Can aortic stenosis reduce ejection fraction and lead to sodium and fluid retention?

Aortic Stenosis and Its Effects on Ejection Fraction and Fluid Status

Yes, aortic stenosis can reduce ejection fraction and lead to sodium retention with fluid overload, though the relationship is complex and depends on disease stage and left ventricular compensation.

Ejection Fraction in Aortic Stenosis

Initial Compensatory Phase

• In early severe aortic stenosis, ejection fraction typically remains preserved despite increased afterload, as the left ventricle develops concentric hypertrophy to maintain wall stress and contractility 1.
• Approximately 10% of patients with severe aortic stenosis do not develop increased LV dimensions, and 4% show no LV mass increase, yet many maintain normal systolic function initially 1.

Progressive Systolic Dysfunction

• As aortic stenosis progresses, ejection fraction eventually declines, particularly when myocardial fibrosis accumulates and the compensatory mechanisms fail 1.
• Lower ejection fraction predicts worse outcomes: patients with LVEF <50% have significantly higher 5-year mortality (41%) compared to those with LVEF ≥70% (22%) after aortic valve replacement 2.
• Even patients with LVEF 50-59% demonstrate increased mortality risk (HR 1.58) compared to those with LVEF ≥60%, independent of symptom status 2.

Paradoxical Findings

• Increased LV mass itself predicts systolic dysfunction and heart failure, regardless of stenosis severity 1.
• In patients with critical aortic stenosis, those without LV mass increase actually had better preserved ejection fraction and less heart failure compared to those with increased LV mass 1.

Fluid Retention and Sodium Overload

Mechanism of Fluid Accumulation

• Aortic stenosis causes elevated LV diastolic and left atrial pressures, directly leading to fluid retention through increased pulmonary capillary wedge pressure 1.
• The canonical symptoms of heart failure from aortic stenosis include shortness of breath, peripheral edema, and pulmonary edema 1.

Diastolic Dysfunction Contribution

• LV hypertrophy and myocardial fibrosis impair both active and passive relaxation, causing disturbed filling characteristics that elevate filling pressures and promote fluid retention 1.
• Progressive collagen accumulation between hypertrophied myocytes increases LV myocardial stiffness, directly contributing to elevated diastolic pressures 1.

Clinical Management of Fluid Overload

• Diuretics should be prescribed to all patients with aortic stenosis who have evidence of fluid retention or heart failure symptoms, as they relieve pulmonary and peripheral edema within hours to days 3.
• Loop diuretics must be used cautiously in patients with severe AS, LV hypertrophy, and small ventricular cavities to avoid excessive preload reduction in these preload-dependent ventricles 3.
• Diuretics should be started at low doses and gradually titrated upward with frequent monitoring of weight, blood pressure, renal function, and electrolytes 3.

Clinical Implications by Disease Stage

Moderate Aortic Stenosis with Reduced EF

• Moderate AS in patients with HFrEF is associated with increased rates of HF hospitalization and mortality (62.7% composite outcome vs 45.9% in those without AS) 4.
• These patients experience fewer days alive outside the hospital and have outcomes similar to those with severe AS 4.

Severe Aortic Stenosis with Low Flow, Low Gradient

• When LVEF is reduced (<50%) with low stroke volume index (<35 mL/m²) and mean gradient <40 mmHg, this represents true severe AS with decompensated LV function 1.
• This phenotype requires careful assessment with dobutamine stress echocardiography to distinguish true severe AS from pseudo-severe AS and to assess flow reserve 1.

Important Caveats

• Not all patients with severe AS develop reduced ejection fraction—the timing and extent of systolic dysfunction varies based on individual compensatory capacity, comorbidities (especially hypertension), and rate of stenosis progression 1.
• After transcatheter aortic valve intervention, despite significant afterload reduction and LV remodeling, systolic function may not improve and can even decrease in elderly patients with multiple comorbidities 5.
• The presence of fluid retention indicates advanced disease with elevated filling pressures, warranting consideration for valve replacement in addition to medical management 3, 6.