Paradoxical Low-Flow, Low-Gradient Aortic Stenosis–a Tough Nut to Crack in Echocardiographic Diagnosis

Refer to the page 82-88 In this issue, Abudiab et al. 1) evaluated the characteristics of paradoxical low-flow low-gradient (PLF-LG) aortic stenosis (AS) among subjects who had been diagnosed with severe AS using conventional transthoracic echocardiography (TTE). The authors tried combining transesophageal echocardiography (TEE) with TTE to measure the left ventricular outflow tract (LVOT) diameter and calculate the aortic valve area (AVA). Such AVA calculation reclassified a significant proportion of patients previously diagnosed with PLF-LG severe AS by conventional TTE as moderate AS instead. The present study is interesting for several reasons. First, the prevalence of PLF-LG AS was much lower than previously believed among severe AS, and meticulous examination using multiple modalities can increase diagnostic accuracy for complicated diseases. Second, TTE often overestimates AS severity, particularly in patients with a low volume status such as old age and small body mass index (BMI). Current diagnostic criteria for the low-flow state (stroke volume index <35 mL/m 2) are likely to be insufficient in subjects with extremely small or large body builds. Third, TEE may play an additional role in the diagnosis of PLF-LG AS, and detailed anatomic information regarding the aortic valve and perivalvular structure are complementary to conventional TTE.