Valvuloarterial impedance in aortic stenosis: look at the load, but do not forget the flow.

The vast majority of patients with severe calcified aortic stenosis (AS) have normal left ventricular (LV) ejection fraction, even in the presence of symptoms. Nevertheless, ≈20% of patients with AS and undergoing valve surgery were found with reduced LV ejection fraction (,50%) in the last Euro Heart Survey. This characteristic is often the result of a concomitant coronary artery disease. In some patients, however, LV hypertrophy, due to the chronic pressure overload, is inadequate to normalize systolic wall stress, resulting in an afterload mismatch and a decrease in LV ejection fraction. Reduced LV function may lead to low-flow state and thus to lowgradient, despite the presence of severe AS. In fact, three main types of patients with severe AS, according to LV function and flow, are generally observed: (i) normal LV ejection fraction and normal flow, (ii) reduced LV ejection fraction and reduced flow, and (iii) normal LV ejection fraction and reduced flow. Low-ejection fraction/low-gradient severe AS represents a challenging clinical entity. The classification of patient in the so-called low-flow/low-gradient (LF/LG) severe AS subset may considerably vary from different studies and is generally based on the presence of the three following haemodynamic criteria: (i) an aortic valve area (AVA) ,1 cm, (ii) a LV ejection fraction ,30–45%, and (iii) a mean transvalvular pressure gradient (MPG) ,30–40 mmHg. LF/LG severe AS is associated with a poor outcome under conservative management and a high operative mortality risk. Moreover, even after aortic valve replacement (AVR), the prognosis of such patients is worse than those with preserved LV function, and the improvement of symptoms remains limited.