Determination of Aortic Valve Area by Doppler Echocardiography Using the Continuity Equation: A Critical Evaluation

Baumgartner, Helmut; Krätzer, H; Helmreich, G; Kuehn, P

doi:10.1159/000174590

Cited by 81 publications

(45 citation statements)

References 7 publications

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“…Some authors recommend the same level for both velocity flow and area measurement [1]; according to others, the sampling site of the flow velocity measurement is of lesser significance. This is in accordance with the plug theory which claims that effective blood flow can be considerably smaller than the anatomical aortic root borders, because the flow out of the left ventricle is determined by the aortic orifice [13]. As many patients with chronic aortic regurgitation have gitation index with the invasively estimated regurgita tion fraction (r = 0.78).…”

Section: Discussionsupporting

confidence: 87%

“…Ihlen et al [8] and Tribouilloy et al [9] prefer the aortic ring, Taylor [10] and Wong et al [1] the left ventricular outflow tract near the aortic leaflet insertion, Gutgesell and French [11] 1 cm below and Reimold et al [ 12] above the aortic valve. Because of the oval shape of the left ventricular outflow tract the one-diame ter measurement is less accurate than the planimetrie or two-diameter measurements [13]. However, this method is time-consuming and not possible in pulmonary flow area calculation.…”

Section: Discussionmentioning

confidence: 99%

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Comparison of the Echo-Doppler- and Radionuclide Angiography- Derived Regurgitation Fraction in Isolated Chronic Aortic Regurgitation

Łastowiecka¹,

Rydlewska-Sadowska²,

Szumilak³

1994

Am J Noninvas Cardiol

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The regurgitation fraction (RF) despite dependence on many factors remains a valuable quantitative index in chronic aortic regurgitation (AR) assessment. In order to verify échocardiographie (Echo) estimation of this parameter a comparison with radionuclide ventriculography (RNY) values was done. 35 patients with chronic pure AR, 30 male, 5 female, mean age 35.5 ± 11.2 years (18-70 years) were examined. Echo RF was calculated according to the formula: RF = [(LVSY - RVSV)/LVSV] x 100, where LVSY and RVSV are the left and right ventricular stroke volumes; LVSV or RVSV = CSA x VFI, CSA = n (D/2)^2, where CSA = aortic or pulmonary cross-sectional area, D = aortic or pulmonary ring diameter, VFI = aortic or pulmonary velocity flow integral. On the following 0-22 days (mean 7 ± 5.12), gated equilibrium RNA with red blood cell-labelled 99mTc were done. All images were obtained with a small field of view Cardiac (Siemens) gamma camera with a Max Delta computer system. The study was done with a high-sensitivity colimator and contained 6 million counts (250 thousand/frame). RF calculation is based on the visual images of the end-systolic, enddiastolic counts and stroke volume of both ventricles. RNA RF was calculated according to the formula: RNA RF = [(LVEDc - LVESc) - (RVEDc - RVESc)/(LVEDc - LVESc)] x 100, where LVEDc, RVEDc, LVESc, RVESc are the left and right ventricular end diastolic and end systolic stroke counts. The mean Echo RF value was: 54.29 ± 12.44% (21-74%) and the meanRNVRF 52.06 ± 13.16% (17—80%). The correlation coefficient between the Echo and RNV RF was r = 0.68, p < 0.0001 (Pearson’s test). Excluding 9 patients with normal left ventricular internal diastolic dimension (LVIDD) (< 5.6 cm) increased the correlation coefficient up to r = 0.84, p < 0.0001. Using paired Student’s t test no significant difference between Echo and RNV RF was found. The mean difference of the RF values obtained with the two methods was -2.23 ± 10.17%. The highest discrepancy has occurred only in 4 patients with normal LVIDD (-30 to +25%).

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Section: Discussionsupporting

confidence: 87%

Section: Discussionmentioning

confidence: 99%

Comparison of the Echo-Doppler- and Radionuclide Angiography- Derived Regurgitation Fraction in Isolated Chronic Aortic Regurgitation

Łastowiecka¹,

Rydlewska-Sadowska²,

Szumilak³

1994

Am J Noninvas Cardiol

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“…This literature search revealed 14 studies comparing aortic valve areas determined noninvasively by the continuity equation with those determined invasivly using the Gorlin formula [2][3][4][5][6][7][8][9][10][11][12][13][14][15], Except for one study [5], they all show a valve area underestimation by the continuity equation, as expressed by their re gression line equations (table I). Taken to gether, these 14 studies reveal approximately the same 15% systematic underestimation of the valve area determined using the continu ity equation (VAc) compared to the valve area obtained by the Gorlin formula (VAgf)-This is shown by the summarized regression line equation:…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the Valve Area Underestimation by the Continuity Equation

