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Archives of cardiovascular diseases
Volume 111, n° 8-9
pages 518-527 (août 2018)
Doi : 10.1016/j.acvd.2017.11.004
Received : 25 June 2017 ;  accepted : 22 November 2017
Clinical research

Prospective assessment of the frequency of low gradient severe aortic stenosis with preserved left ventricular ejection fraction: Critical impact of aortic flow misalignment and pressure recovery phenomenon
Évaluation prospective de la fréquence du rétrécissement aortique sévère à bas gradient et fraction d’éjection ventriculaire gauche préservée : impact critique du mauvais alignement du flux aortique et du phénomène de restitution de pression
 

Anne Ringle a, b, Anne-Laure Castel a, Caroline Le Goffic a, François Delelis a, Camille Binda a, Yohan Bohbot c, Pierre Vladimir Ennezat d, Raphaëlle A. Guerbaai d, Franck Levy e, André Vincentelli f, Pierre Graux a, Christophe Tribouilloy b, c, Sylvestre Maréchaux a, b,
a Service de cardiologie, faculté libre de médecine, université catholique de Lille, GCS-groupement des hôpitaux de l’Institut catholique de Lille, 59160 Lomme, France 
b Inserm U1088, université de Picardie, 80054 Amiens, France 
c Service de cardiologie B, centre hospitalier universitaire d’Amiens, 80054 Amiens, France 
d Service de cardiologie, centre hospitalier universitaire de Grenoble, 38700 Grenoble, France 
e Centre cardio-thoracique de Monaco, 98000 Monaco, France 
f Service de chirurgie cardiaque, centre hospitalier régional universitaire de Lille, 59000 Lille, France 

Corresponding author. Echocardiography Laboratory, Cardiology Department, faculté libre de médecine, université catholique de Lille, Heart Valve Disease Centre, GCS-groupement des hôpitaux de l’institut catholique de Lille, rue du Grand-But, 59160 Lomme, France.Echocardiography Laboratory, Cardiology Department, faculté libre de médecine, université catholique de Lille, Heart Valve Disease Centre, GCS-groupement des hôpitaux de l’institut catholique de Lille, rue du Grand-But, 59160 Lomme, France.
Summary
Background

The frequency of paradoxical low-gradient severe aortic stenosis (AS) varies widely across studies. The impact of misalignment of aortic flow and pressure recovery phenomenon on the frequency of low-gradient severe AS with preserved left ventricular ejection fraction (LVEF) has not been evaluated in prospective studies.

Aims

To investigate prospectively the impact of aortic flow misalignment by Doppler and lack of pressure recovery phenomenon correction on the frequency of low-gradient (LG) severe aortic stenosis (AS) with preserved LVEF.

Methods

Aortic jet velocities and mean pressure gradient (MPG) were obtained by interrogating all windows in 68 consecutive patients with normal LVEF and severe AS (aortic valve area [AVA] ≤1cm2) on the basis of the apical imaging window alone (two-dimensional [2D] apical approach). Patients were classified as having LG or high-gradient (HG) AS according to MPG <40mmHg or ≥40mmHg, and normal flow (NF) or low flow (LF) according to stroke volume index >35mL/m2 or ≤35mL/m2, on the basis of the 2D apical approach, the multiview approach (multiple windows evaluation) and AVA corrected for pressure recovery.

Results

The proportion of LG severe AS was 57% using the 2D apical approach alone. After the multiview approach and correction for pressure recovery, the proportion of LG severe AS decreased from 57% to 13% (LF-LG severe AS decreased from 23% to 3%; NF-LG severe AS decreased from 34% to 10%). As a result, 25% of patients were reclassified as having HG severe AS (AVA ≤1cm2 and MPG ≥40mmHg) and 19% as having moderate AS. Hence, 77% of patients initially diagnosed with LG severe AS did not have “true” LG severe AS when the multiview approach and the pressure recovery phenomenon correction were used.

Conclusions

Aortic flow misevaluation, resulting from lack of use of multiple windows evaluation and pressure recovery phenomenon correction, accounts for a large proportion of incorrectly graded AS and considerable overestimation of the frequency of LG severe AS with preserved LVEF.

