Pitfalls and Challenges in the Echocardiographic Diagnosis of Aortic Stenosis
calculated valve area (AVA <1cm2) and who present with a mean gradient in the mild to moderate range (<40mmHg) despite normal LV contractility. Obviously, technical errors have to be excluded, but this possible presentation of severe AS has recently been increasingly recognised11–14
patients with severe AS and normal LV contractility.5
and has been described in up to 42% of Importantly,
these patients do not seem to have a better prognosis than their ‘high-gradient’ counterparts.12–14 haemodynamic pattern include:12–14
Possible explanations for this
• relatively low stroke volume, which is not suggested by an apparently normal EF – this could be related to small LV cavity (small-sized patients, severely hypertrophic ventricles) or occult LV systolic dysfunction (elderly patients, LV hypertrophy); and • higher systemic vascular resistance and LV afterload.
The importance of recognising this not uncommon haemodynamic pattern cannot be overemphasised, since AVR, when appropriate, should not be denied to these patients due to a possibly misleading ‘not severe enough’ gradient.
Echocardiographic–Catheterisation Discrepancies
Invasive confirmation of gradients and AVA by Gorlin formula should not be routinely sought as part of the work-up of patients with AS.3,4 Although there is generally good agreement between echocardiography and direct measurements,15,16
discrepancies are noted. Occasionally,
catheterisation gradients may be higher than Doppler gradients due to possible underestimation of the true gradient by echocardiography (see ‘Sources of Error for Gradient Calculation’ above). A more puzzling and, in fact, more frequent scenario occurs when the catheterisation gradient is significantly lower than the echocardiographic one. As seen in Figure 2, while catheterisation records the virtual ‘peak-to-peak’ gradient, Doppler interrogation records the true, instantaneous transvalvular gradient at the time of peak LV systolic pressure, which is uniformly higher due to the relative morphologies and timings of the aortic and ventricular pressure waveforms. The more severe the AS, the higher this discrepancy may be, due to a more delayed aortic pressure peak. In addition, the pressure difference between the left ventricle and the ascending aorta may diminish distal to the valve, a haemodynamic phenomenon described as ‘pressure recovery’.17
This pattern is more likely to occur in patients with
small aortic roots and may be responsible for marked discrepancies between echocardiographic and invasive gradients in 10–14% of patients.17,18
A combination of these two mechanisms explains the reality
of vexing disagreements between catheterisation and echocardiographic assessment of AS patients. There are no rules to decide which method is ‘right’, but careful inspection of valve appearance by echocardiography and integration of all clinical data should provide the answer. If the echocardiographic data seem ‘solid’, the diagnosis of severe AS should not be discarded because the catheter-derived gradient is in the mild to moderate range (see Figure 3). Even better, the dilemma of a catheterisation–echocardiography discrepancy can be avoided ‘by not crossing the aortic valve with a catheter’.1
1. Chambers JB, Eur J Echocardiogr, 2009;10(1):i11–19. 2. Carabello BA, Paulus WJ, Lancet, 2009;373(9667):956–66. 3. Vahanian A, et al., Eur Heart J, 2007; 28(2):230–68. 4. Baumgartner H, et al., Eur J Echocardiogr, 2009;10(1):1–25. 5. Minners J, et al., Eur Heart J, 2008;29(8):1043–8. 6. Tribouilloy C, Levy F, Heart, 2008;94(12):1526–7. 7. Clavel MA, et al., Circulation, 2008;118(Suppl. 14):S234–42.
B
Echo Doppler demonstrated a mean gradient of 30mmHg with a calculated aortic valve area (AVA) 1.1cm2, while catheterisation showed a ‘withdrawal’ peak gradient of <20mmHg. Inspection of the valve appearance by 2D and awareness of possible discrepancies between invasive and Doppler gradients and of possibly moderate gradients only with severe aortic stenosis (AS) supported the diagnosis of significant AS, which was confirmed at surgery.
Conclusions
Echocardiography is the first-line diagnostic tool in the assessment of patients with AS. Cut-off values define severity criteria used to decide appropriateness of intervention. A large minority of patients does not fulfil all accepted criteria and may present with perplexing haemodynamic patterns and echocardiographic results. Awareness of the sources of possible errors and of less typical echocardiographic results is essential for the correct management of AS patients whose echocardiographic studies are, apparently, confounding. n
Adrian Chenzbraun is a Consultant Cardiologist and Clinical Lead of Echocardiography at the Royal Liverpool University Hospital and the Liverpool Heart and Chest Hospital and is on the Advisory Board of the Cheshire–Merseyside Cardiac Network for cardiac imaging. He was a Consultant Cardiologist in Jerusalem and a Senior Lecturer at the Hebrew University and Hadassah Medical School. He was a post-doctoral fellow in echocardiography at Stanford University
Medical School. Dr Chenzbraun has published numerous papers in leading scientific journals, and is the author of Emergency Echocardiography.
Figure 3: Echocardiographic (A) and Catheterisation Results (B) in a Patient with Symptomatic Severe Aortic Stenosis
A
8. Chenzbraun A, et al., Am J Cardiol, 2003;92(12):1451–4. 9. Bermejo J, Yotti R, Heart, 2007;93(3):298–302. 10. Tunick PA, Kronzon I, Circulation, 2004;109(5):e33, author reply e33.
11. Dumesnil JG, et al., Eur Heart J, 2009 (Epub ahead of print). 12. Flachskampf FA, Eur Heart J, 2008;29(8):966–8. 13. Barasch E, et al., J Heart Valve Dis, 2008;17(1):81–8.
14. Hachicha Z, et al., Circulation, 2007;115(22):2856–64. 15. Oh JK, et al., J Am Coll Cardiol, 1988;11(6):1227–34. 16. Currie PJ, et al., Circulation, 1985;71(6):1162–9. 17. Baumgartner H, et al., J Am Coll Cardiol, 1999;33(6):1655–61.
18. Parameswaran AC, et al., Echocardiography, 2009;26(9):1000–1005, quiz 1999.
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