Abstract
Analysis of jugular tracings in seven normal subjects in sinus rhythm whose heart rate varied spontaneously from one moment to another during expiratory apnoea, showed that a pronounced variation occurred in the size of the "a" waves in relation to that of the "v" waves and in accordance with the corresponding RR interval. In the 53 measurements which were carried out, the "a/v" ratio had a mean value of 0.9 for a heart rate above 87, 1.4 for a heart rate between 87 and 68, and 1.1 for a heart rate less than 68. The variations in the size of the "a" waves in relation to heart rate are explained by the place of atrial systole during the different phases of ventricular filling. This variation in the height of the "a" wave has also been found in patients with an atrial septal defect for heart rates between 62 and 86, and this could lead to misdiagnosis, either dismissing the diagnosis of atrial septal defect when the heart rate is around these values, or suspecting it wrongly when the heart rate is either slower or faster. When examining jugular tracings, one should therefore be cautious about interpreting the size of the "a" wave which should be evaluated as a function of heart rate.