The full text of this article is available in PDF format.
Résumé
Contexte

La fréquence du rétrécissement aortique (RAO) à bas gradient paradoxal varie largement selon les études. L’impact du défaut d’alignement du flux Doppler et de la restitution de pression sur la fréquence du rétrécissement aortique paradoxal n’a pas été évalué dans des études prospectives.

Buts

Évaluer prospectivement l’impact du défaut d’alignement du flux en Doppler et de l’absence de correction par le phénomène de restitution de pression sur la fréquence du rétrécissement aortique paradoxal, serré à bas gradient malgré une fraction d’éjection ventriculaire gauche (FEVG) préservée.

Méthodes

Les vitesses et le gradient moyen transaortique étaient obtenus en interrogeant toutes les fenêtres acoustiques/échographiques chez 68 patients consécutifs porteurs d’un RAO serré (surface fonctionnelle ≤1cm2) et une FE VG préservée. Les patients étaient classifiés en sous-groupes selon le gradient moyen transvalvulaire (haut ou bas gradient) et le niveau de flux transvalvulaire (débit normal ou bas débit). Les quatre groupes étaient constitués successivement : à partir des données de l’approche apicale 2D seule, à partir des données de l’approche multivues obtenues par les sondes 2D et Pedoff et en tenant compte de la surface aortique corrigée à la restitution de pression.

Résultats

La proportion de patients avec RAO serré et bas gradient était de 57 % selon l’approche apicale 2D seule. Avec l’approche multivues et après correction par la restitution de pression, la proportion de patients avec un bas gradient diminuait de 57 % à 13 % (diminution des « bas débit-bas gradient » de 23 % à 3 % et des « débit normal-bas gradient » de 34 % à 10 %). Ainsi, 25 % des patients étaient reclassifiés comme porteurs d’un RAO classique à haut gradient (surface ≤1cm2 et gradient moyen40mmHg) et 19 % comme porteurs d’un RAO modéré. Au total, 77 % des RAO serrés à bas gradient par l’approche apicale 2D seule ne l’étaient pas réellement si l’on tenait compte de l’approche multivues et du phénomène de restitution de pression.

Conclusions

Une mauvaise évaluation du flux transaortique, par défaut d’utilisation d’une approche multivues, et l’absence de correction par le phénomène de restitution de pression sont responsables d’une large proportion de discordances dans le diagnostic de sévérité du RAO et conduisent à une surestimation considérable de la fréquence du RAO serré paradoxal à bas gradient malgré une FEVG préservée.

The full text of this article is available in PDF format.

Keywords : Aortic stenosis, Doppler echocardiography, Low gradient, Pressure recovery

Mots clés : Rétrécissement aortique, Échocardiographie Doppler, Bas gradient, Restitution de pression

Abbreviations : 2D, Ap, AS, AT, AVA, ELI, ET, HG, LF, LG, LV, LVEF, LVOT, MPG, Multi, NF, SVi, Vmax, VTI


Background

Aortic stenosis (AS) is considered severe when the mean transvalvular pressure gradient (MPG) is ≥40mmHg and the aortic valve area (AVA) is ≤1.0cm2 [1]. However, these variables are discordant in 20–30% of patients [2], and a significant number of patients have lower than expected mean transvalvular gradients (low gradient [LG]), even in the presence of preserved left ventricular ejection fraction (LVEF). The frequency of patients with LG severe AS and preserved LVEF differs widely in previous reports, ranging from 24% to 68% [3, 4, 5, 6, 7]. Among these patients, controversies remain concerning those with so-called “paradoxical low-flow/low-gradient (LF-LG) AS”, who are usually elderly women with a background history of hypertension and a small left ventricular (LV) cavity responsible for a reduction in stroke volume and hence a low transaortic gradient despite preserved LVEF [8, 9]. Initially considered to be common (up to 35% of cases of severe AS) [8], the frequency of paradoxical LF-LG AS among severe AS in recently-published series ranges from 3% to 13% [4, 5, 6, 7].

