CLINICAL PROGRESS External and Internal Electric Cardiac Pacemakers

IT HAS long been known that electric cur-rents have important effects on the heart as they do on other excitable tissues. Only re-cently, however, have technics been developed for the therapeutic use of electric currents on the human heart. Two important clinical applications have now been established: elec-tric stimulation of the heart for the produc-tion of an effective beat, which is the subject of this review, and electric countershock for the termination of ventricular fibrillation1-3 and other serious tachyeardias.4 Direct electric stimulation of the heart is a familiar laboratory technic. It is commonly demonstrated in elementary courses in physi-ology, it provides control of the heart rate in many physiologic and pharmacologic experi-ments, and much of our knowledge of cardiac excitability has developed from it. The clin-ical use of direct electric cardiac stimulation via a percutaneous needle electrode in the atrium for resuscitation from cardiac arrest was suggested by Hyman in 1932.5 Electric stimulation of the heart was first applied suc-cessfully in man in 1952 externally by way of electrodes on the chest wall.