Aortic valve stenosis: evaluation and management of patients with discordant classification (2023)

introduction

Accurate assessment of the severity of aortic stenosis (AS) is essential for patient management and risk stratification, and for the legitimate attribution of symptoms to valvular disease. Echocardiography is the most important method to assess the severity of AD. It is based on three parameters, namely maximum velocity (PVel), mean pressure gradient (MPG), and aortic valve area (AVA). The first two parameters are measured directly by continuous wave Doppler, while the last one is calculated based on the continuity equation and the measurement of the diameter of the left ventricular outflow tract (LVOT), the time-velocity integral (TVI ) of the LVOT and TVI aorta. Ideally, these parameters should coincide, with severe AS defined as maximum velocity > 4 m/s, MPG > 40 mmHg, and AVA < 1 cm² (Table 1). Over the past decade, this apparently simple and straightforward classification has been undermined by the observation that up to one-third of patients have a discordant AS classification and by the identification of a subgroup with severe, low-gradient, paradoxical, and low-gradient aortic regurgitation. low flow. stenosis despite preserved ejection fraction. In the present study, we present the pitfalls to avoid to ensure that the patient really has a dissonant degree, we evaluate the prevalence and evolution of this entity and, finally, we highlight the importance of computed tomography to independently determine the severity of AD. to judge. We will not discuss the assessment of AD severity in patients with ejection depression, but will focus on patients with normal/preserved ejection fraction.

Table 1. Grades of severity of aortic stenosis assessed by echocardiography and computed tomography (calcium score).

Difficulties in the evaluation of aortic valve stenosis

Discordant classification is defined based on the observation that one parameter suggests moderate AS while the other suggests severe AS. Discordant grading is defined by AVA < 1 cm² with MPG ≥ 40 mmHg/PVel < 4 m/sec or by AVA ≥ 1 cm² and MPG ≥ 40 mmHg/PVel ≥ 4 m/sec in a much more common situation . MPG and PVel are strongly correlated (collinear) and can be used almost interchangeably. So for the rest of the article we will use MPG.

The AVA calculation depends on the measurement of three parameters; With all three, a measurement error may occur. The measurement of the LVOT diameter is probably the main source of error when calculating the AVA. LVOT diameter should be measured in the parasternal long-axis view in zoom mode at midsystole and repeated at least three to five times. It is still a matter of debate whether the LVOT diameter should be measured at the level of the leaflet insertion, that is, the aortic annulus, or more apically, that is, 5 to 10 mm below the annulus. The recent recommendation on echocardiographic evaluation of AS by the European Association of Cardiovascular Imaging and the American Society of Echocardiography [1] does not provide a definitive answer, but underscores the fact that LVOT measurement at the annular level offers greater reproducibility of the measurement and this ensures the diameter. and Doppler pulse are measured in the same anatomical plane. This is our standard practice and personal recommendation. It is important to note that a 1 mm change in the LVOT diameter measurement results in a 0.1 cm² difference in the AVA calculation. Intense calcification and poor echogenicity are the main challenges to accurately measure LVOT diameter. Like any anatomical structure, LVOT correlates with body size. We previously established a protection formula using body surface area (BSA) (theoretical LVOT diameter = 5.7 * BSA + 12.1). [2] The standard deviation was 1 mm, which means that 50% of patients were 1 mm above or below this predicted value and 95% of patients were 2 mm above or below this predicted value. theoric value.

The second source of error is the measurement of the TVI of the aortic valve obtained by continuous Doppler. PVel and MPG are obtained in the same image acquisition. With the improvement of echocardiographic systems and the combined 2D/Doppler probe, the glass probe tends to be forgotten and obsolete. However, even with the most modern materials, it is essential to record the highest aortic velocity in several views, namely the apical view, but also the right parasternal view, the suprasternal view, and the subcostal view. If other views are not used, the severity of AD is underestimated in 20% or more of patients. [3] If the glass probe is not available, the normal two-dimensional probe can be used in the right parasternal view and, in our experience, gives similar results to the glass probe.

The importance of the third parameter, the TVI of the LVOT, is often underestimated. Placing the Doppler probe too far from the aortic opening is responsible for overestimating the severity of AS. On the other hand, if it is placed too close, within the flow acceleration, it will be responsible for underestimating the severity of AS. It is recommended to move the Doppler probe up and down to obtain a good Doppler trace with a closing click (may not be present in very severe AS) without the opening click.

Finally, an AVA less than 1 cm² can also be seen in small patients. In these circumstances, the AVA should be set at BSA with a limit of 0.6 cm²/m². It is important to remember that ASC correction should only be performed in patients of short and tall stature (small, elderly or male, professional basketball players) and should be avoided in obese patients. Height-adjustable thresholds are currently missing.

