Quantification of aortic valve stenosis in MRI—comparison of steady-state free precession and fast low-angle shot sequences

Abstract

We compared two different magnetic resonance (MR) sequences [steady-state free precession (SSFP) and gradient echo fast low-angle shot (FLASH)] for the assessment of aortic valve areas in aortic stenosis using transesophageal echocardiography (TEE) as the standard of reference. Thirty-two patients with known aortic stenosis underwent MR (1.5 T) using a cine SSFP sequence and a cine FLASH sequence. Planimetry was performed in cross-sectional images and compared to the results of the TEE. In seven patients the grade of stenosis was additionally assessed by invasive cardiac catheterization (ICC). The mean aortic valve area measured by TEE was 0.97+/-0.19 mm(2), 1.00+/-0.25 mm(2) for SSFP and 1.25+/-0.23 mm(2) based on FLASH images. The mean difference between the valve areas assessed based on SSFP and TEE images was 0.15+/-0.13 cm(2) (FLASH vs TEE: 0.29+/-0.17 cm(2)). Bland-Altman analysis demonstrated that measurements using FLASH images overestimated the aortic valve area compared to TEE. Comparing ICC with MRI and TEE, only a weak to moderate correlation was found (ICC vs TEE: R=0.52, p=0.22; ICC vs SSFP: R=0.20, p=0.65; ICC vs FLASH: R=0.16, p=0.70). Measurements of the aortic valve area based on SSFP images correlate better with TEE compared to FLASH images.

Cardiovascular Magnetic Resonance Imaging for Valvular Heart Disease

“…A trend can be identified for CMR to underestimate the peak velocity, most likely because of partial volume averaging within the vena contracta (Table 2). [23][24][25][26][27][28][29][30][31] In patients with mitral stenosis, inflow velocities as assessed by Doppler echocardiography and CMR phasecontrast imaging correlate well (Table 3). 23,[32][33][34][35][36][37] If not stated in the publication, statistics were calculated from the data provided in the manuscript.…”

Accurate Assessment of Aortic Stenosis

“…Despite these limitations, multiple studies have sought to investigate the use of MRI for measuring the EOA, by using MRI data in combination with either the continuity or modified forms of the Gorlin equation to calculate EOA. [70][71][72][73][74][75] Studies have also attempted to directly measure the vena contracta of the peak systolic jet in AS patients by calculating the width of the jet with the use of velocity data. This direct measurement does not rely on any assumptions that may be necessary while calculating EOA from catheterization or echocardiography.…”

“…Multiple studies have measured GOA by direct visualization of the valvular orifice with the use of echocardiography, CT, or MRI. 73,[85][86][87][88] However, planimetry may be inaccurate when valve calcification causes shadows or reverberations limiting identification of the orifice. Caution is needed to ensure that the minimal orifice area is identified rather than a larger apparent area proximal to the cusp tips.…”

“…Přes tyto limitace se řada studií snažila hodnotit použití MR při měření EOA kombinováním údajů z MR buď s kontinuitou nebo modifi kovanými formami Gorlinovy rovnice pro výpočet EOA. [70][71][72][73][74][75] Autoři studií se rovněž pokusili přímo měřit jet ve VC ve vrcholové fázi systoly u pacientů s AS vypočítá-váním šířky jetu pomocí údajů o rychlosti. Toto přímé měření není založeno na žádných předpokladech, které jsou nutné při vypočítávání EOA katetrizací nebo echokardiografi cky.…”

“…84 Planimetrie by mohla být přijatelnou alternativou v přípa-dech, kdy je dopplerovské stanovení rychlosti průtoku nespolehlivé. Řada studií stanovovala hodnotu GOA přímým zobrazením ústí chlopně pomocí echokardiografi e, CT, nebo MR. 73,[85][86][87][88] Planimetrie však může být nepřesná, pokud kalcifikace chlopně způsobuje stíny nebo odrazy omezující identifikaci ústí. Je třeba určit minimální plochu ústí spíše, než zdán-livě velkou plochu proximálně ke koncům cípů.…”