Application of the Proximal Isovelocity Surface Area Method for Estimation of the Effective Orifice Area in Aortic Stenosis

Abstract Purpose: Because existence of high flow velocity at the left ventricular outflow tract (LVOT) potentially causes an overestimation of effective orifice area (EOA) by continuity equation in aortic stenosis (AS), we tested the proximal isovelocity surface area (PISA) method as an alternative tool for AS.Methods: EOA was calculated using the continuity equation (EOACont) and PISA method (EOAPISA), respectively, in 114 patients with at least moderate AS. The geometric orifice area (GOA) was also measured in 51 patients who also underwent three-dimensional transesophageal echocardiography (TEE). Patients were divided into two groups according to the median LVOT flow velocity.Results: Feasibility of EOAPISA was 95% in the 114 patients. While there was a strong correlation between EOACont and EOAPISA, EOACont was greater than EOAPISA especially in patients with high LVOT velocity. In TOE cohort, both EOACont and EOAPISA similarly correlated with GOA. However, a fixed bias, which is supposed to exist in AS, was observed only between EOAPISA and GOA with smaller EOAPISA than GOA. The difference between EOACont and GOA was significantly greater with a larger EOACont relative to GOA in patients with high LVOT velocity than in those without (0.16±0.25 vs -0.07±0.10 cm2, P<0.001). In contrast, the difference between EOAPISA and GOA was consistent in both groups (-0.07±0.12 vs -0.07±0.15 cm2, P = 0.936). Conclusion: The PISA method was applied to estimate EOA of AS. EOAPISA could be an alternative parameter for AS severity grading in patients with high LVOT velocity in whom EOACont would overestimate the orifice area.

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Application of the proximal isovelocity surface area method for estimation of the effective orifice area in aortic stenosis

Heart and Vessels ◽

10.1007/s00380-021-01945-5 ◽

2021 ◽

Author(s):

Masahiro Nakabachi ◽

Hiroyuki Iwano ◽

Michito Murayama ◽

Hisao Nishino ◽

Shinobu Yokoyama ◽

...

Keyword(s):

Aortic Stenosis ◽

Surface Area ◽

Effective Orifice Area ◽

Orifice Area ◽

Area Method ◽

Proximal Isovelocity Surface Area

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Comparison of the effective orifice area of prosthetic mitral valves using two-dimensional versus three-dimensional transesophageal echocardiography

Journal of International Medical Research ◽

10.1177/0300060521997621 ◽

2021 ◽

Vol 49 (3) ◽

pp. 030006052199762

Author(s):

Lei Zhou ◽

Hai-yan Wei ◽

Ya-li Ge ◽

Zheng-nian Ding ◽

Hong-wei Shi

Keyword(s):

Transesophageal Echocardiography ◽

Continuity Equation ◽

Ventricular Outflow Tract ◽

Left Ventricular ◽

Effective Orifice Area ◽

Valve Prosthesis ◽

Two Dimensional ◽

Orifice Area ◽

Mitral Valves ◽

2D And 3D

Objective This study compared the continuity equation-based effective orifice area (EOA) of prosthetic mitral valves between two-dimensional (2D) and 3D transesophageal echocardiography (TEE). Methods Thirty-four patients without major aortic valve abnormalities underwent mitral valve replacement surgery. The EOAs of prosthetic mitral valves were calculated using the continuity equation with 2D and 3D TEE. For 18/34 patients using a biological valve prosthesis, the EOA of the prosthesis was obtained from commercial records. Results The EOA of prosthetic mitral valves significantly varied between the 2D and 3D methods (2.22 ± 0.71 vs 2.35 ± 0.70 cm2, n = 34). The area of the diameter of the left ventricular outflow tract as determined by the 3D method was significantly higher than that by the 2D method (mean difference: −0.14 ± 0.20 cm2), with 95% coherence boundaries of −0.53 and 0.25 cm2. The regression equation for the EOA by 3D and 2D TEE was y = 0.27 + 0.94x, with a good correlation. Conclusions The EOA of prosthetic mitral valves is underestimated using the 2D TEE method compared with the 3D TEE method. The 3D-TEE method has the advantage of higher precision over the 2D TEE method, and it may be helpful for better assessment of prosthetic mitral valves intraoperatively.

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Impact of left ventricular outflow tract flow acceleration on aortic valve area calculation in patients with aortic stenosis

Echo Research and Practice ◽

10.1530/erp-19-0017 ◽

2019 ◽

Vol 6 (4) ◽

pp. 97-103 ◽

Cited By ~ 1

Author(s):

Andaleeb A Ahmed ◽

Robina Matyal ◽

Feroze Mahmood ◽

Ruby Feng ◽

Graham B Berry ◽

...

