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July/August 2010
TAVI With the Edwards Sapien Valve
An update on the latest trial data and the future of aortic valve technology.
The first transcatheter aortic valve implantation (TAVI) was performed in 2002.1 During the last 8 years, the procedure has been refined and is now relatively predictable in terms of immediate outcomes. The Edwards Sapien transcatheter heart valve (Edwards Lifesciences Corporation, Irvine, CA) can be delivered via the transfemoral (TF) or transapical (TA) route and is a balloon-expandable valve.
PATIENT SELECTION
The TAVI procedure is indicated for patients who
represent high risk for standard open surgical aortic
valve replacement (SAVR) and usually have a logistic
EuroSCORE of > 20 or a Society of Thoracic Surgeons
score of > 10. Other potential indications include a
porcelain aorta and previous mediastinal radiotherapy.
Patients should be selected for TAVI by a multidisciplinary
team including interventional cardiologists, cardiac
surgeons, cardiac anesthesiologists,
and imaging specialists. It is generally
agreed that patients undergoing the TA
approach represent a higher-risk group
than those undergoing TF. In cohort 1 of
the SOURCE registry,2 the logistic
EuroSCORE was 29.1 with TA compared
to 25.7 with TF (P < .001). Therefore, the
outcomes of the two procedures cannot
be directly compared. The principal determinant
on whether a patient undergoes
the TF or TA approach is the presence of
significant peripheral vascular disease.
Because of the large French size of the TF
delivery catheter, a minimum luminal
diameter of the femoral and iliac vessels
(8 mm for the 26-mm valve and 7.5 mm
for the 23-mm valve) is required for this approach.
Screening imaging before patient selection should
include transthoracic echocardiography, aortic computed
tomography, and coronary/peripheral angiography.
THE PROCEDURE AND 30-DAY OUTCOMES
The Edwards Sapien valve is currently commercially
available in 23- and 26-mm sizes. Most of the published
literature and presentations for the TF approach use the
Edwards Sapien valve and require a 22- or 24-F sheath,
and for the TA approach, a 26-F TA delivery system is
used. Procedural results are now highly acceptable, with
a success rate of 7gt; 95% and a very low on-table mortality
rate. Valve embolization rates (aortic and ventricular)
are low (0.3%), as are coronary obstruction rates
(0.6%).2 If coronary obstruction occurs, it is generally
due to a native valve leaflet covering the coronary
ostium rather than because of the device itself. This complication can often be predicted by
the height and bulkiness of the native
leaflets, the “depth” of the sinuses of
Valsalva, and the distance between the
leaflets and the coronary ostia. Therefore,
careful attention should be paid to the
preprocedural morphology of the native
valve and to the anatomy of the aortic
root and sinuses of Valsalva.
The most important potential complication of both the TF and the TA approach is major vascular access site complications. With the TF approach, this occurs in approximately 8% to 13% of cases.2-4 Major vascular access site complications include obstructive dissections with limb-threatening ischemia and femoral or iliac rupture. These complications can now be managed with vascular occlusion balloons and stents (both covered and uncovered).
In the SOURCE registry, the improved management of complications means that there was no association between these early complications and 30-day mortality. 2 However, the data are different for the TA approach. A major apical access site complication is associated with a 50% mortality. Permanent pacemaker requirements for both the TF and TA approaches are approximately 5% to 7%.2,5 The incidence of stroke at 30 days is 2.5%, which is the same for both the TA and TF approach. The exact mechanisms for these strokes are unclear but may be different for the two approaches. The 30-day mortality rate for the TAVI population is now in the region of 6% to 10%.6,7 In the SOURCE registry, it was 8.5% for the entire population, 6.3% for TF, and 10.8% for TA; this mostly likely reflects the higherrisk nature of the TA patients.2
ONE-YEAR OUTCOMES
The 1-year outcomes for cohort 1 of the SOURCE registry
have recently been presented and represent the
most up-to-date results using the current technology.8
The Kaplan-Meier survival curves for the entire cohort,
TA patients, and TF patients are shown in Figure 1.
Kaplan-Meier survival rates were 76.1% for the cohort
as a whole, 72.1% for the TA patients, and 81.1% for the
TF patients. These data represent the best 1-year survival
rates to date using this technology.
The majority of deaths between 30 days and 1 year were noncardiac and most likely reflect the comorbidities of the patients. There was a very low incidence of myocardial infarction and bacterial endocarditis. The incidence of stroke at 1 year was approximately 4.5%. Additionally, late vascular complications or pacemaker requirements were extremely low.8
One important issue in discussing the outcomes of TAVI procedures is the definition of various adverse events. Thus far, there has been no consensus on how to accurately define and measure such events as vascular complication or stroke. This has led to difficulty in interpreting different trials and registries across the current literature. This problem has now been resolved by the agreement of consensus definitions by a large group of expert individuals: the Valvular Academic Research Consortium definitions.9 It is expected that these definitions will be used for all future trials and registries, which will lead to harmonization of the data and the ability to improve the integration of data.
ALTERNATIVE VASCULAR ACCESS
AND DEVICES
There are two TAVI devices that are currently commercially
available: the Edwards Sapien transcatheter
heart valve, a balloon-expandable valve, and the
Medtronic CoreValve (Medtronic, Inc., Minneapolis,
MN), a self-expanding device. Alternative approaches to
TF and TA, which have previously been described, are
the subclavian and the transaortic. Both the subclavian
and transaortic approaches have shown encouraging
results in what is by definition a higher-risk patient population
than those undergoing a TF approach. The subclavian
approach has mainly been reported with the
CoreValve device because of its lower profile, and the
transaortic approach is still in its infancy.
