Accurate noninvasive quantification of stenotic aortic valve area by Doppler echocardiography

Laminar flow through a conduit is equal to the mean velocity times the cross-sectional area of the orifice. Therefore, volume is equal to the time-velocity integral multiplied by the cross-sectional area. In aortic stenosis, flow in the stenotic jet is laminar and the aortic valve area should be equal to the volume of blood ejected through the valve divided by the time-velocity integral of the aortic jet velocity recorded by continuous-wave Doppler echocardiography. To test whether this concept can be used to accurately determine aortic valve area noninvasively by the Doppler method, 39 patients (age 35 to 82 years, mean 63) underwent pulsed Doppler combined with two-dimensional echocardiography for measurement of stroke volume at the aortic, pulmonic, and mitral anulus as well as continuous-wave Doppler recording of the aortic jet. Aortic valve area determined at cardiac catheterization by the Gorlin equation ranged between 0.4 and 2.07 cm2 (mean 0.89 +/- 0.45). Doppler-derived valve area, determined with the stroke volume value from either the aortic, pulmonic, or mitral anulus, correlated well with the area determined at cardiac catheterization (r = .95, .97, and .96, respectively). A simplified method for measuring aortic valve area derived as the cross-sectional area of the aortic anulus times peak velocity just proximal to the aortic valve divided by peak aortic jet velocity correlated well with measurements obtained at cardiac catheterization (r = .94). An excellent separation between critical and noncritical aortic stenosis was seen using either one of the Doppler methods.(ABSTRACT TRUNCATED AT 250 WORDS)     

Noninvasive determination of valve area in adults with aortic stenosis using Doppler echocardiography

Doppler ultrasound has been used to determine the pressure gradient P1-P2 across the valve in patients with aortic stenosis (AS), but since the gradient varies over time and may be deceptively low in patients with impaired cardiac output, the key parameter to obtain is the orifice area (A). By calculating stroke volume (SV) from the modal flow velocity [Vmode(t)] over the systolic ejection period (sep) or diastolic filling period (dfp), wherever laminar flow exists in the heart across an area of known diameter D, (pulmonary artery or atrioventricular valves), and by substituting P1-P2 = 4Vmax2, (Vmax = peak velocity in the aortic jet), the Gorlin formula becomes: (Formula: see text) where theta = flow intercept angle at D. This approach was applied in nine adult patients with AS (age 64 +/- 8 years) in whom recent catheterization data was available for comparison. Close correlation was found between the calculated areas: A(Doppler) = 0.82 A(Cath) + 0.17 (r = 0.94, p less than 0.001). Two patients with Doppler gradients of less than 40 mmHg were shown by this Doppler method nevertheless to have severely narrowed orifice areas of less than or equal to 0.78 cm2. Although there is a tendency to overestimate slightly the valve area, Doppler ultrasound assessment using this technique adds valuable noninvasive information concerning the degree of aortic valve disease.     

Determination of stenotic mitral valve area using Doppler echocardiography. A comparison with hemodynamic studies

In order to assess the reliability of Doppler echocardiography in the determination of mitral valve area (MVA) 21 consecutive patients (pts) affected by rheumatic disease and mitral valve stenosis (MS) were analyzed by continuous wave doppler echocardiography (CWD). Cardiac catheterization (cath) was performed within 24 hours from echocardiographic examination. MVA by CWD was calculated with a computerized system from the "pressure half-time" (T1/2) using the equation: 220/T1/2 in cm2. MVA was calculated from cath data by applying the modified Gorlin formula. MVA determined by CWD ranged from 0.9 to 2.8 cm2 (mean 1.39 +/- 0.55). MVA determined by Gorlin formula ranged from 0.5 to 2.8 cm2 (mean 1.31 +/- 0.63). The correlation between CWD and cath was good (r = 0.93, SEE = 0.19 cm2, P less than 0.001). In conclusion this study indicates that CWD is quite accurate in estimation of MVA and can reliably discriminate the "critical" size of the orifice. CWD has the advantage of allowing MVA determination in patients with associated mitral regurgitation.     

