Effects of variations in flow on aortic valve area in aortic stenosis based on in vivo planimetry of aortic valve area by multiplane transesophageal echocardiography

Impact and predictors of noncircular left ventricular outflow tract shapes on estimating aortic stenosis severity by means of continuity equations

Determining aortic stenosis (AS) severity is clinically important. Calculating aortic valve (AV) area by means of the continuity equation assumes a circular left ventricular outflow tract (LVOT). The full impact of this assumption in calculating AV area is unknown. Predictors of noncircular LVOT shape in patients with AS are undefined. In 109 adult patients with AS who underwent multiplanar transesophageal echocardiography, we calculated AV area by means of the standard continuity method and by a modified method involving planimetric LVOT area. We found 54 circular, 37 horizontal-oval, 8 vertical-oval, and 10 irregular LVOTs. Area derived by direct planimetry correlated better with the modified than the standard continuity method (r=0.89 vs r=0.85; both P=0.0001). Valve areas of patients with mild, moderate, or severe AS by planimetry were more often mischaracterized with use of the standard than modified method (29 vs 18; P <0.0001). Horizontal-oval AV area derived by planimetry (1.28 ± 0.55 cm(2)) was underestimated by the standard method (1.05 ± 0.47 cm(2); P=0.001), but not by the modified method. Congenital AV morphology and low cardiac index were the only multivariate predictors of horizontal-oval shape. Low cardiac index was the only predictor of noncircular shape. More than half our patients with AS had noncircular LVOTs. Using the modified method reduces mischaracterizations of AS severity. Congenital AV morphology and low cardiac index predict horizontal-oval or noncircular shape. These data suggest the value of direct LVOT measurement to calculate AS severity in patients who have congenital AV or a low cardiac index.

Role of echocardiography in aortic stenosis

Aortic stenosis is a valve disorder that includes not only valve narrowing but also changes in the left ventricle and intracardiac hemodynamics. Older patients with aortic stenosis often have co-existing pathologic disorders, which influence the pathophysiology, symptom expression and prognosis. There is also increasing awareness that severe aortic stenosis could be associated with low transvalvular pressure gradient caused by a variety of mechanisms. Surgical and transcutaneous valve replacements are currently available interventions for patients with severe aortic stenosis. This article reviews the role of echocardiography in the comprehensive assessment of aortic stenosis, its severity and associated pathophysiologic abnormalities.

Hakki's formula for measurement of aortic valve area by magnetic resonance imaging

Hakki's formula (simplified Gorlin formula) can be used during cardiac catheterization to calculate the stenosed cardiac valve areas and can also be adapted to magnetic resonance imaging (MRI) to measure the stenosed cardiac valve areas. We evaluated the reliability of this approach to determine the severity of aortic stenosis compared to the continuity equation using transthoracic echocardiography and planimetry using MRI. We included all eligible symptomatic patients with known aortic stenosis referred to our department during a 1-year period. The aortic valve area (AVA) was estimated using Hakki's formula (MRI), planimetry (MRI), and the continuity equation (transthoracic echocardiography). The agreement among the measurement methods was analyzed using the Bland-Altman method. A total of 63 patients were included (mean age 72 +/- 10 years, 35 men [56%]). The mean AVA was 0.70 +/- 0.21 cm(2) using the continuity equation (transthoracic echocardiography), 0.67 +/- 0.18 cm(2) using planimetry (MRI), and 0.64 +/- 0.21 cm(2) using Hakki's formula (MRI). The mean difference was 0.03 cm(2) (95% limits of agreement -0.32 to 0.25) between planimetry and the continuity equation, 0.05 cm(2) (95% limits of agreement -0.40 to 0.29) between Hakki's formula and the continuity equation, 0.02 cm(2) (95% limits of agreement -0.20 to 0.25) between Hakki's formula and planimetry. The inter- and intraobserver reproducibility using Hakki's formula was excellent. In conclusion, measurement of the AVA using Hakki's formula yielded similar results to those obtained using planimetry and slightly different ones from those obtained using the continuity equation. However, Hakki's formula has the advantage of being easy to use, fast, and reproducible and can be used regardless of the status of the valve (in contrast to planimetry).

