Subnormalization of left ventricular shape after successful coronary revascularization.

BACKGROUND: It is asumed that the shape and size of the left ventricle could change after successful revascularization and that the shape and size reflect left ventricular function. METHODS: Echocardiography and Simpson's rule were used for evaluating the endocardial surface area of the left ventricle and elongation of the left ventricle as shape index in 13 patients before coronary arterio-venous bypass grafting (CABG) and 1 year after successful CABG. RESULTS: After successful CABG, the left ventricle becomes bigger and less elongated than before CABG. Results show a change from concentric hypertrophy of the left ventricle before CABG to subnormalization after CABG. DISCUSSION: We suppose that the subnormalization of left ventricular size and shape is the result of successful CABG and successful rehabilitation. The change of left ventricular size and shape after CABG might depend more on the original state of the left ventricle before surgery.

Shape of the left ventricle and its computer modelling.

A simple computer program was made to draw different left ventricle shapes in order to support the theory of elongation and to get a visual presentation of the shape of the left ventricle. Experimental data, obtained from echocardiography and Simpson's rule, were used for this program. The results yielded different shapes under different physiological circumstances, indicating the sensitivity of the method. It was concluded that these figures (shapes) support the use of elongation as a shape index.

Elongation as a new shape index for the left ventricle.

OBJECTIVES: This study was done to quantify the shape of the left ventricle (LV). It was proposed that the shape of the LV is intimately related to its performance and that its elongation (ELO) is a sensitive measure of this performance. The performance was tested against classical cardiovascular parameters. METHODS: Using echocardiography and Simpson's rule, the endocardial surface area of the LV was calculated noninvasively with a simple experimental-mathematical model at enddiastole and endsystole. ELO as shape index was derived from the endocardial surface area of the LV with a simple formula. The endocardial surface area of the LV and ELO were determined in volunteers, in patients with mild heart failure and in patients with severe heart failure. RESULTS: The normal value of endocardial surface area of LV at enddiastole is 138.3 cm2 while the normal value at endsystole is 99 cm2. The endocardial surface area of the LV is significantly bigger in patients with mild heart failure than in volunteers (p < 0.01) while the parameters ELO, ejection fraction and Doppler measurements are similar. The normal values of ELO at diastole and systole are 12 and 25 respectively. The value of ELO at endsystole is lower only in patients with severe heart failure. This means a more spherical shape and poor systolic function of the LV. CONCLUSION: ELO is usefull as quantitative and qualitative index of left ventricular shape. ELO could be integrated and applied with new diagnostic tools such three-dimensional and contrast echocardiography.

Dynamic characteristics of the thorax connected with the heart action.

We determined the indices of local vibrations (resonance frequency, damping coefficient, stiffness constant, extinction time) and transfer function H(s) . 10(-6) for three somatotypes and three respiratory positions on 88 points of the thorax. The examinees were males (age 21 years). We found the resonance frequencies of 36.86--54.75 cps, damping coefficient (delta) 0.121--0.217. This means the damping is less than critical (delta = 1). We applied shocks (a force of 2 N) with a reflex hammer on 88 points of the thorax. The force diminished from the exciting place (say ictus) to the recording place (accelerometer on the sternum) from 2 to 0.2 N. The athletic type has the highest resonance frequency and stiffness constant; the leptosomic type has the highest damping; the longest extinction time belongs to the pyknic type. The pyknic type has also the highest value of the transfer function. The respiratory position (quiet respiration, Valsalva and Müller experiment) influences the values of the indices of local vibrations and of the transfer function. The influence is evident especially on the intercostal points: the transfer of the oscillations is alleviated at a higher stiffness of the thorax (Valsalva; the value of H(S) . 10(-6) rises from 7.00 to 9.39 sec2), it deteriorates at a small stiffness of the thorax (in Müller's experiment falls to 2.78 sec2). With the fall in the intrathoracic pressure the damping in the intercostal points decreases. On the basis of experiments the conclusion was made that a short testing of the thorax of an examinee will give the dynamic characteristics of the thorax (indices of local vibrations and transfer functions) of the individual. This procedure will alleviate the quantitative use of noninvasive mechanical methods in the assessment of the cardiovascular function.

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.

Genesis of the sphygmogram from the kinetocardiogram.

The functional uniformity of the heart and vessels is studied. The idea of the genesis of the carotid sphygmogram from the kinetocardiogram (GS-KCG) was developed on the basis of the analysis of the KCG and carotid-sphygmographic (CSG) pattern obtained in 10 young healthy adults. Two of these examinees were additionally examined under the influence of a s.c. injection of adrenaline (A) and noradrenaline (NA). Two kinds of transducers for the displacement of the chest wall and of the carotid region were used (photoelectric and resonance receiver). They did not touch the skin and were placed in four positions on the thorax; three of them are routine auscultatory positions (ictus, ERB, aorta), one was the carotid artery pulse position. Amplitude and time intervals at rest and under the influence of catecholamines were determined and their interrelationship studied. The amplitudes are more variable than the intervals. The genesis of the waves was studied on the basis of the records in four positions. On this basis, a uniform hypothesis about the genesis of the KCG and CSG waves is derived. From this hypothesis and from the existence of a reflection wave starting at the aorta, the concept of the genesis of the sphygmogram from the kinetocardiogram was developed: the deformation starts at the aorta, is directed to the apex, is there reflected and propagated to the carotid artery. The validity of this concept of the GS-KCG is proved on the basis of experiments with adrenaline and noradrenaline. The quantitative data of peaks and waves from four positions show a stability of the KCG and CSG pattern despite the influence of catecholamines. A comparison is made between the apex cardiogram (ACG) and KCG and determinants of the characteristic pattern of chest movements are given. It was further concluded that the technique of measuring reflection wave velocity (=intracardiac velocity) and pulse wave velocity (=vascular, mixed) can be used as a test for individual reactivity of the cardiovascular system. The wave velocities and the carotid amplitude can help in detecting a disposition towards coronary disease.

Simulation of catecholamine action in an improved electrical model.

A further development of an electrical model of circulation is presented. The progress consists in: (1) the ventricles are represented as a changing capacity; (2) a constant amount of charge is re-circulating in the system; (3) the contractility of the heart can be varied; (4) the valves are represented by relays, and (5) the pulse wave velocity can be represented. Catecholamine action is studied by changing the heart rate, contractility, elastic resistance and peripheral resistance; the influence on systolic, diastolic pulse pressure and flow pulse in different parts of the arterial system is measured. In the discussion the importance of the concept of deformation-capacity-internal surface of the ventricles for the understanding of the cardiovascular system as a unity is stressed.