Introduction: Global left ventricular (LV) afterload as assessed by valvulo-arterial impedance (Zva), may be an independent predictor of mortality in patients with severe aortic stenosis (AS) and preserved LV ejection fraction (LVEF). However, its quantification using echocardiography may be subject to error measurement. We aimed to determine the prevalence and impact on long-term survival of high Zva, purposely measured by cardiac catheterization.
Methods and results: 676 patients with preserved LVEF and severe AS without other valvular heart diseases underwent cardiac catheterization. Zva was derived from catheterization and calculated as follows: mean aortic gradient+systolic blood pressure/indexed LV stroke volume. Zva was considered high when >5mmHg/mL/m(2) based on previous studies. Overall, high Zva was found in 42% of all AS patients. Four-year survival and 8-year survival were significantly reduced in patients with high Zva (74±3% and 57±4%) as compared to those with low Zva (85±2% and 74±3%; p=0.002). After adjustment for all other risk factors, Zva was independently associated with reduced long-term survival (hazard ratio [HR]=1.47 95% CI: 1.04-2.09; p=0.029). Of interest, high Zva remained associated with reduced survival as compared to low Zva, in patients with normal LV stroke volume, but was no longer significant in low flow patients (p=0.98).
Conclusion: High Zva, estimated invasively in our study, is frequent in patients with severe AS, and appears as a robust and independent predictor of survival. Zva should be used as an additional parameter for risk stratification of severe AS, more particularly in patients with normal flow.
Keywords: Aortic stenosis; Catheterization; Impedance; Stroke volume; Survival.
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