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Brain & Heart TAVR in low gradient aortic stenosis

Table 1. (Continued)
Imaging modality Objectives/Key concept Clinical utility and advantages Limitations
Cardiac magnetic • Accurate estimation of LV function and • Guides patient selection for TAVR • Poor visualization of calcium
resonance aortic root and valve morphology • Estimate the extent of myocardial deposition
• LGE imaging to identify myocardial scar viability in patients with Inadequate spatiotemporal resolution
tissue and quantify myocardial fibrosis. concomitant ischemic heart disease • Expensive
• Phase-contrast velocity mapping to determine the potential benefits Unavailability in resource-limited setups
of TAVR
• Quantification of the severity of
concomitant aortic regurgitation
• Lack of radiation exposure
Abbreviations: AS: Aortic stenosis; AVA: Aortic valve area; AVR: Aortic valve replacement; CAD: Coronary artery disease; CT: Computed tomography;
LGE: Late gadolinium enhancement; LV: Left ventricular; LVOT: Left ventricular outflow tract; TAVI: Transcatheter aortic valve implantation;
TAVR: Transcatheter aortic valve replacement; THV: Transcatheter heart valve; TTE: Transthoracic echocardiography.

guidelines recommend the use of low-dose DSE to further reconstruction. However, the threshold for severe AS
ascertain AS severity in patients with cLFLGAS. The value on CTA may be slightly higher, with a value of <1.2 cm
2
of exercise stress echocardiography testing in this setting proposed in some studies. To determine AS severity, the
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is more controversial. Its primary function is to evaluate aortic valve calcium score can also be assessed through
the exercise capacity in asymptomatic patients, along non-contrast CT, with thresholds of >2000 and >1200
with the hemodynamic response of AS to exercise, both Agatston units for men and women, respectively. 2,20
with prognostic implications, rather than AS severity,
and is contraindicated in symptomatic patients due to the 3.5. Cardiac magnetic resonance (CMR)
potential for precipitating complications (Figure 1). CMR is primarily used during TAVR workup in patients
with contraindications to contrast CT, such as renal
3.3. Transesophageal echocardiography (TEE) dysfunction or contrast allergy. The principal function is
TEE is a valuable adjunct to TTE in the pre-TAVR to use the non-contrast three-dimensional whole heart
assessment of patients with LFLGAS, providing higher- sequence to assess the aortic annulus and root anatomy,
resolution imaging of the aortic valve and adjacent similar to CT-based analysis. 21,22 CMR is more restricted in
structures. 14,16 TEE provides a detailed visualization of the its ability to evaluate the severity of AS than TTE. Although
aortic valve leaflets, including morphology, calcification, planimetry of the AVA is feasible, the results are not always
and mobility assessment. Compared with TTE, it typically accurate. Furthermore, compared with TTE, the peak
achieves a higher level of accuracy in AVA planimetry, velocity measurement on phase-contrast sequence with
particularly when utilizing three-dimensional techniques velocity-encoding gradients is typically underestimated. 23
and multiplanar reconstruction. Furthermore, TEE allows However, it is important to acknowledge that CMR is
16
for the estimation of LVOT/aortic annulus dimensions the reference standard for quantifying cardiac chamber
(although Computed tomography (CT) is preferred for parameters, including volumes, EF, and myocardial mass,
the latter), subvalvular and valvular abnormalities that which can also help classify and stratify risk in patients
24
may influence TAVR feasibility and procedural planning 17 with AS. (Figures 3 and 4).
(Figure 2).
4. Indications for AVR
3.4. Computed tomography angiography (CTA) In general, the 2020 ACC/AHA guidelines for the
CTA generates high-resolution images that enable precise management of patients with valvular heart disease
measurement of the aortic annulus, including its diameter, provide a class I recommendation for AVR in patients
perimeter, area, and calcifications, which are crucial for with severe symptomatic AS, asymptomatic severe AS
selecting the appropriate size and type of transcatheter with an EF of <50%, asymptomatic patients with severe
heart valve (THV) during TAVR. Retrospective ECG- AS who are undergoing other cardiac surgery, patients
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gated four-dimensional CTA with contrast enhancement with cLFLGAS and reduced EF, and symptomatic patients
facilitates detailed visualization of the aortic valve leaflets, with cLFLGAS if AS is the most likely cause of symptoms.
including an assessment of their mobility, calcification, and Both the European 2021 and American 2020 valvular heart
morphology, to determine the suitability of the native valve disease guidelines provide guidance for the appropriate
for TAVR and plan the implantation technique. The AVA timing of intervention in patients with LFLGAS. 11,25 Both
can be measured through planimetry using multiplanar guidelines recommend that patients with true cLFLGAS

Volume 3 Issue 1 (2025) 4 doi: 10.36922/bh.4017