The objective was to establish whether an intravascular volume increase leads to a heart rate (HR) increase without increased sympathetic tonus. HR changes at rest and at deep breathing (6/min - simulated increase of atrial filling pressure) were measured in patients after heart transplantation. Evaluation of dependency of HR changes on breathing depth was done through a new time series methodology. The data was evaluated through graphs displaying a significant increase in the graph area at deep breathing, when compared with breathing at rest (p < 0.01). We presume that an increase in HR corresponds to increased intravascular volume and malfunctioning kidneys., M. Souček, T. Kára, P. Jurák, J. Halámek, L. Špinarová, J. Meluzím, J. Toman, I. Řiháček, J. Šumbera, P. Fráňa., and Obsahuje bibliografii