In the European Heart Journal, Clavel et al. have just published exciting data about ‘paradoxical low-flow/low-gradient aortic stenosis’ (1). This condition has recently been discussed extensively in the context of transcatheter aortic valve replacement (TAVR/TAVI) as reviewed in our journal (2-4). Clavel et al. have previously described that patients with small aortic valve area (AVA) and low flow despite preserved left ventricular ejection fraction (LVEF), i.e. 'paradoxical' low flow (PLF), have worse outcomes compared with patients with normal flow (NF), although they generally have a lower mean gradient (MG) (5). The aortic valve weight (AVW) excised at the time of valve replacement is a flow-independent marker of stenosis severity. The objective of their current study was to compare the AVW of patients with PLF and MG<40 mmHg with the AVW of patients with NF and MG≥40 mmHg.

The authors recruited 250 consecutive patients undergoing valve replacement (Cohort A) for severe stenosis. Among them, 33 (13%) were in PLF [LVEF > 50% but stroke volume index (SVi) ≤ 35 mL/m²] with MG < 40 mmHg (PLF-LG group) and 105 (42%) were in NF (LVEF > 50% and SVi > 35 mL/m²) with MG ≥ 40 mmHg (NF-HG group). Despite a much lower MG (29 ± 7 vs. 53 ± 10 mmHg; P < 0.0001), patients in the PLF-LG group had a similar AVA (0.73 ± 0.12 vs. 0.69 ± 0.13; P = 0.19) compared with those in the NF-HG group. The AVW [median (interquartile): 1.90 (1.63-2.50) vs. 2.60 (1.66-3.32)] and prevalence of bicuspid phenotype (15 vs. 42%) were lower in the PLF-LG group than in the NF-HG group. However, AVWs analysed separately in the tricuspid and bicuspid valves were similar in both groups [tricuspid valves: 1.80 (1.63-2.50) vs. 2.30 (1.58-3.00) g; P = 0.26 and bicuspid valves: 2.72 (1.73-3.61) vs. 2.60 (2.10-3.55) g; P = 0.93]. When using cut-point values of AVW established in another series of non-consecutive patients (n = 150, Cohort B) with NF and concordant Doppler-echocardiographic findings, the authors found that the percentage of patients with evidence of severe stenosis in Cohort A was 70% in patients with PLF-LG and 86% in patients with NF-HG.

The authors conclude that aortic valve weight data reported in their study provide evidence that a large proportion of patients with PLF and low-gradient have severe stenosis and that the gradient may substantially underestimate stenosis severity in these patients. Clavel et al. suggest that multi-parametric approach including all Doppler-echocardiographic parameters of valve function as well as other complementary diagnostic tests may help correctly identify these patients.

This data is very interesting and of critical importance in the context of TAVR/TAVI (2,3).

References:

1. Clavel MA, Côté N, Mathieu P, Dumesnil JG, Audet A, Pépin A, Couture C, Fournier D, Trahan S, Pagé S, Pibarot P. Paradoxical low-flow, low-gradient aortic stenosis despite preserved left ventricular ejection fraction: new insights fromweights of operatively excised aortic valves. Eur Heart J. 2014 Apr 21. [Epub ahead of print]
2. Ozkan A. Low gradient "severe" aortic stenosis with preserved left ventricular ejection fraction. Cardiovasc Diagn Ther. 2012 Mar;2(1):19-27.
3. Lancellotti P. Grading aortic stenosis severity when the flow modifies the gradientvalve area correlation. Cardiovasc Diagn Ther. 2012 Mar;2(1):6-9.
4. Schoenhagen P, Hausleiter J, Achenbach S, Desai MY, Tuzcu EM. Computed tomography in the evaluation for transcatheter aortic valve implantation (TAVI). Cardiovasc Diagn Ther. 2011 Dec;1(1):44-56.
5. Le Ven F, Freeman M, Webb J, Clavel MA, Wheeler M, Dumont É, Thompson C, De Larochellière R, Moss R, Doyle D, Ribeiro HB, Urena M, Nombela-Franco L, Rodés-Cabau J, Pibarot P. Impact of low flow on the outcome of high-risk patients undergoing transcatheter aortic valve replacement. J Am Coll Cardiol. 2013 Aug 27;62(9):782-8.