Frequency and prognosis of the discordant classification of AS

Following the precise and rigorous methodology presented above, the rate of patients with discordant classification is still between 20% and 30%, which is a common clinical problem. The uncertainties about the incidence and evolution of these patients are a consequence of the use of a different nosology between the articles and possible measurement errors. For example, in the seminal article by the Quebec team [4], stroke volume index was used as the criterion to distinguish groups. The proposed limit of 35 ml/m² is already widely accepted, although its validation has never been successful. In contrast, in the SEAS study [5], the authors considered the discrepancy between AVA and MPG independent of flow. The most appropriate way to classify patients is to first check whether AVA and MPG match and secondly consider flow (stroke volume index). Thus, four groups can be identified in patients with an AVA of less than 1 cm² (Figure 1). The patients on the left of the figure are easily classified as severe AS, while resting echocardiography is inconclusive in the other two groups, that is, patients with low gradient and normal or low flow. The latter group is close to the paradoxical heavy underflow AS described by the Quebec team. [4] The Mayo Clinic group provided us with important data on the prevalence of different subgroups. [6] Of 1,704 patients with valve area less than 1 cm², 24% had a discordant classification (AVA < 1 cm² and MPG < 40 mmHg). Flow was normal in the vast majority (21% of the general population), while low flow was observed in only 3% of the general population. This study confirms the high prevalence of patients with discordant classification and also shows that these patients had normal blood flow most of the time. Importantly, this study also showed that the subgroup of patients with discordant classification (AVA < 1 cm², MPG < 40 mmHg) and low flow had the worst prognosis (Figure 2). Our understanding from the literature is that flow is a prognostic factor regardless of the reason or cause of depressive flow. The initially postulated typical phenotype of an elderly woman, often with atrial fibrillation with preserved ejection fraction, but clear left ventricular hypertrophy, which is responsible for low flow, is therefore the exception rather than the rule. It should be noted that rare cases of discordant grading with AVA > 1 cm² and MPG > 40 mmHg are commonly seen in patients with bicuspid aortic valves and LVOT/large annular size. They are generally classified as patients with severe AD.

Figure 1. Classification of patients with aortic valve area <1 cm² (and preserved ejection fraction) into four groups according to mean pressure gradient (MPG) and stroke volume index (SVI).

Figure 2. Prognosis for the four subgroups defined in Figure 1. Patients with low flow (stroke volume index < 35 mL/m²) and low gradient (< 40 mmHg) had the worst prognosis (reference [6])

Use of computed tomography to assess the severity of AS

The fact that discordant staging is common and low flow is rare but has prognostic implications does not help to assess whether these patients really had severe AD. One of the main discussions in the field of valve disease in recent years has been whether these patients should be treated with a discordant classification according to valve area (ie, as severe AS) or according to MPG (usually moderate AS). ). Accounting for the flow added an additional layer of confusion. Since echocardiography at rest is not significant, it requires the use of additional methods.

With the use of computed tomography in the pre-TAVI pre-TAVI scan, the anatomy of the aortic annulus has been well described. More specifically, the CT clearly showed that the LVOT and aortic annulus are oval rather than circular. To calculate the AVA, a diameter is measured and the area of ​​the LVOT is calculated assuming that the LVOT is circular, which introduces an apparent error. For this reason, some have suggested combining CT (for LVOT area measurement) and echocardiography for aortic LVOT and TVI when calculating AVA. [7] Although such a methodology is attractive, it suffers from a significant bias. First, it is well known that echocardiography underestimates the LVOT annulus by 1 to 2 millimeters. Therefore, AVA is expected to increase and mathematically to decrease the number of patients with MPG < 40 mmHg and AVA < 1 cm². Second, the prognostic value of the AVA was established by echocardiographic evaluation, while the prognostic value of the combined AVA calculation is uncertain. Third, no reference method (rather than a gold standard) was used in any study that combined LVCT measurement of the LVOT area.