Aortic valve area assessment: multidetector CT compared with cine MR imaging and transthoracic and transesophageal echocardiography

PURPOSE

To prospectively compare the accuracy of multidetector computed tomographic (CT) measurements of the aortic valve area (AVA) with transesophageal echocardiography (TEE) and cine magnetic resonance (MR) measurements of this area for preoperative examination of patients undergoing cardiac surgery, with transthoracic echocardiography (TTE) as the reference standard.

MATERIALS AND METHODS

After giving informed consent for the institutional review board-approved study protocol, 48 patients (33 men, 15 women; mean age, 62 years+/-13 [standard deviation]) with (n=27) or without (n=21) aortic stenosis underwent multidetector CT, cine MR, TTE, and TEE before undergoing cardiac surgery. AVAs derived with manual planimetry by using cine short-axis multidetector CT, MR, and TEE images obtained through the aortic valve were compared among each other and with AVAs measured by using continuity equation TTE at regression and Bland-Altman analyses. The diagnostic accuracy of multidetector CT for detection of aortic stenosis was compared with that of TTE by using kappa statistics and receiver operating characteristic curves.

RESULTS

Multidetector CT-derived AVA correlated highly with MR-derived (r=0.98, P<.001), TEE-derived (r=0.98, P<.001), and TTE-derived (r=0.96, P<.001) AVA. Multidetector CT planimetry AVAs (mean AVA+/-standard deviation, 2.5 cm2+/-1.7) were not significantly different from MR planimetry (2.4 cm2+/-1.8, P>.99) or TEE planimetery (2.5 cm2+/-1.7, P=.21) AVAs, but they were significantly larger than TTE-derived AVAs (2.0 cm2+/-1.5, P<.001). With TTE as the reference standard, multidetector CT correctly (kappa=0.88, P<.001) depicted all 21 normal, six of eight mildly stenotic (AVA>or=1.2 cm2 and <2.0 cm2), seven of eight moderately stenotic (AVA>or= 0.8 cm2 and <1.2 cm2), and 10 of 11 severely stenotic (AVA<0.8 cm2) valves. It also correctly depicted all 14 bicuspid valves identified with TEE, eight of which were missed with TTE.

CONCLUSION

Multidetector CT enables accurate noninvasive assessment of the AVA.

Quantification of aortic valve stenosis in MRI—comparison of steady-state free precession and fast low-angle shot sequences

We compared two different magnetic resonance (MR) sequences [steady-state free precession (SSFP) and gradient echo fast low-angle shot (FLASH)] for the assessment of aortic valve areas in aortic stenosis using transesophageal echocardiography (TEE) as the standard of reference. Thirty-two patients with known aortic stenosis underwent MR (1.5 T) using a cine SSFP sequence and a cine FLASH sequence. Planimetry was performed in cross-sectional images and compared to the results of the TEE. In seven patients the grade of stenosis was additionally assessed by invasive cardiac catheterization (ICC). The mean aortic valve area measured by TEE was 0.97+/-0.19 mm(2), 1.00+/-0.25 mm(2) for SSFP and 1.25+/-0.23 mm(2) based on FLASH images. The mean difference between the valve areas assessed based on SSFP and TEE images was 0.15+/-0.13 cm(2) (FLASH vs TEE: 0.29+/-0.17 cm(2)). Bland-Altman analysis demonstrated that measurements using FLASH images overestimated the aortic valve area compared to TEE. Comparing ICC with MRI and TEE, only a weak to moderate correlation was found (ICC vs TEE: R=0.52, p=0.22; ICC vs SSFP: R=0.20, p=0.65; ICC vs FLASH: R=0.16, p=0.70). Measurements of the aortic valve area based on SSFP images correlate better with TEE compared to FLASH images.

Flow-Dependent Changes in Doppler-Derived Aortic Valve Effective Orifice Area Are Real and Not Due to Artifact

OBJECTIVES

We sought to determine whether the flow-dependent changes in Doppler-derived valve effective orifice area (EOA) are real or due to artifact.

