Download Transcatheter aortic valve implantation: emerging role in poor left

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ISSN: 2409-3424
Editorial | ICF November 2014 – Issue 5
DOI: 10.17987/icfj.v1i5.57
Transcatheter aortic valve implantation:
emerging role in poor left ventricular function
severe aortic stenosis?
K. M. John Chan1,3 and John R. Pepper2,3
1 Sarawak General Hospital Heart Centre, Kuching, Sarawak, Malaysia,
2 NIHR, Cardiovascular BRU, Royal Brompton Hospital, London, U.K.
3 National Heart and Lung Institute, Imperial College London, U.K.
Abstract
Transcatheter aortic valve implantation (TAVI) has become an established treatment option for high risk elderly patients with
symptomatic severe aortic stenosis. Its role in less high risk patients is being evaluated in clinical trials. Patients with severely
impaired left ventricular function may be another group who may benefit from this emerging percutaneous treatment option.
Key words:
bicuspid aortic valve, genetics, fibrillin-1, Marfan syndrome, clinical approach
Surgical aortic valve replacement (AVR) has long been
recognized as the gold standard treatment for symptomatic
severe aortic stenosis improving symptoms, survival and
functional class. Recently, transcatheter aortic valve implantation
(TAVI) has also become an established procedure for the
treatment of higher risk patients with symptomatic severe
aortic stenosis.1 These include the frail, elderly patient with
multiple co-morbidities and disabilities. TAVI has been shown
to successfully reduce aortic valve gradients to a similar
degree as conventional AVR but the incidence of paravalvular
aortic regurgitation (AR) is significantly higher.2, 3 Compared to
conventional AVR, TAVI has a shorter recovery period, avoids a
sternotomy and cardiopulmonary bypass, and has a lower risk of
bleeding, acute kidney injury, atrial fibrillation and early mortality,
but the risk of vascular complications, pacemaker implantations
and cardiac perforations are higher.1, 3 Stroke rates were initially
reported to be higher following TAVI compared to conventional
AVR but recent studies suggest no difference in stroke rates.3
these patients with cardiopulmonary bypass and cardioplegic
arrest of the heart requires meticulous myocardial protection, to
avoid the risk of further myocardial injury in an already impaired
LV and consequent need for high doses of inotropic support,
or failure to wean from cardiopulmonary bypass requiring
mechanical circulatory support, with the resulting prolonged
stay in intensive care associated with increased morbidity and
mortality. Operative mortality in these patients has been reported
to be between 5-20% and is better in younger patients with
evidence of contractile reserve, minimal coronary disease and
no myocardial fibrosis.1, 7, 8 An improvement in functional status,
ejection fraction and survival has been reported following
successful AVR in these patients.7, 9 Sutureless valves have been
introduced which allows an aortic valve to be implanted without
the need to suture it onto the aortic annulus thus reducing the
duration of myocardial ischaemia and cardiopulmonary bypass.
These valves are increasingly being used in LGLEF aortic
stenosis with good results.
Many patients in the highest risk group who would not
previously have been offered surgery are now eligible for TAVI
and this has been shown to improve their symptoms, functional
class, survival and quality of life compared to best medical
treatment; hospital admissions were reduced, although the risk
of stroke, vascular complications and need for pacemaker were
increased.1, 3, 4 In randomized trials, TAVI has been shown to
have a similar survival to conventional AVR at up to one year in
the highest risk elderly patients; while in those at less high risk,
TAVI has been shown to have a lower mortality.3, 5 However,
the longer-term results of TAVI beyond 5 years is unknown and
while TAVI may be suitable for the higher risk elderly patient with
multiple co-morbidities who would not be expected to survive
beyond 5 years, its role in the lower risk younger patient is
uncertain; clinical trials are needed to evaluate this.6
Is there also a role for TAVI in these patients? TAVI would
of course avoid the need for cardiopulmonary bypass and
aortic cross clamping altogether, although there is still a risk
of myocardial injury during the period of rapid pacing. Indeed,
intra-aortic balloon pump and in some instances more intense
mechanical circulatory support may be needed in these patients
during TAVI. Unfortunately, most of the TAVI studies to date
have excluded patients with severely impaired LV function. An
analysis of low flow severe aortic stenosis was performed in
the PARTNER Trial but the mean ejection fraction in this group
was 49%.10 In this analysis, low flow was associated with
increased mortality at two years, with no difference between
the TAVI and AVR arms. In a separate observational study,
LGLEF severe aortic stenosis with a mean ejection fraction of
32% was associated with increased mortality following TAVI.11
In both studies, low flow, rather than low ejection fraction, were
independently predictive of increased mortality at two years.
