The spectrum of low-output low-gradient aortic stenosis with normal ejection fraction

Low-flow, low-gradient (LF/LG) severe aortic stenosis (AS) with preserved ejection fraction refers to the condition of AS with aortic valve area <= 1 cm(2), stroke volume index <35 mL/m(2), mean aortic valve gradient <40 mm Hg and left ventricular ejection fraction >= 50%. This mismatch of aortic valve area suggesting severe stenosis and 'low' gradient in some patients has led to confusion as to the severity of stenosis. Conditions previously labelled as LF/LG severe AS include a spectrum, with measurement error probably being the most common cause of marked inconsistency between gradient, valve area and patient presentation. The presence of LG severe AS may be overestimated in petite patients, who may have aortic valve area slightly less than 1 cm2 with only moderate AS. Concomitant cardiac conditions besides AS, including significant mitral and tricuspid regurgitation, intracardiac shunts and constrictive pericarditis, may contribute to reduced stroke volume, and evidence for these must be sought at the time of echocardiography. True LF/LG severe AS is associated with a unique and probably maladaptive remodelling pattern with smaller ventricles, increasing relative wall thickness, progressive worsening of diastolic function and higher afterload, as demonstrated by lower systemic arterial compliance, higher systemic vascular resistance and higher valvuloarterial impedance. Control of hypertension is essential to the appropriate management of patients with AS. Aortic valve replacement should be considered in patients with compelling evidence of severe AS who remain symptomatic despite optimal treatment of hypertension.