BACKGROUND

It has frequently been reported that the EOA may vary with transvalvular flow in patients with aortic stenosis. However, the explanation of the flow dependence of EOA remains controversial and some studies have suggested that the EOA estimated by Doppler-echocardiography (EOA(Dop)) may underestimate the actual EOA at low flow rates.

METHODS

One bioprosthetic valve and three rigid orifices were tested in a mock flow circulation model over a wide range of flow rates. The EOA(Dop) was compared with reference values obtained using particle image velocimetry (EOA(PIV)).

RESULTS

There was excellent agreement between EOA(Dop) and EOA(PIV) (r2 = 0.94). For rigid orifices of 0.5 and 1.0 cm2, no significant change in the EOA was observed with increasing flow rate. However, substantial increases of both EOA(Dop) and EOA(PIV) were observed when stroke volume increased from 20 to 70 ml both in the 1.5 cm2 rigid orifice (+52% for EOA(Dop) and +54% for EOA(PIV)) and the bioprosthetic valve (+62% for EOA(Dop) and +63% for EOA(PIV)); such changes are explained either by the presence of unsteady effects at low flow rates and/or by an increase in valve leaflet opening.

CONCLUSIONS

The flow-dependent changes in EOA(Dop) are not artifacts but represent real changes in EOA attributable either to unsteady effects at low flow rates and/or to changes in valve leaflet opening. Such changes in EOA(Dop) can be relied on for clinical judgment making.

Role of echocardiography in the diagnosis and treatment of patients with aortic stenosis

PURPOSE OF REVIEW

Echocardiographic assessment plays a major role in the evaluation of aortic stenosis (AS). Because of its proven accuracy, ease of applicability, and safety, it is replacing cardiac catheterization for the assessment of AS in many centers.

RECENT FINDINGS

In this review, we discuss the basic principles of echocardiographic assessment of AS and clinically challenging scenarios including AS with low cardiac output state or other structural heart disease. Dobutamine stress echocardiography is a useful tool for assessing low cardiac output AS. The role of transesophageal echocardiography in the evaluation of AS is also reviewed.

SUMMARY

Echocardiographic techniques provide critical information in the assessment of patients with known or suspected AS and guide decision-making regarding the appropriateness of valve replacement.

Dobutamine echocardiography in patients with aortic stenosis and left ventricular dysfunction: predicting outcome as a function of management strategy

STUDY OBJECTIVE

To prospectively address the question whether the assessment of valvular hemodynamics and myocardial function during low-dose dobutamine infusion can guide decision making in patients with aortic stenosis and left ventricular (LV) dysfunction.

PATIENTS AND MEASUREMENTS

Twenty-four patients with aortic stenosis and LV dysfunction (mean ejection fraction, 28%; New York Heart Association class, II to IV) were studied by dobutamine echocardiography assessing mean pressure gradient, aortic valve area, and aortic valve resistance. Patients were prospectively divided into severe and nonsevere aortic stenosis groups according to the response of the valve area to the augmentation of systolic flow. The clinical decision was considered to be concordant with the results of dobutamine echocardiography, when patients with severe aortic stenosis and preserved contractile function were referred by a specialist for aortic valve replacement and when patients with nonsevere aortic stenosis were not. Patients were observed for up to 3 years.

RESULTS

All eight patients with severe aortic stenosis who were referred for surgery survived and had good cardiovascular outcomes, and six of eight patients who were not initially referred for surgery had poor outcomes, including heart failure and sudden cardiac death. The eight patients with nonsevere aortic stenosis did comparatively well without valve replacement. Cardiac death or pulmonary edema occurred in 4 of 16 patients (25%) when the clinical decision was concordant with the results of the dobutamine echocardiogram and occurred in 6 of 8 patients (75%) when the clinical decision was discordant (p = 0.019 [chi(2) test]).

CONCLUSION

Patients with aortic stenosis, LV dysfunction, and relatively low gradients have better outcomes when management decisions are based on the results of dobutamine echocardiograms. Those patients identified as having severe aortic stenosis and preserved contractile reserve by dobutamine echocardiography should undergo surgery, while patients identified as having nonsevere aortic stenosis can be managed conservatively.

