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Low-Gradient, Low-Flow Severe Aortic Stenosis With Preserved Left Ventricular Ejection Fraction: Characteristics, Outcome, and Implications for Surgery | Journal Scan
Study Questions:
What are the outcomes of patients with low-gradient, low-flow (LG/LF) severe aortic stenosis (AS) with preserved left ventricular ejection fraction (EF) compared with moderate AS and with high-gradient AS?
Methods:
In an observational study, 809 patients (75 ± 12 years) diagnosed with at least mild AS and preserved EF (≥50%) were divided into four groups: mild-to-moderate AS, high-gradient AS, LG/LF AS, and low-gradient normal-flow (LG/NF) AS. Information on outcomes was obtained retrospectively (median follow-up with medical management, 23 [interquartile range (IQR) 7-53] months). The measured outcome was overall survival after the first echocardiogram.
Results:
Compared to patients with mild-to-moderate AS patients, LG/LF AS patients had smaller valve areas and stroke volumes, higher mean gradient, but comparable degrees of ventricular hypertrophy. Under medical management, compared with mild-to-moderate AS patients, high-gradient AS patients were at higher risk of death (adjusted hazard ratio [HR], 1.47 [1.03-2.07]), while LG/LF AS patients did not exhibit excess mortality risk (adjusted HR, 0.88 [0.53-1.48]). During the entire follow-up with medical and surgical management (median 39 [IQR 11-69] months), the mortality risk associated with LG/LF AS was close to that of mild-to-moderate AS (adjusted HR, 0.96 [0.58-1.53]), while the excess risk of death associated with high-gradient AS was confirmed (adjusted HR, 1.74 [1.27-2.39]). The benefit associated with aortic valve replacement was confined to the high-gradient AS group (adjusted HR, 0.29 [0.18-0.46]) and was not observed for LG/LF AS (adjusted HR, 0.75 [0.14-4.05]).
Conclusions:
In this study termed by the authors to be real-world/routine practice, the outcome of LG/LF severe AS with preserved EF was similar to that of mild-to-moderate AS, and was not favorably influenced by aortic surgery. The authors concluded that further research is needed to better understand the natural history and the progression of LG/LF AS.
Perspective:
Since its initial description and association with adverse outcome (Hachicha Z, et al. Circulation 2007;115:2856-64), there have been conflicting reports about the clinical implications of LF/LG severe AS with preserved EF. Notably, the diagnosis of LF/LG severe AS is based on an (continuity equation-derived) effective orifice area (EOA) consistent with severe AS, but mean gradient suggesting less-than-severe disease. Because of this, LF/LG severe AS in a ‘real-world’ setting is a heterogeneous mixture of patients with actual severe AS (and low stroke volume) and patients in whom the EOA is either incorrectly calculated or not representative of true AS severity. One downside of ‘real-world’ studies might be that they represent a mixture of patients with and without real disease.
Keywords: Aortic Valve Stenosis, Echocardiography, Heart Valve Prosthesis, Hypertrophy, Stroke Volume
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