[Determination of active components of amrinone by analysis of pressure-volume results; use of the conductance (volume) catheter technic and rapid load change by balloon occlusion of the inferior vena cava].

Endsystolic pressure-volume relationships (ESPVR) were determined using the conductance (volume) catheter-technique and the required rapid load changes by applying vasoactive drugs (nitroprusside = NP; phenylephrine = PE) or brief preload reduction by balloon occlusion of the vena cava inferior (BOVCI). With this load-independent index of contractility, we analyzed the hemodynamically active components of amrinone (AM) over a range of different LV-loading conditions. In 19 patients (study I) with still normal LV-function (LVF) in group A (dP/dtmax 1585 +/- 386 mmHg/s; n = 10) and impaired LVF in group B (dP/dtmax 1044 +/- 164 mmHg/s; n = 9) an infusion of AM, 1.5 mg/kg over 2 min, failed to induce changes in ESPVR (p greater than 0.05), but rather caused load changes, resembling like those seen with NP. During continuously paced heart rates (90/min) brief infusion phases with NP and PE provided the necessary load changes. In 11 patients (study II) with impaired LVF (dP/dtmax = 1177 +/- 163 mmHg/s) 2.5 mg/kg AM i.v. induced an increase in contractility, which was more pronounced after the additional application of dobutamine (DOB) at 10 micrograms/kg/min.; (1) Slope k rose from 0.52 to 0.80 mmHg/ml; (2) dP/dtmax increased by an average of 39% and 57% (p less than 0.01), respectively. The BOVCI provided the necessary load changes. Thus AM demonstrates its contractility-increasing effects in a dose-related fashion, probably (at least in part) via an increase in heart rate; inotropic effects further increased with the combination of AM and DOB. The use of the conductance technique for the assessment of ESPVR during acute decrease of preload by temporary BOVCI is innocuous to the patient, reproducible and can be carried out under the conditions of a routine cardiac catheter procedure. This technique seems to be useful in the assessment of relative inotropic effects of the newer cardiotonic drugs.