Transesophageal echocardiographic evaluation of native aortic valve area: utility of the double-envelope technique

OBJECTIVE

To assess the accuracy of aortic valve area (AVA) calculations using the continuity equation with data obtained from the double envelope (DE) (simultaneously obtained left ventricular outflow tract [V1]) and aortic valve [V2] velocities) during intraoperative transesophageal echocardiography (TEE).

DESIGN

Prospective study; measurements were performed on-line.

SETTING

University hospital.

PARTICIPANTS

Cardiac and noncardiac surgical patients (n = 75) with recent aortic valve assessment (<3 months) undergoing general anesthesia or endotracheal intubation.

INTERVENTIONS

Intraoperative AVA was measured by the continuity equation using the DE technique (DE/TEE) and by planimetry (PL/TEE). Left ventricular outflow tract diameter was obtained from midesophageal views, whereas subvalvular (V1) and valvular (V2) velocities were obtained simultaneously using continuous-wave Doppler from transgastric views. V1 was also obtained using pulsed-wave Doppler. Measurements were compared with AVA obtained preoperatively by the Gorlin equation during cardiac catheterization (G/CATH) or by transthoracic echocardiography using the traditional continuity equation (C/TTE) (nonsimultaneously obtained V1 and V2).

MEASUREMENTS AND MAIN RESULTS

A DE was obtained in 73 of 75 patients (97%). Four patients had atrial fibrillation at the time of the examination, whereas the rest were in sinus rhythm. PL/TEE was performed in 54 of 71 patients with sinus rhythm (76%). Agreement was good between DE/TEE and G/CATH (mean bias, 0.02 cm(2) [SD, 0.24 cm(2)]), and C/TTE (mean bias, -0.05 cm(2) [SD, 0.16 cm(2)]). Agreement was not as good between PL/TEE and G/CATH (mean bias, -0.07 cm(2) [SD, 0.28 cm(2)]) and C/TTE (mean bias, -0.13 cm(2) [SD, 0.30 cm(2)]). V1 obtained by pulsed-wave Doppler and with DE closely agreed (mean bias, 0.01 m/sec [SD, 0.05 m/sec]).

CONCLUSION

TEE evaluation of native AVA using the DE technique is feasible and in good agreement with that obtained by C/TTE and G/CATH. Compared with DE/TEE, PL/TEE did not agree as well. Use of DE/TEE should simplify the continuity equation and may minimize errors resulting from beat-to-beat variability in stroke volume.

Hemodynamic-induced changes in aortic valve area: implications for Doppler cardiac output determinations

Monitoring cardiac output (CO) by transesophageal echocardiography involves measurements of ascending aortic flow and an initial measurement of aortic valve area (AVA). Hemodynamic-induced changes in AVA are a potential source of error for this simplified method. Our goal was to quantify these changes in AVA and their effects on CO calculations. In 17 anesthetized patients, a dobutamine infusion was titrated to achieve a 50% increase in ascending aortic flow velocity (V(max)). Hemodynamic and echocardiographic variables, including V(max) and planimetry of AVA, were determined at baseline and at maximal dobutamine dose. Dobutamine produced a 3.0 +/- 1.4 L/min increase in CO, a 54.5% +/- 19.6% increase in V(max), and a 50.6% +/- 34.2% increase in systolic blood pressure. AVA increased by 4.3% +/- 2.6% during dobutamine infusion (P < 0.001). The simplified CO method, which does not account for increases in AVA, produced a 0.32 +/- 0.24 L/min underestimation of CO. This investigation demonstrates hemodynamic-induced changes in AVA. The use of a single AVA measurement for all subsequent CO calculations introduces a clinically acceptable degree of error, supporting a simplified CO protocol requiring less probe manipulation and reduced procedural time.

IMPLICATIONS

An intraoperative dobutamine infusion was used to increase aortic blood flow and demonstrate hemodynamic-induced changes in aortic valve area. These valve-area changes affect the accuracy of Doppler cardiac output determinations.

