The other day, I met a man without a heartbeat.  I knew him as a passing acquaintance, but I had not seen him in several years.  In that time, he had experienced heart failure, and is currently on the waiting list for a heart transplant.  Until his heart transplant comes through, he is being kept alive by a portable heart pump, or LVAD (Left Ventricular Assist Device).  

Instead of the two beat motion we are used to with a heart, he simply has a rotary pump which pushes blood through his heart in a steady motion, not unlike the air pump in a tropical fish aquarium.  So instead of a heartbeat, he now has a steady "whoosh."  This is a "continuous flow" model, whereas other LVADs employ "pulsatile" pumps, which do provide a heartbeat of sorts.  In recent years, Ventricular Assist Devices have moved more towards the "continuous flow" motor.  Because this kind of motor is simpler in construction, they can be made smaller, and therefore easier to insert and less cumbersome to wear.

LVAD technology has come a long way in the last few years.  A heart pump used to be a giant machine the size of a room, and you were essentially bedridden while using it.  Heart pumps can now be implanted into the heart, with the essential machinery kept in a small bag which patients can wear out and about in the world.  In fact, what I originally took to be a fanny pack turned out to be his LVAD unit.

There are three categories of patient who are implanted with LVADs: people who are waiting for a heart transplant ("bridge to transplant"), people who have just come out of surgery and who need an assist until their hearts can pump on their own ("bridge to recovery"), and (still in a clinical trial basis) people who have experienced heart failure, for whom the LVAD is a permanent fix ("destination therapy").

The Left Ventricular Assist Device is implanted, as you might guess from the name, in your left ventricle.  This is the chamber of the heart which takes returning blood from the pulmonary veins, and pushes it into the aorta to be returned to the rest of the body.  

A Ventricular Assist Device is a pump that helps your heart move blood, as opposed to an artificial heart.  An artificial heart is a device which replaces your heart entirely.  While VADs are usually meant to be temporary devices, artificial hearts are permanent.  A doctor will often choose a Ventricular Assist Device instead of an artificial heart if the patient's other three heart chambers are working well.

VAD technology has progressed in leaps and bounds since the first generation LVADs were approved for use by the FDA in 1994.  Ventricular Assist Devices have very few risks, the risk of infection from the subcutaneous cord (which connects the pump to the backpack device through the wall of the chest) being the most common.  Mechanical failures are practically unknown, and VADs have been approved for use for up to 18 months.  Considering the length of time a patient can be on the heart transplant list before their number comes up, the LVAD represents a huge advance in both the length of life and the quality of life.