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Brain & Heart TAVR in low gradient aortic stenosis

exhibits diverse phenotypes, including classical low-flow 3. Role of multimodality imaging in AS
low-gradient AS (cLFLGAS), paradoxical low-flow low- evaluation and pre-procedural planning
gradient AS (pLFLGAS), and normal-flow low-gradient
AS (NFLGAS). Low-flow low-gradient AS (LFLGAS) A multimodality imaging approach is essential to accurately
poses a challenge due to the discrepancy between reduced assess LFLGAS, as various imaging modalities provide
AVA and a non-severe increase in the transvalvular mean complementary information regarding aortic valve
pressure gradient, which is frequently accompanied with morphology, function, and associated cardiac abnormalities.
impaired stroke volume at rest. This subset of patients Transthoracic echocardiography (TTE) remains the initial
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exhibits a high-risk profile for SAVR. The management imaging modality of choice, providing critical information
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of LFLGAS is complex because the discrepancy between on aortic valve morphology, peak velocity, mean pressure
the AVA and pressure gradient raises concerns about the gradient, and AVA using the continuity equation 13,14 (Table 1).
severity of stenosis and the need for intervention. In this 3.1. TTE
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review, we aim to discuss the management of LFLGAS,
including diagnostic modalities, the efficacy of TAVR, and TTE provides critical data regarding aortic valve
procedural considerations and complications to be aware morphology, left ventricular (LV) function, and
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of in this subset of patients with severe AS. hemodynamics. Various phenotypes of LGAS were
determined based on the ejection fraction (EF; ≤ or >50%)
2. Epidemiology and risk stratification and stroke volume index (SVI; < or ≥35 mL/m ). cLFLGAS
2
Approximately 40% of patients with an AVA of ≤1.0 cm² is characterized by an EF ≤50%, mean gradient <40 mmHg,
2
exhibit a discordantly low mean gradient. Similar to those and SVI <35 mL/m . Patients with pLFLGAS also exhibit a
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with high-gradient severe AS, patients with LFLGAS may low gradient and low SVI but with a preserved EF. Patients
be asymptomatic or may exhibit typical symptoms such with NFLGAS exhibit a low gradient of <40 mmHg,
2
as shortness of breath and/or heart failure, pre-syncope but with a preserved SVI of ≥35 mL/m . The accurate
and/or syncope, and angina, as was first described in Ross assessment of AVA using TTE in patients with LFLGAS
and Braunwald’s seminal work in 1968. Furthermore, poses challenges due to difficulties in achieving optimal
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patients with LFLGAS, similar to those with HGAS, imaging quality, precisely measuring Doppler velocities
exhibit poor outcomes, with a 3-year survival rate of across the valve, and ensuring reliable calculations of
<50% with medical treatment. In fact, cLFLGAS and AVA, particularly in the presence of concomitant LV
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13
pLFLGAS have frequently been linked to worse outcomes dysfunction or discordant hemodynamic parameters.
than HGAS, which further gives credence to the idea that To ensure optimal measurements, it is important to use
the treatment approach should be at least as aggressive. multiple views to evaluate the aortic valve, ensure accurate
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In a meta-analysis conducted by Ueyama et al., aortic alignment of the continuous wave Doppler probe in the
valve replacement (AVR) was associated with a significant direction of the aortic jet to obtain the highest peak and
decrement in all-cause mortality in all types of LFLGAS, mean gradients, obtain meticulous tracings of the velocity
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irrespective of TAVR or SAVR. A plethora of risk scores time integrals of the aortic valve and LV outflow tract
have been developed to assist in the stratification of the (LVOT), and incorporate these measurements with a non-
patient’s operative risk. The American college of cardiology quantitative, visual assessment of the aortic valve anatomy,
(ACC)/American heart association (AHA) valvular heart calcification, and opening. 15
disease guidelines reference the use of the Society of 3.2. Stress echocardiography
Thoracic Surgeons (STS) risk score and Euroscore II,
both originally derived for SAVR, and the ACC’s TAVR Dobutamine stress echocardiography (DSE), has been
in-hospital mortality risk score. Various other TAVR- utilized to assess AS severity and operative risk in patients
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specific scores have been recently developed, including the with LFLGAS and impaired LV function. DSE is a useful
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German AV score I and II, EuroSCORE I, CAPRI, STT, modality for identifying patients with pseudo-severe AS
TARIS, transcatheter aortic valve implantation-2 (TAVI-2), induced by limited valve opening due to the low-flow
2
TRIM, CoreValve US, ACC TAVI, STS-PROM, UK TAVI, state. An increase in the AVA to over 1.0 cm and a 20%
NIS TAVR, OCEAN, FTS< TAVI Futility risk model 1 increase in the stroke volume indicate pseudo-severe
and 2, TARI, J-TVT, UNN/OUS, Logistic EuroScore, AS. The dobutamine challenge has been recognized as a
Charleston comorbidity index, frailty index, KCMH TAVI, valuable method for selecting patients who would benefit
Relief TAVI, GNRI, ERS, OBSERVANT score, IRRMA from valve replacement and for providing prognostic
score, and FRANCE‐2, though related external validation information on operative risks and long-term outcomes in
and comparative studies are limited. 12 patients with cLFLGAS. Both the American and European
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Volume 3 Issue 1 (2025) 2 doi: 10.36922/bh.4017