Transesophageal echocardiographic (TEE) evaluation of the aortic valve, left ventricular outflow tract, and pulmonic valve

The most important role of TEE in aortic valve disease is in the diagnosis of endocarditis and its complications. Examination of the annulus and subvalvular region is essential in any patient with possible aortic valve endocarditis. Assessment of the severity of aortic stenosis is a useful application of TEE when other data are either inconsistent or unavailable. TEE can provide a diagnosis of the origin of acute severe aortic insufficiency; this information may play a critical role in surgical planning. The diagnosis of a variety of aortic valve diseases can be made when TEE is performed to find an embolic source or to rule out dissection. In the case of mass lesions, such as papillary fibroelastomas and Libman-Sacks vegetations, the results of TEE carry major therapeutic implications. TEE offers generally excellent quality images of the LVOT and images of the RVOT and pulmonic valve that are superior to transthoracic echocardiography. The major clinical usefulness of TEE stems from its ability to identify pulmonic valve mass lesions and the causes of left and right ventricular outflow obstruction. TEE is also an important adjunct in the surgical management of left ventricular outflow obstruction.

Aortic Stenosis: The Role of Transesophageal Echocardiography

Noninvasive assessment of aortic valve area by echocardiography has become the standard of practice over the past few years. The advent of transesophageal echocardiography (TEE) has provided a new method for the assessment of aortic valve area (AVA) using planimetry by two-dimensional imaging. Clear visualization of the anatomy of the valve, as well as accuracy of AVA assessment, makes TEE an invaluable tool for the evaluation of aortic valve stenosis. TEE is especially helpful in clinical settings when there is a discrepancy between the AVA obtained by transthoracic echocardiography and cardiac catheterization. TEE is particularly helpful in the assessment of the aortic valve during intraoperative echocardiography. This review discusses the techniques, imaging planes, and details for assessing AVA by TEE. The role of TEE in AVA assessment is described, with specific clinical case examples cited.

Stress Echocardiography in Aortic Stenosis: Insights into Valve Mechanics and Hemodynamics

Stress interventions have been classically combined with cardiac catheterization recordings to understand the hemodynamic principles of valvular stenosis. Indices of aortic stenosis such as pressure gradient and valve area were based on simple hydraulic principles and have proved to be clinically useful for patient management during a number of decades. With the advent of Doppler echocardiography, these hemodynamic indices can be readily obtained noninvasively. Abundant evidence obtained using exercise and pharmacological stress echocardiography has demonstrated that the assumptions of classic hemodynamic models of aortic stenosis were wrong. Consequently, it is recognized that conventional indices may be misleading indicators of aortic stenosis significance in particular clinical situations. To improve diagnostic accuracy, several alternative hemodynamic models have been developed in the past few years, including valve resistance and left ventricular stroke work loss, among others. Nevertheless, these more-accurate indices should be obtainable noninvasively and need to demonstrate greater diagnostic and prognostic power than conventional indices; preliminary data suggest such superiority. Stress echocardiography is well established as the tool of choice for testing hypothesis and physical models of cardiac valve function. Although the final role of alternative indices is not yet well established, the new insights into valvular hemodynamics provided by this technique may change the clinical assessment of aortic stenosis.

Dobutamine stress Doppler hemodynamics in patients with aortic stenosis: feasibility, safety, and surgical correlations

OBJECTIVES

This study was designed to describe the experience of our center with the safety and feasibility of dobutamine stress echocardiography (DSE) in aortic stenosis (AS), to characterize the hemodynamic response to dobutamine infusion, and to examine the hemodynamic response in relation to the anatomic evaluation of the valve among patients who underwent valve replacement.

BACKGROUND

The diagnosis of the hemodynamic severity of AS can be difficult when the cardiac output is reduced and the gradient is low, but the effective valve area calculates to be small. DSE has been proposed as a means of assessing the severity of AS in this setting.

METHODS

We reviewed 27 patients (18 men, 9 women; mean age 71 +/- 12 years) with AS who underwent DSE between 1991 and 1996.

