Further observations on modelling of the cardiovascular function in the electrical model.

In 1976 the fourth type of the electrical model of the cardiovascular function was constructed, showing formal and electronic changes: inverting system, hysteresis comparator (for the valve function), simulation of the insufficiency and the stenosis of the valves. The analog values were established but they are not yet definitive. The important values are: pressure 100 mm Hg = 100mV; flow 100 ml/sec = 137 microA. The action of the heart is given by changing capacity; the contractility is characterized by systolic capacity (CS). The diastolic capacity (CD) is not yet variable (CD = 4,000 microF) and consequently the diastolic pressure is always near to zero. The pressure curves of the left ventricle and of the aorta of cardiac patients with aortic valve disease were simulated. For comparison purposes only two clinical records and electrical model simulation records are given in this paper. In the patients (only aortic stenosis is given here) left heart catheterization was carried out. A case of coronary heart disease is also shown. The curves (simulated) are satisfactory and reflect the events in the compression chamber. The values of the parameters, which were used in the stimulation, represent the analysis of the clinical curves and a functional characterization of the situation. Besides these simulations the effect of valve changes on the pressure in the left ventricle, aorta and large arteries was also studied. With the aim of extending the integrative view of the use of the electrical model, an attempt of comparing the time course of capacity changes and the time course of inner surface changes of the left ventricle was made. The cinecardioangiographic data, obtained in an invasive way, were used for the purpose of obtaining the inner surface of the left ventricle. From pressure and surface data the cardiac forces (isometric, average and also total force per minute) were calculated and compared with the normal state, taken from the literature. The total force per minute includes the sum of systolic durations per minute and characterizes the energy expenses of the heart. Further data must be obtained by different cardiographic techniques in order to obtain a solid basis for the use of indirect methods, where the electrical model would be helpful as a noninvasive integrative tool in the assessment of the cardiovascular function.