Valvulo-arterial impedance (Zva): a new index of global hemodynamic load in the evaluation of severe aortic stenosis treated by transcutaneous aortic valve prosthetic implantation (Corevalve)

Background: Some authors have recently proposed a new index of global left ventricular hemodynamic load, ie, valvulo-arterial impedance (Zva), which can quantify the severity of valvular aortic stenosis better than the standard indexes. Indeed Zva is able to provide an estimate of global left ventricular hemodynamic load induced by aortic valve stenosis, as the integration of valvular and vascular loads. Objectives: Our aim was to evaluate the early changes of valvulo-arterial impedance, integrated with other performance parameters of valvular and left ventricle (LV), induced after transcatheter aortic valve implantation (TAVI), in patients with severe symptomatic aortic stenosis, assessed by trans thoracic Background: Some authors have recently proposed a new index of global left ventricular hemodynamic load, ie, valvulo-arterial impedance (Zva), which can quantify the severity of valvular aortic stenosis better than the standard indexes. Indeed Zva is able to provide an estimate of global left ventricular hemodynamic load induced by aortic valve stenosis, as the integration of valvular and vascular loads. Objectives: Our aim was to evaluate the early changes of valvulo-arterial impedance, integrated with other performance parameters of valvular and left ventricle (LV), induced after transcatheter aortic valve implantation (TAVI), in patients with severe symptomatic aortic stenosis, assessed by trans thoracic echocardiography. Methods: Sixty-five consecutive patients, with an average age of 82.6±5.9 years and an average of 19.4% EuroScore, who underwent TAVI had transthoracic echocardiography immediately before and immediately after aortic valve implantation together with the invasive hemodynamic measurements. Results: Promptly after TAVI, we assessed by echocardiography an immediate reduction of transaortic peak pressure gradient (before: 87,8±23,2 vs after: 13,5±6,1 mmHg, p<0,0001), of mean pressure gradient (55,1±15,6 vs 7,2±3,9 mmHg, p<0,0001) and a concomitant increase in aortic valve area (0,26±0,09 vs 0,97±0,28 cm2/m2, p<0,0001) and concomitant recovery in energy loss index (0.33±0.14 vs 0.98±0.29 cm2/m2; p<0.0001). LV ejection fraction (EF) significantly increased immediately after TAVI in all patients (47.7±11.3 vs 54.1±11.7%; p<0.0001). Regarding the global left ventricular hemodynamic load, we found an acute and significant reduction of σm(es) (79.1±34.7 vs 55.2±28.9 kdyne cm-2; p<0.0001) and of Zva (7.63±2.51 vs 5.75±2.23 mmHg ml-1 m-z2; p<0.0001). Therefore Zva improved even in those patients with low baseline LV ejection fraction (p<0,0001). Conclusions: Accurate assessment of global left ventricular hemodynamic load (valvulo-arterial impedance - Zva), integrated with other performance parameters to evaluate the aortic stenosis severity (aortic pressure gradient, aortic valve area, aortic valve area indexed, energy loss index and LV systolic performance), allows a better selection of patients with severe and symptomatic aortic stenosis who may undergo TAVI, in particular regarding the effective procedural results.