RESULTS

Fifteen (55%) patients were New York Heart Association class III or IV, 8 (30%) had angina Canadian class III or IV, and 3 (11%) syncope. Dobutamine peak dose was 27 +/- 11 micrograms/kg/min. Sixteen (59%) patients had mild side effects. DSE resulted in a significant increase in the cardiac output from 4.1 +/- 1.2 L/min at rest to 7.3 +/- 1.9 L/min at peak dose, and in heart rate (76 +/- 16 beats/min to 124 +/- 20 beats/min), systolic blood pressure (128 +/- 26 mm Hg to 137 +/- 26 mm Hg), ejection fraction (38% +/- 20% to 42% +/- 20%), and transvalvular mean gradient (28 +/- 10 mm Hg to 39 +/- 9 mm Hg) (P <.05). There was also a significant increase in the valve area from 0.77 +/- 0.14 cm2 at rest to 0.97 +/- 0.21 cm2 (P <.001). Seven patients underwent surgery; all valves were severely calcified, confirming anatomic disease. In this group, an increase in the mean gradient but also a trend toward an increase in the valve area were noted in response to dobutamine: 33 +/- 10 mm Hg to 47 +/- 6 mm Hg and 0.79 +/- 0.11 cm2 to 0.95 +/- 0.19 cm2, respectively.

CONCLUSION

Although more data are needed to fully establish the safety of the test in this indication, this study suggests that patients with AS can safely undergo DSE. Dobutamine results in an increase not only in the mean gradient, but also in the valve area. An increase in valve area with dobutamine was observed in some patients with anatomically confirmed severe AS and thus does not exclude fixed valve disease.

Variation of anatomic valve area during ejection in patients with valvular aortic stenosis evaluated by two-dimensional echocardiographic planimetry: comparison with traditional Doppler data

OBJECTIVES

Flow variations can affect valve-area calculation in aortic stenosis and lead to inaccuracies in the evaluation of the stenosis. Knowing that transvalvular flow varies normally within one beat, we designed this study to assess the response of the valve to intrabeat variation of flow during systole. Results were compared with flow-derived measurements.

BACKGROUND

Technological improvements now allow us to evaluate aortic valve area directly by short axis planimetry. This offers the possibility to perform serial planimetries during one ejection phase and analyze the intrabeat dynamic behavior of the stenotic-aortic valve and compare these measurements with flow-derived measurements.

METHODS

Forty echocardiograms displaying different degrees of aortic stenosis were analyzed by frame-by-frame planimetry of the valve area from onset of opening to complete closure. Maximal-mean area, opening and closing rates and ejection times were obtained and compared with Doppler-derived data.

RESULTS

Valve area varied during ejection. Stenotic valves opened and closed more slowly than normals and remained maximally open for a shorter period. Mean area by Doppler data corresponded more closely to maximal than to mean-planimetered area. Duration of flow was shorter than valve opening in severely stenotic valves. Discrepancies between Doppler-derived and two-dimensional (2D) measurements decreased in less stenotic valves.

CONCLUSIONS

Our observations reveal striking differences between the dynamics of normal and stenotic valves. Surprisingly, Doppler-derived mean-valve area correlated better with maximal-anatomic area than with mean-anatomic area in patients with aortic stenosis. Discrepancies between duration of flow and valve opening could explain this phenomenon.

Flow dependence of valve area in aortic stenosis: relation to valve morphology

OBJECTIVES

We sought to develop an index of flow dependence of valve area in aortic valve (AoV) stenosis and to determine whether this index is related to structural characteristics of the diseased valve.

BACKGROUND

Many studies of AoV stenosis using Gorlin or continuity equation methods have demonstrated flow dependence (an increase in valve area with increased flow). Variation in flow dependence between patients despite similar flow rates remains unexplained.

METHODS

Dobutamine Doppler echocardiography was used to calculate flow rate and valve area by the continuity equation in 27 patients with aortic stenosis. For each patient the slope of the regression line of valve area to flow rate was determined (slope of flow dependence). Transesophageal echocardiography was used to evaluate features of valve morphology potentially related to the etiology of AoV stenosis and the mechanism of flow dependence.