Determination of aortic valve area by two-dimensional and Doppler echocardiography in patients with normal and stenotic bioprosthetic valves

To assess the feasibility and accuracy of determining bioprosthetic aortic valve area from two-dimensional and Doppler echocardiographic measurements, three partially overlapping groups were selected from 55 patients with such bioprosthetic valves and adequate Doppler studies. These were Group 1, 37 patients with recent aortic valve replacement surgery and no clinical or echocardiographic evidence of valve dysfunction; Group 2, 12 patients with prosthetic valve stenosis documented by cardiac catheterization; and Group 3, 22 patients with both Doppler and catheterization studies in whom noninvasive and invasive determinations of aortic valve area could be directly compared. Left ventricular outflow tract diameter was measured from two-dimensional still frame images. Flow velocity proximal to the aortic valve, transvalvular velocity and acceleration time were determined from pulsed and continuous wave Doppler spectra. Aortic valve gradient was calculated with the modified Bernoulli equation and valve area by the continuity equation. In the 37 patients with a normally functioning valve, the calculated mean gradient ranged from 5 to 25 mm Hg (average 13.6 +/- 5.2) and valve area from 1.0 to 2.3 cm2 (mean 1.6 +/- 0.31). Linear regression analysis of prosthetic aortic valve area determined by Doppler imaging and cardiac catheterization demonstrated a high correlation (r = 0.93) between the two techniques. Comparison of the patients with and without prosthetic valve stenosis revealed statistically significant differences in mean gradient (42.8 +/- 12.3 versus 13.6 +/- 5.2 mm Hg; p = 0.0001), acceleration time (116 +/- 15 versus 80 +/- 13 ms; p = 0.0001) and valve area by the continuity equation (0.80 +/- 0.16 versus 1.6 +/- 0.31 cm2; p = 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Determination of aortic valve area by Doppler echocardiography using the continuity equation: a critical evaluation

In 35 patients with aortic stenosis the Doppler-derived values of the aortic valve area (continuity equation) were compared with those determined at cardiac catheterization (Gorlin's formula). The comparison of three modifications of the continuity equation showed that the procedure generally proposed (calculating the area of the left ventricular outflow tract from its diameter) significantly underestimated the valve area (modification 1). Modification 2, which used direct planimetry of the left ventricular outflow tract, yielded results quite consistent with invasive measurements. The employment of peak velocities instead of velocity-time integrals (modification 3) did not significantly alter the results. However, the scatter was considerable in all three modifications. When critical aortic stenosis was defined with a valve area less than or equal to 0.70 cm2, modifications 1, 2, and 3 accurately predicted the severity of stenosis in 80, 86, and 80%, respectively.     

Noninvasive determination of the orifice area of aortic valve prostheses using Doppler echocardiography

In aortic valve stenosis, Doppler echocardiography enables reliable estimation of the orifice area with the use of the continuity equation. This study was carried out to determine the usefulness of the method in evaluation of prosthetic aortic valve area. Accordingly, 32 patients with normally-functioning mechanical Bj?rk-Shiley prostheses underwent Doppler investigations two to three weeks after aortic valve replacement. Pre(v1)- and post(v2)-prosthetic velocities were recorded by pulsed and continuous-wave Doppler, respectively, and the prosthetic annulus used as cross-sectional area of flow (A1). For calculation of prosthetic orifice area (A2), the continuity equation at peak flow (v1,p) was employed where A2 = A1 X v1,p/v2 (at the point in time of v1,p). Mean pressure gradients across the prostheses were determined with the use of the modified Bernoulli equation. In addition, the ratio of acceleration to ejection time (AT/ET) was derived from the velocity profile of v2. Consistent with increasing prosthetic sizes (A 23 to A 29), there were increases in the calculated orifice areas A2 (A 23: 1.46 +/- 0.26, A 25: 1.71 +/- 0.24, A 27: 2.12 +/- 0.26, A 29: 2.53 +/- 0.35 cm2). Albeit with a substantial overlap between the various sizes, mean values for the respective sizes differed statistically significant and were comparably within the range established by in-vitro measurements. Pressure gradients across the prostheses were also different for the various sizes and were within the range reported from hemodynamic studies. In contrast, the AT/ET-ratio showed no significant difference between different prosthetic sizes.(ABSTRACT TRUNCATED AT 250 WORDS)     

Noninvasive quantification of the aortic valve area in aortic stenosis by Doppler echocardiography

