Summary The participation of the heart in shock syndrome formation during endotoxin shock is a problem still awaiting solution. The task undertaken is to assess the work of the left ventricle and arterial pressure in rabbits before and after endotoxin injection at a dose of 2 mg kg-1. Heart rate is the first to reach significantly lower values-at 30 min (p <0.05). At 45 min, there are significant reductions in dP/dtmax (p <0.01), (dp/dt)/P40 (p <0.001), LVP (p <0,05), and increase in dP/dtrieg (p <0.02). Both the systolic and diastolic blood pressures were significantly decreased at 60 min. The data obtained warrant the assumption that impaired myocardial contractility plays a part in the formation of shock syndrome in rabbits exposed to endotoxin.Key words : ventricular contractility, endotoxin shock.The vascular insufficiency is a major pathogenetic factor of endotoxin shock. The participation of the heart in shock syndrome formation is a problem that is still not clarified (HINSHAw,1985). GILBERT (1960) and subsequently HINSHAW et al. (1972) were successful in demonstrating that the myocardium is affected in late stages of endotoxin shock. Data has been submitted pointing to a much earlier impairment of the myocardial function in Gram-negative shock in humans (CERRA et al., 1978;Woo et al., 1979), and in endotoxin shock in animals (SoLIS and DOWNING, 1966;PARKER and ADAMS, 1985), than previously supposed (ADAMS et al., 1984).The purpose of the present study is to evaluate and compare the changes in contractility of the left ventricle and arterial pressure in endotoxin-treated rabbits.
In four-month-old spontaneously hypertensive rats (SHR) the effect of a calcium blocking agent verapamil on blood pressure, ventricular contractility indices, parathyroid hormone (PTH), plasma renin activity (PRA), plasma and adrenal corticosterone content and catecholamines in hypothalamus, myocardium and adrenal gland was evaluated. Calcium and phosphorus in plasma were also determined. Verapamil treatment resulted in a significant decrease in systolic and diastolic blood pressure and a reduction in maximum left ventricular pressure. Verapamil exerted a negative inotropic effect, evaluated by a decrease in dP/dt max and dP/dt neg. PRA was elevated, calcium tended to decrease, and no changes in PTH and phosphorus were found. The hypotensive effect of verapamil in SHR was accompanied by a decrease in plasma and adrenal corticosterone content, and a fall in catecholamine concentration in adrenal glands and myocardium.
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.
Summary Two groups of SHR were treated with Captopril (Squibb): the first group (1 month old)-30 mg/kg i.p. twice daily for 77 days, and the second group (8 months old)-20 mg/kg p.o. twice a day for 23 days. The recording of electrocardiogram (ECG), systolic blood pressure (SBP), diastolic blood pressure (DBP), and some isometric indices of the leftventricular contractility indicate that in all treated animals the values of most of the parameters are considerably lowered compared to the controls. The ratio between velocity of pressure increase and intraventricular pressure/equal to 50 mmHg-(dP/dt)/ICP50/does not change significantly. It can be concluded that in SHR, captopril practically does not influence the inotropic condition of the myocardium.
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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.