Transaortic Flow Rate and Risk-Stratification in moderate Aortic Stenosis.

Abstract

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, are 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 (FR_der) and validated in 90 random patients in whom transaortic FR was also directly calculated as stroke volume/ejection time (FR_dir). The primary study endpoint 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 endpoint (22 HHF and 51 deaths). Patients who met the primary endpoint had a lower transaortic FR_der value compared to those not experiencing events (201±47 mL/s vs 225±48 mL/s). The transaortic FR_der presented excellent correlation with FR_dir (R²=0.93, p<0.0001). The transaortic FR_der threshold for excess risk of adverse outcome was approximately 218 mL/ms. Below this value, the risk increased steeply, showing no plateau effect. Several factors were independently associated with transaortic FR_der<218 mL/s, including female sex, renal insufficiency, previous myocardial infarction, SV index, and at least moderate tricuspid regurgitation (all p<0.02). After comprehensive adjustment, transaortic FR_der<218 ml/s resulted independently associated with events (adjusted Hazard Ratio 2.17 [C.I. 95% 1.14-4.12], p=0.018).

Conclusions: Transaortic FR_der<218 ml/s is independently associated with adverse outcomes in moderate AS. Further research is needed to determine if patients with moderate AS and impaired transaortic FR would benefit from more intensive monitoring or earlier aortic valve replacement.