Paradoxical Aortic Stenosis: Simplifying the Diagnostic Process

Keywords:
Aortic Valve Stenosis; Echocardiography; Aortic Valve

Severe aortic stenosis (AS) is defined as a significant reduction of the aortic valve area (aortic valve area [AVA] ≤ 1.0 cm²) associated with evidence of left ventricular hypertrophic response (aortic jet velocity > 4 m/s or mean gradient between the left ventricle and the aorta > 40 mmHg).^1-3 However, as Minners et al.⁴ have demonstrated, inconsistencies in echocardiographic measurements are extremely frequent in daily clinical practice. In about 30% of the cases evaluated by AS, we found AVA ≤ 1.0 cm², indicative of severe AS, with a mean gradient < 40 mmHg, suggestive of moderate AS.⁴ This dissociation makes it difficult to establish an adequate and definitive diagnosis to the patient with AS, fundamental point in the therapeutic decision making. If, on the one hand, patients with moderate AS do not benefit from valve intervention, those with severe AS require surgical aortic valve replacement or a transcatheter aortic bioprosthesis implant, especially if they are symptomatic.^1-3

In 2007, Hachicha et al.,⁵ in a pioneering work, defined such patients as having "paradoxical AS" (or low-flow, low-gradient AS with preserved ejection fraction). These patients present a pathophysiology similar to that of diastolic heart failure, with hypertrophy and left ventricular compliance reduction, leading to a "low-flow" state, defined by an ejected volume (stroke volume) of < 35 ml/m² (stroke volume = Diastolic Volume - Systolic Volume / Body Surface).^5-7

Another important contribution of Hachicha et al⁵, corroborated by some subsequent studies,^8-11 was the demonstration of a better survival of symptomatic patients with paradoxical AS after valve intervention when compared to clinical treatment. However, patients with paradoxical AS, despite being benefited by valve intervention, present higher surgical mortality when compared with patients with classic AS (mean gradient > 40mmHg).^1-3,8,9,11

In this paper, we propose an algorithm to facilitate the diagnostic confirmation of paradoxical AS. In three steps, we perform the Recognition of Paradoxical AS, Measurement Error Evaluation and Pathophysiological Confirmation (Figure 1):

Figure 1
Algorithm proposed for the diagnosis of paradoxical aortic stenosis. * In patients with BMI above 30 kg/m², we must use 0.5 cm²/m² value as reference for iAVA. AS: aortic stenosis; AVA: aortic valve area; Vel: jet velocity; Grad: gradient; EF: ejection fraction; iAVA: indexed aortic valve area; sBP: systolic blood pressure; CT: computed tomography.

1. 1. Recognition of Paradoxical AS: this step is the first and most important. The delay in the diagnosis of paradoxical AS causes delayed intervention, leading to an increase in mortality. The classification of "moderate to severe" or even "moderately-severe" valvulopathy is not described in any of the current guidelines and impairs clinical reasoning.^1-3 For this reason, patients with AVA ≤ 1.0 cm², jet velocity < 4 m/s or mean gradient < 40 mmHg and ejection fraction > 50% should be classified as having paradoxical AS or low-flow, low-gradient AS with preserved ejection fraction.

2. 2. Evaluation of Measurement Errors: In this stage, we must identify eventual measurement errors that justify an underestimated gradient or AVA. The echocardiographer should be aware of the correct alignment of the Doppler continuous wave for velocity and gradient measurement, avoiding underestimating these measurements. Another orientation is to avoid AVA measurement by continuity equation and using whenever possible measurement by planimetry. AVA measurement by continuity equation may underestimate AVA, since such measurement takes into account left ventricular outflow tract area calculation (VSVE) (AVA = area of VSVE x VTI of VSVE/VTI of aortic valve; where VTI is time-velocity integral). The VSVE dimension is usually measured with a 2D echocardiogram, assuming that the VSVE is circular. However, such a structure can often be elliptical, causing measurement errors.⁷ 3D echocardiogram is a promising test for more accurate evaluation of VSVE and AVA by planimetry, however, specific studies for the population with paradoxical AS are necessary for its routine indication. Two points are extremely important for the clinical cardiologist. First, in patients with small corporeal surface, a reduced AVA may correspond to moderate AS. In this way we must always index AVA by the corporeal surface (iAVA), being that an iAVA ≤ 0.6 cm²/m² suggests important AS. In obese patients (BMI ≥ 30 kg/m²) we must assume a lower cut-off value (< 0.5 cm²/m²) so as not to overestimate the anatomical severity.¹² The second data that should be evaluated is systolic blood pressure in gradient measurement moment, which should be less than 140 mmHg.¹ Higher pressures contribute to underestimating the mean gradient and generate an increase in the valvulo-arterial impedance, a measure that estimates the ventricular afterload added to arterial and valvular overload ventricle, and it is also associated with mortality.¹³ In summary, the clinical cardiologist should remember to index the AVA and make sure that the systolic blood pressure was < 140 mmHg at the time of gradient measurement, while the echocardiographer should be attentive to errors in gradient measurement and measure the AVA by the planimetry.

