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What is an LVAD?
An LVAD replaces the LV’s pumping function and potentially provides adequate systemic perfusion to pre-vent multi-system organ failure. Blood is drained through a conduit from the LV apex and is diverted to a pump implanted in the pre-peritoneal space or posterior rectus sheath. Output from the device is directed through a conduit into the ascending aorta. Current models have a percutaneous power cable/driveline that exits the abdomi-nal wall in the right lower abdomen to connect with an external power pack and system controller. Currently avail-able LVADs do not provide oxygenation/ventilation of the blood, nor dialysis.
The Novacor LVAS® (World Heart, Ottawa, Canada) and the Heartmate LVAS® (Thoratec Corporation, Woburn, MA) are fully implantable LVADs approved for long-term mechanical circulatory assistance as bridges to transplanta-tion for patients with end-stage cardiomyopathy. A new indication, “destination therapy,” refers to intentionally permanent implantation of an LVAD, in a non-transplant-eligible patient with cardiac failure. At the time of writing, the Heartmate is FDA-approved for destination therapy in the United States. Trials to establish efficacy of the Novacor for this indication are ongoing.
Although the two devices are conceptually similar, differences exist in engineering, durability, and the need for anticoagulation. Both the Novacor and the Heartmate are implanted similarly, both can operate in either fixed-rate or automatic “full-to-empty” modes (explained below), and both will provide flows on the order of 5–8 L/min as long as intravascular volume status is adequate. Filling of both devices relies on gravity drainage augmented by residual ventricular contractions. Ejection is accomplished in both by mechanical compression of a blood chamber. Ejection from the LVAD occurs asynchronously with respect to any underlying cardiac rhythm.
Following perioperative recovery and rehabilitation, LVAD patients are often discharged home to await trans-plantation. Implantable LVADs provide sophisticated control algorithms enabling device outputs to change as physiologic needs are altered. Some LVAD patients are confined to bed or remain limited to activities of daily liv-ing, but many experience a return to activities they had not enjoyed for years.
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