What is the significance of ejection fraction in patients with aortic stenosis and how is it managed?

Ejection Fraction in Aortic Stenosis: Significance and Management

Critical Threshold and Intervention Timing

Reduced ejection fraction (<50%) in severe aortic stenosis is a Class I indication for aortic valve replacement (AVR), regardless of symptoms, as it represents myocardial decompensation with significantly worse prognosis. 1, 2

However, the traditional 50% threshold may be too conservative:

• LVEF 50-59% already predicts increased mortality (hazard ratio 1.58) compared to LVEF ≥60%, even after AVR, in both symptomatic and asymptomatic patients 3
• LVEF decline begins before AS becomes severe and accelerates once aortic valve area falls below 1.2 cm² 4
• LVEF <60% in the presence of moderate AS predicts further deterioration and represents abnormal systolic function in the context of AS 4

Pathophysiology of EF Changes

The ejection fraction trajectory follows a predictable pattern 5:

• Early severe AS: EF typically remains preserved (>60%) despite increased afterload due to compensatory concentric hypertrophy 5
• Progressive stage: As myocardial fibrosis accumulates and compensatory mechanisms fail, EF declines 5
• Decompensated stage: Reduced EF reflects excessive afterload that improves after AVR, with typical increases of 10 ejection fraction units post-intervention 2

Flow-Gradient Patterns and Their Significance

Low-Flow Low-Gradient AS with Reduced EF (Stage D2)

This represents classical severe AS with decompensated LV function 1:

• Characteristics: AVA <1.0 cm², mean gradient <40 mmHg, LVEF <50%, stroke volume index <35 mL/m² 1
• Management: Requires dobutamine stress echocardiography to distinguish true severe AS from pseudo-severe AS and assess contractile reserve 1
• Prognosis: Poor outcomes with medical therapy but high surgical risk; however, patients with contractile reserve (>20% increase in stroke volume with dobutamine) have better outcomes with AVR than medical management 1

Paradoxical Low-Flow Low-Gradient AS with Preserved EF (Stage D3)

This challenging entity has preserved LVEF but reduced stroke volume 1:

• Characteristics: AVA <1.0 cm², mean gradient <40 mmHg, LVEF ≥50%, stroke volume index <35 mL/m² 1
• Mechanism: Pronounced LV concentric remodeling with small cavity and restrictive diastolic pattern 1
• Clinical outcome: Echocardiographic parameters and outcomes resemble classical severe AS more than moderate AS 6

Guideline-Based Management Algorithm

Symptomatic Severe AS

Immediate AVR is indicated (Class I, Level of Evidence B) 1, 2:

• High-gradient severe AS with any symptoms (dyspnea, heart failure, angina, syncope) 1
• Low-flow low-gradient AS with reduced LVEF (after confirming severity) 1

Asymptomatic Severe AS with Reduced EF

AVR is recommended when LVEF <50% (Class I, Level of Evidence C) 1:

• ESC/EACTS guidelines recommend intervention if LVEF <55% without another cause 1
• ACC/AHA guidelines use LVEF <60% threshold when declining over serial echocardiography 1

Moderate AS with Heart Failure

Consider AVR during concomitant cardiac surgery (Class IIa, Level of Evidence B) 1:

• The TAVR UNLOAD trial is investigating whether earlier intervention in moderate AS with reduced EF improves outcomes 7
• Current guidelines recommend surveillance until AS becomes severe, but this approach is being challenged 7

Medical Management Considerations

Fluid Retention Management

Diuretics should be prescribed for all patients with fluid retention or heart failure symptoms 5:

• Loop diuretics relieve pulmonary and peripheral edema within hours to days 5
• Critical caveat: Use cautiously in severe AS with LV hypertrophy and small ventricular cavities to avoid excessive preload reduction in these preload-dependent ventricles 5

Hypertension Management

Treat hypertension with gradual titration while awaiting AVR 1, 2:

• Target systolic BP 130-139 mmHg, diastolic BP 70-90 mmHg 1
• ACE inhibitors may be advantageous due to beneficial effects on LV fibrosis 2
• Start at low doses with frequent clinical monitoring 1, 2

Prognostic Implications

Every 10% decrease in LVEF independently predicts increased mortality (HR 0.88-0.90 per 10% increase), even after correcting for coronary artery disease, LV mass, and stroke volume 3:

• 5-year mortality: 41% for LVEF <50%, 35% for LVEF 50-59%, 26% for LVEF 60-69%, 22% for LVEF ≥70% 3
• This gradient persists in patients without coronary artery disease 3

Key Clinical Pitfalls

Do not wait for LVEF to fall below 50% before considering intervention 4, 3:

• LVEF 50-59% already represents compromised function with worse outcomes 3
• Consider earlier intervention when LVEF begins declining from baseline, especially if approaching 60% 4

Do not assume preserved LVEF means preserved systolic function 8:

• First phase ejection fraction (EF1 <25%) may detect early dysfunction before total EF declines 8
• Global longitudinal strain decreases progressively with AS severity even when EF is preserved 6

Do not dismiss low-gradient AS with preserved EF as non-severe 1, 6:

• Paradoxical low-flow low-gradient AS requires multimodality imaging confirmation but represents true severe disease 1