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      Comparison between cardiovascular magnetic resonance and transthoracic doppler echocardiography for the estimation of effective orifice area in aortic stenosis

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          Abstract

          Background

          The effective orifice area (EOA) estimated by transthoracic Doppler echocardiography (TTE) via the continuity equation is commonly used to determine the severity of aortic stenosis (AS). However, there are often discrepancies between TTE-derived EOA and invasive indices of stenosis, thus raising uncertainty about actual definite severity. Cardiovascular magnetic resonance (CMR) has emerged as an alternative method for non-invasive estimation of valve EOA. The objective of this study was to assess the concordance between TTE and CMR for the estimation of valve EOA.

          Methods and results

          31 patients with mild to severe AS (EOA range: 0.72 to 1.73 cm 2) and seven (7) healthy control subjects with normal transvalvular flow rate underwent TTE and velocity-encoded CMR. Valve EOA was calculated by the continuity equation. CMR revealed that the left ventricular outflow tract (LVOT) cross-section is typically oval and not circular. As a consequence, TTE underestimated the LVOT cross-sectional area (A LVOT, 3.84 ± 0.80 cm 2) compared to CMR (4.78 ± 1.05 cm 2). On the other hand, TTE overestimated the LVOT velocity-time integral (VTI LVOT: 21 ± 4 vs. 15 ± 4 cm). Good concordance was observed between TTE and CMR for estimation of aortic jet VTI (61 ± 22 vs. 57 ± 20 cm). Overall, there was a good correlation and concordance between TTE-derived and CMR-derived EOAs (1.53 ± 0.67 vs. 1.59 ± 0.73 cm 2, r = 0.92, bias = 0.06 ± 0.29 cm 2). The intra- and inter- observer variability of TTE-derived EOA was 5 ± 5% and 9 ± 5%, respectively, compared to 2 ± 1% and 7 ± 5% for CMR-derived EOA.

          Conclusion

          Underestimation of A LVOT by TTE is compensated by overestimation of VTI LVOT, thereby resulting in a good concordance between TTE and CMR for estimation of aortic valve EOA. CMR was associated with less intra- and inter- observer measurement variability compared to TTE. CMR provides a non-invasive and reliable alternative to Doppler-echocardiography for the quantification of AS severity.

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          Guidelines on the management of valvular heart disease: The Task Force on the Management of Valvular Heart Disease of the European Society of Cardiology.

          Alec Vahanian, Helmut Baumgartner, Jeroen J. Bax … (2007)
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            Inconsistencies of echocardiographic criteria for the grading of aortic valve stenosis.

            Christa Gohlke-Bärwolf, Nikolaus Jander, Rolf-Peter Kienzle … (2008)
            The present study tests the consistency of echocardiographic criteria for the grading of aortic valve stenosis. Current guidelines/recommendations define severe stenosis as an aortic valve area (AVA) 40 mmHg, or peak flow velocity (Vmax) >4 m/s. We tested the consistency of the three criteria for the grading of aortic valve stenosis in 3483 echocardiography studies performed in 2427 patients with normal left ventricular (LV) systolic function and a calculated AVA of < or =2 cm2. We calculated curve fits for the relationship between AVA and DeltaPm using the Gorlin equation and between AVA and Vmax based on the continuity equation for our study population. An AVA of 1.0 cm2 correlated to a DeltaPm of 21 mmHg and a Vmax of 3.3 m/s. Conversely, a DeltaPm of 40 mmHg corresponds to an AVA of 0.75 cm2 and a Vmax of 4.0 m/s to an AVA of 0.82 cm2. Consequently, severe stenosis was diagnosed in 69% of patients based on AVA, 45% on Vmax, and 40% on DeltaPm. Stroke volume was lower in inconsistently graded patients (65 +/- 11 mL vs. consistently graded: 70 +/- 14 mL, P < 0.001). The criteria for the grading of aortic stenosis are inconsistent in patients with normal systolic LV function. On the basis of AVA, a higher proportion of patients is classified as having severe aortic valve stenosis compared with mean pressure gradient and peak flow velocity. Discrepant grading in these patients may be partly due to reduced stroke volume.
            Article 0 comments Cited 73 times – based on 0 reviews     Review now
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              Practical value of cardiac magnetic resonance imaging for clinical quantification of aortic valve stenosis: comparison with echocardiography.

              Shelton D Caruthers, S. Lin, Jennifer A Williams … (2003)
              Valvular pathology can be analyzed quickly and accurately through the use of Doppler ultrasound. For aortic stenosis, the continuity equation approach with Doppler velocity-time integral (VTI) data is by far the most commonly used clinical method of quantification. In view of the emerging popularity of cardiac magnetic resonance (CMR) as a routine clinical imaging tool, the purposes of this study were to define the reliability of velocity-encoded CMR as a routine method for quantifying stenotic aortic valve area, to compare this method with the accepted standard, and to evaluate its reproducibility. Patients (n=24) with aortic stenosis (ranging from 0.5 to 1.8 cm2) were imaged with CMR and echocardiography. Velocity-encoded CMR was used to obtain velocity information in the aorta and left ventricular outflow tract. From this flow data, pressure gradients were estimated by means of the modified Bernoulli equation, and VTIs were calculated to estimate aortic valve orifice dimensions by means of the continuity equation. The correlation coefficients between modalities for pressure gradients were r=0.83 for peak and r=0.87 for mean. The measurements of VTI correlated well, leading to an overall strong correlation between modalities for the estimation of valve dimension (r=0.83, by means of the identified best approach). For 5 patients, the CMR examination was repeated using the best approach. The repeat calculations of valve size correlated well (r=0.94). Velocity-encoded CMR can be used as a reliable, user-friendly tool to evaluate stenotic aortic valves. The measurements of pressure gradients, VTIs, and the valve dimension correlate well with the accepted standard of Doppler ultrasound.
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                Author and article information

                Journal
                Journal ID (nlm-ta): J Cardiovasc Magn Reson
                Title: Journal of Cardiovascular Magnetic Resonance
                Publisher: BioMed Central
                ISSN (Print): 1097-6647
                ISSN (Electronic): 1532-429X
                Publication date Collection: 2011
                Publication date (Electronic): 28 April 2011
                Volume: 13
                Issue: 1
                Page: 25
                Affiliations
                [1 ]Québec Heart and Lung Institute, Laval University, Québec, Canada
                [2 ]Laboratory of Cardiovascular Fluid Dynamics, Concordia University, Montréal, Canada
                Article
                Publisher ID: 1532-429X-13-25
                DOI: 10.1186/1532-429X-13-25
                PMC ID: 3108925
                PubMed ID: 21527021
                SO-VID: 9aef2f3f-08ae-4689-aa5c-7e8779e058d5
                Copyright © Copyright ©2011 Garcia et al; licensee BioMed Central Ltd.
                License:

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                Date received : 20 November 2010
                Date accepted : 28 April 2011
                Categories
                Subject: Research

                ScienceOpen disciplines: Cardiovascular Medicine
                Data availability:
                ScienceOpen disciplines: Cardiovascular Medicine

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