Determining Prosthesis-Patient Mismatch after TAVR: Which is the
Best Method?
Authors: Cesar E. Mendoza, MD1 and Diego
Celli, MD2
Affiliations: 1Division of Cardiovascular
Disease, Jackson Memorial Hospital, Miami, Florida;2Internal Medicine, University of Miami Miller School
of Medicine/Jackson Memorial Hospital, Miami, Florida.
Affiliation addresses: 11801 NW
9th Ave, Suite #209 33136 Miami, Florida, United
States; 21611 NW 12th Ave 33136, Miami, Florida,
United States.
Corresponding author: Cesar E. Mendoza, MD;
cesar.mendoza2@jhsmiami.org;
1611 NW 12th Ave, East Tower 3019, Miami, Florida
33136.
Disclosures: Authors have no relationships with the industry.
This work is not under consideration in any other journal.
Funding: No grants, contracts, and other forms of financial
support were used to perform this manuscript.
In the last decade, the medical community has witnessed an accelerated
development of multiple devices for the transcatheter management of
aortic stenosis. Recently, transaortic valve replacement (TAVR) was
granted approval for its use in all types of surgical risk patients
underscoring its importance in cardiovascular practice. While evidence
has shown non-inferiority of TAVR versus surgical aortic valve
replacement (SAVR) [1], it still has inherent intra- and
post-procedural complications, prosthesis-patient mismatch (PPM) is one
of them.
Since the seminal work published by Rahimtoola in 1978 [2], several
studies have investigated PPM. The incidence of PPM after SAVR ranges
from 20% to 50% with severe cases having an occurrence rate from 5%
to 25%. [3-5]. Severe PPM has been associated with significantly
abnormal prosthetic valve echocardiographic parameters and adverse
clinical outcomes including a higher risk of mortality [3,5-7].
Although initial studies showed a lower incidence of PPM after TAVR
[8, 9], most recent data surprisingly depict an uptrend incidence of
PPM with later-generation TAVR prostheses [10]. Regardless of the
true global PPM incidence, the number of cases in the severe category
remain within robust margins (5% - 36%). Perhaps, more interestingly,
the association of TAVR with adverse outcomes is not firm. Indeed, there
are conflicting reports, with some studies showing a weak association
[11,12], no association [13, 14, 15], or association in
particular group of patients [9].
PPM occurs when the effective orifice area (EOA) of a normally
functioning prosthesis is too small in relation to the patient’s body
size and cardiac output requirements, and this diagnosis must be done
after ruling out dysfunction of the prosthesis heart valve.
Historically, surgical aortic valve replacement was the method of choice
in the management of aortic stenosis; as such, surgeons relied on the
manufacturer’s predicted EOA charts to aid in the determination of the
minimum valve size for any given valve model. The predicted EOA index
(EOAi), which is calculated by dividing the reference value for the
prosthesis model and size by the body surface area (BSA) of the patient,
has been frequently used to identify PPM in the SAVR studies. Similarly,
all contemporary TAVR studies have used the same index for the same
purpose; but it nevertheless was measured using Doppler-echocardiography
data.
In this issue of JOCS, Catalano et al report that the utility of EOAi
charts to predict PPM after TAVR for native aortic stenosis may be
limited. Indeed, they found in their study that the pre-TAVR prediction
of PPM using tables of expected EOA varies significantly from actual
PPM measured on intraoperative transesophageal echocardiography using
the continuity equation. Although this is a relatively small
single-center study, the authors provided information worthy of
additional consideration.
First, they identified that EOAi charts overestimated the number of
patients with PPM for Sapien 3 valves (25.3% predicted versus 13.7%
actual) and underestimated the number of patients with PPM for Evolut
valves (1.8% predicted versus 11.6% actual), yielding a limited
utility for this instrument on pre-operative prediction of PPM in TAVR.
Interestingly, a recent publication by Ternacle et al. [16] provides
a different perspective on this topic. It reports that the predicted
EOAi was found to be useful to reclassify the majority of patients
diagnosed with measured PPM following TAVR to no PPM at all.
Furthermore, they found that both methods had a different association
with hemodynamic outcomes. In this regard, EOAi and mean transprosthetic
gradient had a more powerful correlation when using the predicted EOAi
versus the measured EOAi. Based on these findings, the Ternacle’s study
suggests that the use of measured EOAi grossly overestimates the
incidence of PPM. The discrepancy between both studies may be explained
by the inherent variability in using different Doppler echocardiography
imaging modalities to measure EOA. As Catalano et al rightly pointed
out, the prosthesis data acquisition and measurements obtained by
intraoperative transesophageal echocardiography in their study may not
be comparable with its counterpart transthoracic modality, and this
particular difference should be taken into account when interpreting the
results above mentioned.
Second, it is also clear from Catalano’s study that determining the best
method to diagnose PPM following TAVR is paramount, but at the same time
troublesome due to several factors. First, the pressure recovery
phenomenon, a portion of the transprosthetic pressure gradient lost
initially at the vena contracta level that recovers later after the
prosthetic valve, is not accounted for by Doppler assessment of the
maximum transvalvular flow velocities. This may cause overdiagnosis of
PPM after TAVR. Second, measured EOA is influenced by the patient’s
hemodynamic condition at the time of the evaluation and by the known
technical pitfalls on the acquisition of images and measurement
performance. Third, the use of the EOA indexed for body surface area may
overestimate the severity of PPM in obese patients (body mass index ≥30
kg/m2).
Certainly, Catalano’s study allows for a better discussion on the
diagnosis and clinical implications of PPM following TAVR. However, the
question of what method is a more accurate parameter to determine PPM
remains unanswered. Clearly, further research is needed as TAVR is more
frequently performed and new TAVR prostheses become available. Accurate
prediction of PPM in this setting will help guide the operator’s
decision on proper prosthesis size and type.