Although the limited use of multiple windows evaluation in clinical practice may lead to an underestimation of the aortic flow velocity time integral (VTI), the impact of misalignment of aortic flow on the frequency of LG severe AS with preserved LVEF has not been evaluated in prospective studies [10]. Pressure recovery phenomenon also accounts for 10% of misclassifications of AS [11]. However, its impact on the diagnosis of LG severe AS with preserved LVEF has not been investigated specifically.

Hence, we sought to investigate prospectively the impact of Doppler misalignment of aortic flow using the apical imaging window alone and the lack of pressure recovery phenomenon correction on the frequency of LG severe AS with preserved LVEF.

Methods
Patients

Among all consecutive patients diagnosed with AS from November 2015 to August 2016 in the echocardiography laboratory of the Saint Philibert Hospital (GHICL, Lille Catholic University, France), those with severe AS according to an AVA ≤1cm2, calculated by Doppler flow obtained from the two-dimensional (2D) apical four-chamber view, were enrolled prospectively. Exclusion criteria were: LVEF<50%; more than mild-to-moderate concomitant aortic regurgitation; specific causes of low flow including concomitant severe mitral regurgitation, mitral stenosis or atrial septal defect [12, 13]; and inability to perform a multiview evaluation of aortic valve variables because of reduced patient mobility.

Clinical evaluation was standardized, and included assessment of cardiac and extracardiac co-morbidities and current medication. The study was conducted in accordance with institutional policies, national legal requirements and the revised Declaration of Helsinki.

Echocardiography

Echocardiograms were performed on commercially-available ultrasound machines: iE33 (Philips, Amsterdam, the Netherlands); Epiq 7 (Philips); and Vivid E9 (GE Healthcare, Little Chalfont, UK). All echocardiographic studies were stored on dedicated workstations for offline analysis: (EchoPAC PC (GE Healthcare); and Intellispace Cardiovascular (Philips)). Standard echocardiographic variables were collected according to current European Association of Cardiovascular Imaging/American Society of Echocardiography guidelines on the practice of transthoracic echocardiography [14, 15] by experienced senior cardiologists with expertise in echocardiography and valvular heart diseases. Left ventricular outflow tract (LVOT) diameter was measured in mid systole at the aortic annulus [16, 17], on a magnified parasternal long-axis view. Great attention was paid to obtain magnified views providing the largest annular dimension in the measurement of the LVOT diameter. The stroke volume was calculated by multiplying the area of the LVOT by the outflow tract velocity time integral (VTI) and indexed to the body surface area. Transvalvular aortic VTI, MPG and peak aortic jet velocity (Vmax) were obtained using continuous-wave Doppler. For each study, aortic jet velocities and gradients (Vmax_Ap, MPG_Ap and VTI_Ap) were obtained from the apical view using an imaging transducer (2D apical approach). After this initial evaluation, continuous-wave Doppler interrogation of the aortic jet velocities and gradients (Vmax_multi, MPG_multi and VTI_multi) were performed using a non-imaging transducer from the apical, suprasternal notch, supraclavicular and right parasternal views, and using an imaging transducer from the subcostal view (multiview approach) [18]. For these Doppler evaluations, standard echocardiograph settings were used; gains and filters were adjusted for each window to obtain a smooth velocity curve with a dense outer edge and clear maximum velocity. The maximum velocity was measured at the outer edge of the dark signal, and fine linear signals at the peak of the curve caused by transit-time effects were not included in measurements, as recommended [18]. AS severity was also assessed using ejection dynamics variables, as previously reported [19, 20] Acceleration time (AT) and the ratio of AT over ejection time (AT/ET) were calculated. AT was defined as time from aortic valve opening to peak velocity of aortic flow by continuous-wave Doppler. ET was defined from aortic valve opening to aortic valve closure. The AT/ET ratio was then calculated. The degree of aortic valve calcification was visually scored as follows: “0” if mildly calcified (small isolated spots) or moderately calcified (multiple larger spots); and “1” if heavily calcified (extensive thickening and calcification of all cusps).

