Does TAVI make you smarter? Exploring the effects of Transcatheter Aortic Valve Implantation on Cognitive Function-Juniper Publishers
JUNIPER PUBLISHERS-OPEN ACCESS JOURNAL OF CARDIOLOGY & CARDIOVASCULAR THERAPY
Background: Tran catheter aortic
valve implantation (TAVI) is an alternative to surgical aortic valve
replacement in high-risk patients. While early cognitive decline is
commonly seen in patients undergoing cardiac surgery, the effect of TAVI
on cognitive function is less well understood. The purpose of this
study was to evaluate the effect of TAVI on cognitive function.
Methods: A prospective cohort
study, evaluating 91 patients undergoing TAVI between September 2010 and
September 2014 was performed. Cognitive function was assessed using the
Montreal Cognitive Assessment (MoCA) prior to TAVI and at 6 months
follow-up. MoCA is a comprehensive test that assesses a variety of
cognitive domains including visuospatial/executive, naming, memory,
attention, language, abstraction and orientation.
Results: Mean age was 79.2 years
(SD ± 8.8) and median Society of Thoracic Surgeon mortality risk was
6.5% (IQR 4.3-11.0%). Overall cognitive function, expressed as a median
MoCA score [IQR], did not differ prior to TAVI as compared to 6 months
following the procedure (24 [22, 26] vs. 25 [22, 27]) (p=0.13). However,
in subgroup analysis of patients who were cognitively impaired at
baseline, a significant increase in their overall MoCA score was noted
(22 [20, 24] vs. 23 [21, 25]) (p=0.03).
Conclusion: In a high-risk
surgical cohort, overall cognitive function remained unchanged 6 months
following TAVI. However, among patients with cognitive impairment at
baseline, an improvement in overall cognitive function was noted
following TAVI.
Abbreviations: TAVI: Tran catheter Aortic Valve Implantation; MoCA: Montreal Cognitive Assessment; CABG: Coronary Artery Bypass Graft; STS: Society of Thoracic Surgeons; AVA: Aortic Valve Area; NYHA: New York Heart Association; DASI: Duke Activity Status Index; DW-MRI: Diffusion-Weighted MRI; MMSE: Mini Mental Status Examination; NINDS-CSN: National Institute of Neurologic Disorders and Stroke-Canadian Stroke Network
Introduction
Tran catheter aortic valve implantation (TAVI) has
emerged as a superior alternative to medical therapy in patients with
severe symptomatic aortic stenosis who are high risk for standard
surgical aortic valve replacement [1]. Patients undergoing cardiac
surgery frequently experience postoperative cognitive decline [2-5].
Whether or not TAVI patients experience a similar decline in cognitive
function as found in patients undergoing cardiac surgery is unclear.
Multiple studies have evaluated cognitive function in patients
undergoing TAVI at various ranges of follow-up with differing measures
of cognitive function [6-14], making conclusions from systematic reviews
difficult to interpret [15].
Few studies [16-19] have used the Montreal Cognitive
Assessment (MoCA), a more sensitive tool for cognitive impairment, which
is recommended by the National Institute
of Neurologic Disorders and Stroke-Canadian Stroke Network
(NINDS-CSN) in this patient population. Previous studies
using MoCA have demonstrated improvement, however they
are limited by short duration of follow up [17-19] and small
sample size [16]. Understanding the effects of TAVI on cognitive
function will help the treating team in its approach to optimal
patient selection and also in the prediction of patient outcomes
following TAVI procedures. The purpose of this study was to
determine the effect of TAVI on cognitive function at 6 months
using the MoCA.
The study cohort consisted of all patients undergoing TAVI
for treatment of severe aortic stenosis from September 2010
until September 2014 at a single institution. Patients were
selected to undergo TAVI by an interdisciplinary TAVI team on
the basis of surgical risk and comorbid disease burden. Severe
aortic stenosis was defined as an aortic valve area< 1.0 cm2
and/or an aortic valve mean gradient of > 40 mmHg and/or a
peak aortic velocity of > 4.0 m/sec. The study was approved by
the Horizon Health Network Research Ethics Board. All patients
consented to be included in the New Brunswick Heart Centre’s
TAVI registry.
All procedures were performed by a dedicated institutional
TAVI team, which included members from the departments
of cardiac surgery, interventional cardiology, interventional
radiology, and cardiac anaesthesia. All procedures were performed
under general anaesthesia with standard hemodynamic
monitoring and transesophageal echocardiography. Most cases
utilized transfemoralor transapical access with a smaller number
of cases being performed via a transaortic or axillary approach.
In all cases, pre-dilatation of the aortic valve was performed
under rapid pacing. The valves used included the Sapien and
Sapien XT balloon-expandable valves (Edwards Life sciences,
Inc., Irvine, CA) and the Portico self-expanding valve (St. Jude
Medical, Inc., St. Paul, MN).All patients were transferred to the
intensive care unit following the procedure for monitoring.
