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Left ventricular recovery is common after placement of left ventricular assist devices (LVAD).
Patients who are candidates for heart transplantation should never have an LVAD placed.
Palliative care consultation is inappropriate for patients being considered for a destination therapy LVAD.
The development of reliable left ventricular assist devices (LVADs) has revolutionized heart failure (HF) management.
In the cardiac intensive care unit (CICU) context, LVADs are encountered in three situations:
Selection of the appropriate patient with heart failure for mechanical circulatory support (MCS) and preoperative evaluation
Treatment of these patients perioperatively
Treatment of complications and prevention of adverse events.
The initial LVADs were volume displacement pumps known as pulsatile-flow devices.
However, pumps had multiple moving parts, including bearings, valves, and pusher plates that were subject to failure.
A paradigm shift in the field of assisted circulation occurred with the introduction of durable, implantable continuous-flow devices.
The rationale for continuous flow was the observation that the initial pulsatile flow in the aorta is progressively dampened, transforming into continuous nonpulsatile flow at the level of the capillary ( Fig. 25.1 ).
Continuous-flow LVADs have only a single moving part and propel blood forward in a steady, continuous fashion with an axial or centrifugal rotor or an impeller.
With this simplified design, the risk of mechanical failure has been greatly reduced.
Currently, the HeartMate II (St. Jude Medical) and the HeartWare HVAD (HeartWare) are the only US Food and Drug Administration (FDA)–approved continuous-flow LVADs ( Fig. 25.2 ).
The HeartMate II is capable of providing up to 10 L/min of support and is surgically inserted into a preperitoneal pocket (See Fig. 25.2A ).
Blood is pulled out of the LV into the LV inflow cannula, accelerated by a rotor, and then ejected into the outflow graft, which is anastomosed to the ascending aorta.
A percutaneous driveline exits in the upper abdomen and connects the device with a portable controller and two batteries for mobile operation, or to a power base unit and a wall outlet when a patient is stationary for several hours (e.g., while sleeping).
The device provides a constant flow of blood with one backup speed used in case of a sudden drop of preload.
The typical operating speed range is 8600 to 9600 rpm.
Despite antithrombotic coating with titanium microbeads, anticoagulation with a target international normalized ratio (INR) of 2.0 to 3.0 and aspirin are recommended.
In distinction to the axial-flow HeartMate II, the HVAD is a miniaturized centrifugal pump (see Fig. 25.2B ).
The smaller size of this device allows implantation into the pericardial space and, often, a shorter operation.
The housing contains an impeller suspended by magnets and the device is capable of providing 10 L/min of flow.
The usual operating speed range is 2400 to 2800 rpm.
The presence of a continuous-flow device does not necessarily eliminate the presence of a palpable pulse on physical examination.
This has an important consequence when measuring a patient's blood pressure.
In the absence of a palpable pulse, mean arterial pressure (MAP) is measured via Doppler.
The blood pressure cuff is inflated above where the Doppler tones are heard, and then the return of sounds auscultated via Doppler is taken as the MAP.
MAP measured by Doppler overestimates pressure in the presence of palpable pulse and should not be reported.
Instead, auscultation of the Korotkoff sounds should be performed.
BTT refers to the implantation of a durable LVAD in a patient with end-stage HF with the intent of improving the hemodynamics and clinical course until a donor heart is available.
As the donor shortage has worsened, the proportion of transplant recipients who required bridging with a durable LVAD increased from 26% in 2004 to more than 50% in 2014.
Early studies in patients with a BTT have proven that prompt implantation of an LVAD is the only meaningful chance for survival available to the sickest patients.
These studies also demonstrated a substantial reversibility of organ damage: that is, implantation of LVADs was followed by a significant improvement in biochemical markers of kidney and liver injury.
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