All echocardiograms were subsequently reviewed off-line by a single investigator (A. R.) to determine aortic valve variables from each imaging window. Non-indexed and indexed AVAs were determined by the continuity equation method, using the ratio of the VTI in the LVOT obtained using pulsed-wave Doppler and the VTI across the valve obtained by the apical approach (AVA_Ap) and by the multiview approach (AVA_multi). AVA_multi was corrected with pressure recovery according to the following formula: energy loss index (ELI)=(AVA_multi×Aa)/(Aa–AVA_multi), where Aa is the aortic cross-sectional area calculated from the diameter of the aorta measured at the sinotubular junction [21]. LF was defined by an indexed stroke volume (SVi) ≤35mL/m2. HG was defined by an MPG ≥40mmHg.

The patient population was divided into two subgroups depending on transaortic pressure gradients and AVA: LG severe AS (AVA ≤1cm2 and MPG<40mmHg); and HG severe AS (AVA1cm2 and MPG ≥40mmHg). Patients with either LG or HG severe AS were divided into two subgroups depending on LV flow state [3]: normal-flow (NF)-HG and LF-HG (SVi>35mL/m2 and SVi35mL/m2, respectively) and NF-LG and LF-LG (SVi>35mL/m2 and SVi ≤ 35mL/m2, respectively). These subgroups were determined:

initially using aortic Doppler variables obtained only from the apical approach;
then, we analysed the impact of the multiview approach and the pressure recovery phenomenon, respectively, on the frequency of these subgroups. A third subgroup, moderate AS (ELI>1cm2), was created after correction for pressure recovery;
finally, the impact of both the multiview approach and the pressure recovery phenomenon correction on the frequency of these subgroups was evaluated.

Statistical analysis

Quantitative variables are expressed as means±standard deviations if normally distributed (as assessed by Shapiro-Wilk test), or medians [interquartile ranges] otherwise, and were compared using Student's t test if normally distributed (or the Mann-Whitney U test otherwise). Qualitative variables are expressed as frequencies and percentages, and were compared using Pearson's χ 2 test or Fisher's exact test, as appropriate. To evaluate the changes in patient repartition depending on the echocardiographic approach to assess AS severity (2D apical versus multiview, 2D apical versus 2D apical with correction for pressure recovery and 2D apical versus combined approach), k -statistics were used. To evaluate AS severity variable data from each “view approach”, correlation analysis using the intraclass correlation coefficient and Bland-Altman plots were performed. A two-tailed P value<0.05 was considered statistically significant. Statistical analyses were performed using SPSS version 21.0 (SPSS Inc., Chicago, IL, USA).

Results
Study population

From November 2015 to August 2016, 107 consecutive patients were diagnosed with severe AS (AVA ≤1cm2) using the best 2D apical view Doppler flow alignment. Thirty patients were excluded for LV dysfunction (LVEF<50%), two for severe aortic regurgitation, one for severe mitral regurgitation and six for inability to perform a multiview approach because of reduced mobility, resulting in a final study population of 68 patients.

Clinical characteristics are displayed in Table 1. Twenty-eight patients (41%) were asymptomatic.

Echocardiography

Echocardiographic data are reported in Table 2. LV hypertrophy was found in 36 patients (53%). Co-existing mild and mild-to-moderate aortic regurgitation were present in 40% and 18% of subjects, respectively.

Impact of the multiview approach on the AS grading classification

Overall, aortic variables were modified using the multiview approach compared with the apical view approach: Vmax_Ap was 4.0±0.7m/s while Vmax_multi was 4.3±0.7m/s; MPG_Ap was 41±17mmHg while MPG_multi was 47±17mmHg. Consistently, AVA_Ap was 0.79±0.16cm2, while AVA_multi was 0.74±0.16cm2 (P <0.001) (Table 3). Correlation analyses evaluating data obtained using each additional view are presented in Appendix A. Maximal MPG was obtained firstly from the right parasternal view (37%), followed by the apical imaging view (34%), the apical non-imaging view (16%), the supraclavicular view (6%), the suprasternal view (4%) and the subcostal view (3%) (Table 4). Among patients with severe calcifications, 85% of patients had an MPG_multi of ≥40mmHg, while only 56% had an MPG_Ap of40mmHg.

