There are two main types of VADs: Pulsatile and nonpulsatile. The pulsatile or displacement VADs use valves and a pusher plate, displacing blood drained from the LV through a reservoir into the aorta. Pulsatile devices are further divided into extracorporeal or paracorporeal (Abiomed BVS 5000, Abiomed, Inc., Danvers, MA and the Thoratec, Thoratec Corp., Pleasanton, CA), in which the pump is external to the body. These LVADs are in use only for temporary assist (up to 30 days). The other type is intracorporeal (HeartMate I Thoratec IVAD, Thoratec Corp., Pleasanton, CA and Novacor World Heart Inc., Oakland, CA), in which the pump is implanted inside the peritoneum or the thorax, and only the power supply is external. The nonpulsatile or rotary VADs are also divided into two types: The centrifugal (either extracorporeal or intracorporeal), which are rarely used anymore, and the more modern axial flow pumps (Jarvik 2000, Jarvik Heart, Inc., New York, NY and the HeartMate II, Thoratec Corp., Pleasanton, CA), in which a small electromagnetically actuated impeller drive shaft rotates and propels blood at a flow that can be controlled according to the needs of the individual patient. The axial flow pumps are smaller, less than one-fifth the size of the
pulsatile pumps, allowing their implantation in children and small adults. Axial rotary pumps can also be easily adjusted to operate in parallel to the pulsating LV, thus allowing the heart to gradually recover and wean from the LVAD.

Indications. Candidates for heart transplant are those with a cardiac index <2 L/minute/m² and a pulmonary capillary wedge pressure (PCWP) >20 mm Hg.

Contraindications. Contradictions include infection (blood cultures are negative, especially for fungus, at least 1 week before device placement), renal failure (creatinine >5.0 mg/dL), severe liver impairment, stroke, severe pulmonary dysfunction, and severe pulmonary dysfunction. Anesthetic Considerations. These patients are critically ill, are often dependent on inotropes and/or intra-aortic balloon pump counterpulsation therapy, and have often had previous cardiac operations and other end-organ dysfunctions. Their fixed low stroke volume strongly depends on preload and heart rate to maintain marginal performance, which is already on the flat or even descending limb of the Starling curve. Excessive increase in afterload may decrease stroke volume and output dramatically. They are often maintained on angiotensin-converting enzyme (ACE) inhibitors and β-blockers to decrease afterload and diuretics to minimize volume overload. Amiodarone is also commonly used; this blocks the sympathetic system by noncompetitive α- and β-blockade. Its combination with ACE inhibitors that block the renin-angiotensin system and decrease cardiovascular responsiveness to catecholamines may lead to increased vasoconstrictor requirements during cardiopulmonary bypass (CPB). Circulating endogenous catecholamines are high in patients with heart failure, which makes them prone to cardiovascular decompensation during induction or maintenance of anesthesia. Changes in volume of distribution and the decreased clearance of drugs are likely due to altered metabolism by the liver and elimination by the kidney.