Paradoxical low-flow, low-gradient aortic stenosis despite preserved left ventricular ejection fraction: new insights from weights of operatively excised aortic valves

Abstract

Aims: We reported 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). The aortic valve weight (AVW) excised at the time of valve replacement is a flow-independent marker of stenosis severity. The objective of this 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.

Methods and results: We 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/m(2)] with MG < 40 mmHg (PLF-LG group) and 105 (42%) were in NF (LVEF > 50% and SVi > 35 mL/m(2)) 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, we 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.

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

Keywords: Aortic stenosis; Echocardiography; Low flow; Surgery.