The clinical significance of these changes was investigated by comparing the classification in AS subgroups obtained using the 2D apical approach and the multiview approach (Figure 1). Using the 2D apical approach alone, 29 patients (43%) had HG severe AS and 39 (57%) had LG severe AS. Twenty-three patients (34%) had NF-LG severe AS and 16 (23%) had LF-LG severe AS. Using the multiview approach, 17 patients (25%) were reclassified from LG to HG subgroups: eight were reclassified from NF-LG to NF-HG; and nine were reclassified from LF-LG to LF-HG. Hence, 44% of LG patients from the 2D approach alone were reclassified into HG subgroups using the multiview approach. The agreement between the two approaches (2D apical approach versus multiview approach) is detailed in Appendix A. Among these patients, reclassification was achieved using the right parasternal view in 53%, the apical non-imaging view in 29%, the right supraclavicular view in 12% and the suprasternal view in 6%. The comparison between patients reclassified by the multiview approach and those who were not reclassified is presented in Table 5; no significant difference between patients reclassified and not reclassified by the multiview approach was found in any of clinical or echocardiographic variables listed in Table 5, except for stroke volume and indexed stroke volume. Stroke volume was lower in patients who were reclassified (67±13 vs 74±13mL; P =0.04), as was indexed stroke volume (36±7 vs 40±7mL/m2; P =0 .04).



Figure 1


Figure 1. 

Patient repartition according to evaluation of aortic stenosis: two-dimensional (2D) apical approach versus multiview approach. HG: high gradient; LF: low flow; LG: low gradient; NF: normal flow.

Zoom

Impact of the pressure recovery phenomenon on the AS grading classification

Overall, AVA_Ap was 0.79±0.16cm2, and after correction for pressure recovery ELI was 0.90±0.19cm2 (P <0.001). Nineteen patients (28%) had an AVA_Ap1cm2 and an ELI>1cm2. As shown in Figure 2, 12 patients with NF-LG severe AS (52% of NF-LG) were reclassified as having moderate AS, and seven patients with LF-LG severe AS (44% of LF-LG) were reclassified as having moderate AS. Among the 19 reclassified patients, 10 (53%) had a small aortic root (≤30mm) and nine (47%) had an aortic root of>30mm. The agreement between the two approaches (2D apical approach versus 2D apical approach with correction for pressure recovery) is detailed in Appendix A.



Figure 2


Figure 2. 

Patient repartition according to evaluation of aortic stenosis: two-dimensional (2D) apical approach versus 2D apical approach with correction for pressure recovery. HG: high gradient; LF: low flow; LG: low gradient; NF: normal flow.

Zoom

Combined impact of the multiview approach and the pressure recovery phenomenon correction on the AS grading classification

The combined impact of misalignment of aortic flow and pressure recovery phenomenon on the AS grading classification is reported in Figure 3.



Figure 3


Figure 3. 

Patient repartition according to evaluation of aortic stenosis: two-dimensional (2D) apical approach versus combined approach (multiview approach followed by correction for pressure recovery). ELI: energy loss index; HG: high gradient; LF: low flow; LG: low gradient; NF: normal flow.

Zoom

Overall, the proportion of patients with LG severe AS decreased from 57% (n =39) to 13% (n =9) (Figure 4). The proportion of patients with NF-LG severe AS decreased from 34% (n =23) to 10% (n =7) and the proportion of patients with LF-LG severe AS decreased from 23% (n =16) to 3% (n =2). As a result, 25% of patients (n =17) were reclassified as having HG severe AS (ELI ≤1cm2 and MPG40mmHg), and 19% (n =13) were reclassified as having moderate AS (ELI>1cm2). Hence, 77% of patients initially diagnosed with LG severe AS did not have “true” LG severe AS when using both the multiview approach and the pressure recovery phenomenon correction. The agreement between the two approaches (2D apical approach versus multiview approach with correction for pressure recovery) is detailed in Appendix A.



Figure 4


Figure 4. 