Wippermann¹,

Schranz²,

Stopfkuchen³

et al. 1992

Cardiology

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During the last years, noninvasive determination of the aortic valve area by Doppler echocardiography using the continuity equation became popular. However, a systematic valve area underestimation of about 15 % compared to invasive measurements using the Gorlin formula has been reported. The cause therefore is unknown. The purpose of this study was to evaluate whether the valve area underestimation by the Doppler method might be due to differences in the hydrodynamic background of both methods. This comparison is facilitated by the fact that the Gorlin formula is based on the continuity equation. Compared to the continuity equation, there are four changes within the Gorlin formula: (1) the additional use of a discharge coefficient, which leads to valve area overestimation by the factor 1.17; (2) neglect of the prestenotic velocity, causing further overestimation by the factor 1.036 (in mild stenosis this factor may be 1.18 and more); (3) the wrong calculation of the mean pressure drop, which leads to a mean change by the factor 0.95, and (4) the incorrect substitution of the height by the pressure drop in the derivation of the Gorlin formula causes underestimation by the factor 0.97. Combining these four factors results in valve area overestimation of the Gorlin formula compared to the continuity equation by the factor 1.12. This explains to a large extent the valve area underestimation by the continuity equation.

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“…Echocardiography tends to underestimate the left ventricular outflow tract (LVOT) diameter, partly because of the tract's elliptical rather than circular anatomy. 25,33 Small errors in the measurement of LVOT diameter will result in substantial errors in calculating AVA, since the square of the radius is used in the continuity equation. Because this subgroup of patients has normal LVEF, it is presumed that these patients have normal cardiac output.…”

Section: Probable Mechanism Of Lgasmentioning

confidence: 99%

Natural Progression of Low-Gradient Severe Aortic Stenosis with Preserved Ejection Fraction

Innasimuthu¹,

Kumar²,

Lazar³

et al. 2014

Texas Heart Institute Journal

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Because the natural progression of low-gradient aortic stenosis (LGAS) has not been well defined, we performed a retrospective study of 116 consecutive patients with aortic stenosis who had undergone follow-up echocardiography at a median interval of 698 days (range, 371-1,020 d I n the western world, aortic stenosis (AS) is the most prevalent valvular heart disease and the 3rd most prevalent cardiovascular disease, after hypertension and coronary artery disease.1 The prevalence of AS increases with age, from 2% of adults older than 65 years to 4% of adults older than 85.2 As the average lifespan increases, the burden of senile AS is expected to increase. Aortic stenosis is a progressive condition in which patients are often asymptomatic for years. 3 The duration of the asymptomatic phase can vary widely among individuals. After the onset of symptomic heart failure, only 50% will survive longer than 2 years without valve replacement. 4 Although sudden cardiac death is a frequent cause of death in symptomatic patients, it appears to be rare (<1% per year) in asymptomatic patients. [5][6][7] Close monitoring and aortic valve replacement surgery (when patients become symptomatic) remain the standard of care. 8,9 Current American and European guidelines define severe AS as an aortic valve area (AVA) of <1 cm 2 or, indexed by body surface area, <0.6 cm 2 /m 2 . 8,10 The corresponding values are a peak aortic valve velocity of 4 m/s and a mean aortic valve pressure gradient (MG) of ≥40 mmHg in the presence of normal cardiac output-that is, normal left ventricular ejection fraction (LVEF). Moderate stenosis is characterized by an AVA of 1 to 1.5 cm 2 and an MG of 25 to 40 mmHg. However, not all patients fall into these specific categories of moderate or severe AS as determined by both AVA and MG. Approximately one third of patients sent for echocardiographic evaluation of the severity of AS show a discrepancy in echocardiographic measurements: severe stenosis on the basis of AVA, but non-severe stenosis on the basis of MG, in the presence of a normal LVEF. 11,12 These discrepancies were at first attributed to inaccuracies in echocardiographic measurements and to interobserver variability.In the past few years, increasing data have suggested that patients with normal LVEF in the presence of severe AS as defined by valve area (AVA, <1 cm 2 ) and low valve gradient (MG, <40 mmHg) form a true subgroup. These results appear not to be an anomaly arising from the misreading of echocardiographic measure-

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Determination of Aortic Valve Area by Doppler Echocardiography Using the Continuity Equation: A Critical Evaluation

Cited by 81 publications

References 7 publications

Comparison of the Echo-Doppler- and Radionuclide Angiography- Derived Regurgitation Fraction in Isolated Chronic Aortic Regurgitation

Comparison of the Echo-Doppler- and Radionuclide Angiography- Derived Regurgitation Fraction in Isolated Chronic Aortic Regurgitation

Evaluation of the Valve Area Underestimation by the Continuity Equation

Natural Progression of Low-Gradient Severe Aortic Stenosis with Preserved Ejection Fraction

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