Ventricular Assist DevicesThe Challenges of Outpatient Management
Sean R. Wilson, MD*,
Michael M. Givertz, MD ,
Garrick C. Stewart, MD and
Gilbert H. Mudge, Jr, MD,*
* Cardiovascular Division, New York Presbyterian Hospital, Weill Cornell Medical College, New York, New York
Cardiovascular Division, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts
View larger version (43K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 1 Components of a Continuous Flow VAD
A continuous flow ventricular assist device (VAD) consists of a pump connected to the heart and aorta via an inflow cannula and an outflow cannula, respectively, an external driveline that powers the motor within the device, and a system controller. Power may be delivered through a power base unit (PBU) or battery packs, allowing increased mobility. Figure illustration by Rob Flewell. LVAD = left ventricular assist device.
|
|
View larger version (84K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 2 Components of a Pulsatile VAD
A pulsatile VAD consists of a pump, battery pack, and controller. An LVAD decompresses the ventricle into a pump that directs blood into the aorta. The inflow cannula is surgically implanted into the ventricular apex and the outflow cannula is inserted into the ascending aorta. Figure illustration by Rob Flewell. Abbreviations as in Figure 1.
|
|
View larger version (64K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 3 Schematics of Commonly Used VADs
Mechanical support systems: Thoratec VAD (top left), Novacor LVAD (top right), HeartMate II LVAD (bottom left), and HeartMate XVE LVAD (bottom right). Illustrations depicting the mechanisms of action of an axial flow and volume displacement pumps are shown for the HeartMate II and HeartMate XVE devices. The axial flow pump is a small device consisting of a continuously spinning impeller along a central shaft. Blood is drawn from the spinning blades of the impeller and propelled at 4 to 6 l/min with minimal hemolysis. The pulsatile pump of the HeartMate XVE uses an electromagnetic pusher plate to cyclically expand and decompress a chamber. The pusher plate can provide between 5 and 10 l/min of pulsatile blood flow. Figure illustration by Rob Flewell. Abbreviations as in Figure 1.
|
|
View larger version (60K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 4 HeartMate XVE Hand Pump
In cases of an emergency such as a failure of the primary and backup drivers, a hand pump should be used immediately to restore flow to a pulsatile ventricular assist device (VAD). To use a hand pump properly, the system controller must be disconnected from the power source. Next, the hand pump bulb should be connected to the end of the driveline vent filter and the system primed by holding down the purge valve on the pump and collapsing the bulb. The hand pump delivers pulses of air to the pusher plate, generating a stroke volume. One hand pump is needed for each VAD. The pump should be squeezed approximately 60 to 90 times per minute to empty and fill the blood chambers. Figure illustration by Rob Flewell.
|
|
View larger version (48K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 5 Suggested Algorithm to Assess a Patient With a VAD With Fever or Leukocytosis
Guidelines for the evaluation of an infectious process in a patient with a ventricular assist device (VAD). CBC = complete blood count; MRSA = methicillin-resistant Staphylococcus aureus; TEE = transesophageal echocardiography.
|
|
|
