SERUM ELECTROLYTES AND CATECHOLAMINES AFTER CARDIOVERSION FROM VENTRICULAR-TACHYCARDIA AND ATRIAL-FIBRILLATION

We have observed hypokalemia after cardioversion from spontaneous out- of-hospital ventricular fibrillation and induced ventricular tachycard ia. To test the hypothesis that the hormone response to the hemodynami c stress of the arrhythmia initiated the change in potassium, we compa red the electrolytes and hormones in three groups of patients. We obse rved a decrease in serum potassium and magnesium after cardioversion f rom ventricular tachycardia induced by programmed stimulation, but not after normal programmed stimulation of the ventricle or after cardiov ersion from stable atrial fibrillation. These changes were preceded fi rst by a rise in norepinephrine and epinephrine, then a rise in glucos e, followed by a rise in insulin. The stimulus for these changes was p robably the hypotension associated with ventricular tachycardia. The s equence of changes suggests that the decrease of potassium and magnesi um after ventricular tachycardia was due to a shift of the electrolyte s into cells, related to the insulin-mediated movement of glucose from the blood into cells.