Frontal and sagittal electrocardiograms of normal and hypertensive subjects during an experimentally produced phase of lowered blood pressure.

Reduction of the blood pressure in normal and hypertensive subjects by intravenous pyrogen caused the electrocardiograms to assume a more abnormal configuration as judged by present criteria of electrocardiographic normality. A temporary reduction of the blood pressure by the intravenous administration of tetraethylammonium chloride caused only minor and variable modifications of the electrocardiogram. The results of the experiments as done do not support the concept of strain as applied to certain electrocardiographic abnormalities which occur in the course of hypertension. P ATIENTS with hypertension often have electrocardiograms which are characterized by a high voltage of QRS and deviation of its mean axis to the left, a depression of the S-T segment in leads I, II and VL, and lowering or inversion of the T wave in leads I, VL, and sometimes lead IJ.P-9 Similar abnormalities and a late RS deflection6 may be encountered in leads from the left side of the precordium. The changes, particularly in the final ventricular deflections, have been ascribed to cardiac '"strain.""'12 This mechanical interpretation is strengthened by the observation that the abnormalities, particularly in the T wave, sometimes disappear after sympathec-tomy, or after therapeutic measures which presumably cause a prolonged fall in blood pressure .1j-36 It seemed proper to investigate the possibility of reversing the electrocardiographic abnormalities found in certain hypertensive patients by lowering the blood pressure acutely. With this in mind, the blood pressure was reduced in hypertensive patients and in normal control subjects by the intravenous injection of typhoid vaccine37' 38 or of tetraethylammonium chloride (Etamon).* 39 TECHNIC In order to prevent the febrile phase of the pyro-genic reaction, the patients who were to receive the vaccine were given 2.4 to 3.6 Gm. of amidopyrine during the preceding 12 hours. Control electrocardio-grams were obtained before and after amidopyrine. Triple typhoid vaccine,t 0.1 cc., was given intravenously in the morning with the patient in a basal state. Pulse rate, rectal temperature and blood pressure measured with the ordinary mercury sphyg-momanometer were recorded before and for every hour of the first day after the injection of the vaccine with the patient recumbent. Tracings were made when a significant fall in blood pressure occurred , which was usually two to five hours after the injection. The blood pressure generally returned to its control level the next day; occasionally the process took several days. As long as the blood pressure remained low, additional electrocardio-grams were obtained, and …