Transaortic Flow Rate and Risk Stratification in Moderate Aortic Stenosis

Background: While left ventricular stroke volume (SV) is commonly used to define flow status in patients with aortic valve stenosis (AS), flow rate (FR) serves as a more precise descriptor of blood flow. However, evidence regarding the prognostic significance and determinates of transaortic FR, specifically in patients with a moderate AS, is limited. Objectives: We aimed to evaluate the association of transaortic FR with outcomes in patients with moderate AS. Methods: We included 292 outpatients (mean age, 80 ± 9 years; 45% women) with moderate AS (aortic valve area, 1-1.5 cm2) and complete clinical evaluation. Transaortic FR was calculated using the derivation-method (FRder) and validated in 90 random patients in whom transaortic FR was also directly calculated as SV/ejection time (FRdir). The primary study end point was a composite of all-cause mortality and hospitalization for heart failure (HHF). Results: After median follow-up of 19.3 (interquartile range, 12.3-26.0) months, 73 patients reached the primary end point (22 HHF and 51 deaths). Patients who met the primary end point had a lower transaortic FRder value compared to those not experiencing events (201 ± 47 mL/sec vs 225 ± 48 mL/sec). The transaortic FRder presented excellent correlation with FRdir (R2 = 0.93, P < .0001). The transaortic FRder threshold for excess risk of adverse outcome was approximately 218 mL/sec. Below this value, the risk increased steeply, showing no plateau effect. Several factors were independently associated with transaortic FRder < 218 mL/sec, including female sex, renal insufficiency, previous myocardial infarction, SV index, and at least moderate tricuspid regurgitation (all P < .02). After comprehensive adjustment, transaortic FRder < 218 mL/sec turned out to be independently associated with events (adjusted hazard ratio, 2.17 [95% CI, 1.14-4.12], P = .018). Conclusions: Transaortic FRder < 218 mL/sec is independently associated with adverse outcomes in moderate AS. Further research is needed to determine whether patients with moderate AS and impaired transaortic FR would benefit from more intensive monitoring or earlier aortic valve replacement.