Many inorganic salts, especially of the alkaline earth elements, have been used experimentally in control of the heart rhythm of lower animals, but as far as is known potassium salts have never been applied for this purpose to man, prior to the time of our preliminary report1 in November, 1930.
The rationale of potassium therapy of human cardiac arrhythmias is based on experimental evidence, from various sources, that potassium ion excess in the fluid perfusing a heart will prevent extrasystole formation from mechanical, electrical or pharmacologic stimuli. Ringer2 and later investigators have studied the influences of other ions, and especially the conflicting actions of calcium and potassium. A definite ratio of calcium and potassium ions, or certain substitutes, is a recognized necessity for the maintenance of normal cardiac activity.
Excessive calcium was found to increase the strength of contraction and to lengthen the duration of systole. It also