Here's an interesting (lengthy!) piece on LVAD's and their current and potential uses. I hadn't come across the possibility of a heart muscle atrophying from use of a LVAD before. That's one to check out with World Heart...
Researchers seek more bridges to
cross with mechanical pumps
From CHF Disease Management | February 1999
Will left-ventricle assist devices span from CHF to recovery?
The day is coming, researchers say, when mechanical pumps will offer CHF
patients a range of options for improvement and recovery.
Refinements continue to be made in using left-ventricular assist devices
(LVADs) as a bridge to transplantation. But investigators now want to find out
how they can offer the devices to more patients — such as those who are not
transplant candidates because of their advanced age or degree of heart
disease.
And today's tantalizing but rare cases of patients being weaned from their
LVADs hint at a time in the future where doctors can use a pump to let a
failing heart rest and heal until it can work well on its own again.
Getting to these goals, and crossing what some doctors call "a bridge too
far," means pushing the limits of the technology and running the trials.
Investigators are optimistic.
"You might decide that today's pumps are not right for you and your patients,"
says Mehmet C. Oz, MD, an LVAD researcher and cardiothoracic surgeon at
Columbia-Presbyterian Medical Center in New York City.
"But with the advances being made, you should see a pump that's right for
you within a decade," he explains.
Buying patients more time as they await transplantation is a huge niche for
LVADs to fill. Recent published reports determine only 2,500 organs are
available each year to some 60,000 patients who need them or some type of
mechanical help. And in 1996, more than 10% of the transplantation
candidates died waiting for a new heart.
What about those not up for transplants?
Oz says doctors should be thinking about when LVADs may be appropriate
for their patients today, whether or not they're on the transplant list.
"The first rule of thumb is that no one should die of heart failure without being
considered for heart pumps." That doesn't mean giving one to every patient,
Oz notes, but rather, thinking about how a patient can be treated with an
LVAD after traditional therapies are ruled out with a line of questioning such
as the following:
1. Does the patient have a problem that can be repaired, such as aortic or
mitral valve disease or an aneurism?
2. If there isn't a physical defect that can be targeted for repair, can the
patient's heart failure be controlled with medication?
3. If medication cannot keep the patient's condition stable, could
transplantation be implemented to reverse the patient's declining
cardiovascular performance? (In this case, a heart pump can help sustain
the patient until a permanent organ becomes available.)
4. If the patient is not a transplantation candidate, could an LVAD be used?
(Today, patients can be part of the clinical trial testing the devices when other
options are not appropriate or can no longer be helpful by themselves.)
This last consideration may not sit well with some doctors, who may feel that
if a patient is not up to the surgery and recovery from transplantation, he or
she would not benefit from using an LVAD.
But Oz says his team is learning how LVADs can be helpful to these patients.
The researchers have a $7 million government grant for their REMATCH
study (Randomized Evaluation of Mechanical Assistance for the Treatment of
Congestive Heart failure). Oz says patients have to apply to participate in the
study, but for those who are not transplant eligible, an LVAD may provide a
treatment option.
How long on an LVAD?
Two end points in heart pump therapy are crystal clear:
transplantation;
infection requiring removal.
In other cases, knowing when to stop using the LVAD is not as certain. Oz
says there will be a growing number of patients not going on to transplant
who will continue with their device, incorporating other treatments such as
surgery and drug therapy to improve their heart performance.
And researchers also are looking at the chances of using the LVAD to help
the patient's own heart recover enough to work on its own. This role is called
a bridge to recovery.
In 1997, German investigators reported in Circulation (1997; 96:542-549) that
they were able to wean a third of their 17 patients from their LVADS.
"We haven't been able to reproduce their results," Oz says. In a recent article
in Circulation (1998; 98:2,383-2,389), his team reported a retrospective study
and an explanation evaluation that used exercise tolerance as an indicator of
success.
The team found that among 111 LVAD recipients being bridged for
transplants since 1991, only five were explanted. In three of these instances,
the devices were removed because of infection. The other two patients had
their LVADS removed because they were not going on to transplantation: one
after 186 days and another after two years.
Of these five explant cases, two died three months after explantation. Two
patients needed reimplantation after being without them — one after two
years, the other after 170 days. The fifth patient was still alive in class I CHF
after 15 months without the device.
In the second part of the study, 39 recent LVAD recipients were considered
for explantation, according to how well they could exercise with their LVAD
output reduced to 20 cycles per minute. Seven of the 39 patients were able to
exercise at this rate of assistance and still keep stable hemodynamics. One
was able to be explanted.
Oz says the Germans' success may be due to the way Europeans wean their
patients off the LVAD three months after implantation. The practice may be a
good idea because researchers still have a lot to learn about how the heart
responds to its mechanical helper and how long the partnership should last.
It's possible that patients reach a point where the heart pump no longer
works well with the compromised heart. A device could even cause atrophy in
the heart muscle, depending on its synchrony with the ventricle as it contracts
and relaxes.
More research is needed, Oz says, to determine how long a patient should
use the heart pump, whether or not weaning should begin, and how weaning
should be done.
Right now, he says his team does not implant LVADs with the intention of
weaning patients off of them. Nearly all the heart pumps used now are
bridges to transplantation. Oz notes he recently had a case where a patient
had a massive heart attack and an LVAD was used as part of his overall
treatment, but those situations are not as common.
Other physicians see three standard uses for an LVAD, including helping
patients who suddenly run into trouble, says Ross Zimmer, MD, a
Philadelphia cardiologist with the joint heart failure program at Presbyterian
Medical Center and the Hospital of the University of Pennsylvania.
These uses are:
A device can sometimes help patients who suffer complications
during surgery.
An LVAD is used as a transplantation bridge (the most common use).
LVADs are used in a clinical trial.
Research will bring more uses for device
The editors commenting on Oz's study in Circulation note they hoped
clinicians would one day be able to assess how a failing heart has been
damaged on a cellular level — and whether the damage is reversible. This
would give clinicians an indication of which hearts may go on to heal if given
some mechanical assistance.
Oz says it would be even more helpful to understand the cellular changes of
the heart so they can be reversed long before treatments like heart pumps
are needed. Answers may come from looking at how patients may not be
metabolizing free fatty acids or calcium properly. Harvesting heart tissue from
deceased CHF patients could allow scientists to probe the mitochondria and
hunt for missing or defective genes, which could lead to a whole new arsenal
of cardiovascular genetic therapies.
Until that point, doctors say LVADs have a role in treating CHF.
"I hope that as [LVADs] become more common, they are developed not just
as a bridge but as an alternative to transplant," says Jim Fitzpatrick, MD,
clinical assistant professor of medicine in the division of cardiology at
Thomas Jefferson Medical Center in Philadelphia. "The economics are
staggering."
He says last year, Jefferson implanted two LVADs into CHF patients as
bridges to transplantation. The site is not a transplantation center, so the
patients continued with treatment at other centers to get new hearts.
And patients can find some reassurance when they learn that LVADs can
help during the wait for a heart, says Zimmer: "It's nice psychologically for
patients to know that it's there."
Editor's note: For more information about the LVAD study and to learn how to
become involved, call (888) REMATCH.
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