To develop a noninvasive approach to the quantification of thestenotic aortic valve area, Doppler echocardiography and cardiaccatheterisation were performed in 24 patients with pure aorticstenosis. The transmitral volumetric flow was measured by Dopplerechocardiography and calculated as the product of the correctedmitral orifice area (CM A) and the diastolic velocity integral(DVI). The maximal aortic jet velocities were recorded by Dopplertechnique and integrated to obtain the systolic velocity integral(SVl). Assuming that the aortic and mitral volumetric flowsare equal, the aortic valve area (A VA) was calculated as: AVA= CM A x DVI/SVI. Mean pressure gradient and cardiac outputwere measured during catheterisation and the aortic valve areawas calculated by the Gorlin formula. Comparison between theaortic valve area determined by Doppler technique and catheterisationyielded a close correlation (r = 0.92, P<0.001), and therewas no significant difference between the two measurements.Good correlations of the instantaneous pressure gradient andthe stroke volume were also obtained between the two techniques(r = 0.91 and r = 0.90, respectively, P<0.001). These resultsdemonstrate that our Doppler echocardiographic method providesa promising approach to the noninvasive quantification of theaortic valve area in aortic stenosis     

Quantifying aortic valve insufficiency using color Doppler echocardiography

51 consecutive patients with the clinical signs of aortic valve incompetence (AI) were evaluated by color-coded Doppler flow mapping (CDF) before angiography (AG). Quantitation of the severity of AI was performed by measurement of length and width of the extension of regurgitant jet (grade I-IV). After AG results both -AG and CDF- were compared. In 36 patients the results of both methods concurred exactly by use length in CDF. With CDF, the regurgitation was overestimated in 7 cases by one grade and underestimated in 8 patients also by one grade. Width of regurgitant jet relative to size of outflow space is a useful parameter to distinguish between mild and severe A1 (limit 0.50). Conclusion: CDF is a suitable method for semiquantitative assessment of AI. In presence of unequivocal CDF signs and in consideration of clinical and other patients findings AG will be dispensable before aortic valve replacement.     

Doppler echocardiography determination of the orifice area in aortic valve stenosis using a continuity equation

The continuity equation, derived from the study of fluid mechanics, may serve as the basis for calculation of orifice area of stenosed cardiac valves. As applied to aortic stenosis, the continuity equation states that the flow across the narrowed valve is equal to the flow in the left ventricular (LV) outflow tract such that A1 X v1 = A2 X v2, where A1 = LV outflow tract area, v1 = prestenotic velocity, A2 = stenotic orifice area and v2 = poststenotic velocity. Accordingly, at each point in time during pulsatile flow, the respective valve orifice area can be calculated. Hence, from the sum of all areas throughout the ejection time, the mean valve orifice area can be constructed as integral of A2/ET = A1 X integral of (v1/v2)/ET, assuming A1 to be constant, where integral of denotes the integral over the ejection time ET. To assess the usefulness of this method with respect to its clinical relevance, in 36 patients with aortic stenosis, the Doppler echocardiographically-determined orifice areas were compared with those calculated by the Gorlin formula based on invasively-obtained data. LV outflow tract area A1 was measured by echocardiography from a parasternal long-axis view. Prestenotic velocity v1 was recorded in the LV outflow tract by pulsed Doppler from an apical transducer position, whereby care was taken in positioning the sample volume not too close to the stenotic valve to avoid the prestenotic area of increased velocity. Continuous-wave Doppler was used, usually from an apical or right parasternal transducer position, to record the stenotic jet velocity v2.(ABSTRACT TRUNCATED AT 250 WORDS)     

Quantitative assessment of normal and stenotic aortic valve using transesophageal three-dimensional echocardiography

The present study demonstrates the feasibility of transesophageal three-dimensional reconstruction of normal, sclerotic, and stenotic aortic valves using a computed tomographic ultrasound system. The study also shows the potential clinical usefulness of this technique in delineating aortic valve morphology (extent and severity of valve thickening and calcification and size and number of cusps) and assessing aortic orifice areas by direct planimetry of the three-dimensional images.     

Evaluation of aortic valve insufficiency using color Doppler echocardiography

Colour flow mapping Doppler echocardiography is a new, noninvasive method for studying the direction and velocity of blood flow within the cardiac chambers. In order to estimate the sensitivity and specificity of this method in the evaluation of aortic regurgitation, 44 patients were examined consecutively. In 24 patients, aortic valve incompetence was proven by angiography; in 20 patients aortography revealed no regurgitation. Quantification of the severity of aortic insufficiency was performed by grading the amount of colour of the regurgitant flow (grade I-IV) and comparing it with the angiographic data. In 43 out of 44 patients diagnostic images could be obtained with colour flow mapping Doppler echocardiography. With this method aortic insufficiency was detected in all cases (sensitivity 100%). The specificity was 97% (one false positive diagnosis). For quantification of the severity of regurgitation agreement with the angiographic findings was obtained in 18 out of 24 cases. In the remaining 6 patients the difference was one grade. Conclusion: Colour flow mapping Doppler echocardiography is an important advance in the noninvasive preoperative diagnostics of aortic incompetence.     

