What is the severity of aortic stenosis in a patient with low cardiac output syndrome, heart failure with preserved ejection fraction (HFpEF), and iron deficiency, given echocardiographic measurements including an aortic valve area of 2.54 cm², peak velocity of 1.05 m/s, and mean gradient of 2 mmHg?

Severity Assessment in Low-Flow, Low-Gradient Aortic Stenosis with Preserved Ejection Fraction

This patient has paradoxical low-flow, low-gradient aortic stenosis (PLG-AS) with preserved ejection fraction, and the severity cannot be definitively determined from the provided measurements alone—you must obtain CT calcium scoring to distinguish true-severe from pseudo-severe stenosis. 1, 2, 3

Understanding the Discordant Measurements

Your patient presents with conflicting echocardiographic data that defines PLG-AS:

• Aortic valve area of 2.54 cm² suggests no stenosis (severe AS requires AVA <1.0 cm²) 1, 2
• Peak velocity of 1.05 m/s and mean gradient of 2 mmHg are far below severe thresholds (severe AS requires peak velocity ≥4.0 m/s or mean gradient ≥40 mmHg) 1, 2
• However, the calculated valve area index of 1 cm²/m² and stroke volume index <35 mL/m² indicate low-flow state 1, 2

The most likely explanation is measurement error, specifically underestimation of LVOT area, which is the single most common source of error in continuity equation calculations. 1, 2 The LVOT diameter of 1.8 cm appears reasonable, but the assumption of circular geometry systematically underestimates true LVOT area because the outflow tract is elliptical. 1

Critical Diagnostic Steps

1. Verify Measurement Accuracy First

Before proceeding with advanced imaging, you must:

• Remeasure LVOT diameter in mid-systole from inner edge to inner edge in parasternal long-axis view 1
• Ensure LVOT velocity is recorded from the apical approach with the sample volume positioned just proximal to the aortic valve, obtaining a laminar flow curve without spectral dispersion 1
• Record aortic jet velocity from multiple acoustic windows using a dedicated small dual-crystal continuous-wave Doppler transducer to ensure you capture the highest velocity 1, 2
• Measure blood pressure at the time of examination, as hypertension can alter peak velocity and mean gradient 2, 4

2. Assess for Alternative Explanations

Search for concomitant cardiac conditions that reduce stroke volume independent of AS severity: 5

• Significant mitral regurgitation (you note MV stenosis pressure half-time of 54 ms, which is normal and excludes mitral stenosis)
• Significant tricuspid regurgitation
• Intracardiac shunts
• Constrictive pericarditis

In patients with HFpEF and low cardiac output, the reduced flow may prevent adequate valve opening even when severe stenosis is not present. 1, 5

3. Consider Body Size

In petite patients, an AVA slightly less than 1.0 cm² may represent only moderate AS, which is why indexed AVA <0.6 cm²/m² is the more appropriate threshold. 2, 5 Your patient's indexed AVA of 1.0 cm²/m² does not meet criteria for severe stenosis.

Definitive Diagnostic Strategy

Because dobutamine stress echocardiography is less helpful in PLG-AS with preserved ejection fraction (unlike in reduced ejection fraction where it distinguishes true-severe from pseudo-severe AS), CT calcium scoring becomes your primary diagnostic tool. 1, 2, 3

CT Calcium Score Interpretation:

• ≥2000 Agatston units (men) or ≥1200 Agatston units (women): Severe AS likely 1, 2, 3
• ≥3000 Agatston units (men) or ≥1600 Agatston units (women): Severe AS very likely 1, 2, 3
• Low calcium scores exclude severe AS 3
• Intermediate scores remain diagnostically uncertain and require integration with clinical presentation, symptoms, valve morphology, and LV function 3

Clinical Context Integration

The presence of symptoms in PLG-AS is associated with significantly worse prognosis, but symptoms may relate to underlying HFpEF rather than AS severity itself. 6 Your patient has:

• Heart failure with preserved ejection fraction
• Low cardiac output syndrome
• Iron deficiency (which should be corrected as it worsens heart failure outcomes)

PLG-AS is associated with a unique maladaptive remodeling pattern: smaller ventricles, increasing relative wall thickness, progressive diastolic dysfunction, and higher afterload due to lower systemic arterial compliance and higher systemic vascular resistance. 5

Management Priorities

Control of hypertension is essential before determining AS severity, as elevated afterload reduces stroke volume and can create the appearance of more severe stenosis. 5 Optimize:

• Blood pressure control
• Volume status in HFpEF
• Iron deficiency correction
• Medical therapy for heart failure

Aortic valve replacement should only be considered if CT calcium scoring confirms severe AS and the patient remains symptomatic despite optimal medical management of hypertension and HFpEF. 5

Common Pitfalls to Avoid

• Do not rely on a single echocardiographic parameter when measurements are discordant 1
• Do not proceed to cardiac catheterization for AS severity assessment—it provides no additional information beyond high-quality Doppler echocardiography and CT calcium scoring 1, 7
• Do not assume symptoms are due to AS when HFpEF and low cardiac output are present 6
• Do not use the same LVOT diameter for serial measurements without verifying it remains accurate 1