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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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Left ventricular outflow tract dimensions and cross-section area measurements by CMR. Left ventricular outflow tract (LVOT) cross-sectional (ALVOT; red solid line), anterior-posterior (AP) diameter (blue line), right-left (RL) diameter (blue line), and AP/RL diameter ratio for two different patients. The dashed red line represents the cross-sectional area of LVOT estimated on the basis of the AP diameter and assuming a circular LVOT shape. This estimation yielded values of LVOT cross-sectional area of 6.15 and 3.46 cm2 for these 2 patients compared to the actual area of 6.23 and 5.35 cm2, respectively.
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Figure 2: Left ventricular outflow tract dimensions and cross-section area measurements by CMR. Left ventricular outflow tract (LVOT) cross-sectional (ALVOT; red solid line), anterior-posterior (AP) diameter (blue line), right-left (RL) diameter (blue line), and AP/RL diameter ratio for two different patients. The dashed red line represents the cross-sectional area of LVOT estimated on the basis of the AP diameter and assuming a circular LVOT shape. This estimation yielded values of LVOT cross-sectional area of 6.15 and 3.46 cm2 for these 2 patients compared to the actual area of 6.23 and 5.35 cm2, respectively.

Mentions: CMR images acquisitions and analyses were performed by investigators blinded to clinical and TTE results. A custom-made research application was developed using Matlab software (Mathworks, Natick, Ma) to process and analyze velocity-encoded images [17]. Spatial resolution of CMR images was artificially improved by a factor of three using bicubic averaged interpolation and the magnitude image stack was processed to filter background noise. Regions of interest (ROIs) were defined on each of the 24 phases of magnitude images to include the lumen of the LVOT and of the aorta. The following measurements were performed within each ROI: i) on magnitude images: anterior-posterior (AP) diameter, left-right (LR) diameter, and cross-sectional area of LVOT at the -12 mm position; the ratio of AP/LR diameters was calculated to characterize the shape of LVOT (the lower the ratio the more oval the shape of LVOT) (Figure 2) and ii) on matched phase images: velocity profiles at -12 mm, +6 and +10 mm positions.


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)

Left ventricular outflow tract dimensions and cross-section area measurements by CMR. Left ventricular outflow tract (LVOT) cross-sectional (ALVOT; red solid line), anterior-posterior (AP) diameter (blue line), right-left (RL) diameter (blue line), and AP/RL diameter ratio for two different patients. The dashed red line represents the cross-sectional area of LVOT estimated on the basis of the AP diameter and assuming a circular LVOT shape. This estimation yielded values of LVOT cross-sectional area of 6.15 and 3.46 cm2 for these 2 patients compared to the actual area of 6.23 and 5.35 cm2, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: Left ventricular outflow tract dimensions and cross-section area measurements by CMR. Left ventricular outflow tract (LVOT) cross-sectional (ALVOT; red solid line), anterior-posterior (AP) diameter (blue line), right-left (RL) diameter (blue line), and AP/RL diameter ratio for two different patients. The dashed red line represents the cross-sectional area of LVOT estimated on the basis of the AP diameter and assuming a circular LVOT shape. This estimation yielded values of LVOT cross-sectional area of 6.15 and 3.46 cm2 for these 2 patients compared to the actual area of 6.23 and 5.35 cm2, respectively.
Mentions: CMR images acquisitions and analyses were performed by investigators blinded to clinical and TTE results. A custom-made research application was developed using Matlab software (Mathworks, Natick, Ma) to process and analyze velocity-encoded images [17]. Spatial resolution of CMR images was artificially improved by a factor of three using bicubic averaged interpolation and the magnitude image stack was processed to filter background noise. Regions of interest (ROIs) were defined on each of the 24 phases of magnitude images to include the lumen of the LVOT and of the aorta. The following measurements were performed within each ROI: i) on magnitude images: anterior-posterior (AP) diameter, left-right (LR) diameter, and cross-sectional area of LVOT at the -12 mm position; the ratio of AP/LR diameters was calculated to characterize the shape of LVOT (the lower the ratio the more oval the shape of LVOT) (Figure 2) and ii) on matched phase images: velocity profiles at -12 mm, +6 and +10 mm positions.

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