The Effect of Volume-Flow Discordance on Survival in Severe Aortic Stenosis

Current flow (Q) assessment in aortic stenosis (AS) uses stroke volume index (SVi), a volume (V)-based measure. However, V differs fundamentally from Q, which is defined as volume per unit time (mL/s).

This study evaluates the prognostic significance of volume-flow (V-Q) discordance in patients with severe AS (aortic valve area <1 cm²) undergoing transcatheter aortic valve replacement (TAVR).

We studied 291 patients >65 years of age who underwent TAVR over 5 years (median follow-up, 3.0 years; [Q1-Q3: 3.0-3.0 years]). Aortic flow was assessed using Doppler echocardiography; transaortic flow rate (TFR) was calculated mathematically. Low V-Q discordance was defined as SVi <35 mL/m² with TFR >210 mL/s; normal V-Q discordance as SVi >35 mL/m² with TFR <210 mL/s.

V-Q discordance was observed in 29% of patients (15% low, 14% normal). Among those with SVi <35 mL/m², discordance was more frequent in patients without hypertension (75% vs 65%), coronary disease (57% vs 35%), or diabetes (15% vs 2%; all P < 0.05). Diastolic blood pressure was lower (mean SD: 66+15 vs 59+14 mm Hg; P = 0.018), and arterial compliance was higher (median and Q1-Q3: 1.3 [1.1-1.6] vs 1.0 [0.9-1.2] mL/mm Hg; P = 0.028), independent of SVi and left ventricular ejection fraction (both P > 0.05). Low V-Q discordance was associated with improved 3-year survival (86.0% [95% CI: 72.3%-95.1%] vs 73.8% [95% CI: 64.3%-82.1%]; log-rank P = 0.030) and was a stronger survival predictor (Akaike information criterion [AIC]: 23.79; P = 0.013) than SVi <35 mL/m² (AIC: 29.59; P = 0.047) or TFR <210 mL/s (AIC: 32.80; P = 0.049).

V-Q discordance occurs in nearly one-third of patients with AS post-TAVR and offers superior prognostic value over existing SVi and TFR thresholds.