In an elderly patient with low‑flow, low‑gradient aortic stenosis and ascites, whose computed tomography shows a possible omental metastasis, what is the appropriate next diagnostic and management step?

Diagnostic Workup for Possible Omental Metastasis in Low-Flow, Low-Gradient Aortic Stenosis

The immediate priority is tissue diagnosis of the omental lesion through paracentesis with cytology or image-guided biopsy, as malignancy fundamentally changes both prognosis and the risk-benefit calculation for aortic valve intervention. 1

Initial Diagnostic Steps

Confirm Aortic Stenosis Severity First

Before addressing the omental finding, you must definitively establish whether the aortic stenosis is truly severe, as this determines all subsequent management:

• Obtain CT aortic valve calcium scoring immediately as the primary confirmatory test in this elderly patient with paradoxical low-flow, low-gradient AS (preserved LVEF ≥50%, stroke volume index <35 mL/m², mean gradient <40 mmHg). 2, 3

• Severe AS is confirmed if calcium score is ≥3000 Agatston units (men) or ≥1600 units (women); scores ≥2000 (men) or ≥1200 (women) make it likely. 2, 3

• Remeasure LVOT diameter at the annulus or within 2mm below it using 3D TEE or cardiac CT, as 2D echo systematically underestimates this in small hypertrophied ventricles, leading to overestimation of stenosis severity. 2, 3

• Calculate the dimensionless index (ratio of LVOT velocity to aortic velocity), which is less affected by flow state and helps confirm severity. 2

Characterize the Omental Lesion

• Perform paracentesis with ascitic fluid cytology as the least invasive method to establish malignancy if ascites is present. 1, 4

• Evaluate MRI characteristics if already obtained or obtain dedicated abdominal MRI to differentiate malignant from benign omental thickening:

  • Malignant features: hyperintensity on high b-value DWI (88% sensitivity), hyperenhancement (75% sensitivity), convex outer omental contour (75-88% sensitivity), and discrete nodules. 1
  • Benign features (portal hypertension-related): vessels coursing through omentum, splenomegaly, mesenteric edema. 1

• Consider image-guided biopsy of the omental mass if cytology is negative or ascites is absent, as tissue diagnosis is essential. 4

Risk Stratification Based on Findings

If Malignancy is Confirmed

• Identify the primary tumor through:

  • PSA level and prostate examination (omental metastasis from prostate cancer is rare but reported). 5, 4
  • Age-appropriate cancer screening (ovarian, gastric, pancreatic, colon in order of likelihood for omental metastasis).
  • Tumor markers (CA-125, CEA, CA 19-9).

• Reassess life expectancy, as metastatic cancer with ascites typically indicates advanced disease with limited prognosis (4 months median survival in reported prostate cancer cases). 4

• Reconsider valve intervention candidacy:

  • If life expectancy is <1 year from malignancy, aortic valve replacement is not indicated regardless of AS severity, as the patient will not survive long enough to benefit. 6
  • If potentially treatable malignancy with reasonable prognosis (e.g., hormone-responsive prostate cancer), defer valve intervention until cancer treatment response is established. 5

If Benign Omental Thickening (Portal Hypertension)

• Evaluate for cirrhosis and portal hypertension as the cause of both ascites and omental changes. 1

• Assess surgical risk using Model for End-Stage Liver Disease (MELD) score, as cirrhosis significantly increases perioperative mortality for both SAVR and TAVR.

• Consider TAVR over SAVR if valve intervention is indicated, given lower procedural stress in patients with hepatic dysfunction. 6

Management Algorithm for Confirmed Severe AS

If Symptomatic (Stage D2/D3)

• Aortic valve replacement is indicated (Class IIa) only after careful confirmation that AS is severe AND malignancy is excluded or has favorable prognosis. 2, 3

• TAVR is preferred over SAVR in elderly patients with low-flow states, especially when contractile reserve is absent, as outcomes are superior. 3

• Defer intervention if metastatic cancer is confirmed with poor prognosis, focusing on medical management and palliative care. 6

If Asymptomatic

• Conservative management with close surveillance every 3-6 months is recommended, as deterioration can be rapid in paradoxical low-flow AS. 2, 3

• Consider early intervention (Class IIa) if:

  • Stroke volume index <30 mL/m² (independent predictor of mortality, adjusted HR 1.60). 2, 3
  • Markedly elevated BNP without other explanation. 2, 3
  • Peak velocity ≥5.0 m/s. 3

Critical Pitfalls to Avoid

• Do not dismiss low gradients (30-40 mmHg) as "moderate" stenosis in low-flow states, as gradients underestimate anatomic severity when flow across the valve is reduced. 2, 3

• Do not proceed with valve intervention without tissue diagnosis of the omental lesion, as occult malignancy is a contraindication that fundamentally changes management. 1, 4

• Do not perform dobutamine stress echo in paradoxical low-flow AS with marked hypertrophy and small cavity, as it may be hazardous; use CT calcium scoring instead. 3

• Do not rely solely on 2D echo AVA calculations, as LVOT measurement errors are extremely common in this population and lead to overestimation of stenosis severity. 2, 3