What is the role of echocardiography in the preoperative assessment of aortic stenosis (AS) in noncardiac surgery patients?

Updated: Jul 16, 2021
  • Author: Lindsay A (Finger) Raleigh, MD; Chief Editor: Sheela Pai Cole, MD  more...
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Answer

Answer

Although the physical examination can help detect the presence of aortic pathology, determining the severity of such pathology requires further investigation with echocardiography or cardiac catheterization. Because of its noninvasive approach, its good safety profile, and its ability to obtain diagnostic images in nearly all patients, echocardiography is the most commonly used means of diagnosing and quantifying aortic valve pathology.

On transthoracic echocardiography (TTE) or transesophageal echocardiography (TEE), the severity of AS can be assessed by using Doppler measurements of Vmax, mean pressure gradient, and estimated AVA as determined by the continuity equation. During cardiac catheterization, transaortic pressures are directly measured, and AVAs are derived by using Gorlin’s equation. (See Table 2 below.)

Table 2. Classification of Aortic Stenosis Severity (Open Table in a new window)

Parameter Mild Moderate Severe
Vmax (m/s) 2.6-2.9 3.0-3.9 ≥4.0
Mean pressure gradient (mm Hg) < 20 20-39 ≥40
AVA (cm2) >1.5 1.1-1.5 ≤1
AVA indexed to BSA (cm2/m2) >0.85 0.61-0.85 ≤0.6
Velocity ratio (LVOT TVI/AV TVI) >0.5 0.26-0.5 ≤0.25
AV = aortic valve; AVA = aortic valve area; BSA = body surface area; LVOT = left ventricular outflow tract; TVI = time-velocity integral; Vmax = maximum aortic jet velocity.

Hemodynamically, severe AS is defined as follows:

  • Vmax of 4.0 m/s or greater
  • Mean transvalvular pressure gradient of 40 mm Hg or greater
  • AVA of 1.0 cm 2 or less, or AVA indexed for body surface area (BSA) of 0.6 cm 2/m 2 or less (as estimated by the continuity equation)

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