Role of transesophageal echocardiography in the diagnosis of paradoxical low flow, low gradient severe aortic stenosis

Background and Objectives: Prior studies indicate that up to 35% of cases of severe aortic stenosis (AS) have paradoxical low flow, low gradient despite preserved left ventricular ejection fraction (LVEF). However, error in left ventricular outflow tract (LVOT) diameter may lead to misclassification. Herein, we determined whether measurement of LVOT diameter by transesophageal echocardiography (TEE) results in reclassification of cases to non-severe AS. Subjects and Methods: Patients with severe AS with aortic valve area (AVA) <1 cm2 by transthoracic echocardiography (TTE) within 6 months were studied. Paradoxical low flow, low gradient was defined as mean Doppler gradient (MG) <40 mm Hg and stroke volume index (SVI) ≤35 mL/m2. Preserved LVEF was defined as ≥0.50. Results: Among 108 patients, 12 (15%) had paradoxical low flow, low gradient severe AS despite preserved LVEF based on TTE measurement. When LVOT diameter by TEE in 2D was used, only 5 (6.3%) patients had low flow, low gradient severe AS (p<0.001). Coefficients of variability for intraobserver and interobserver measurement of LVOT were <10%. However, the limits of agreement between TTE and TEE measurement of LVOT ranged from 0.43 cm (95% confidence interval [CI]: 0.36 to 0.5) to -0.31 cm (95% CI: -0.38 to -0.23). Conclusion: TEE measured LVOT diameter may result in reclassification to moderate AS in some patients due to low prevalence of true paradoxical low flow, low gradient (PLFLG) severe AS.