H.: Electrocardiographic observations on the carotid sinus reflex

IN previous communications 1,2 's I reported the incidence and the degree of cardiac slowing induced by the carotid sinus reflex in a series of 345 cases. The cases were divided into five groups as follows: Group I, coronary artery disease with definite myocardial damage; Group II, hypertension and hyper-tensive heart disease; Group III, rheumatic heart disease; Group IV, in-dividuals with cardiac symptoms but no demonstrable cardiac disease; Group V, general constitutional disease (non-cardiac). It was shown that the order of frequency and degree of response were Groups I, II, III, V and IV—the first showing the highest frequency and degree of response and the last the lowest. Males showed a higher fre-quency and degree of response than females, and there was an increase in frequency of response with advancing age. The present communication deals with an analysis of 426 additional cases, consisting of 243 males and 183 females. These were all ambulatory cases, most of whom had cardiovascular disease. The grouping of this series was as follows: Group I, arteriosclerotic heart disease; Group II, hypertension and hypertensive heart disease; Group III, arteriosclerotic and hypertensive heart disease; Group IV, rheumatic heart disease; Group V, psychoneurotic heart disturbances; Group VI, heart disturbances or disease of various other causes; and, Group VII, cases with-out cardiovascular disease. This finer subdivision was adopted in order to see how the carotid sinus reflex exhibits itself in more precise types of disease. As in the previous paper only the cardio-inhibitory part of the carotid sinus reflex is reported. The vasomotor depressor effect of the reflex, ex-hibited by fall in blood pressure, and the other reflex effects induced by the carotid sinus pressure were not studied