Haemodynamic effects of the quaternary ammonium compound QX 572 in anaesthetized cats. I. Cardiac chronotropic effects.

The haemodynamic effects of the antiarrhythmic compound, QX 572, have been studied in anaesthetized cats. It was found that QX 572 increased the heart rate and decreased the blood pressure of the cats during the infusion of the drug. A slight increase in blood pressure was seen after the infusion was terminated. The same results have been obtained in patients. Experiments on cats pretreated with propranolol or reserpine showed that infusions of QX 572 caused an increase in heart rate by increasing the sympathetic activity in the cats. It is also shown that changes in vagal tone may contribute to the effects of QX 572 on the heart rate.