RESULTS

Mean slope of flow dependence was 0.28 cm2/100 ml per s (range -0.06 to 0.53); flow dependence was significantly >0 in 21 patients and was lower for bicuspid valves (slope 0.21 cm2/100 ml per s) than for tricuspid valves with <10% commissural fusion (slope 0.35, p < 0.01). Off-center/ovoid orifices demonstrated the least flow dependence (slope 0.19), whereas star-shaped orifices showed the most (slope 0.36, p < 0.01). Greater flow dependence was related to a lower percentage of commissural fusion (r = -0.46, p = 0.02) as well as diffuse sclerosis, primarily involving the cusp bodies, rather than localized sclerosis, with involvement of cusp margins.

CONCLUSIONS

The slope of flow dependence of valve area in AoV stenosis differs markedly between patients. More flow dependence was associated with tricuspid valves and the morphologic features characteristic of calcific AoV stenosis, whereas less flow dependence was associated with bicuspid valves and the features of rheumatic disease.

Echocardiographic quantitation of mitral regurgitation: a new Doppler technique

Our objective is to develop a new transthoracic Doppler echocardiographic technique to determine mitral regurgitant fraction. The standard color Doppler method for assessment of mitral regurgitation is semiquantitative and dependent on instrument gain. By using the mitral and aortic valve continuous wave Doppler velocities, one can determine regurgitant fraction. This technique takes into account the flow dependence of the mitral valve area. Two constants, A and B, which represent the flow dependence of the mitral valve area and the ratio of the mitral valve area to aortic valve area at zero flow, respectively, were determined by regression in 36 patients without valvular disease (r = .89). Thirty patients with isolated mitral regurgitation were then studied. The mitral regurgitant fraction was calculated from the following: Regurgitant fraction = 1 - TVIav/Bf[Vmv/(1 - AVmv)]dt, where TVIav is the time velocity integral across the aortic valve, Vmv is the continuous wave velocity across the mitral valve, and A and B are constants. The regurgitant fraction was then compared with color Doppler assessment of mitral regurgitation assessed by independent observers. In patients with mitral regurgitation, there was a strong correlation between standard visual assessment and our new Doppler method (Kendall's tau b rank correlation = 0.65; p < .001). The new Doppler method was able to correctly categorize 90% of patients with mild mitral regurgitation and 88% of patients with severe mitral regurgitation; however, there was poorer agreement with the color Doppler assessment of moderate mitral regurgitation. Mitral regurgitant fraction can be calculated with our new Doppler method. This method is quantitative, objective, nongain dependent, and separates mild from severe mitral regurgitation well.

Planimetry and transthoracic two-dimensional echocardiography in noninvasive assessment of aortic valve area in patients with valvular aortic stenosis

OBJECTIVES

The aim of this study was to evaluate the reliability of transthoracic two-dimensional echocardiography in measuring aortic valve area (AVA) by planimetry.

BACKGROUND

Planimetry of AVA using two-dimensional transesophageal echocardiographic images has been reported to be a reliable method for measuring AVA in patients with aortic stenosis. Recent advances in resolution of two-dimensional echocardiography permit direct visualization of an aortic valve orifice from the transthoracic approach more easily than before.

METHODS

Forty-two adult patients with valvular aortic stenosis were examined. A parasternal short-axis view of the aortic valve was obtained with transthoracic two-dimensional echocardiography. AVA was measured directly by planimetry of the inner leaflet edges at the time of maximal opening in early systole. AVA was also measured by planimetry using transesophageal echocardiography, by the continuity equation and by cardiac catheterization (Gorlin formula).

RESULTS

In 32 (76%) of the 42 study patients, AVA could be detected by using the transthoracic planimetry method. There were good correlations between results of transthoracic two-dimensional echocardiographic planimetry and the continuity equation (y = 0.90x + 0.09, r = 0.90, p < 0.001, SEE = 0.09 cm2), transesophageal echocardiographic planimetry (y = 1.05x - 0.02, r = 0.98, p < 0.001, SEE = 0.04 cm2) and the Gorlin formula (y = 1.02x + 0.05, r = 0.89, p < 0.001, SEE = 0.10 cm2).

CONCLUSIONS

Transthoracic two-dimensional echocardiography provides a feasible and reliable method in measuring AVA in patients with aortic stenosis.