Data regarding the following baseline characteristics
were
collected: age, sex,smoking history, diabetes, dyslipidemia,
hypertension, peripheral vascular disease, stroke, transient
ischemic attack, renal failure, pulmonary disease, atrial
fibrillation or flutter, hospitalization for aortic stenosis in
previous 6 months, previous Percutaneous coronary intervention,
previous coronary artery bypass graft (CABG) surgery, previous
pacemaker or implantable cardiac defibrillator insertion,
residential status (home independent, home dependent, assisted
living, hospital), and surgical risk as determined by the Society of
Thoracic Surgeons (STS) Score. Echocardiographic evaluation of aortic
annulus size, aortic valve area (AVA), aortic peak gradient,
aortic mean gradient, and ejection fraction prior to surgery was
also performed. Baseline functional status was assessed using
the New York Heart Association (NYHA) classification, while
baseline physical function was assessed using the Duke Activity
Status Index (DASI).
MoCA is a questionnaire-based tool with a maximum score
of 30, was used to assess baseline cognition. The MoCA score is
calculated based on a combined score obtained in the following
domains: visuospatial/executive (/5), naming (/3), attention
(/6), language (/3), abstraction (/2), delayed recall (/5), and
orientation (/6). A MoCA score of ≥26 is considered normal
[20], while patients with a MoCA score <26 are considered to
be cognitively impaired. Education level was adjusted for by
allocating an additional point to patients who had not achieved
grade 12 or equivalent. The Blind MoCA, adapted for the visually
impaired, omits visuospatial/executive (/5) and naming (/3),
giving a combined maximal score of 22, with a score ≥18 being
considered normal, and scores <18 considered cognitively
impaired at baseline.
Patients were evaluated in the TAVI clinic at 6 months for
evaluation of functional status, physical function and cognitive
function.
Descriptive statistics of the sample consisted of means
and standard deviations for normally distributed continuous
variables, medians and interquartile ranges for non-normally
distributed continuous variables, and counts and proportions
for categorical variables. Characteristics of patients with
normal vs. impaired cognition at baseline were compared using
Wilcoxon-Mann-Whitney tests, chi-squared tests, and Fisher’s
exact tests as appropriate. Baseline and 6-month follow-up
measures of functional status, physical function and cognition
were compared using the Wilcoxon signed-rank test to account
for the repeated measures design and non-normal distribution
of the data. P-values < 0.05 were considered significant. All
statistical analyses were performed using the SAS statistical
software package, v9.3 (Cary, North Carolina).
A total of 127 patients were consented for a TAVI procedure
between September 2010 and September 2014. Of these patients,
3 patients were converted to surgical aortic valve replacement,
4patients had the procedure aborted due to technical reasons or
complications, 5 patients expired before the 6 month follow up,
1 patient had the device explanted 2 months after the procedure,
2 patients did not complete the baseline MoCA assessment, 12
patients were followed up via the province’s tele health system
and as such did not complete the 6 month MoCA, and 9 patients
refused follow up. The remaining 91 patients formed the final
study population.
Of the 91 patients, 70% of patients [64] underwent TAVI
by via the transfemoral approach, 29% of patients [26] via the
transapical approach, and 1%of patients [1] via the subclavian
approach. The Sapien and Sapien XT balloon-expandable valves
(Edwards Life sciences, Inc., Irvine, CA) were used in 95% of
patients [86], while the Portico self-expanding valve (St. Jude
Medical, Inc., St. Paul, MN) was used in 5% of patients [5].
Mean age was 79.2 years (SD ± 8.8) and median Society of
Thoracic Surgeons mortality risk was 6.5% (IQR 4.3-11.0%) (Table 1). The blind MoCA was used for 3 patients both at
baseline and following TAVI. The remaining patients completed
the full MoCA. At baseline 40.6% of patients [37] were found
to have normal cognition while 59.3% of patients [54] were
found to be mildly cognitively impaired. When compared to
patients with normal cognition, cognitively impaired patients
were significantly older and had higher STS scores (Table 1).
Otherwise, no significant differences existed. In both patient
subgroups, TAVI resulted in a significant improvement in
functional status and physical function (Table 2).
With respect to cognition, there was no significant change
in overall cognitive status between baseline and6 months for
either the entire cohort (24 [22, 26] vs. 25[22. 27], p=0.13) or for
the cognitively intact group (27 [26, 28] vs. 27 [24, 28], p=0.55)
(Table 3). However, for patients who were already cognitively
impaired at baseline (MoCA<26), there was a significant improvement in overall MoCA Score (22 [20.24] vs. 23 [21, 25],
p=0.03)(Table 3). Analysis of sub domains of the MoCA score
in this patient subgroup demonstrated a significant increase in
delayed recall ability in cognitively impaired patients (1.5 [1, 3]
vs. 3 [1, 4], p=0.0001) with all other sub domains showing no
significant change.
