For in-stance, non–transplant-eligible patients may be salvaged with a temporary device and then switched to lifetime therapy should the heart not recover.. If a transplant candidate’s h
Trang 1now achieve 85% 1-year and 65% 2-year survival,
which parallels that for hemodialysis in end-stage
renal disease There are other similarities between
these end-stage populations Chronic hemodialysis
is only able to sustain life for several years in
younger and otherwise healthy patients When the
number of patients older than 65 years of age
increased to 80%, the overall 2-year survival for
hemodialysis decreased to 60% The average life
expectancy for older hemodialysis patients is
2.6 years[13]
As experience increases, the strategic
bound-aries between bridge to transplantation, bridge to
recovery, or lifetime use no longer exist The
LVAD sustains life, whereas the patient’s
re-sponse determines the clinical course For
in-stance, non–transplant-eligible patients may be
salvaged with a temporary device and then
switched to lifetime therapy should the heart not
recover If a transplant candidate’s heart improves
during LVAD unloading, there is the option for
device removal instead of transplantation In the
future LVADs may also provide the platform for
myocardial regeneration by neoangiogenesis, gene
therapy, or stem cell therapy[14]
In REMATCH, late deaths occurred not
through heart failure but from LVAD mechanical
failure (35%), infective complications (41%), or
stroke (10%) Advances in blood pump
bioengi-neering have already dramatically reduced these
risks [15] Important developments include the
fact that high-speed impellers do not damage red
or white blood cells and that attenuated pulse
pressure is well tolerated in the long term by the
human circulation[16] External components can
be made exchangeable to combat wear and tear
and the product is more user friendly for surgeon
and patient (Fig 3)[17]
In July 2006 the New England Journal of
Medicine reported 6-year survival in the first
patient to receive a miniaturized axial flow pump
for lifetime use[18] The Jarvik 2000 LVAD
(Jar-vik Heart, New York) was tested in laboratory
programs in Houston and Oxford (Fig 4a, b)
The 61-year-old English patient had idiopathic
di-lated cardiomyopathy with longstanding
biven-tricular failure He was breathless at rest with
pitting edema to the thighs, ulcerated legs, and
as-cites Left ventricular ejection fraction was less
than 10% He was rejected for cardiac
transplan-tation because of renal impairment and
subse-quently declined the procedure Almost 7 years
later he is NYHA Class II with an active life
in the community Pump output is around 5.0
L/min against a mean blood pressure of between
70 to 80 mm Hg, usually with a pulse pressure
of 10 to 15 mm Hg Power is delivered by way
of a skull-mounted titanium pedestal, which has remained infection free (seeFig 3) The external cables, controller, and batteries have all required exchange for wear and tear Less than 5% of the follow-up period has been spent in hospital and total cost has been around $200,000
After extensive laboratory testing suggested that continuous pump flow and attenuated pulse pressure were safe in the long term, the Oxford Group proceeded to a pilot study of lifetime support in nine Stage D patients who had end-stage dilated cardiomyopathy All had been turned down for cardiac transplantation because of renal dysfunction with or without elevated pulmonary vascular resistance Two died in hospital from right heart and multiorgan failure Three are alive and well without an adverse event between 13 months and 6.8 years postoperatively Three others have died at 12 months, 26 months, 35 months post-operatively, all from noncardiac causes A fourth patient had enjoyed 3.5 years of event-free in-dependent life more than 200 miles away from the implanting center He died of acute left ventricular failure after failing to take a replacement battery on
an excursion At autopsy in all these patients the pump and vascular graft were free from thrombosis and there were no signs of thromboembolism The skull pedestal remained free from infection in each case The explanted LVADs continued to function normally on the bench So far the Jarvik 2000 has proven to be 100% mechanically reliable in 150 implants and has a lower complication rate than pulsatile pumps[19]
Careful medical management plays an impor-tant part in the symbiotic relationship between
a rotary blood pump and an improving native heart These LVADs are particularly sensitive to differential pressure across the rotor (afterload) [15] An increase in peripheral vascular resistance can dramatically reduce pump flow leading to renewed symptoms The patients benefit from continuous afterload reduction by angiotensin-converting enzyme inhibition, a beta-blocker, or both The native heart responds to exercise by in-creasing cardiac output through the apical LVAD and the aortic valve Longstanding Jarvik 2000 patients are maintained with a mean systemic blood pressure of 60 to 70 mm Hg and little more than 10 to 20 mm Hg pulse pressure [18] They can exercise without changing the pump speed from 10,000 rpm
371
LIFETIME CIRCULATORY SUPPORT
Trang 2Note: Page numbers of article titles are in boldface type
A
Aldosterone antagonists, in advanced heart
failure, 323
American Heart Association (AHA)/American
College of Cardiology (ACC), management
of heart failure and, 325
Angiotensin receptor blockers, in advanced heat
failure, 324
Aortic regurgitation, chronic volume overload
in, 293
conditions causing, 292–294
decision for aortic valve surgery in, 293
impaired systolic function in, 293
natural history of, 292–293
pressure overload in, 292
severe chronic, 293
Aortic stenosis, aortic valve replacement in,
294–295
causes of, 294
mild, natural history of, 294
transition from asymptomatic to symptomatic
stage of, 294
Aortic valve, percutaneous replacement of,
296–297
Aortic valve disease, surgical treatment of,
292–295
tricuspid valve disease in, 295
Aortic valve replacement, in aortic stenosis,
294–295
return of congestive heart failure following,
295
Aortic valve surgery, decision for, in aortic
regurgitation, 293
in advanced heart failure, 329–330
B
Biomedical devices, for heart failure, 295–296
C Cardiac assist devices, mechanical, 299, 300 Cardiac defibrillator, automatic implantable, in advanced heart failure, 326–327
inflatable, 269 Cardiac resynchronization therapy See Resynchronization therapy
Cardiac support systems, fully implantable pulsatile, 299, 300
Cardiac transplantation See Transplantation, cardiac
Cardiomyopathy, dilated See Dilated cardiomyopathy
hypertrophic See Hypertrophic cardiomyopathy Circulatory support, lifetime, must not be restricted to transplant centers, 369–375 mechanical, in advanced heart failure, 331, 332 Coagulopathies, destination mechanical
circulatory support devices and, 331, 353 Congestive heart failure See Heart failure, congestive
Coronary artery bypass surgery, in advanced heart failure, 328
Coronary interventions, percutaneous, in advanced heart failure, 327–328
D Defibrillator, cardiac, automatic implantable, in advanced heart failure, 326–327
inflatable, 269 Destination mechanical circulatory support devices, adverse events associated with, incidence of, 352
areas of research for, 358 biocompatibility of, 362–363 clinical implementation delay and, 357 clinically evaluated, characteristics of, 354–355
1551-7136/07/$ - see front matter Ó 2007 Elsevier Inc All rights reserved.
Heart Failure Clin 3 (2007) 377–380