Simultaneous determination of aortic valve area by the Gorlin formula and by transesophageal echocardiography under different transvalvular flow conditions. Evidence that anatomic aortic valve area does not change with variations in flow in aortic stenosis

OBJECTIVES

The purpose of this study was to determine the impact of changes in flow on aortic valve area (AVA) as measured by the Gorlin formula and transesophageal echocardiographic (TEE) planimetry.

BACKGROUND

The meaning of flow-related changes in AVA calculations using the Gorlin formula in patients with aortic stenosis remains controversial. It has been suggested that flow dependence of the calculated area could be due to a true widening of the orifice as flow increases or to a disproportionate flow dependence of the formula itself. Alternatively, anatomic AVA can be measured by direct planimetry of the valve orifice with TEE.

METHODS

Simultaneous measurement of the planimetered and Gorlin valve area was performed intraoperatively under different hemodynamic conditions in 11 patients. Left ventricular and ascending aortic pressures were measured simultaneously after transventricular and aortic punctures. Changes in flow were induced by dobutamine infusion. Using multiplane TEE, AVA was planimetered at the level of the leaflet tips in the short-axis view.

RESULTS

Overall, cardiac output, stroke volume and transvalvular volume flow rate ranged from 2.5 to 7.3 liters/min, from 43 to 86 ml and from 102 to 306 ml/min, respectively. During dobutamine infusion, cardiac-output increased by 42% and mean aortic valve gradient by 54%. When minimal flow was compared with maximal flow, the Gorlin area varied from (mean +/- SD) 0.44 +/- 0.12 to 0.60 +/- 0.14 cm2 (p < 0.005). The mean change in Gorlin area under different flow rates was 36 +/- 32%. Despite these changes, there was no significant change in the planimetered area when minimal flow was compared with maximal flow. The mean difference in planimetered area under different flow rates was 0.002 +/- 0.01 cm2 (p = 0.86).

CONCLUSIONS

By simultaneous determination of Gorlin formula and TEE planimetry valve areas, we showed that acute changes in transvalvular volume flow substantially altered valve area calculated by the Gorlin formula but did not result in significant alterations of the anatomic valve area in aortic stenosis. These results suggest that the flow-related variation in the Gorlin AVA is due to a disproportionate flow dependence of the formula itself and not a true change in valve area.

Effects of dobutamine on Doppler echocardiographic indexes of aortic stenosis

OBJECTIVES

This study sought to assess the diagnostic implications of the flow dependence of Doppler echocardiographic indexes of aortic valve stenosis.

BACKGROUND

Although valve area has been shown to change with alterations in flow rate, the diagnostic consequences of this phenomenon remain unknown. Valve resistance has been suggested as a more stable index for evaluating aortic stenosis.

METHODS

A low dose dobutamine protocol was performed in 35 patients with aortic stenosis. Hemodynamic indexes were obtained by Doppler echocardiography at baseline and at each dobutamine dose.

RESULTS

As a result of the shortening of the systolic ejection period, flow increased from (mean +/- SD) 164 +/- 48 to 229 +/- 102 ml/s (p < 0.0001). At peak flow, valve area increased by 28% (from 0.5 +/- 0.2 to 0.6 +/- 0.3 cm2, p < 0.0001), whereas valve resistance decreased by 4% (from 498 +/- 252 to 459 +/- 222 dynes.s.cm-5, p = 0.04). This observed change in resistance was smaller than that for valve area (p < 0.01). The flow dependence of valve area varied among individual patients (p < 0.0001). Multivariate analysis identified calcific degenerative etiology (beta 0.29, p = 0.002), left ventricular velocity of fiber shortening (beta 0.22, p = 0.01), baseline flow (beta -0.28, p = 0.04) and amount of flow increased induced by dobutamine (beta 0.90, p < 0.0001) as factors related to valve area flow dependence.

CONCLUSIONS

Although all Doppler echocardiographic indexes of aortic stenosis are affected by flow, valve resistance is more stable than valve area under dobutamine-induced hemodynamic changes. Baseline valve area may be unreliable in patients with calcific degenerative aortic stenosis and low output states.

Stenotic lesions

Images