Impact of the use of the multiview approach and correction for pressure recovery on the frequency of low-gradient severe aortic stenosis (AS) with preserved left ventricular ejection fraction (LVEF).

Zoom

Consistently, patients reclassified as having moderate AS had a significantly lower AT (98 [81–96] vs 115 [105–135] ms; P <0.001), a significantly lower AT/ET ratio (0.32 [0.26–0.35] vs 0.38 [0.34–0.41]; P <0.001) and less calcified aortic valves (22% vs 78% heavily calcified valves; P =0.014) than patients who remained in the severe AS groups.

Discussion

In this prospective study involving consecutive patients with AS and normal LVEF, we demonstrated that misalignment of aortic flow, caused by lack of use of multiple windows evaluation and lack of correction for pressure recovery, accounts for a large proportion of incorrect grading of AS and considerable overestimation of the frequency of LG severe AS.

Impact of aortic flow misalignment on the AS grading classification

In the present study, a significant proportion of patients were misclassified when AS severity was evaluated by the apical imaging window alone. Using the multiview approach, one in four patients was reclassified from discordant AS (LG subgroups) to concordant AS (HG subgroups). Thirty-five percent of patients with NF-LG AS actually had NF-HG AS, and 56% of patients with LF-LG AS actually had LF-HG AS. Hence, misalignment was a major cause of misclassification of LG severe AS, and the multiview approach lowered the proportion of discordant AS in both LF and NF subgroups. Importantly, 53% of reclassifications were achieved using the right parasternal view, and 29% were achieved using the apical non-imaging view, demonstrating the major importance of both these views in clinical practice. Acute angulation of the aortic root, more common with aging, can result in a more anteriorly-directed stenotic jet in AS, making it more difficult to align the ultrasound beam properly from the apical position, and thus making it more likely that the peak velocity is located outside the apical window. Consistently, Thaden et al. found that subjects with acute angulation more commonly had a higher Vmax at the right parasternal window (65% vs 43%; P =0.05) and less commonly had a higher Vmax at the apical window (19% vs 48%; P =0.005) [10]. The finding that the apical non-imaging window reclassified patients compared with the apical imaging window reinforces the importance of this dedicated probe. Indeed, the use of the non-imaging transducer should be recommended, because of its higher signal-to-noise ratio, and because it allows optimal transducer positioning and angulation as a result of its small footprint. Lastly, of 107 consecutive patients, only six (5%) were excluded for inability to perform a multiview approach, because of reduced patient mobility or poor clinical state (patients with femoral fractures undergoing preoperative assessment or patients with poor clinical states [e.g. orthopnoea]). In these six patients, the multiview approach was not feasible, but was feasible in all remaining patients.

Impact of the pressure recovery phenomenon on the AS grading classification

The MPG measured on echocardiography, compared with the gradient estimated by catheterization, does not take into account the pressure recovery phenomenon, leading to an overestimation of MPG and an underestimation of AVA [21, 22, 23]. In a study pooling in vitro, animal and patient data, Garcia et al. [11] found excellent correlation and concordance between ELI and AVA estimated by catheterization. In total, 10% of cases of AS were classified as severe on the basis of AVA measured by echocardiography, but moderate on the basis of catheterization-derived AVA. Moreover, ELI has demonstrated important prognostic information in the setting of asymptomatic AS [24]. Despite these striking results, no further study has focused on the specific impact of pressure recovery on the clinical classification of AS based on transvalvular flow state and pressure gradient. In the present report, 19% of patients would have been reclassified as having moderate AS on the basis of the pressure recovery phenomenon. Interestingly, an in vitro flow-model study found a relevant impact of pressure recovery, particularly when the aorta was small (aortic size<30mm) [22]. However, we found in the present report that 47% of reclassified patients had an ascending aorta of ≥30mm, suggesting that the ELI measurement should not be confined to patients with a small aortic root. Importantly, patients reclassified by the pressure recovery phenomenon displayed features of moderate AS, such as mild-to-moderate aortic valve calcifications, shorter AT and a lower AT/ET ratio.

