On the relation between cardiodynamics and heartbeat perception.

The mediation of heartbeat perception by cardiodynamic parameters was investigated by experimentally introducing changes in heart performance. Twenty-five subjects (14 women, 11 men) underwent bicycle ergometric exercises (0-75 W) at different tilt angles (90 degrees-0 degree). After each of the 31 tilt/exercise phases, the following measures of cardiac performance were taken using impedance cardiography: stroke volume, Heather Index (as an indicator of contractile force), heart rate, and an estimate of the momentum of the ejected blood mass. Additionally, a heartbeat perception task was performed. The different tilt/exercise combinations induced profound changes in all cardiodynamic measures. The correlation between heartbeat perception and cardiodynamic parameters was highest for "momentum" (r = .67) and for stroke volume (r = .59). From our data, we infer that intraindividually occurring changes in cardiac perception are mediated partially by characteristics of heart dynamics and that the source of these interoceptive signals lies in the heart or in its close vicinity.