Keyword(s):

Aortic Valve ◽

Aortic Stenosis ◽

Continuity Equation ◽

Ventricular Outflow Tract ◽

Left Ventricular ◽

Area Measurement ◽

Aortic Valve Area ◽

Flow Acceleration ◽

The Impact ◽

Valve Area

Objective Due to its circular shape, the area of the proximal left ventricular tract (PLVOT) adjacent to aortic valve can be derived from a single linear diameter. This is also the location of flow acceleration (FA) during systole, and pulse wave Doppler (PWD) sample volume in the PLVOT can lead to overestimation of velocity (V1) and the aortic valve area (AVA). Therefore, it is recommended to derive V1 from a region of laminar flow in the elliptical shaped distal LVOT (away from the annulus). Besides being inconsistent with the assumptions of continuity equation (CE), spatial difference in the location of flow and area measurement can result in inaccurate AVA calculation. We evaluated the impact of FA in the PLVOT on the accuracy of AVA by continuity equation (CE) in patients with aortic stenosis (AS). Methods CE-based AVA calculations were performed in patients with AS once with PWD-derived velocity time integral (VTI) in the distal LVOT (VTILVOT) and then in the PLVOT to obtain a FA velocity profile (FA-VTILVOT) for each patient. A paired sample t-test (P < 0.05) was conducted to compare the impact of FA-VTILVOT and VTILVOT on the calculation of AVA. Result There were 46 patients in the study. There was a 30.3% increase in the peak FA-VTILVOT as compared to the peak VTILVOT and AVA obtained by FA-VTILVOT was 29.1% higher than obtained by VTILVOT. Conclusion Accuracy of AVA can be significantly impacted by FA in the PLVOT. LVOT area should be measured with 3D imaging in the distal LVOT.

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Abstract 12586: Assessing Valvuloarterial Impedance in Aortic Stenosis: A Comparison of Echocardiographic- and Cardiac Magnetic Resonance-derived Methods

Circulation ◽

10.1161/circ.142.suppl_3.12586 ◽

2020 ◽

Vol 142 (Suppl_3) ◽

Author(s):

Sara L Hungerford ◽

Audrey Adji ◽

Nicole K Bart ◽

Linda Lin ◽

Andrew Jabbour ◽

...

Keyword(s):

Cardiac Magnetic Resonance ◽

Magnetic Resonance ◽

Aortic Stenosis ◽

Flow Velocity ◽

Cuff Pressure ◽

Ventricular Outflow Tract ◽

Left Ventricular ◽

Applanation Tonometry ◽

Aortic Flow ◽

Entire Cross Section

Introduction: Valvuloarterial impedance (Z VA ) represents the valvular and arterial factors that oppose Left Ventricular (LV) ejection and is recognised as an important index to assess global LV load in patients with Aortic Stenosis (AS). Z VA is traditionally determined by Transthoracic Echocardiogram (TTE) and brachial cuff pressure. Hypothesis: Our study sought to compare Z VA-TTE with Z VA calculated using a simultaneous Cardiac Magnetic Resonance (CMR) and Applanation Tonometry (AT) (Z VA-CMR ) technique to determine whether TTE measurement of aortic flow velocity resulted in an underestimation of Z VA. Methods: Twenty AS patients underwent a protocol of CMR/AT followed by TTE. Z VA-CMR was determined as the relationship of derived aortic pressure (radial) to CMR aortic flow velocity in the frequency domain. Z VA-TTE was determined from digitised flow velocity within the left ventricular outflow tract (LVOT) on pulsed-wave Doppler and derived central pressure waveforms. Systemic vascular resistance (SVR) was calculated from mean pressure and flow. Values from both methods were compared. Results: Our study found that Z VA-TTE values (mean±SD, 638±381 dyne.s.cm -3 ) were consistently lower (p=0.07) than Z VA-CMR values (946±318 dyne.s.cm -3 ), and attribute this to an overestimation of LVOT flow velocity on TTE. SVR calculated by CMR/AT (2215±616 dyne.s.cm -5 ) was almost four times higher than TTE (618±245 dyne.s.cm -5 ) (p<0.001). This is due to more robust axi-symmetrical sampling of aortic flow across the entire cross-section of the ascending aorta (well above the stenotic jet) during CMR, than using operator-dependent TTE. Conclusions: Whilst Z VA -TTE is commonly performed in patients with AS to assess global LV load, newer methods to assess Z VA using simultaneous CMR/AT likely represent a more accurate non-invasive assessment.

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Abstract 18065: Combining Echo Doppler and CT Derived LVOT Measurements Improve Accuracy of Continuity Equation Based Aortic Valve Area Determination

Circulation ◽

10.1161/circ.130.suppl_2.18065 ◽

2014 ◽

Vol 130 (suppl_2) ◽

Author(s):

Sami Alnasser ◽

Asim Cheema ◽

Vamshi Kotha ◽

Djeven Deva ◽

Jeremy Edwards ◽

...