3. 3. Pathophysiology Confirmation: Finally, we must confirm the pathophysiology of AS and low-flow, low-gradient. In developed countries, the main etiology of AS is degenerative, also known as calcific. Valvular calcification correlates with anatomic severity and values greater than 1650 AU, verified by computed tomography, suggest anatomically severe AS.¹⁴ However, females may present the same anatomic severity as men, but with lower values of calcification, being advised to apply differentiated cutoff values for female patients (> 1200 AU).¹⁵ Pathophysiology of low flow should be confirmed by stroke volume calculation, as previously described. In order to justify low gradient in a patient with severe AS, he must necessarily present a small cavity with stroke volume < 35 ml/m².^1-3,5-7

Thus, through this 3 steps algorithm, we help in the recognition of paradoxical AS anatomical severity, facilitating the clinician to identify the ideal moment for intervention in this difficult diagnosis entity.

• Sources of Funding
  There were no external funding sources for this study.
• Study Association
  This study is not associated with any thesis or dissertation work.

References

• ¹
  Nishimura RA, Otto CM, Bonow RO, Carabello BA, Erwin JP 3^rd, Guyton RA, et al. 2014 AHA/ACC guideline for the management of patients with valvular heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. Circulation. 2014;129(23):e521-643. doi: 10.1161/CIR.0000000000000031.
  » https://doi.org/10.1161/CIR.0000000000000031
• ²
  Vahanian A, Alfieri O, Andreotti F, Antunes MJ, Barón-Esquivias G, Baumgartner H, et al; Joint Task Force on the Management of Valvular Heart Disease of the European Society of Cardiology (ESC) and the European Association for Cardio-Thoracic Surgery (EACTS). Guidelines on the management of valvular heart disease (version 2012). Eur Heart J. 2012;33(19):2451-96. doi: 10.1093/eurheartj/ehs109.
  » https://doi.org/10.1093/eurheartj/ehs109
• ³
  Tarasoutchi F, Montera MW, Ramos AIO, et al. Atualização das Diretrizes Brasileiras de Valvopatias: Abordagem das Lesões Anatomicamente Importantes. Arq Bras Cardiol 2017; 109(6 Supl.2):1-34. doi: http://dx.doi.org/10.1590/S0066-782X2011002000001
  » http://dx.doi.org/10.1590/S0066-782X2011002000001
• ⁴
  Minners J, Allgeier M, Gohlke-Baerwolf C, Kienzle RP, Neumann FJ, Jander N. Inconsistencies of echocardiographic criteria for the grading of aortic valve stenosis. Eur Heart J. 2008;29(8):1043-8. doi: 10.1093/eurheartj/ehm543.
  » https://doi.org/10.1093/eurheartj/ehm543
• ⁵
  Hachicha Z, Dumesnil JG, Bogaty P, Pibarot P. Paradoxical low flow, low gradient severe aortic stenosis despite preserved ejection fraction is associated with higher afterload and reduced survival. Circulation. 2007;115(22):2856-64. doi: 10.1161/CIRCULATIONAHA.106.668681.
  » https://doi.org/10.1161/CIRCULATIONAHA.106.668681
• ⁶
  Pibarot P, Dumesnil JG. Low-flow, low-gradient aortic stenosis with normal and depressed left ventricular ejection fraction. J Am Coll Cardiol. 2012;60(19):1845-53. doi: 10.1016/j.jacc.2012.06.051.
