Cardiodynamic determinants of heart perception

Subjective perception of one's heartbeat is augmented by psychological factors (stress, fear) as well as by physiological influences (e.g., physical work). It is still unclear on which cardiac or circulatory parameters the "signal" for cardiac perception is based. In this study, the relation between cardiac performance and the ability to perceive one's heartbeat was investigated. Sixteen healthy subjects (8 female, 8 male, aged from 21 to 31 years) participated. Cardiac activity was varied by a combination of passive tilt and physical work on a bicycle ergometer. Subjects had to perform physical work (0, 25, 50, 75, 100 W) on the bicycle at seven different angles (90 degrees, 75 degrees, 60 degrees, 45 degrees, 30 degrees, 15 degrees, 0 degrees). A cardiac perception test was carried out after each load. The following cardiodynamic parameters were measured: stroke volume, contractility, and heart rate. The mean correlation coefficient between cardioceptive performance and cardiodynamic parameters was .62 for stroke volume, .45 for contractility, and .12 for heart rate. Obviously, a remarkable relation exists between the mass and--to a lesser degree--the velocity of ejected blood and cardiac perception. From this we infer, tentatively, that the subjectively perceivable heartbeat stimulus is generated by mechanical events that occur close to the left ventricle.