Effects of potassium chloride on isolated, blood-perfused canine atrial or ventricular muscle preparations

The effects of potassium chloride were studied on pacemaker activity in the sinoatrial (SA) node and on contractility in isolated, blood-perfused atrial and left ventricular preparations of dogs, which were suspended in the bath and perfused with arterial blood from the carotid artery of the heparinized support dog. Potassium chloride given directly into the sinus node artery in a dose range of 100 micrograms--1 mg produced a dose-related positive chronotropic and a negative inotropic effect in isolated atrium preparations. Potassium chloride into the cannulated anterior descending branch of the left coronary artery caused only a negative inotropic effect in isolated ventricular preparations. A larger dose of potassium chloride caused temporary atrial or ventricular arrest. These effects of potassium chloride were not modified by pretreatment with atropine or propranolol.