Therefore, the best way to address this question is to use a reliable, quantitative, flow-independent method to assess AD severity, which is the hallmark of calcium scoring. Aortic valve calcification is the main process of AD. [8] Contrary to what is seen in vessels, hydroxyapatite deposition and leaflet infiltration are the main mechanisms of leaflet restriction and hemodynamic obstruction. The degree of aortic valve calcification can be quantitatively and accurately assessed in vivo using computed tomography. [9] The methodology is simple and widely available. A closed CT scan is performed from the apex of the heart to the base of the heart, including the aortic valve. An injection of contrast dye is not required. With semi-automated software, areas considered calcified (defined by a tissue density > 130 Hounsfield units) are highlighted in red. The "single" operator must select the area that he believes belongs to the aortic valve. By avoiding simple pitfalls such as calcification of the mitral annulus, aortic wall, and coronary orifices, the method is highly reproducible. Quantification is performed using the Agatston score (expressed in arbitrary units [AU]) based on area of ​​calcification and peak density. We have shown that the calcium score is highly correlated with echocardiographic hemodynamic severity, validating its diagnostic value for the diagnosis of severe AS. [10] Interestingly, the thresholds for severe AS were different in women and men. [11] Women had greater hemodynamic obstruction for the same degree of aortic valve calcification, or to put it another way, a mean gradient of 40 mmHg is associated with a lower calcium load in women than in men. In addition to the fact that the thresholds are different in males and females (approximately 2000 and 1250 AU, respectively), these results show that the pathophysiology of AS is different in males and females and that female leaflets are actually more fibrous than male ones. . [12] It is important to note that these thresholds are not valid for rheumatic diseases and deserve specific validation in the bicuspid aortic valve. We applied this methodology to 646 patients with moderate/severe AS and normal ejection fraction. [13] Confirming the results of other studies, a discordant classification (AVA < 1 cm² and MPG < 40 mmHg) was observed in 27% of the population; most (85%) had normal blood flow. As expected, CT and calcium scoring accurately classified patients with consistent classification, but more importantly, 50% of patients with misclassification can be considered true severe AD, while 50% did not meet criteria for severe AD, regardless of blood flow calculation.

Calcium score measurements and anterior thresholds were recently implemented in the latest version of the ESC/EACTS Valvular Heart Disease Guidelines. [14] If the classification differs, calcium scoring should be performed as a first-line test after checking for possible measurement errors. When severe AD is diagnosed (and the patient is symptomatic), immediate intervention should be considered. When the calcium score is below the threshold, the AD tends not to be severe and is likely to be treated conservatively, although it is necessary to assess whether an intervention may be of benefit. It is also important to note that the suggested limits are not "magic numbers", but rather indicate the probability of having severe AD or not. For example, a woman with a score of 3000 is highly likely to have severe AD, while a man with a score of 700 is highly unlikely to have severe AD.

message to go

The key points discussed in this article can be summarized as follows:

Discordant classifications are common in clinical practice.

The first step is to look for dimensions of error.

Adjust for BSA in patients with extreme height (but this should be avoided in obese patients).

In patients with discordant classification (AVA < 1 cm² and MPG < 40 mmHg), those with low flow are much less common than those with normal flow.

Flow does not provide diagnostic information about the severity of AD, but it does provide prognostic information.

Transthoracic echocardiography cannot help you solve the problem of AS severity in most cases with discordant classification.

The aortic calcium score is a flow-independent quantitative method to assess the severity of AS (recommended cut-off points are 2000 in men and 1250 in women).

Intervention is recommended in symptomatic patients with established severe AD, as well as in classic severe AD.

