[Different sensitivities of two mechanisms of excitation waves in heart tissue to anti-arrhythmia agents--blockers of fast sodium currents].

In experiments with rabbit ventricular tissue sensitivity of two kinds of spiral wave sources of excitation to fast sodium current inhibition was compared. These spiral wave sources were circulation in a ring around an obstacle and circulation in tissue without an obstacle (reverberator). It was observed that after application of antiarrhythmic drugs lidocaine or mexiletine there was a prominent growth of cycle length of reverberator during first few seconds of circulation and a little change of cycle length for the circus movement around obstacle.

[Refractory properties of cardiac tissue at fast sodium current decrease. Comparison of atrium and ventricle].

Investigation of the membrane potential of Neurospora crassa mycelial cells was carried out by standard microelectrode technique. The resting potential is equal to--156 +/- 11 mV (negative inside the cell). The light of the spectrum blue-violet zone causes transient hyperpolarization of the cell membrane reaching --38 +/- 5 mV after 25 minutes of illumination.

[Mechanisms of differences of the cycle length of excitation spiral waves in atrial and ventricular tissues].

Ectopic spiral wave sources--reverberators--were produced in pieces of rabbit atrium and ventricle by an induction of a single properly timed premature impulse. It was found that the cycle length (T) of the ectopic source gradually increased immediately after its appearance in atrial and changed a little bit after its appearance in ventricular tissue. Relationship between changes of T and refractorines of the heart tissues was investigated.

[Investigation of anomalous growth of heart refractoriness during tachycardia].

Action potential (AP) characteristics during anomalous growth of refractoriness (R) in rabbit atrium were investigated. Anomalous growth of R arises under the stimulation frequency more than 4-5 s-1. Anomalous R growth is accompanied by AP duration, amplitude and upstroke velocity decrease.

[Refractoriness of cardiac tissue and mechanism of destruction of sources of spiral waves of excitation in the heart].

Ectopic spiral wave sources were produced in pieces of 15 X 15 mm of rabbit atrium by an induction of a single properly timed premature impulse. The cycle length of the ectopic source (T) gradually increased immediately after its appearance. It was shown that T growth is determined by the rise of refractoriness (R).