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CLINICAL RESEARCH: VALVULAR HEART DISEASE

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

Institut Universitaire de Cardiologie et de Pneumologie de Québec/Québec Heart and Lung Institute, Department of Medicine, Laval University, Québec City, Québec, Canada

Manuscript received December 2, 2008; revised manuscript received March 20, 2009, accepted April 21, 2009.

^_* Reprint requests and correspondence: Dr. Jean G. Dumesnil or Dr. Philippe Pibarot, Québec Heart and Lung Institute, 2725 Chemin Sainte-Foy, Québec City, Québec G1V 4G5, Canada (Email: jean.dumesnil{at}med.ulaval.ca).

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·m² (65 ± 5%) compared with those with Z_va between 3.5 and 4.5 mm Hg·ml^–1·m² (78 ± 4%) and those with Z_va 3.5 mm Hg·ml^–1·m² (88 ± 3%). The risk of mortality was increased by 2.76-fold in patients with Z_va 4.5 mm Hg·ml^–1·m² and by 2.30-fold in those with a Z_va between 3.5 and 4.5 mm Hg·ml^–1·m² 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.

Key Words: aortic valve • aortic stenosis • hypertension • arterial compliance • mortality

Abbreviations and Acronyms   AS = aortic stenosis   AVA = aortic valve area   AVR = aortic valve replacement   CABG = coronary artery bypass graft   CI = confidence interval   ELI = energy loss index   LV = left ventricle/ventricular   LVEF = left ventricular ejection fraction   PP = pulse pressure   SV = stroke volume   SVI = stroke volume index   Zva = valvuloarterial impedance

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