Equipment For Implant; Principles Of Operation; Background; Blood Flow Characteristics - HeartWare Ventricular Assist System Instructions For Use Manual

6.6 Equipment for Implant

Figure 9 shows the HeartWare System components used at implant (provided ETO sterilized).
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1. HVAD Pump
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2. Outflow graft – a 10mm diameter gel impregnated graft
3. Sewing ring (made of titanium and polyester) – to secure the HVAD
4. Driveline cap – to protect the driveline connector when tunneling
5. Strain relief – to prevent outflow graft kinking
6. Inflow cap – to cover the pump inflow cannula after the wet test and prior to implantation
7. Driveline extension cable – used only during the pre-implant wet test to keep the non-sterile controller isolated from
the sterile field. The driveline extension cable is not intended to be used after the pump is implanted in the patient
A set of surgical tools (provided ETO sterilized) is also required for implantation of the device (Figure 10):
1. Tunneler handle and rod – to tunnel the pump's percutaneous driveline through the skin to the exit site
2. Sewing ring wrench – to tighten the screw on the sewing ring
3. Driveline cover – to cover the driveline connection to the controller
4. Apical coring tool – to core the LV apex
5. Hex driver – to secure the strain relief and outflow graft to the HVAD
All the tools and accessories used during implantation are for single-use only. A Patient Pack (carrying case) is available to
hold the controller and two batteries.

7.0 PRINCIPLES OF OPERATION

7.1 Background

Continuous flow pumps contain a rotating impeller that adds energy to the blood by converting the rotational kinetic
energy into mechanical energy (Figure 11). Impeller blades push the fluid through the pump using hydrodynamic and
centrifugal forces. The net effect is to build up the fluid pressure, sometimes referred to as pump head (i.e., related to the
differential pressure across the device) or just head, such that the fluid is moved from the inlet to the outlet of the pump.
Pump head is the difference between the afterload and the preload. Energy to rotate the impeller is provided through
electromagnetic coupling between permanent magnets (rotor magnet) attached or enclosed within the impeller and the
motor stators. The motor stators consist of coils of wire that are sequentially charged by electrical current, turning the coils
into electromagnets. These electromagnets have the effect of dragging the rotor magnets around an axis of rotation. The
HVAD ® Pump is efficient at pumping moderate quantities of blood against moderate amounts of resistance.

7.2 Blood Flow Characteristics

The amount of flow a rotary pump can generate is dependent upon the diameter of the impeller, the geometry of the
impeller blades, housing design, motor capacity, rotational speed, and pressure differential that exists across the pump.
This allows for in-vitro pump characterization for a specific pump and is the basis for blood flow estimation.
The HeartWare System estimates blood flow rate using HVAD pump characteristics (electrical current, impeller speed) and
blood viscosity. Viscosity is calculated from the patient's hematocrit. To obtain the most accurate estimate of blood flow,
the patient's hematocrit must be entered into the HeartWare monitor. Flow estimation should be used as a trending tool only,
as it cannot adapt to changing fluid conditions (see Section 7.3.1 "Flow Estimation").
The volume of flow generated by the HVAD
pressure differential across the pump. The pressure that the HVAD
arterial pressure. If the pump speed (RPM) is set too low then the device may not generate enough forward pressure.
This can lead to retrograde flow (flow from the aorta back through the device and into the left ventricle).
The maximum rotational speed is determined by how much flow is available from the right heart. If the speed is set too
high and the pump attempts to pump more blood than is available, ventricular suction may occur.
The controller operates in "Fixed" mode, which maintains a constant motor speed. The motor speed range is between
1800 and 4000 RPM. The appropriate speed should be determined based on the patient condition.
CaUTiOn: Speeds below 2400 RPM or above 3200 RPM should be used with caution.
® Pump to the LV
® Pump
Pump is determined by the rotation speed of the impeller and by the
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Pump must work against is similar to the mean
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Ventricular Assist System
Figure 9: Components used at implant
Figure 10: Surgical tools
Figure 11: Exploded view of HVAD Pump
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1. Inflow Cannula
2. Front Housing Assembly
3. Impeller
4. Center Post
5. Rear Housing Assembly
Instructions For Use
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