A new non-invasive estimation of the stenotic aortic valve area by pulsed Doppler mapping

A new pulsed Doppler mapping technique has been used to measure the severity of aortic valve stenosis. The Doppler examination was performed at the site of the aortic orifice in the parasternal short axis echocardiographic view and the method was based on the detection of the area of systolic flow through the stenotic orifice. This area was derived by planimetry and the measurements obtained by the Doppler method were compared with the aortic valve area calculated at catheterisation according to the Gorlin formula. The method was applicable in 41 of the 44 patients studied. The Doppler data were consistent with the haemodynamic measurements even in patients with decreased cardiac index. It is concluded that this new application of the flow mapping procedure is reliable and is easily applied to adult patients with a wide range of clinical conditions.     

Determination of aortic valve orifice area in aortic valve stenosis by two-dimensional transesophageal echocardiography

Two-dimensional transesophageal echocardiography was used to measure aortic valve orifice area in 24 patients with aortic valve stenosis (AS) and 15 patients without aortic valve disease. Using transesophageal echocardiography, orifice area could be measured in 20 of 24 patients with AS. With transthoracic echocardiography, orifice area could be determined in only 2 of 24 patients. In patients with AS, orifice area determined by transesophageal echocardiography was 0.75 +/- 0.34 cm2 and that calculated with Gorlin's formula was 0.75 +/- 0.32 cm2. In normal aortic valves, orifice area was 3.9 +/- 1.2 cm2 by transesophageal echocardiography. A good correlation was demonstrated between aortic valve orifice area determined using transesophageal echocardiography and calculated orifice area using Gorlin's formula in patients with AS: r = 0.92, standard error of estimate = 0.14 cm2. The absolute difference between orifice area measured with both methods ranged from 0.0 to 0.4 cm2 (mean 0.09 +/- 0.1). In 4 patients orifice area could not be determined with transesophageal echocardiography. The orifice could not be identified in 2 patients because an appropriate cross-sectional view of the aortic valve could not be achieved and in 2 patients with pinhole stenosis (aortic valve orifice area 0.3 cm2). These data show that aortic valve orifice area can be measured reliably using 2-dimensional transesophageal echocardiography.     

A new non-invasive estimation of the stenotic aortic valve area by pulsed Doppler mapping.

A new pulsed Doppler mapping technique has been used to measure the severity of aortic valve stenosis. The Doppler examination was performed at the site of the aortic orifice in the parasternal short axis echocardiographic view and the method was based on the detection of the area of systolic flow through the stenotic orifice. This area was derived by planimetry and the measurements obtained by the Doppler method were compared with the aortic valve area calculated at catheterisation according to the Gorlin formula. The method was applicable in 41 of the 44 patients studied. The Doppler data were consistent with the haemodynamic measurements even in patients with decreased cardiac index. It is concluded that this new application of the flow mapping procedure is reliable and is easily applied to adult patients with a wide range of clinical conditions.     

A simple noninvasive measurement of stenotic mitral valve area: an alternative approach using M-mode and Doppler echocardiography.

Doppler echocardiography is a widely used noninvasive technique to examine the mitral valve area (MVA) by obtaining mitral pressure half-time (PHT) and to assess the severity of the stenosis. However, several hemodynamic factors influence the PHT and may render the PHT data inaccurate in any measurement of MVA under certain conditions. Using a simple echo-Doppler (E-D) method, we assessed the MVA in a physiological equation. The mitral flow volume (MFV) is represented by MVA x transmitral mean flow velocity (mV) x diastolic filling time (DFT). Thus, the formula can be restated as MVA (cm2) = MFV (cm3)/mV (cm/sec) x DFT (sec). We measured MFV by M-mode, and mV and DFT by continuous wave Doppler echocardiography. This formula was tested in 43 patients with isolated mitral stenosis. MVA was obtained by the PHT and E-D methods, and the data obtained were validated against the results of cardiac catheterization. The results obtained using the E-D method showed much better correlation (r = 0.82) with those of catheterization than those with the PHT method (r = 0.52). The inter- and intraobserver variabilities were checked. The results obtained with the E-D method were found to be reproducible. To further validate the accuracy of the E-D method, MVA was measured by both methods at different R-R intervals after exercise and the results were compared. The MVA obtained by the PHT method showed marked variations; whereas, that obtained by the E-D method remained nearly constant. Similarly, in a patient with atrial fibrillation, the MVA assessed by the PHT method varied from beat to beat; whereas, the fluctuations in MVA were minimal using the E-D method. We concluded that the E-D method can be reliable and clinically easily applicable for the accurate assessment of MVA.     

