Severe MR and effective forward flow
64-year-old female, tibial osteotomy. LVEF 64% — preserved — but EROA 0.42 cm² and RF 52% meet both quantitative thresholds for severe MR.
Clinical scenario
64-year-old female, scheduled for high tibial osteotomy for knee osteoarthritis. Prior records noted 'mild MR' on a screening echo years ago, details unavailable. Preoperative TTE obtained.
Key TTE findings
LVEF 64% (preserved), EROA 0.42 cm² (threshold < 0.40 cm²), regurgitant fraction (RF) 52% (threshold < 50%), LAVI 42 mL/m² (elevated), CO and LVOT VTI not measured, TAPSE 2.2 cm (normal).
How the tool reads this
Mitral regurgitation: Severe criteria met (EROA ≥ 0.40 and RF ≥ 50%). LV systolic reserve: Not fully evaluated (CO and LVOT VTI not measured). Filling pressure: Possible (LAVI > 34).
Why a preserved EF can hide reduced forward output in severe MR
In mitral regurgitation, the left ventricle ejects blood in two directions — forward through the aortic valve into the systemic circulation, and backward into the left atrium. LVEF measures the total ejection, so it includes the regurgitant volume. With RF of 52%, roughly half of each stroke volume is going backward rather than forward. LVEF can look normal or even elevated while effective forward output is substantially reduced.
In this case, CO and LVOT VTI were not measured, so the tool flags LV systolic reserve as not fully evaluated. This is the appropriate response — without those measurements, forward output cannot be quantified. LAVI of 42 mL/m² suggests the left atrium has been exposed to chronic pressure and volume load, consistent with longstanding significant MR. The old 'mild MR' label was likely outdated.
Perioperative management in severe MR
Afterload reduction (vasodilation) tends to reduce regurgitant flow and improve forward output. Conversely, excessive vasoconstriction can increase regurgitant volume. Bradycardia prolongs LV filling time and can increase the regurgitant burden — maintain a normal to mildly elevated heart rate.
Teaching points
- When both quantitative criteria (EROA and RF) exceed threshold, severe MR is likely — not just 'significant'
- LVEF overestimates effective forward output in severe MR — it includes the regurgitant volume
- Measuring CO or LVOT VTI alongside LVEF gives a more accurate picture of what actually reaches the systemic circulation
What to watch in the OR
- Avoid abrupt afterload increases — this can worsen regurgitant volume and reduce effective forward flow
- Maintain heart rate in the normal to slightly elevated range — bradycardia increases regurgitant burden in MR
- Watch for signs of pulmonary congestion postoperatively — elevated LAVI indicates a background of chronic pressure load