Clinical impact of the combined approach on the AS grading classification

After a thorough evaluation, taking into account both misalignment and the pressure recovery phenomenon, the remaining proportion of patients with LG severe AS with preserved LVEF was 13%, which is in the lower range of previously reported data (62% for Dumesnil et al. [3], 24% for Adda et al. [4], 38% for Lancellotti et al. [5], 35% for Mohty et al. [6] and 24% for Eleid et al. [7]). Interestingly, the frequency of patients with NF-LG AS (10%) was higher in the present report than the frequency of patients with LF-LG AS (3%). These findings lead to substantial clinical consequences for the assessment of patient outcome and management.

According to current guidelines [1], severe AS is unlikely if transvalvular flow is normal and MPG is<40mmHg. NF-LG “severe” AS may result from inherent guideline inconsistences, as an AVA of 1cm2 does not correspond to a MPG of 40mmHg [25], or measurement errors in AVA, and may not require surgical management. However, some reports [3] have suggested that prognosis remained significantly worse if treated medically. In light of our above-mentioned results, a significant proportion of these patients may, in fact, have true severe AS with an NF-HG pattern, which has a worse prognosis and requires surgical management. This could explain the poor prognosis of these true severe AS patients when treated medically, and underlines the critical impact of Doppler flow misalignment.

The subgroup of paradoxical LF-LG severe AS is currently a topic of intense debate, regarding frequency, severity, prognosis and management [26]. According to the present results, the frequency of LF-LG AS decreased from 23% to 3% when taking into account the multiview approach and the pressure recovery phenomenon. Thus, only 13% of patients with LF-LG AS initially diagnosed with an apical approach remained in this subgroup after a thorough evaluation. Overall, 87% were reclassified: 56% from LF-LG AS to LF-HG AS; and 31% from severe LF-LG AS to moderate AS. The group of paradoxical patients with LF-LG AS is probably heterogeneous, including patients with LF-HG severe AS, moderate AS and a small proportion of “true” paradoxical LF-LG severe AS. According to European Society of Cardiology guidelines [1], paradoxical patients with LF-LG AS have a class IIa indication for aortic valve replacement if haemodynamic and anatomical data support valve obstruction as the most likely cause of symptoms. Reclassification into an HG subgroup has important clinical implications, as it leads to a class I indication in symptomatic patients [1]. On the opposite side of the spectrum, a smaller proportion of patients with LF-LG severe AS were reclassified as having moderate AS after correction for pressure recovery. These patients with actual moderate AS may not derive benefit from aortic valve replacement, especially as they are often elderly hypertensive patients with co-existent coronary artery disease, atrial fibrillation and extracardiac co-morbidities.

Study limitations

Previous reports using cardiac computed tomography or three-dimensional transoesophageal echocardiography have shown that the LVOT may be elliptical, and that AVA calculation with the continuity equation by echocardiography may underestimate the true valve area [27]. Although computed tomography and three-dimensional transoesophageal echocardiography were not performed systematically in the present study, it is the first study to prospectively assess the critical impact of the use of multiple windows evaluation and correction for pressure recovery on the frequency of LG severe AS with preserved AS. Further studies with larger groups, longitudinal follow-up and outcome data are needed to corroborate these results. There is a learning curve, especially for the right parasternal and subclavicular views, but also for other unusual views. In the present report, all echocardiograms were acquired by senior cardiologists with particular expertise in echocardiography and valvular disease. However, given the important clinical consequences of our findings, this multiview approach should be performed systematically in all patient with AS, to gain enough practice and to maintain this technical skill after the learning curve.

Conclusions

Aortic flow misalignment, arising from a lack of use of multiple windows evaluation and a lack of correction for pressure recovery, accounts for a significant proportion of incorrect grading of AS, and leads to considerable overestimation of the frequency of LG severe AS with preserved LVEF.

Role of the funding source

None.

Disclosure of interest

The authors declare that they have no competing interest.


Acknowledgments

The authors thank Amélie Lansiaux, MD, PhD, Domitille Tristram, RN and Camille Trouillet for technical assistance in the performance of this study.


Appendix A. Supplementary data

(19 Ko)
  
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