Discussion
Valve-in-valve TAVR is a seductive option in case of degenerated
bioprostheses. Apparently the advantages are obvious: the procedure is
safe, easy and convenient to perform, positioning of the valve is
simplified due to radiopaque markers and paravalvular leakages as a risk
factor for mortality are not an relevant issue [1-3, 12, 13].
Furthermore, waiving surgery is a striking and convenient point for the
patient. Therefore, the crucial point remains durability. If the
initially unargued excellent results proof to be stable over time,
VIV-TAVR is ready for the many. If not, it must remain a bailout-option
for risky patients. The presently available literature does not allow to
answer this crucial question conclusively [13-18].
The primary clinical efficacy of VIV-TAVR is unargued. Regarding this
point, the present study continuous excellent early results of our group
and is in line with the data given by the VIVID-registry [3, 13].
The present patient cohort represents a typical TAVR patient population.
Likewise, procedural data and hospital outcome are comparable with VIVID
[13]. The procedure itself is convenient and technically less
demanding - radiopaque markers of the bioprosthesis clearly indicate the
perfect landing zone and facilitate an easy and orthograde positioning
of the valve. Additionally, the sealing is much more effective compared
to “native”-TAVR and though, paravalvular leakages are no matter of
greater concern in VIV-TAVR as the present study and the VIVID-registry
could demonstrate [20]. Nonetheless, one point has to be taken into
account: coronary obstruction. Despite rare with an overall incidence of
0.7%, coronary obstruction is an issue being associated with a high
mortality up to 42% [21]. To prevent from this fatal course, some
considerations should be taken into account during procedure planning.
There exist some predicting variables like female gender, low coronary
ostial height (<10mm), Sinus Valsalva width <30mm
and presence of biological valves with externally mounted leaflets or
even worse, stentless valves [22]. For those conditions the BASILICA
procedure or alternatively the OPEN-BASILICA-procedure were described
before [22-24]. Anyhow, in the present series coronary obstruction
played no role.
Generally, the procedural and hospital outcomes observed in this study
confirmed the safety of VIV-TAVR. Indeed, the hospital survival as well
as stroke rate were better than the results reported in the VIVID (1.3%
vs. 7.6% for mortality and 0.0% vs. 1.7% for major stroke).
During the implantation, particularly with self-expanding prostheses it
is aimed to release the valve in a pronounced high position to ensure
supra-annular positioning and to allow a good hemodynamic result.
According to this supra-annular concept, the immediate hemodynamic
outcomes are superior with self-expandable prostheses compared to
intra-annularly implanted balloon-expandable valves. This fact could be
confirmed by the present study demonstrating a significantly higher rate
of early device success according to the VARC-2 criteria for
balloon-expandable devices. These observations made are mainly in line
with those reported by the Dvir and colleagues [13, 18].
Concluding procedural aspects and initial outcomes, it seems to be
evident, that VIV-TAVR as a heterogeneous group consisting of different
procedures (by means of combinations of surgical and TAVR valves) - with
respect to some special cases - basically is safe and provides good or
at least acceptable initial hemodynamic results [3, 13, 16].
Furthermore, it is evident, that VIV-TAVR in small surgical valves as
well as stented valves is associated with higher postprocedural
gradients [16].
As far as good – but Dvir and colleagues identified a sore spot already
in the VIVID [13]. Patients presenting with an internal diameter
equal or less 20mm of the surgical valve showed to have an inferior
1-year survival [13]. Accordingly, the PARTNER 2 Valve-in-Valve
Study at 3-years priorly defined a labeled size <21mm as a key
exclusion criterion [17]. The present study confirms these findings.
Despite experiencing an initial sufficient reduction of transvalvular
pressure gradients in true-ID’s equal or less 21mm, gradients
continuously were significantly higher up to 1-year of follow-up,
compared to larger valve. After 2 and 3-years the gradients stayed to be
high, but not anymore being significantly higher compared to larger
valves. This development could be explained by two facts. First, the
larger valves likewise experienced a fundamental increase in
transvalvular pressure gradients and second, a potential bias within the
small-ID group due to patients with assumably higher gradients dying
earlier. This explanation fits into the observed higher mortality of the
small-ID group during follow-up. Bleiziffer et al. reported in the
5-years outcome of the VIVID likewise a significantly increased
mortality in small-ID patients [18]. Hence, the presently available
results allow to conclude, that VIV-TAVR in patients with a small ID
(≤21mm or ≤20mm depending on the definition) are likely to have inferior
outcomes after their primary hospital stay.
A quite more unclear situation applies to larger valves with an ID ≥
21mm. For example, Webb and colleagues reported in the 3-Year outcomes
of 365 patient in the PARTNER 2-registry sustained hemodynamic status
with at least only minimal changes in mean transvalvular pressure
gradients [17]. The observation we made in the present series are
contradictory: the predischarge hemodynamic outcomes were quite
comparable to those reported by Webb and colleagues (16.8 ± 7.1 mmHg vs.
17.4 mmHg) [17] - despite 100% use of balloon-expandable valves in
the PARTNER 2-registry and the large portion (68.8%) of self-expanding
devices in the present series.
In the present series the mean gradients steadily increased over the
following 3-years (Figure 2A ), which happened independently
from the true-ID of the surgical valve (Figure 2B ) or the type
of implanted transcatheter valve (Figure 3 ). This could not be
explained by size of the surgical valves: the ratio of patients with a
true-ID less or equal 21mm was even higher in the PARTNER 2-registry
compared to our data (76.7% vs. 58.4%).
Up to date, there exist no further long-term hemodynamic data in the
present literature for further comparison. Most studies dealing with
hemodynamic results, end after 1-year of outpatient follow-up
[14-16]. Accordingly, hemodynamic long-term-follow-up has much more
to be elaborated in further studies.
A particular matter of concern beside hemodynamics is survival. All
presently available essential long-term-trials describe mainly
comparable survival outcomes [17, 18, 25, 26]. In the PARTNER
2-registry Webb and colleagues reported an estimated all-cause mortality
of 32.7% after 3-years of follow-up, which fits to 27.7% mortality
after 3-years described in the CoreValve US Expanded Use Study [17,
25]. The data given by the present study is with an estimated
mortality of 42.9% after 3-years mainly in range, but being somewhat
higher.
Further long-term-outcomes are provided by a small multicenter study
with 116 patients reporting 5-years mortality of 32.1% as well as by
the long-term data of the VIVID with 62.0% mortality after 8-years
[18, 26]. In the present series a poor estimated 7-years survival of
20.6 ± 16.1% was found. Interpreting these poor survival data should
respect the average age ranging between 76.0 ± 11.0 and 79.4 ± 5.8 years
[17, 18, 25, 26].
Meanwhile the large VIVID-registry identified smaller true-IDs as a risk
factor for mortality beginning from 1-year of follow-up, the smaller
PARTNER 2-registry as well as the present study could not confirm that
observation findings [13, 17, 18]. Potentially, the overall high
mortality rate in the study population conceals possible significant
differences.