Determination of the severity of tricuspid valve insufficiency using Doppler echocardiography

In 187 patients with combined mitral and aortic valve lesions, to assess and quantify tricuspid regurgitation, biplane right ventriculograms were obtained and Doppler echocardiography performed for study of the tricuspid valve and right atrium. After definition of regurgitant turbulance across the tricuspid valve with pulsed Doppler, on mapping the right atrium the maximal length of regurgitant flow in the right ventricular inflow tract was determined from the short-axis parasternal view. In seven of 70 patients in whom angiographically tricuspid regurgitation was not detected, Doppler echocardiography demonstrated holosystolic insufficiency of the valve. In all patients with the angiographic diagnosis of tricuspid regurgitation grades I to III, this lesion was also documented Doppler echocardiographically with only slight divergence of the regurgitant area in the right atrium as viewed from the short-axis parasternal transducer position. In all patients, the tricuspid valve was morphologically unremarkable. In 32 patients, in agreement with angiographic findings, grade I tricuspid regurgitation was diagnosed; in seven patients the angiographic severity was overestimated by one grade. In 44 patients, in agreement with angiographic findings, tricuspid regurgitation grade II was detected; in four patients the Doppler echocardiographic severity was overestimated and five patients underestimated by one grade. In 23 patients with grade II tricuspid regurgitation angiographically, there was agreement with Doppler echocardiographic findings; in two patients the severity was underestimated by one grade.(ABSTRACT TRUNCATED AT 250 WORDS)     

Doppler echocardiography in the assessment of the homograft aortic valve

To determine the utility of Doppler echocardiography in the evaluation of the homograft valve in the aortic position, 27 patients with normally functioning valves (group 1) and 30 patients with suspected malfunctioning valves (group 2) were examined. Simultaneous cardiac catheterization and Doppler echocardiography were performed in 23 group 2 patients. Doppler and surgical findings were compared in 7 patients too ill for invasive studies. In group 1 patients, the maximal velocity (+/- standard deviation) was 1.8 +/- 0.37 m/s, the mean pressure gradient was 7.1 +/- 3.07 mm Hg and the mean aortic valve area was 2.2 +/- 0.79 cm2. The maximal velocity in group 2 patients with aortic regurgitation (AR) classified as moderate or greater was 2.5 +/- 0.55 m/s, compared with 1.8 +/- 0.44 m/s in patients with mild AR or less (p less than 0.01). In the quantitation of AR, pulsed-wave mapping and angiographic grades were identical in 18 patients and differed by 1 grade in 5. Seven patients too ill for catheterization had severe destruction of valve leaflets at cardiac surgery. In 6 patients, both Doppler grading methods suggested severe AR. In a seventh patient, who had an obstructed Starr-Edwards valve in the mitral position, AR was graded as mild by pulsed-wave mapping. Only 1 patient had homograft valve stenosis, with a withdrawal gradient at catheterization of 34 mm Hg and a Doppler maximal gradient of 36 mm Hg.(ABSTRACT TRUNCATED AT 250 WORDS)     

Noninvasive determination of the valvar area in aortic valve disease by Doppler echocardiography and radionuclide angiography

To assess the severity of outlfow obstruction in patients with aortic valve disease, the aortic valvar area was noninvasively determined in 22 patients with isolated aortic stenosis or combined stenosis and regurgitation. The ejection time (ET), maximal velocity (Vmax), and systolic velocity integral (SVI) of the aortic flow was obtained by continuous wave Doppler ultrasound. Left ventricular stroke volume (SV) was determined by radionuclide angiography, using a counts-based nongeometric technique with individual attenuation correction. Aortic valve area (AVA) was calculated using a modified Gorlin formula; AVA = SV/(71.2 X ET X Vmax), and also by dividing the stroke volume by the systolic velocity integral; AVA = SV/SVI. The two noninvasive determinations correlated closely with the valve areas obtained by invasive measurements; r = 0.95, SEE = +/- 0.13 cm2 by the modified Gorlin formula, and r = 0.94, SEE = +/- 0.14 cm2 by the integration method. The two noninvasive calculations showed almost uniform results; r = 0.98, SEE = +/- 0.09 cm2. In conclusion, aortic valve area can be determined with reasonable accuracy by combining Doppler echocardiography and radionuclide angiography. This noninvasive approach may reduce the need for invasive measurements in patients with suspected aortic valve disease. In addition, radionuclide angiography provides important information about left ventricular function.