Keyword(s):

Aortic Valve ◽

Aortic Stenosis ◽

Correlation Coefficient ◽

Continuity Equation ◽

Severe Aortic Stenosis ◽

Ventricular Outflow Tract ◽

Left Ventricular ◽

Aortic Valve Area ◽

Left Ventricular Outflow ◽

Valve Area

Background: Left ventricular outflow tract (LVOT) measurement by Echo falsely assumes circular LVOT with implications for aortic valve area (AVA) determined using continuity equation. In this study, we investigated the utility of combining Echo Doppler and computed tomography (CT) based LVOT area for precise AVA assessment. Methods: AVA-echo was calculated using continuity equation and standard echocardiography techniques. CT-LVOT area was measured by 3 independent readers. Blinded measurements were obtained in candidates for percutaneous aortic valve replacement. AVA-CT was calculated using CT-LVOT area and echo Doppler measurements. The inter-observer variability for CT-LVOT area and correlation between AVA-echo and AVA-CT was analyzed using intra-class (ICC) and Spearman correlation coefficient. Results: Complete data for 66 patients was analyzed. The ICC for CT derived LVOT measurement by three observers was 0.96 demonstrating excellent reliability. The LVOT area by echo was significantly smaller than that obtained by CT (3.43±0.8 vs. 4.45±1.2 cm2, p<0.0001) and showing moderate correlation (r=0.66, p=0.006). Similarly, the AVA-echo was significantly lower compared to AVA-CT (0.76±0.46 vs. 0.97±0.53 cm2, p<0.0001). The correlation coefficient for AVA-echo and AVA-CT was 0.7 (p < 0.0001), 0.4 (p=0.06) and 0.9 (p<0.0001) for AVA-echo of 0.8 cm2 respectively. The regression analysis showed that AVA-CT could be predicted by applying a correction factor to the AVA-echo as AVA-CT = AVA-echo x 1.1+0.14. Conclusion: CT provides accurate and reliable LVOT assessment. Combining CT-LVOT and echo Doppler measurements result in a larger AVA compared to AVA-echo representing a true anatomic measurement. These findings have important implications for grading of aortic stenosis and management of patients with moderate to severe aortic stenosis.

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Aliased Flow Signal Planimetry by Cardiovascular Magnetic Resonance Imaging for Grading Aortic Stenosis Severity: A Prospective Pilot Study

Frontiers in Cardiovascular Medicine ◽

10.3389/fcvm.2021.752340 ◽

2021 ◽

Vol 8 ◽

Author(s):

Cesare Mantini ◽

Mohammed Y. Khanji ◽

Emilia D'Ugo ◽

Marzia Olivieri ◽

Cristiano Giovanni Caputi ◽

...

Keyword(s):

Cardiovascular Magnetic Resonance ◽

Magnetic Resonance ◽

Aortic Stenosis ◽

Phase Contrast ◽

Continuity Equation ◽

Intraclass Correlation ◽

Invasive Technique ◽

Effective Orifice Area ◽

Contrast Imaging ◽

Orifice Area

Objectives: Transthoracic echocardiography (TTE) is the standard technique for assessing aortic stenosis (AS), with effective orifice area (EOA) recommended for grading severity. EOA is operator-dependent, influenced by a number of pitfalls and requires multiple measurements introducing independent and random sources of error. We tested the diagnostic accuracy and precision of aliased orifice area planimetry (AOAcmr), a new, simple, non-invasive technique for grading of AS severity by low-VENC phase-contrast cardiovascular magnetic resonance (CMR) imaging.Methods: Twenty-two consecutive patients with mild, moderate, or severe AS and six age- and sex-matched healthy controls had TTE and CMR examinations on the same day. We performed analysis of agreement and correlation among (i) AOAcmr; (ii) geometric orifice area (GOAcmr) by direct CMR planimetry; (iii) EOAecho by TTE-continuity equation; and (iv) the “gold standard” multimodality EOA (EOAhybrid) obtained by substituting CMR LVOT area into Doppler continuity equation.Results: There was excellent pairwise positive linear correlation among AOAcmr, EOAhybrid, GOAcmr, and EOAecho (p < 0.001); AOAcmr had the highest correlation with EOAhybrid (R2 = 0.985, p < 0.001). There was good agreement between methods, with the lowest bias (0.019) for the comparison between AOAcmr and EOAhybrid. AOAcmr yielded excellent intra- and inter-rater reliability (intraclass correlation coefficient: 0.997 and 0.998, respectively).Conclusions: Aliased orifice area planimetry by 2D phase contrast imaging is a simple, reproducible, accurate “one-stop shop” CMR method for grading AS, potentially useful when echocardiographic severity assessment is inconclusive or discordant. Larger studies are warranted to confirm and validate these promising preliminary results.

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