Usefulness of the Valvuloarterial Impedance to Predict Adverse Outcome in Asymptomatic Aortic Stenosis

Objectives This study was designed to examine the prognostic value of valvuloarterial impedance (Z(va)) in patients with aortic stenosis (AS). Background We previously showed that the Z(va) is superior to standard indexes of AS severity in estimating the global hemodynamic load faced by the left ventricle (LV) and predicting the occurrence of LV dysfunction. This index is calculated by dividing the estimated LV systolic pressure (systolic arterial pressure + mean transvalvular gradient) by the stroke volume indexed for the body surface area. Methods We retrospectively analyzed the clinical and echocardiographic data of 544 consecutive patients having at least moderate AS (aortic jet velocity >= 2.5 m.s(-1)) and no symptoms at baseline. The primary end point for this study was the overall mortality regardless of the realization of aortic valve replacement (AVR). Results Four-year survival was significantly (p < 0.001) lower in the patients with a baseline Z(va) >4.5 mm Hg.ml(-1).m(2) (65 +/- 5%) compared with those with Z(va) between 3.5 and 4.5 mm Hg.ml(-1).m(2) (78 +/- 4%) and those with Z(va) <= 3.5 mm Hg.ml(-1).m(2) (88 +/- 3%). The risk of mortality was increased by 2.76-fold in patients with Z(va) >= 4.5 mm Hg.ml(-1).m(2) and by 2.30-fold in those with a Z(va) between 3.5 and 4.5 mm Hg.ml(-1).m(2) after adjusting for other risk factors and type of treatment (surgical vs. medical). Conclusions Increased Z(va) is a marker of excessive LV hemodynamic load, and a value >3.5 successfully identifies patients with a poor outcome. These findings suggest that beyond standard indexes of stenosis severity, the consideration of Z(va) may be useful to improve risk stratification and clinical decision making in patients with AS. (J Am Coll Cardiol 2009;54:1003-11) (c) 2009 by the American College of Cardiology Foundation