EDITOR’S CORNER
Alfred A. Bove, MD, PhD
Interim Editor-in-Chief, CardioSource WorldNews
Building Better LVADs:
Less a Bridge Than a
Destination?
Eman Hamad, MD, Medical Director, Mechanical Circulatory Support Program at Temple University Hospital,
provided important review and oversight for this editorial.
“H
e can’t come to the phone right now
because he is patching the roof.”
That was the comment I received from the wife of
a patient who had end-stage heart failure, and 8
weeks before my call he had a left ventricular assist
device (LVAD) implanted to support his heart while
awaiting heart transplantation. At our institution,
we started our LVAD program as a bridge to transplantat in 1994, using the bulky pulsatile LVADs
that were implanted in the abdomen but provided
normal cardiac output, allowing patients to resume
a life not limited by severe impairment of exercise
capacity.
The first VADs were driven by a pneumatic system with tubes penetrating the skin of the abdomen
to drive the diaphragm of the pulsatile device. The
driver was large and needed to be wheeled around,
confining the patient to the hospital while awaiting
a donor heart. The technology quickly evolved to an
electrically driven LVAD that had the drive motor
incorporated into the device; the only skin penetration was for a wire to deliver power to the LVAD.
The patient could carry several battery packs,
making the whole system readily portable, meaning
the patient could leave the hospital and live at home
while waiting for a transplant.
In 2001, the REMATCH trial showed that
patients not waiting or ineligible for a heart transplant would benefit from an LVAD as the definitive therapy for their end-stage heart failure, thus
forming the basis of “destination therapy.” Now,
given evidence of structural and molecular changes
that improve cardiac function after LVAD implanta-
ACC.org/CSWN
tion, there is interest in studying these devices as a
bridge to recovery.
As with most mechanical systems, we saw a
constant effort to improve the technology. The
biggest step was to move from a pulsatile LVAD to
a continuous-flow device that was much smaller,
more durable, less noisy, and better tolerated by the
patient. The device was modeled around rocket fuel
injectors that contained a high speed rotor turning
at more than 2,000 rpm that could pump 6 or 7
liters a minute. The device could be implanted in
the thorax and electrically driven, but despite being
better tolerated by the patient, those of us caring
for these patients had some important learning
to do. We needed to adapt to the concept that the
patient had no pulse—as well as to concerns when
care providers, not familiar with the device, tried
to measure a blood pressure and got no result. We
know that the blood pressure in an LVAD patient
is a mean blood pressure, so setting the device to
generate a blood pressure of 120 mm Hg would
actually make the patient severely hypertensive. A
mean systolic blood pressure of 80 to 85 mm Hg is
usually what is established; it is measured with a
Doppler probe and the LVAD patients learn how to
use the probe to assess their blood pressure.
We also noted an increased incidence of gastrointestinal bleeding in patients with a continuousflow LVAD. After much investigation, this appears
to be related to breakdown of von Willebrand factor
(VWF) as blood contacts the high speed rotor. The
components of VWF cause arteriovenous malformations in the gut that eventually bleed (acquired
von Willebrand disease).
In spite of several limitations, the continuousflow LVAD has established itself in the armamentarium of therapies for end-stage heart failure.
Patients are able to resume near-normal lives, don’t
require hospitalization, and in many cases return to
work. But there is more work to be done. Because
there is a limited supply of donor hearts for transplant, and a much greater number of people with
end-stage heart failure, the LVAD will continue to
be a valuable therapy. Technical improvements are
still needed. Eventually, an induction charger will
be developed that will charge an implanted battery
to avoid skin penetration and the resultant infection
risk. A smaller LVAD that supplements rather than
replaces the entire cardiac output will be applicable
for many patients who have some residual left
ventricular function and don’t need a 6 to 7 l/min
flow capacity.
With the pulsatile LVADs, we learned to listen to
the LVAD sounds to detect failure of the bearings in
the pump. With the axial, continuous-flow devices,
we hear only the soft whine of the rotor spinning at
3,000 or 4,000 rpm, and the floating bearings are
resistant to failure, so durability has extended from
1 to 2 years with the pulsatile LVADs to more than
5 years with axial LVADS. As we move forward
with the technology, the demand f