The outcomes between the two devices at 30 days and 1 year are broadly similar, apart from an increased need for a permanent pacemaker with CoreValve (4%–7% with the Edwards Sapien device and 20%–40% with the CoreValve device).
CONTEXT VERSUS SURGICAL AORTIC
REPLACEMENT
Much of the surgical literature on high-risk patients
concentrates on inpatient outcomes for patients such
as octogenarians. Are there any comparators for the
1-year results of TAVI? The Leipzig group provided data
in their article from 200910 regarding octogenarian
patients undergoing SAVR. The patients were divided
into those with a logistic EuroSCORE of < 10, 10 to 20,
or > 20. The 30-day survival rates were similar for all risk
groups, ranging from 89% to 93%. The pattern for
1-year survival was very similar to TAVI and appears to
reflect the risk of the patient rather than the risk of the
procedure. Mortality rates between 30 days and 1 year
for patients with a log EuroSCORE of < 10 was 2.5%
(1-year survival, 90%), a score of 10 to 20 was 11.3%
(1-year survival, 78%), and for those with a log
EuroSCORE of > 20 (potentially a TAVI population), the
mortality rate was 21.3% (1-year survival, 69%) (Figure
2). Therefore, the gold standard for 1-year survival of
high-risk (TAVI-type) SAVR might be seen as 69%. The
1-year survival rate for the overall SOURCE cohort of
76.1% (81.1% for TF and 72.1% for TA) is therefore highly
encouraging within this context.
NEW DEVICE DEVELOPMENTS
The latest iteration of the Edwards valve, the Edwards
Sapien XT valve with the Novoflex delivery system
(Edwards Lifesciences), involves changes for both the TF
and TA system. The valve has changed from stainless
steel to cobalt-chromium, and the valve leaflet design
has been modified. The Novoflex delivery system is now
18 F for the 23-mm valve and 19 F for the 26-mm valve.
This has been achieved by a novel concept of
loading/aligning the delivery balloon onto the Sapien
XT valve in the descending aorta. The new Ascendra
transapical delivery system (Edwards Lifesciences) is 24 F
and has also been made more ergonomically friendly.
Certainly for the transfemoral catheter, it may be
expected that the reduction in the French size of the
device will result in a higher proportion of patients who
are eligible for the TF approach and a reduction in the
incidence of vascular complications. Given that these
complications have traditionally been associated with
increased mortality rates,8,11 the new XT device may
lead to a further increase in the 1-year survival rates.
These new devices are currently being tested in PREVAIL
TF and TA registries and will be further investigated in
the next major European registry, SOURCE XT.
THE FUTURE OF TAVI
TAVI is now maturing as an interventional procedure.
The procedure itself is becoming predictable, and complication
management has greatly improved. The real
skill involved with TAVI now is choosing the correct
patients to undergo the procedure. The next task of the
interventional community is to construct a “TAVI risk
measure,” which will accurately predict the in-hospital
and 1-year outcomes after TAVI. In addition, cost effectiveness
needs to be established for the procedure
because the current TAVI devices are expensive. It is
probable that if new devices begin to appear on the
market, the cost of the currently available transcatheter
valves will be reduced.
Cost effectiveness is generally measured as the cost per quality-adjusted life year gained. To demonstrate cost effectiveness, TAVI will probably have to improve quality of life and longevity compared to an alternative treatment (ie, medical therapy or open SAVR). Currently, this cannot be measured because there are no randomized data available. Randomized data for the Edwards device (the PARTNER trial) will be available toward the end of 2010 for TAVI versus medical therapy and in 2011 for TAVI versus SAVR in high-risk aortic stenosis patients. Further randomized trials are in the planning phase both in the United States and in Europe. It is likely that these future trials will involve a lower-risk group of surgical patients. It may be difficult to demonstrate cost effectiveness in a low-risk cohort because of the excellent result of SAVR.
If TAVI is performed in lower-risk patients, the issue of paravalvular leak may become more important. Currently, the incidence of > 2+ aortic regurgitation after the procedure is low, and this tends to be reduced with time.2,6 However, grade 1 to 2 aortic regurgitation is relatively common. In the context of high-risk surgical patients, this may have little clinical relevance. But, in lower-risk patients with greater life expectancy, this type of residual aortic regurgitation may become important. Further technical advances for dealing with paravalvular leaks are required.
The incidence of clinical stroke after TAVI is generally reported to be 2% to 5%.2,6 However, recently, magnetic resonance imaging has been used to detect new lesions in 84% of 32 patients undergoing TAVI with both balloon- expandable and self-expanding valves.12 These were not associated with detectable clinical neurological consequences. Nonetheless, cerebral deflection/protection devices (delivered via the radial artery) are currently under investigation, and hopefully, these will result in a reduction in silent and apparent cerebral ischemia after TAVI.
CONCLUSION
The results of TAVI are becoming more predictable.
Depending on the vascular access site, a patient can
now be quoted a 30-day mortality rate of 6% to 10%
and a 1-year survival of 7gt; 80% with the TF approach.
Developments of the device and refinement in patient
selection should lead to a further improvement in
these outcomes. It appears highly likely that TAVI is
here to stay and will establish itself as an important
part of the armamentarium available for treating
patients with symptomatic aortic valve stenosis.
Martyn Thomas, MD, FRCP, is Clinical Director of Cardiovascular Services, Guys and St. Thomas' Hospital in London, United Kingdom. He has disclosed that he is a proctor and advisory board member for Edwards Lifesciences. Dr. Thomas may be reached at (0207) 188 1080; mttwins@aol.com.
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