The purpose of this study was to determine the effect of
TAVI on cognitive function. While this study demonstrated
preservation in cognitive function following TAVI in patients
with elevated surgical risk, it also founda statistically significant
improvement in cognitive function among patients who were
cognitively impaired at baseline.
Patients undergoing cardiac operations experience
postoperative cognitive decline with rates ranging from 3%
to 53% [4,5,21]. Micro embolization has been detected using
transcranial Doppler ultra sonography and magnetic resonance
imaging in 15% to 47% of cardiac surgery patients [22-28] and
has been associated with neuro cognitive decline [22,24,25].
However, other studies have found no association between new
embolic lesions and postoperative decline [29], including a study
evaluating patients undergoing aortic valve surgery [26].
Micro embolization during TAVI procedures has also been
detected using transcranial Doppler evaluation [11] and magnetic
resonance imaging studies [30-34]. In a prospective analysis of
125 patients undergoing TAVI, no association was found between
silent infarcts detected by Diffusion-Weighted MRI (DW-MRI)
and decline in neuropsychological status, measured using the
repeatable battery for the assessment of neuropsychological
status [33]. Similar studies have found no association between
new DW-MRI lesions following TAVI and neuro cognitive decline
as measured using the Mini Mental Status Examination (MMSE)
[11,12,14]. This cohort of patients did not experience a decline
in cognitive function at 6 months post TAVI procedure. This
finding, in conjunction with the reassurance that detectable
“silent” infarcts following TAVI are not associated with cognitive
decline, is encouraging for patients hoping to avoid cognitive
decline following such an important procedure. The finding
in our study that TAVI is not associated with cognitive decline
beyond discharge is consistent with findings from other studies
in the literature [8-19], and is reassuring for those patients
who are fearful of experiencing adverse neuro cognitive issues
following replacement of their aortic valve.
The majority of studies have evaluated cognitive function
following TAVI using either the MMSE or another form of
cognitive evaluation [6-14]. Few studies [16-19] have used
the Montreal Cognitive Assessment, a more sensitive tool
for detection of mild cognitive impairment in comparison to
the MMSE [20]. The MoCA is recommended by the National
Institute of Neurologic Disorders and Stroke-Canadian Stroke
Network (NINDS-CSN) in this patient population. Our findings
are consistent with previous studies using the MoCA which have
demonstrated improvement in MoCA scores at 30 days [18,19],
3 months [17] and at 1 year [16], particularly those who were
cognitively impaired at baseline [16,18].
It has been postulated that the relief of aortic valve
obstruction, by improving cardiac output and possibly cerebral perfusion, could potentially improve cognitive function. In an
attempt to evaluate predictors of cognitive improvement and
decline following TAVI, Shoenenberger et al. [35] in an analysis
of 229 patients who underwent cognitive evaluation using the
MMSE, smaller AVA was found to be associated with patients
who experienced cognitive improvement compared to those
who did not experience cognitive improvement [35]. This may
be due to improvement in cerebral perfusion, as patients who
are cognitively impaired at baseline may be more sensitive to
decreased cerebral perfusion and may be more likely to benefit
from the TAVI procedure.
This study has several limitations. First, while this is the
largest TAVI cohort to undergo neurologic evaluation with the
MoCA test, the follow up is limited to 6 months. Other studies
have confirmed preserved neurological status at 1 [16] and
2 [8] years. As TAVI use is expanded to lower risk patients,
information regarding longer term follow up will be warranted.
Second, cerebral imaging was not performed, which could be
used to correlate with cognitive function outcomes. However, as
discussed above, studies have consistently failed to demonstrate
a relationship between clinically silent cerebral infarcts and
neuro cognitive decline in TAVI patients [9,11,14,26].
Despite this, recent studies on the use of cerebral embolic
protection devices have demonstrated greater cognitive
improvement in patients in which a protection device was used
[18,19], suggesting further research into the interplay between
emboli and cognitive function in the setting of TAVI is needed.
Finally, as Trans catheter devices evolve, there will be a constant
paucity of data on current devices, limiting applicability in
current practice. Nonetheless, this study in conjunction with
current literature is reassuring in the preservation and probable
amelioration of cognitive function in patients undergoing TAVI.
Conclusion
In conclusion, this study is reassuring in its finding that
patients undergoing TAVI did not experience postoperative
cognitive decline. Furthermore, it found that TAVI was associated
with improvement in cognitive function among patients who
were impaired at baseline. It is anticipated that these results
may be used to guide patient selection and discussion around
cognitive outcomes in this high-risk patient cohort. Further
research into predictors of early cognitive decline in these
patients is warranted in larger cohorts.Conclusion
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