Another group of patients at high risk for conventional AVR is
the patient with severely impaired left ventricular (LV) function
particularly those with a low gradient, low ejection fraction
(LGLEF) severe aortic stenosis. These include patients with a
resting mean aortic valve gradient of less than 30mmHg and
an LV ejection fraction of less than 35%.7 Conventional AVR in
Although TAVI may seem suitable in LGLEF severe aortic
stenosis to avoid the need for major surgery, there are several
concerns with its use in these patients. Compared with
conventional AVR, TAVI has been shown to have a higher
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ICF November 2014 – Issue 5 | Editorial
incidence of paravalvular aortic regurgitation (AR).1-3 Mild AR
has been reported in between 7-63% of patients following
TAVI, and moderate or severe AR in between 4-37%.2, 3, 12-14
These differences in reported rates of AR may be a reflection
of different techniques and methods of assessing and grading
AR severity, and possibly of differing techniques of performing
the TAVI procedure.14 While patients with preserved LV systolic
function may be able to tolerate some degree of AR following
TAVI, it is uncertain how the severely impaired LV would be able
to cope with AR in the long term. The severely hypertrophic LV
accustomed to the pressure overload of severe aortic stenosis
is often not very compliant and may not cope with the volume
overload of aortic regurgitation particularly if LV systolic function
is already severely impaired. Indeed, it has been demonstrated
that even in those with preserved LV systolic function,
paravalvular AR is associated with decreased survival.14
Conventional AVR in LGLEF severe aortic stenosis, although
a high risk procedure, has been shown to improve long term
survival in younger patients.6, 9 The results of TAVI, however,
do not extend beyond 5-years. Clearly, the long-term durability
and safety of TAVI has to be determined. In addition, indices
of reverse LV remodeling in the long term must be carefully
studied. Should the presence of paravalvular AR following
TAVI adversely affect LV reverse remodeling in the patient
with a severely depressed LV, this may ultimately affect their
survival and functional status. An observational study did report
an improvement in LV ejection fraction at one year following
TAVI in LGLEF severe aortic stenosis, however, changes in LV
mass or volumes were not reported.8 In this non-randomized
observational study, the improvement in ejection fraction at
one year was better in TAVI patients compared to conventional
AVR. However, the improvement in ejection fraction following
conventional AVR was better in other observational studies.15
Clearly, randomized comparisons are needed including
parameters of LV reverse remodeling and clinical outcomes.
TAVI is still a relatively new procedure and just as the results of
conventional AVR have improved over the decades since it was
first performed, the results of TAVI are likely to improve too with
time. Better understanding of pre-procedure sizing of the aortic
annulus and its anatomy with CT and 3-D echocardiography
assessment, selecting the valve prosthesis of the right size and
make, better positioning of the valve prosthesis within the aortic
annulus, and improved design of the valve prosthesis itself such
as the Sapien 3 prosthesis, will almost certainly reduce the
incidence of paravalvular AR with time.12, 14 The indications for
TAVI is likely to increase with time and may include the patient
with severely impaired LV function and symptomatic severe
aortic stenosis. However, clinical evidence for this is necessary
and this is likely to come from further analysis of existing registry
data and ongoing randomized trials.
Correspondence to:
Professor K. M. John Chan
Consultant Cardiothoracic Surgeon
Sarawak General Hospital Heart Centre
94300 Kota Samarahan, Sarawak
Malaysia
Tel: +60 12 828 3718
Email: [email protected]
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