Multi-Detector CT in the Classification of Echo-Doppler Low-Gradient Severe Aortic Stenosis | Journal Scan
Does the use of multi-detector computed tomography (MDCT) data for determination of left ventricular outflow tract (LVOT) area help in the classification of patients with echo-Doppler evidence of low-gradient aortic stenosis (AS) with normal LV ejection fraction (LVEF)?
A group of 191 patients (mean age 80 ± 7 years, 48% male) with effective orifice area index (EOAi) <0.6 cm2/m2 and LVEF ≥50% were further classified according to flow (stroke volume index [SVi] <35 or ≥35 ml/m2) and gradient (mean transaortic pressure gradient ≤40 or >40 mm Hg) into four groups: normal flow–high gradient (n = 72), low flow–high gradient (n = 31), normal flow–low gradient (n = 46), and low flow–low gradient (n = 42). LVOT area was measured by planimetry on MDCT and combined with Doppler hemodynamics using the continuity equation to obtain a ”fusion EOAi.”
The group of patients with normal flow–low gradient had significantly larger LVOT area index and EOAi compared with the other groups. Although MDCT-derived LVOT area index was comparable among the four groups, the “fusion EOAi” was significantly larger in the normal flow–low gradient group. By using the “fusion EOAi,” 52% (n = 24) of patients with normal flow–low gradient AS (mean LVOT area [echo] 3.4 ± 0.6 cm2 vs. LVOT [MDCT] 4.4 ± 0.8 cm2; mean EOAi [echo] 0.49 ± 0.06 cm2/m2 vs. “fusion EOAi” 0.62 ± 0.11 cm2/m2) and 12% (n = 5) of patients with low flow–low gradient (mean LVOT area [echo] 3.0 ± 0.7 cm2 vs. LVOT [MDCT] 4.3 ± 0.8 cm2; mean EOAi [echo] 0.34 ± 0.07 cm2/m2 vs. “fusion EOAi” 0.49 ± 0.11 cm2/m2) would have been reclassified into moderate AS due to EOAi ≥0.6 cm2/m2.
The authors concluded that a MDCT (for LVOT area) plus Doppler echo (for hemodynamics) “fusion EOAi” reclassifies 52% of normal flow–low gradient and 12% of low flow–low gradient severe AS patients into true moderate AS, based on MDCT assessment of a true cross-sectional LVOT area.
The echo-Doppler EOA from continuity equation is known to be limited by measurement reliability of the LVOT diameter, geometric assumptions regarding a circular cross-sectional shape of the LVOT, and assumptions regarding positioning the pulsed-wave Doppler sample volume relative to the LVOT diameter measurement. This study confirms other studies that demonstrate on MDCT a noncircular shape of the LVOT. The re-categorization of patients, though, was based on the investigated ‘fusion aortic valve area index’ being taken as a gold standard, without corroborating invasive hemodynamic assessment of aortic valve area.
Clinical Topics: Cardiac Surgery, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Valvular Heart Disease, Aortic Surgery, Cardiac Surgery and VHD, Interventions and Imaging, Interventions and Structural Heart Disease, Computed Tomography, Echocardiography/Ultrasound, Nuclear Imaging
Keywords: Aortic Valve, Aortic Valve Stenosis, Cardiac Surgical Procedures, Cross-Sectional Studies, Echocardiography, Doppler, Heart Valve Diseases, Heart Ventricles, Hemodynamics, Multidetector Computed Tomography, Stroke Volume, Tomography, Tomography, X-Ray Computed
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