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Absent Contractile Reserve in Low-flow AS — EECC MCQ

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HardValvular Heart DiseaseAbsent Contractile Reserve in Low-flow ASEECC

A 60-year-old man with severe aortic stenosis undergoes low-dose dobutamine stress echocardiography for classical low-flow low-gradient AS (LVEF 28%, AVA 0.7 cm², mean gradient 20 mmHg). Despite dobutamine infusion up to 20 mcg/kg/min, his stroke volume increases by only 8% (below the 20% threshold). What does the absence of contractile reserve indicate?

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Correct answer: B — Absence of contractile reserve (stroke volume increase <20%) means true AS severity cannot be determined by DSE alone; CT aortic valve calcium scoring becomes the primary tool for severity assessment — AVR can still be beneficial if true severe AS is confirmed by CT calcium score

When dobutamine fails to augment stroke volume by ≥20%, contractile reserve is absent. This means: (1) true vs pseudo-severe AS cannot be differentiated by DSE (the valve cannot be assessed at higher flow); (2) CT aortic valve calcium scoring becomes essential — a calcium score in the 'severe AS' range (>2000 AU men, >1200 AU women) confirms true severe AS regardless of flow/gradient; (3) prognosis without intervention is poor (absent contractile reserve is associated with higher operative mortality AND higher medical mortality); (4) AVR can still be beneficial — the 2025 ESC VHD Guidelines recommend AVR (SAVR or TAVI depending on age/risk) when true severe AS is confirmed by CT calcium, even without contractile reserve, as the alternative (medical therapy) has worse outcomes. Decision should be individualised by the Heart Team.

Reference: ESC/EACTS (2025): VHD Guidelines