REsting FLOW rate to determine true Aortic valve Severity (REFLOW-AS)

Patients with low gradient severe aortic stenosis (AS) are clinically challenging cohort requiring additional imaging modalities to secure diagnosis of severe AS. We aimed to assess whether resting aortic valve area (AVA) can determine hemodynamic severity of AS in patients with high trans-valvular flow rate (TFR).

This was a retrospective single centre analysis of consecutive patients undergoing dobutamine stress echo (DSE) for AS work-up. A standard protocol for low-dose DSE was performed and data on resting as well as stress echocardiographic parameters were prospectively entered in a dedicated database. The accuracy of resting aortic valve area was assessed at various TFR. Of 201 patients in this study, the mean age was 78 ± 8 years, and 69% were male. True severe aortic stenosis was identified in 102 (50.7%) of patients. Unlike indexed stroke volume and left ventricle ejection fraction (LVEF), TFR was an independent predictor of true severe AS, even after adjustment for mean gradient and AVA [odds ratio (OR) 0.86, 95%CI (0.74-1.00), P = 0.044]. Receiver-operator characteristics (ROC) analysis using resting aortic valve area demonstrated an area under the curve (AUC) of 0.91, 95% CI 0.82-0.99, P < 0.001 in patients with TFR ≥220 ml/s. A TFR of ≥220 ml/s, with a resting AVA <1.0 cm² had a 100% positive predictive value for true severe AS.

TFR is an easily applied echo measurement. In situations with discordant echo data, TFR ≥220 ml/s supports the diagnosis of severe aortic stenosis and negates the need for further diagnostic imaging.