Apparent depression of right ventricular function after selective reduction of left ventricular inotropy: an interpretation of experimental data utilising a computer-based circulatory model

Abstract

Consequences of ventricular interactions upon commonly used descriptions of ventricular diastolic and systolic properties were inferred from a circulatory model. The model included active heart compartments, vascular interconnections and the pericardium and was adapted on a digital computer. Numerical values assigned to model parameters were such as to resemble the circulatory system of the dog. Model predictions were utilised to analyse experimental observations in a dog preparation with closed chest and pericardium. Dog ventricular and pericardial pressures (P) and volumes (V) were measured in a control situation and after ischaemic depression of left ventricular (l.v.) function. Model predictions and experiment observations were qualitatively identical. During l.v. inotropic depression (in model and experiment the stroke volume was reduced by about 50% and the l.v. end-diastolic pressure (e.d.p.) increased by about 10 mmHg) the right ventricular (r.v.) diastolic P-V relationship shifted leftwards/upwards while that of the l.v. shifted rightwards/downwards. When corrected for the effect of pericardial pressure the r.v. and l.v. diastolic P-V relations fitted single curves. R.v. function curves (stroke work against dastolic pressure or volume) indicated systolic depression of the r.v. The model indicated that the observations were results of encoroachment of a dilating l.v. upon the r.v. The model indicated that the of increased r.v. afterload. The findings imply that the diastolic P-V relationship of one heart compartment cannot be assessed by measurements in this compartment alone, and that function curves of one ventricle are affected by ventricular interactions which cannot be separated from true alterations in the inotropic state.