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Introduction:Many patients undergoing transcatheter aortic valve implantation (TAVI) for severe aortic stenosis (AS) are older and have concomitant hypertension. Accordingly, their left ventricle faces a double load which can be better estimated by the valvulo-arterial impedance (Zva) than the AV gradient alone. Ventriculo-arterial coupling, defined as the ratio of arterial elastance (Ea) to left ventricular contractility (Ees) has been shown to be a marker of mechanical efficiency. An elevated or ?unbalanced? Zva/Ees ratio would indicate that Ees is no longer adequate for the level of systolic load.Hypothesis:We hypothesized that the Zva/Ees ratio could be used to for risk stratification in TAVI.Methods:In all, 134 patients (mean age 81, 50% men, mean EF 51%) undergoing TAVI, with 1 and 3 year follow up, were studied. Zva was indexed to single-beat Ees, modified to incorporate the mean AV gradient. We defined an unbalanced coupling ratio to be Zva/Ees > 2. Statistical significance was assessed using Fisher?s exact test.Results:Zva was similar in the balanced and unbalanced groups (p = NS), while Ees was higher in the balanced group; thus 71% had an unbalanced Zva/Ees. There was a trend towards increased 1-year mortality among patients with an unbalanced Zva/Ees compared to those with a balanced ratio: 14% and 3%, respectively (p = 0.07). Three-year mortality was higher in patients with an unbalanced vs balanced Zva/Ees: 29% and 13%, respectively (p = 0.05). Of note, no patient with an EF > 50% and balanced Zva/Ees died within the first year; the 3-year mortality rate in this cohort was 6% (Figure).Conclusion:Among older patients undergoing TAVI: (1) balanced Zva/Ees identifies a low risk population; (2) unbalanced Zva/Ees was associated with poor outcome, possibly because it reflects failing LV mechanical efficiency and/or inadequate compensatory LVH for the systolic load. Whether coupling or Ees alone is the true predictor of outcome merits further study.