Cardioelectrical field in experimental cardiomegaly in rats

The examinations were carried out on 24 young rats divided in groups: 1st group: Controls (C), 2nd group: swimming rats (S), 3rd group: sympathectomized rats (G) and the 4th group: sympathectomized swimming rats (GS). ECG, VCG and BSPM were recorded on the 42nd day of their life in pentobarbital anaesthesy. We used regular 23-leads system which covers the entire precordium of the rat. The average body weight of the individual groups was (C) 212.4 g, (S) 182.3 g, (G) 183.7 g and (GS) 200.1 g and the heart weight was (C) 695.4 mg, (S) 761.1 mg, (G) 669.7 mg and (GS) 783.8 mg. Heart rate in the groups G, GS and S in comparison to the control group (C) was significantly decreased. In all three experimental groups the voltage of R wave increased. The duration of the QRS complex was unchanged. The heart axis was orientated more downward especially in G and GS rats. In all groups the activation of ventricles in BSPM starts from the upper left precordium and propagates in a circle downward to the right, continuing back upwardly to the left so as to cover the entire precordium. During the repolarization the entire area of precordium is positive. In S group inhomogeneity of electric field with islands of negativity appears and repolarization sequence is late. In the groups G and GS is similar course of activation without inhomogeneities. The potential max values in groups GS (1.76 mV) and S (1.54 mV) are significantly higher than in the C (1.1 mV). We assumed that the observed changes of cardioelectric field in experimental groups probably reflected an increase of the number of cardiomyocytes (see groups G and GS), resp. enlargement of its volume (S): thus the different enlarged area of electrical active membranes of myocardium. (Tab. 3, Fig. 3, Ref. 30.)