Cardiac rhythm in cats during physiological sleep in experimental myocardial infarction and beta-adrenergic receptor...

The authors investigated parameters of the sinus rhythm and of the structure of physiological sleep in 11 cats after ligation of the interventricular artery. ECG of the cerebral cortex, electromyogram, electrooculogram, ECG and respiration were registered, both in the acute period of infarction (4th-10th day of the experiment) and in the subacute and late period (3-12 months). In the acute and subacute period, an abrupt decrease was found in the sinus rhythm variability during the waking-sleep cycle. Propranolol administration (10 mg/kg) reduced in intact animals the heart rate, especially during wakefulness, and the rhythm variability during wakefulness and sleep. Suppression of sinus rhythm automatism due to propranolol in animals with experimental MI was most pronounced in the acute period during REM sleep, in the subacute period during wakefulness. In the acute period of MI, the sleep structure was disorganized, in the subacute period it got partly normalized. Protracted propranolol administration in the subacute period of MI led to disturbances in the sleep structure, with reduced REM sleep and prolongation of stage I-II (superficial sleep).