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Flow-Gradient Patterns in Severe Aortic Stenosis With Preserved Ejection Fraction: Clinical Characteristics and Predictors of Survival
Study Questions:
What is the clinical impact of low stroke volume among patients with severe aortic stenosis (AS) with preserved ejection fraction (EF)?
Methods:
A cohort of 1,704 consecutive patients with severe AS (aortic valve area <1.0 cm2) and preserved EF (≥50%) were examined using two-dimensional echocardiography with Doppler. Patients were stratified by stroke volume index (<35 ml/m2 [low flow, LF] vs. ≥35 ml/m2 [normal flow, NF]) and aortic gradient (<40 mm Hg [LG] vs. ≥40 mm Hg [high gradient, HG]) into four groups: NF/HG, NF/LG, LF/HG, and LF/LG.
Results:
NF/LG (n = 352, 21%) was associated with favorable survival with medical management (2-year estimate, 82% vs. 67% in NF/HG; p < 0.0001). LF/LG severe AS (n = 53, 3%) was characterized by lower EF, more prevalent atrial fibrillation and heart failure, reduced arterial compliance, and reduced survival (2-year estimate, 60% vs. 82% in NF/HG; p < 0.001). In multivariable analysis, the LF/LG pattern was the strongest predictor of mortality (hazard ratio, 3.26; 95% confidence interval, 1.71-6.22; p < 0.001 vs. NF/LG). Aortic valve replacement was associated with a 69% mortality reduction (hazard ratio, 0.31; 95% confidence interval, 0.25-0.39; p < 0.0001) in LF/LG and NF/HG, with no survival benefit associated with aortic valve replacement in NF/LG and LF/HG.
Conclusions:
The authors concluded that among patients with severe AS and preserved EF, those with LG and reduced stroke volume may have an adverse prognosis.
Perspective:
Low mean gradient (<40 mm Hg) in combination with severe AS defined by effective orifice area (EOA) <1.0 cm2 or EOA index <0.6 cm2/m2 can be due to severe AS with a LF state (LF/LG severe AS), due to error in calculation of the EOA using the continuity equation, error in failing to detect the highest aortic valve gradient, or AS that is not truly severe based on the EOA threshold. Although LF/LG initially was considered only among patients with decreased LVEF, the introduction of the concept of LF/LG severe AS with ‘paradoxically’ normal LVEF (Hachicha Z, et al. Circulation 2007;115:2856-64) both raised awareness of this condition and set the stage for some degree of confusion and misdiagnosis. Inherent to a diagnosis of LF/LG severe AS is LF. The relatively favorable prognosis in this study that was associated with LGs, but NF is a reminder that not every EOA <1.0 cm2 accurately reflects a diagnosis of severe AS. In order for a patient to have LF/LG severe AS with normal LVEF, the stroke volume index should be evaluated, reported, and <35 ml/m2.
Keywords: Prevalence, Incidence, Prognosis, Cardiology, Heart Failure, Heart Valve Prosthesis Implantation, Angioplasty, Echocardiography
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