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

Garcia J, Kadem L, Larose E, Clavel MA, Pibarot P - J Cardiovasc Magn Reson (2011)

Bottom Line: 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.Underestimation of ALVOT by TTE is compensated by overestimation of VTILVOT, 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Québec Heart and Lung Institute, Laval University, Québec, Canada.

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 cm2) 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 (ALVOT, 3.84 ± 0.80 cm2) compared to CMR (4.78 ± 1.05 cm2). On the other hand, TTE overestimated the LVOT velocity-time integral (VTILVOT: 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 cm2, r = 0.92, bias = 0.06 ± 0.29 cm2). 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 ALVOT by TTE is compensated by overestimation of VTILVOT, 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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Image planes used for CMR measurements. Panel A shows the flow velocity map was acquired at 3 image planes: -12 mm upstream from aortic valve plane (used as the 0 mm reference) and at +6 and +10 mm downstream of the aortic valve plane. The cross-sectional area of the LVOT is measured at the -12 mm position. Panel B shows the measurement of LVOT diameter at annulus location.
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Figure 1: Image planes used for CMR measurements. Panel A shows the flow velocity map was acquired at 3 image planes: -12 mm upstream from aortic valve plane (used as the 0 mm reference) and at +6 and +10 mm downstream of the aortic valve plane. The cross-sectional area of the LVOT is measured at the -12 mm position. Panel B shows the measurement of LVOT diameter at annulus location.

Mentions: CMR studies were performed 2 to 4 weeks after TTE with patients in comparable hemodynamic state. Imaging was performed with a 1.5 Tesla Philips Achieva scanner operating release 2.6 level 3 and dedicated phased-array cardiac coil during successive end-expiratory breath-holds (Philips Healthcare, Best, The Netherlands). Cine imaging of cardiac function was performed by steady-state free precession technique at 30 phases per cardiac cycle (by vectorcardiographic gating) in 8-14 parallel short-axis and 2-chamber, 4-chamber, and 2 orthogonal LVOT planes (8 mm thickness, 0 mm gap). Typical parameters included TR/TE of 3.4/1.2 ms, flip angle 40°, NEX of 1, yielding in-plane spatial resolution of 1.6 × 2 mm. In addition, through-plane phase-contrast (sQFlow SENSE) imaging was performed in the LVOT at 12 mm upstream from the aortic valve annulus (reference: 0 mm) and in the ascending aorta at +6 mm and +10 mm downstream of the annulus (Figure 1). CMR imaging parameters consisted of: TR/TE of 4.60-4.92/2.76-3.05 ms, flip angle 15°, 24 phases, pixel spacing 1.32-2.07 mm, slice thickness 10 mm and acquisition matrix of 256 × 208. Each phase-contrast velocity mapping acquisition produced 2 cine images: one magnitude image and one phase image. For each patient, peak aortic jet velocity measured by TTE was used to define CMR encoding velocity (CMR encoding velocity = (1.25 to 1.5) × peak jet velocity) to optimally define resolution.


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

Garcia J, Kadem L, Larose E, Clavel MA, Pibarot P - J Cardiovasc Magn Reson (2011)

Image planes used for CMR measurements. Panel A shows the flow velocity map was acquired at 3 image planes: -12 mm upstream from aortic valve plane (used as the 0 mm reference) and at +6 and +10 mm downstream of the aortic valve plane. The cross-sectional area of the LVOT is measured at the -12 mm position. Panel B shows the measurement of LVOT diameter at annulus location.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3108925&req=5

Figure 1: Image planes used for CMR measurements. Panel A shows the flow velocity map was acquired at 3 image planes: -12 mm upstream from aortic valve plane (used as the 0 mm reference) and at +6 and +10 mm downstream of the aortic valve plane. The cross-sectional area of the LVOT is measured at the -12 mm position. Panel B shows the measurement of LVOT diameter at annulus location.
Mentions: CMR studies were performed 2 to 4 weeks after TTE with patients in comparable hemodynamic state. Imaging was performed with a 1.5 Tesla Philips Achieva scanner operating release 2.6 level 3 and dedicated phased-array cardiac coil during successive end-expiratory breath-holds (Philips Healthcare, Best, The Netherlands). Cine imaging of cardiac function was performed by steady-state free precession technique at 30 phases per cardiac cycle (by vectorcardiographic gating) in 8-14 parallel short-axis and 2-chamber, 4-chamber, and 2 orthogonal LVOT planes (8 mm thickness, 0 mm gap). Typical parameters included TR/TE of 3.4/1.2 ms, flip angle 40°, NEX of 1, yielding in-plane spatial resolution of 1.6 × 2 mm. In addition, through-plane phase-contrast (sQFlow SENSE) imaging was performed in the LVOT at 12 mm upstream from the aortic valve annulus (reference: 0 mm) and in the ascending aorta at +6 mm and +10 mm downstream of the annulus (Figure 1). CMR imaging parameters consisted of: TR/TE of 4.60-4.92/2.76-3.05 ms, flip angle 15°, 24 phases, pixel spacing 1.32-2.07 mm, slice thickness 10 mm and acquisition matrix of 256 × 208. Each phase-contrast velocity mapping acquisition produced 2 cine images: one magnitude image and one phase image. For each patient, peak aortic jet velocity measured by TTE was used to define CMR encoding velocity (CMR encoding velocity = (1.25 to 1.5) × peak jet velocity) to optimally define resolution.

Bottom Line: 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.Underestimation of ALVOT by TTE is compensated by overestimation of VTILVOT, 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Québec Heart and Lung Institute, Laval University, Québec, Canada.

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 cm2) 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 (ALVOT, 3.84 ± 0.80 cm2) compared to CMR (4.78 ± 1.05 cm2). On the other hand, TTE overestimated the LVOT velocity-time integral (VTILVOT: 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 cm2, r = 0.92, bias = 0.06 ± 0.29 cm2). 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 ALVOT by TTE is compensated by overestimation of VTILVOT, 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.

Show MeSH
Related in: MedlinePlus