Transvalvular Flow Rates in Patients with Moderate-To-Severe and Severe Aortic Stenosis: Clinical Usefulness and Risk Stratification.

Introduction: The definition of low-flow/low-gradient aortic stenosis (AS) using the stroke volume index (SVI) alone overlooks factors like vascular resistance and valve stiffness. Consequently, an SVI indicating a normal flow might indicate a low flow when used with the transvalvular flow rate (TFR), which incorporates ejection time. We compared the SVI (35 mL/m2) and TFR (250 mL/m2) and analyzed the outcomes for patients with and without aortic valve replacement (AVR).

Methods: From 2013 to 2016, we retrospectively evaluated the clinical data of patients with moderate-to-severe and severe AS, defined as a maximum aortic valve velocity ≥3.5 m/s or a valve area ≤1.3 cm2. Patients were categorized into AVR and non-AVR groups. The non-AVR group was further classified by a TFR above or below 250 mL/m2. Moreover, we compared the SVIs with TFRs. We examined the rates of all-cause mortality and heart failure hospitalizations.

Results: Among 135 patients, 42 (31%) had mismatched SVIs and TFRs; 41 had a high SVI and a low TFR, whereas one had a low SVI and a high TFR. Among the 59 non-AVR patients, 25 (71.4%) of the 35 patients with a low TFR died, whereas 4 (16.7%) of the 24 patients with a high TFR died. The TFR in the 76 AVR patients was similar to that in the non-AVR patients, 3 of whom died (3.9%). The Kaplan-Meier analysis revealed that non-AVR patients with a low TFR had worse outcomes and the AVR patients fared best. The SVI was significantly less suitable than the TFR for risk stratification.

Conclusion: This study highlights that a high TFR, rather than a high SVI, is associated with a better prognosis, even among non-AVR patients, suggesting that the TFR is better for risk assessment and complements the SVI.