Purpose of review: The occurrence of low-flow low-gradient severe aortic stenosis in patients with normal left ventricle (LV) ejection fraction has only been recently described. The purpose of this review is to highlight the diagnostic and management specificities of this entity.
Recent findings: In the American College of Cardiology/American Heart Association guidelines, the criteria for severe aortic stenosis are an effective orifice area less than1.0 cm2 or less than 0.6 cm2/m2, a transvalvular mean gradient greater than 40 mmHg and a peak aortic jet velocity greater than 4.0 m/s. The guidelines also acknowledge that lower gradients may be observed in patients with depressed ejection fraction, with the implication that such an occurrence is not expected in patients with normal ejection fraction. However, recent studies confirm that a bona fide low-flow, low-gradient (LFLG) state may nonetheless be observed in 10–25% of patients with severe aortic stenosis and normal left ventricular ejection fraction (LVEF). This entity bears analogy with normal LVEF heart failure and is due to a restrictive physiology in relation with more pronounced LV concentric remodeling, a smaller LV cavity size and reductions in LV compliance and filling.
Summary: The clinical relevance of LFLG severe aortic stenosis is now recognized in the most recent European (European Society of Cardiology/European Association for Cardio-Thoracic Surgery) guidelines, which also emphasize that it should be confirmed as being due to low-flow conditions. In particular, patients with bona fide paradoxical LFLG aortic stenosis should be distinguished from patients with normal flow and low gradient because of inconsistent cutoff criteria because, among patients with severe aortic stenosis, the former have the worst prognosis, whereas the latter have the best.