Transaortic Flow in Aortic Stenosis: Stroke Volume Index versus Transaortic Flow Rate

Abstract

Diagnostic certainty in determining the severity of aortic stenosis (AS) can be challenging in patients with low-gradient AS. Current guidelines define categories according to mean gradient (MG), left ventricular ejection fraction (LVEF), and stroke volume index (SVi). Low flow low gradient (LFLG) is defined as aortic valve area (AVA) < 1.0 cm2, MG < 40 mm Hg, and SVi < 35 mL/m2.1 Flow rate, however, is a more appropriate indicator of flow than SVi based on the fundamental hydraulic principles. The transaortic flow rate (TFR) = stroke volume/ejection time, and TFR > 250 mL/sec is considered a normal flow rate.