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European Heart Journal 1982 3(3):286-293;
Copyright © 1982 by the European Society of Cardiology.
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© 1982 by The European Society of Cardiology

Influence of acute hemodynamic changes on the normalized negative peak of the first derivative of the apex cardiogram and time constant of ventricular relaxation in dogs

N. KOLEV, G. UZUNOV, V. VLASAKOV and G. TIJANEVA

Medical Academy, Higher Medical Institute, Department of Internal Medicine Varna, Bulgaria

Received 27 May 1981; revised 18 August 1981; .

Request for Reprints to:Dr N.Koel,Medical Academy. Higher Medial Institute, Dept of Internal Medicine,9002 Varas,Bulgaria

Abstract

The effect of various alterations in preload, afterload and inotropic state of the left ventricle on two non-invasive indices of myocardial relaxation was studied in anesthetized dogs, in an attempt to clarify some of the determinants of myocardial relaxation. The first derivative of the displacement left apex cardiogram (dA/dt), the apex cardiogram, left ventricular pressure, the first derivative of left ventricular pressure, electrocardiogram and phonocardiogram were recorded simultaneously. The following mechanocardiographic parameters of myocardial relaxation were investigated: (1) normalized negative peak of dA/dt for simultaneous isovolumic apex cardiographic amplitude (min dA/dt/Ar). and (2) time constant of myocardial relaxation T. The non-invasive time constant was derived from a logarithmic isovolumic calibrated apex cardiographic amplitude v. time plot subsequent to min dA/dt.

The indices min dA/dt/Ar and T compared with analogue parameters of left ventricular catheterization (min dP/dt/Pr and T) showed similarity in magnitude and standard deviation during various acute hemodynamic interventions. The min dA/dt/Ar was related to the level of afterload; furthermore isoprenaline accelerated relaxation as determined by the two investigated indices. During the various hemodynamic changes a high correlation existed between invasive and non-invasive indices. The results presented indicate that the apexcardiographic time constant of myocardial relaxation may be a reliable index for ventricular relaxation since it is independent of pre- and afterload, whereas min dA/dt/Ar are load-dependent.

Key Words: First derivative of apex cardiogram • normalized negative peak • time constant of myocardial relaxation • loading conditions


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