Paradoxical Low-Flow, Low-Gradient Aortic Stenosis: New Evidences, More Questions
In the American Heart Association (AHA) / American College of Cardiology (ACC) and European Society of Cardiology (ESC) / European Association of Cardiothoracic Surgery (EACTS) guidelines,1,2 severe aortic stenosis (AS) is defined as a peak aortic jet velocity >4.0 m/s, a mean gradient >40 mmHg, and/or an aortic valve area (AVA) <1.0 cm2 and it is considered a class I indication for aortic valve replacement (AVR) if the patient has symptoms or LV systolic dysfunction defined as LV ejection fraction (LVEF) <50%. However, the cardiologist is often confronted with patients with discordant echocardiographic findings, the most frequent being the combination of a small calculated AVA (<1.0 cm2) consistent with the presence of severe AS with a low mean gradient (<40 mmHg) suggesting the presence of moderate AS. This type of discordance may raise uncertainty about the actual severity of the stenosis and thus about the therapeutic management, particularly if the patient is symptomatic. Such AVA-gradient discordance is often related to the presence of low LV outflow, which may, even if modest, lead to an important reduction in gradient and thus to underestimation of stenosis severity. A low-flow state is generally defined as a stroke volume index < 35 ml/m2 and it may occur not only in patients with reduced LVEF (i.e. classical low-flow) but also in those with preserved LVEF.3 This latter entity was first described in 2007 by Hachicha et al. and was named "paradoxical" low-flow AS.4 Subsequently, Dumesnil et al. proposed a new classification whereby patients with a priori severe AS on the basis of AVA and a preserved LVEF (i.e. >50%) are separated into 4 groups according to flow (stroke volume index< or ≥35 ml/m2) and gradient (< or ≥ 40 mmHg) as follows: 1) Normal-Flow, High Gradient (NF/HG); 2) Normal-Flow, Low-Gradient (NF/LG); 3) Low-Flow, High-Gradient (LF/HG); and 4) Low-Flow, Low-Gradient (LF/LG).5 In this issue of the journal, Eleid et al. report the characteristics, outcomes, and impact of therapy in a large series of 1704 patients stratified according to this classification.6 The main findings of this elegant study are: 1) Among patients with AVA<1.0 cm2 and LVEF ≥50%, those with LF/LG have lower survival compared to patients with the other flow/gradient patterns but, nevertheless, the outcome of these patients is markedly improved by AVR. 2) Patients with NF/LG have favourable survival with medical management and impact of AVR on their outcome is neutral, thereby suggesting that these patients are likely at a less advanced stage of their disease than patients with other flow/gradient patterns.
- Received September 13, 2013.
- Accepted September 16, 2013.