Abstract
BackgroundTransthoracic echocardiography (TTE) is the diagnostic routine standard for assessing aortic stenosis (AS). However, its inaccuracies in determining stroke volume (SV) and aortic valve area (AVA) call for a more precise and dependable method. Phase-contrast cardiovascular magnetic resonance imaging (PC-CMR) is a promising tool to push these boundaries. Thus, the aim of this study was to validate a novel approach based on PC-CMR against the gold-standard of invasive determination of AVA in AS compared to TTE.MethodsA total of 50 patients with moderate or severe AS underwent TTE, cardiac catheterization and CMR. AVA via PC-CMR was determined by plotting momentary flow across the valve against flow-velocity. SV by CMR was measured directly via PC-CMR and volumetrically using cine-images. Invasive SV and AVA were determined via Fick-principle and Gorlin-formula, respectively. TTE yielded SV and AVA using continuity equation. Gradients were calculated via the modified Bernoulli-equation.ResultsSV by PC-CMR (85 ± 31 ml) correlated strongly (r: 0.73, p < 0.001) with cine-CMR (85 ± 19 ml) without significant bias (lower and upper limits of agreement (LLoA and ULoA): − 41 ml and 44 ml, p = 0.83). In PC-CMR, mean pressure gradient correlated significantly with invasive determination (r: 0.36, p = 0.011). Mean AVA, as determined by PC-CMR during systole (0.78 ± 0.25 cm2), correlated moderately (r: 0.54, p < 0.001) with invasive AVA (0.70 ± 0.23 cm2), resulting in a small bias of 0.08 cm2 (LLoA and ULoA: − 0.36 cm2 and 0.55 cm2, p = 0.017). Inter-methodically, AVA by TTE (0.81 ± 0.23 cm2) compared to invasive determination showed similar correlations (r: 0.58, p < 0.001 with a bias of 0.11 cm2, LLoA and ULoA: − 0.30 and 0.52, p < 0.001) to PC-CMR. Intra- and interobserver reproducibility were excellent for AVA (intraclass-correlation-coefficients of 0.939 and 0.827, respectively).ConclusionsOur novel approach using continuous determination of flow-volumes and velocities with PC-CMR enables simple AVA measurement with no bias to invasive assessment. This approach highlights non-invasive AS grading through CMR, especially when TTE findings are inconclusive.
Highlights
Transthoracic echocardiography (TTE) is the diagnostic routine standard for assessing aortic stenosis (AS)
Our novel approach using continuous determination of flow-volumes and velocities with PC-cardiovascular magnetic resonance imaging (CMR) enables simple aortic valve area (AVA) measurement with no bias to invasive assessment. This approach highlights non-invasive AS grading through CMR, especially when transthoracic echocardiography (TTE) findings are inconclusive
Full list of author information is available at the end of the article
Summary
Transthoracic echocardiography (TTE) is the diagnostic routine standard for assessing aortic stenosis (AS). Cardiac catheterization with invasive hemodynamic evaluation was historically the gold-standard for diagnosis of severe valvular heart disease [3], nowadays, due to the risks of invasive measurement and advances in noninvasive methods, transthoracic echocardiography (TTE) is considered the first-choice imaging modality to diagnose and classify AS [4]. In recent years, cardiovascular magnetic resonance imaging (CMR) has emerged to be a useful tool in characterizing valvular heart disease, and a good and reliable alternative to invasive techniques such as cardiac catheterization and transesophageal echocardiography (TEE) [5]. The aims of our study were, as follows: (1) to compare stroke volumes (SV) as determined by PC-CMR to the ‘gold-standard’ cine-CMR; (2) to determine pressure gradients across the aortic valve (AV) via PC-CMR; and (3) to validate a novel approach of determining AVA by comparing it to the ‘gold-standard’ cardiac catheterization (Fig. 1)
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