Impact of low flow on the outcome of high-risk patients undergoing transcatheter aortic valve replacement

Abstract

Objectives: This study sought to assess the impact of baseline left ventricular (LV) outflow, LV ejection fraction (LVEF), and transvalvular gradient on outcomes following transcatheter aortic valve replacement (TAVR) in patients with severe aortic stenosis (AS).

Background: Low flow (i.e., reduced stroke volume index [SVi]) can occur with both reduced and preserved LVEF. Low flow is often associated with low gradient despite severe stenosis and with worse outcomes following surgical aortic valve replacement. However, there are few data about the impact of low flow on outcomes following TAVR.

Methods: We retrospectively analyzed the clinical, Doppler-echocardiographic, and outcome data prospectively collected in 639 patients who underwent TAVR for symptomatic severe AS in 2 Canadian centers.

Results: In this cohort, 334 (52.3%) patients had a low flow (SVi <35 ml/m(2)) and these patients had increased 30-day mortality (11.4 vs. 5.9%, p = 0.01), 2-year all-cause mortality (35.3 vs. 30.9%, p = 0.005), and 2-year cardiovascular mortality (25.7 vs. 16.8%, p = 0.01) compared with patients with normal flow. Reduced flow was an independent predictor of 30-day mortality (odds ratio: 1.94, p = 0.026), cumulative all-cause mortality (hazard ratio: 1.27 per 10 ml/m(2) SVi decrease, p = 0.016), and cumulative cardiovascular mortality (hazard ratio: 1.29 per 10 ml/m(2) decrease, p = 0.04). Despite significant association in univariable analyses, low LVEF and low mean gradient were not found to be independent predictors of outcomes in multivariable analyses.

Conclusions: Low flow but not low LVEF or low gradient is an independent predictor of early and late mortality following TAVR in high-risk patients with severe AS. SVi should be integrated in the risk stratification process of these patients.

Keywords: AS; CI; Doppler-echocardiography; HG; HR; LEF; LF; LG; LV; LVEF; MG; NEF; NF; OR; SVi; TAVR; aortic stenosis; confidence interval; hazard ratio; high gradient; left ventricle/ventricular; left ventricular ejection fraction; low ejection fraction; low flow; low gradient; mean gradient; normal ejection fraction; normal flow; odds ratio; stroke volume index; transcather aortic valve implantation; transcatheter aortic valve replacement.