[Electric instability of the hearts of animals with differing resistance to immobilization stress]

In 72 Wistar, August, SHR and non-linear rats, a reduction of thresholds for dysrhythmia and elongation of the cardiac cycle vulnerable phase occurred indicating obvious functional shifts following the immobilization stress. The Wistar rats revealed a greater resistance as compared to other rats: no changes of the vulnerable phase duration occurred in 80% and no difference whatever was observed in the remaining 20% of the Wistar rats. In dysrhythmia--prone animals the respective thresholds decreased most sharply and fibrillation of ventricles was mostly irreversible.