatory support for either the left side of the heart, the right side of the heart, or both sides of the heart As of June 2001, the Thoratec VAD System has been used in more than 1,700 patients Has been used in over 170 medical centers worldwide Has been used to support patients weighing from 17 kg to 144 kg and as young as 6 years old Allows for perioperative device selection Use of the Thoratec VAD has yielded increased patient survival rates when compared to control patients supported with conventional therapy only Can inhibit organ deterioration while awaiting a donor heart Is approved for reimbursement Is FDA approved for bridge to cardiac transplantation and postcardiotomy recovery of the natural heart

Thoratec VAD Cannulae

Blood flows to the VAD through an atrial or ventricular cannula, and from the VAD with an arterial cannula. Several cannula options are available for optimal anatomical fit. All cannulae are manufactured with Thoralon to improve thromboresistance, flex life, and strength. Ventricular and arterial cannulae are wire-reinforced to prevent kinking. The reinforced portion of the cannula is covered with customized velour to encourage tissue ingrowth and reduce the risk of infection.

Thoratec Dual Drive Console (DDC)

The Thoratec Dual Drive Console offers two independent and identical drive modules for left and right ventricular support. Each module provides alternating pulses of vacuum and pressure to fill and empty the VAD, thereby providing pulsatile blood flow. Choices of control modes for optimal VAD operation include: asynchronous mode (VAD rate and ejection time set by the user and the driver maintains those conditions indefinitely); volume mode (ejection begins the instant that complete VAD filling occurs); and synchronous mode (similar to intra-aortic balloon pump counterpulsation). The volume mode of operation is used for most patients because of automatic pump response to changes in physiological conditions.