[The effect of endotoxin on the cardiovascular system]. / Vliianie éndtoksina na serdechno-sosudistuiu sistemu.

The dynamics of changes in myocardial contractility and pressure in the left ventricle of the heart and the femoral artery were studied in rabbits before and after intravenous infusion of 2 mg/kg endotoxin. The left ventricle was catheterized. The signal from the left-ventricular pressure transducer was fed into a microcomputer after analog-digital conversion for calculating the maximal rate of increase in intraventricular pressure. All the parameters studied began decreasing as early as the 5th minute after endotoxin administration. A statistically significant decrease (p less than 0.05) of the heart rate was recorded first on the 30th minute, than the left-ventricular pressure and maximal rate of intraventricular pressure increase took place on the 45th minute, and systolic and diastolic pressure in the femoral artery decreased on the 60th minute. The detected disorders of myocardial contractility provoke the appearance of hypotension the main role in the development of which is played by damage to the peripheral vascular network.

Angular velocity and acceleration of the QRS vector in the electrocardiogram of rabbits.

The curves of the spatial angular velocity (AV) and of its first derivative (AA) are described for 103 healthy rabbits. After analog-to-digital conversion, the amplified X-, Y- and Z-signals after McFee and Parungao are fed for calculation on a microcomputer. In 41 per cent of the cases the AV curve has two basic waves, in 29 per cent--three, in 21 per cent--one, and in 9 per cent--four, which coincide with the lowest points in the spatial magnitude curve. The AA curve consists of biphasic waves with approximately identical amplitudes of their positive and negative parts. The results are interpreted in connection with the chronotopography of the ventricular depolarization and reorientation of the activation front.

Spectral analysis of the normal electrocardiogram of rabbits.

A spectral analysis of the QRS complex of the rabbit's electrocardiogram was made. The amplified ECG signals were filtered through low-pass filters with cut-off frequency 500 Hz and steepness 12 dB/oct, and fed to a multichannel oscilloscope monitor. The images obtained were photographed. They were subjected to analog-to-digital conversion. The values were fed for processing to an EC 1035 computer. A standard discrete Fourier transformation was used. The spectral curve exhibited a considerable amplitude of the higher harmonics. Point -20 dB was at 164 Hz and point -30 dB was at 314 Hz. It was concluded that for accurate reproduction of the rabbit's ECG the recording electrocardiograph would have a bandwidth up to 225 Hz. An amplitude error not exceeding 10 per cent would be guaranteed.

Investigation of Frank's vectorcardiographic lead system on homogeneous rabbit torso model.

The applicability of Frank's lead system in experiments on rabbits is studied by using a homogeneous rabbit torso model. The influence of dipole localization on the modules of the lead vectors at the level of 4th, 5th and 6th intercostal spaces is studied. The lead vector modules along the axes X, Y and Z for the level of the dipole are calculated to be equal to 1:0.99:0.92. The maximum angular errors in the planes XY, XZ and YZ are calculated, being for the same level theta yz = -6 degrees 50', theta xy = theta xz = 0 degrees 00'. The authors have reached the conclusion that Frank's system produces good levelling of the lead vector modules and has satisfactory orthogonality on rabbit torso model.