references

1. Baumgartner H., Hung J., Bermejo J., Chambers J.B., Edvardsen T., Goldstein S., Lancellotti P., LeFevre M., Miller F. Jr. & Otto C.M.Recommendations for echocardiographic evaluation of aortic valve stenosis: a focused update from the European Association of Cardiovascular Imaging and the American Society of Echocardiography.Eur Heart J Cardiovasc Imaging, 2017. 18 (3): 254-275.
2. Leye M. , Brochet E. , Lepage L. , Cueff C. , Boutron I. , Häftling D. , Hyafil F. , Lung B. , Vahanian A. and Messika-Zeitoun D .Reference values ​​of size-adjusted left ventricular outflow tract diameter: a safeguard for assessing the severity of aortic stenosis.J Am Soc Echocardiogr, 2009, mayo 22 (5): 445-51.
3. de Monchy , C. C. , Lepage , L. , Boutron , I. , Leye , M. , Detaint , D. , Hyafil , F. , Brochet , E. , Lung , B. , Vahanian , A. , & Messika-Zeitoun , 1999 . 1999. 2004. D. (2006).Utility of the right parasternal view and non-imaging continuous wave Doppler transducer in assessing the severity of aortic stenosis in the modern area.Eur J Echocardiogr, 2009, May 10(3): 420-4. 301.
4. Hachicha Z., Dumesnil J.G., Bogaty P., & Pibarot P. Paradoxical low-flow and low-gradient severe aortic stenosis, despite preserved ejection fraction, is associated with increased postloading and reduced survival. Edition, 2007, June 5th. 115(22):2856-6 6.
5. Jander N , Minners J , Holme I , Gerdts E , Boman K , Brudi P , Chambers JB , Egstrup K , Kesaniemi YA , Malbecq W , Nienaber CA , Ray S , Rossebo A , Pedersen TR , Skjaerpe T , Willenheimer , R . Wachtell K., Neumann F.J. and Gohlke-Barwolf C. Outcome of patients with "severe" low-gradient aortic stenosis and preserved ejection fraction. Edition, 2011, March 1st. 123(8):887-95. 7.
6. Eleid MF, Sorajja P, Michelena HI, Malouf JF, Scott CG and Pellikka PA Flow gradient patterns in severe aortic stenosis with preserved ejection fraction: clinical features and predictors of survival. Edition October 13, 2013. 128(16): 1781-9. 1.
7. Kamperidis V., van Rosendael P.J., Katsanos S., van der Kley F., Regeer M., Al Amri I., Sianos G., Marsan N.A., Delgado V. & Bax J.J.Severe low-gradient aortic stenosis with preserved ejection fraction: reclassification of severity by fusion of Doppler and CT data.Eur Heart J, 2015, August 14th. 36(31): 2087-2096. hv188.
8. Otto C. M., Prendergast B.Aortic valve stenosis: in patients at risk of severe valve obstruction.N Engl J Med, 2014, 21 de agosto. 371 (8): 744-756.
9. Messika-Zeitoun D., Aubry M.C., Detaint D., Bielak L.F., Peyser P.A., Sheedy P.F., Turner S.T., Breen J.F., Scott C., Tajik A.J., & Enriquez-Sarano M.Evaluation and clinical implications of aortic valve calcification by electron beam computed tomography.Edition, 2004, July 2. 110(3):356-62.
10. Cueff C., Serfaty J. M., Cimadevilla C., Laissy J. P., Himbert D., Tubach F., Duval X., Lung B., Enriquez-Sarano M., Vahanian A. & Messika-Zeitoun D.Measurement of aortic valve calcification by multislice computed tomography: correlation with the hemodynamic severity of aortic stenosis and clinical implications for patients with low ejection fraction. Herz, May 2011. 97(9): 721-6.
11. Aggarwal SR , Clavel MA , Messika-Zeitoun D , Cueff C , Malouf J , Araoz PA , Mankad R , Michelena H , Vahanian A & Enriquez-Sarano M .Sex differences in aortic valve calcification as measured by multidetector computed tomography in aortic stenosis. circular cardiovascular images,2013, January 1. 6(1): 40-7.
12. Simard L., Cote N., Dagenais F., Mathieu P., Couture C., Trahan S., Bosse Y., Mohammadi S., Page S., Joubert P. & Clavel M. A.Gender-related discrepancy between aortic valve calcification and hemodynamic severity of aortic stenosis: valve fibrosis as an explanation?Circ Nada, 17. February 2017. 120(4): 681-691.
13. Clavel, MA, Messika-Zeitoun, D, Pibarot, P, Aggarwal, SR, Malouf, J, Araoz, PA, Michelena, HI, Cueff, C, Larose, E, Capoulade, R, Vahanian, A and Enriquez-Sarano, M. ( 1999 ).The complex nature of severe discordant classification of calcifying aortic valve disease: new insights from the combined Doppler echocardiography and computed tomography study.J Am Coll Cardiol 2013 Dec 17. 62(24): 2329-38.
14. Baumgartner , H. , Falk , V. , Bax , J.J. , De Bonis , M. , Hamm , C. , Holm , P.J. , Lung , B. , Lancellotti , P. , Lansac , E. , Munoz , D.R.R. , Sjogren , J. , Mas P. Lathes., A. Vahanian , T. Walther , O. Wendler , S. Windecker and J.L. Zamorano.ESC Scientific Papers Group, 2017. ESC/EACTS Guidelines for the Management of Valvular Heart Disease.Eur Heart J., 2017, September 21. 38: 2739–2791.

notes for editors

Authors:

Diary of David Messika¹, MD, PhD; chico lloyd², MD, FRCP.

1. Bichat Paris VII Hospital and University, Paris, France;
2. Center of the heart of St. Bart. Bartholomew Hospital, West Smithfield, London, UK.

Mailing address:

Professor David Messika-Zeitoun, Bichat Hospital, 46 rue Henri Huchard, 75018 Paris, France

Email:david.messika-zeitoun@aphp.fr

Conflict of interests:

Prof. Messika-Zeitoun: Consultant for Edwards, Valtech, Mardil and Cardiawave. Edwards and Abbott Research Grants.

Dr. Guy Lloyd: Lectures and Advisory Boards, Edwards, Philips, GE. Medtronic Research Grants.