Further Observations on the Effect of Drugs on Induced Cardiac Standstill

The heart possesses several important properties. The function most familiar to the clinician is contractility which, when impaired, leads to the frequently observed slow cardiac failure. Sudden cessation of the cardiac activity, however, results from disturbance in another essential property of the heart, that of stimulus formation, termed rhythmicity or automaticity. Normally the sinus node produces the stimulus necessary for cardiac contraction, and the activity of the heart abruptly ceases if this or other rhythmic centers fail to function. Absence of an impulse-initiating mechanism is the cause of the ventricular standstill in complete heart block. The frequency with which impairment of the rhythmic function occurs in other clinical conditions is uncertain, but it probably plays a part in the sudden cardiac arrest occasionally observed on the operating table. The success with which intracardiac injection has resuscitated the asystolic heart in shock, asphyxia and various types of poisoning indicates that the