  » https://doi.org/10.1016/j.jacc.2012.06.051
• ⁷
  Clavel MA, Burwash IG, Pibarot P. cardiac imaging for assessing low-gradient severe aortic stenosis. JACC Cardiovasc Imaging. 2017;10(2):185-202. doi: 10.1016/j.jcmg.2017.01.002.
  » https://doi.org/10.1016/j.jcmg.2017.01.002
• ⁸
  Eleid MF, Sorajja P, Michelena HI, Malouf JF, Scott CG, Pellikka PA. Flow-gradient patterns in severe aortic stenosis with preserved ejection fraction: clinical characteristics and predictors of survival. Circulation. 2013;128(16):1781-9. doi: 10.1161/CIRCULATIONAHA.113.003695.
  » https://doi.org/10.1161/CIRCULATIONAHA.113.003695
• ⁹
  Lancellotti P, Magne J, Donal E, Davin L, O’Connor K, Rosca M, et al. Clinical outcome in asymptomatic severe aortic stenosis. Insights from the new proposed aortic stenosis grading classification. J Am Coll Cardiol. 2012;59(3):235-43. doi: 10.1016/j.jacc.2011.08.072. Erratum in: J Am Coll Cardiol. 2013;62(3):260.
  » https://doi.org/10.1016/j.jacc.2011.08.072
• ¹⁰
  Herrmann HC, Pibarot P, Hueter I, Gertz ZM, Stewart WJ, Kapadia S, et al. Predictors of mortality and outcomes of therapy in low flow severe aortic stenosis: a PARTNER trial analysis. Circulation. 2013;127(23):2316-26. doi: 10.1161/CIRCULATIONAHA.112.001290.
  » https://doi.org/10.1161/CIRCULATIONAHA.112.001290
• ¹¹
  Clavel MA, Berthelot-Richer M, Le Ven F, Capoulade R, Dahou A, Dumesnil JG, et al. Impact of classic and paradoxical low flow on survival after aortic valve replacement for severe aortic stenosis. J Am Coll Cardiol. 2015;65(7):645-53. doi: 10.1016/j.jacc.2014.11.047.
  » https://doi.org/10.1016/j.jacc.2014.11.047
• ¹²
  Tribouilloy C, Bohbot Y, Maréchaux S, Debry N, Delpierre Q, Peltier M, et al. Outcome implication of aortic valve area normalized to body size in asymptomatic aortic stenosis. Circ Cardiovasc Imaging. 2016;9(11). pii: e005121. doi: 10.1161/CIRCIMAGING.116.005121.
  » https://doi.org/10.1161/CIRCIMAGING.116.005121
• ¹³
  Hachicha Z, Dumesnil JG, Pibarot P. Usefulness of the valvuloarterial impedance to predict adverse outcome in asymptomatic aortic stenosis. J Am Coll Cardiol. 2009;54(11):1003-11. doi: 10.1016/j.jacc.2009.04.079.
  » https://doi.org/10.1016/j.jacc.2009.04.079
• ¹⁴
  Cueff C, Serfaty JM, Cimadevilla C, Laissy JP, Himbert D, Tubach F, et al. Measurement of aortic valve calcification using multislice computed tomography: correlation with haemodynamic severity of aortic stenosis and clinical implication for patients with low ejection fraction. Heart. 2011;97(9):721-6. doi: 10.1136/hrt.2010.198853.
  » https://doi.org/10.1136/hrt.2010.198853
• ¹⁵
  Clavel MA, Messika-Zeitoun D, Pibarot P, Aggarwal SR, Malouf J, Araoz PA, et al. The complex nature of discordant severe calcified aortic valve disease grading: new insights from combined Doppler echocardiographic and computed tomographic study. J Am Coll Cardiol. 2013 Dec 17;62(24):2329-38. doi: 10.1016/j.jacc.2013.08.1621.
  » https://doi.org/10.1016/j.jacc.2013.08.1621

Publication Dates

• Publication in this collection
  May 2018

History

• Received
  28 June 2017
• Reviewed
  27 Sept 2017
• Accepted
  24 Aug 2017