[Role of the characteristic impedance of the ascending aorta in the evolution of indices of left ventricular performance during the ejection stage].

In this study of 61 patients (group I: 37 patients with no signs of cardiac failure, group II: 24 patients with signs of cardiac failure), a comparison is made between the indices of left ventricular performance obtained during the isovolumic phase dp/dt/Pt max of the left ventricle (5F Millar micromanometer) and in the ejection phase (ejection fraction, mean speed of fibre contraction, corrected mean systolic ejection speed (left ventricular cineanigiography) and maximal acceleration of the aortic blood flow (electromagnetic velocimeter). Calculations were also made of the modulus of elasticity (Ep) and the characteristic impedance of the ascending aorta (Zo) in every patient. The results show that, for group I patients the correlation between the indices in the isovolumic and ejection phases is improved by taking Zo into account. This result is not true for group II cases except with respect to the acceleration of aortic blood flow. An analysis has been made of the hypotheses and the discrepancies.