ELECTROCARDIOGRAPHIC STUDIES IN PATIENTS WITH AN ARTIFICIAL PACEMAKER

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Abstract
Ten patients with Adams-Stokes attacks have been treated with artificial pacemakers. Two patients died but there is no reason to suppose that death was caused by ventricular fibrillation produced by the pacemaker. The other patients are in good condition but there is pronounced interference in one patient with a high rate in his "idiocardiac" pacemaker and a low rate in his artificial one. The artificial pacemaker stimuli appeared during the systole of spontaneous beats, very few appearing during the last part of the T wave or during diastole. The reasons for different pacemaker stimulus rates are discussed and it appears that a rate of about 70-75 a minute is preferable to lower rates. The electrodes are best placed near the apex of the left ventricle to produce the most effective contraction from the apex towards the base. Brachial artery pressure curves from patients with interference between the pacemaker rhyghm and the "idiocardiac" rhythm revealed that pacemaker-induced beats perceded by P waves produced systolic peaks as high as the spontaneous beats. When the P waves fell in the ventricular complex of a pacemaker-induced beat or appeared after it, the systolic pressure peaks were satisfactory but not as high as when the P waves preceded the ventricular complex. Hemodynamic studies in one patient showed that on effort the increase in cardiac output was greater, and the arterio-venous oxygen difference was less, at a heart rate of 60 a minute than at a rate of 27 a minute.