Paradoxical low-flow, low-gradient aortic stenosis in an older woman — case discussion

Presentation

Practice case (not a real patient). A 78-year-old woman in a regional Australian town is referred with breathlessness on walking uphill and a systolic murmur. Her TTE report reads: calcified trileaflet aortic valve, AVA 0.75 cm² (indexed 0.48 cm²/m²), Vmax 3.5 m/s, mean gradient 31 mm Hg, stroke volume index 29 mL/m², LVEF 64%, small LV cavity with increased relative wall thickness.^[2] Her blood pressure at the scan was 164/86 mm Hg and her heart rate 58/min.

Step 1 — Name the pattern

ESC/EACTS 2025 would call this low-flow, low-gradient AS with preserved LVEF: mean gradient <40 mmHg, AVA ≤1 cm², SVi ≤35 mL/m² and LVEF ≥50%.^[1] ACC/AHA 2020 Table 13 (Stages of AS) calls Stage D3 symptomatic severe low-gradient AS with normal LVEF or paradoxical low-flow severe AS.^[2] The D3 haemodynamic cell reads AVA ≤1.0 cm² (indexed AVA ≤0.6 cm²/m²) with an aortic Vmax <4 m/s or mean ΔP <40 mm Hg AND stroke volume index <35 mL/m², measured when the patient is normotensive (systolic blood pressure <140 mm Hg).^[2] Her systolic pressure was 164 mm Hg, so the D3 measurement condition is not yet met.^[2]

Step 2 — Fix the conditions of measurement

ACC/AHA 2020 recommends optimisation of blood pressure control before measurement of AS severity in suspected low-flow, low-gradient severe AS with normal LVEF (Stage D3) (COR 1, LOE B-NR).^[3] The legend of ESC/EACTS 2025 Figure 6 (integrative imaging assessment of patients with aortic stenosis) says to check for bradycardia or uncontrolled hypertension, which may lead to prolonged ejection time and reduced flow rate.^[1] Her GP adjusts her antihypertensives. Repeat TTE at a systolic pressure of 128 mm Hg gives the same AVA, Vmax 3.6 m/s, mean gradient 33 mm Hg and SVi 30 mL/m².

Step 3 — Is it really severe?

ESC/EACTS 2025 Recommendation Table 4 gives recommendations on indications for intervention in symptomatic and asymptomatic severe aortic stenosis, and the recommended mode of intervention.^[1] Its footnote c says explanations such as measurement errors, uncontrolled blood pressure and conditions lowering stroke volume, other than severe AS, for a small AVA but low gradient despite preserved LVEF are frequent and must be carefully excluded.^[1] Separately, note a of the Figure 6 legend quoted in Step 2 says: in particular, verify LVOT diameter and multiwindow Doppler interrogation; both are rechecked.^[1] ACC/AHA 2020 calls measurement of the aortic valve calcium score by CT reasonable to further define severity in suspected low-flow, low-gradient severe AS with normal or reduced LVEF (Stages D2 and D3) (COR 2a, LOE B-NR).^[3] ESC/EACTS 2025 says CCT should be performed to quantify the calcium score in women with discordant echocardiographic parameters.^[1] Her score is 1650 Agatston units.

The score exceeds the ESC/EACTS 2025 value of >1200 AU in women, which indicates severe AS with high sensitivity and specificity (∼85%).^[1] The score is also above the ESC/EACTS 2025 higher threshold for women (>1600 AU), which is very specific.^[1] The score exceeds the ACC/AHA 2020 threshold of 1300 for women.^[3] ESC/EACTS 2025 says the pathophysiology of AS seems to differ according to sex, with women having less calcium and more fibrosis, and that paradoxical low-flow, low-gradient constellations are frequent and may contribute to the underdiagnosis of severe AS in women.^[1]

Step 4 — What the grade triggers

With symptomatic low-flow (SVi ≤35 mL/m²), low-gradient (<40 mmHg) AS, normal LVEF (≥50%) and severe AS now carefully confirmed, the ESC/EACTS 2025 row applies: intervention should be considered (Class IIa, Level B).^[1] In its section on symptomatic severe AS, ESC/EACTS 2025 says outcomes are improved with intervention (either TAVI or SAVR) compared with medical treatment alone in patients with low-flow, low-gradient AS and preserved LVEF.^[1] The choice between TAVI and SAVR is covered in the AS treatment topic.

Learning points

• ESC/EACTS 2025 says AS may be further categorised by flow state based on SVi when echocardiographic parameters are discordant; 35 mL/m² is conventionally accepted to discern low from normal flow, although sex-specific thresholds have been proposed.^[1]
• ACC/AHA 2020 Stage D3 is measured when the patient is normotensive (systolic blood pressure <140 mm Hg), and in suspected low-flow, low-gradient severe AS with normal LVEF, optimisation of blood pressure control before measurement of AS severity is recommended (COR 1, LOE B-NR).^[2][3]
• Calcium thresholds differ by body: ESC/EACTS 2025 >1200 AU in women (>2000 AU in men), which indicates severe AS with high sensitivity and specificity (∼85%); ACC/AHA 2020 1300 in women (2000 in men).^[1][3]
• ESC/EACTS 2025 says intervention should be considered in symptomatic low-flow, low-gradient AS with normal LVEF after careful confirmation that AS is severe (Class IIa, Level B).^[1]