Beat-to-beat modulation of right and left ventricular positive dP/dt by afterload. Implications for the evaluation of inotropy.
OBJECTIVE
The rate of pressure rise (dP/dtmax) has mainly been studied in the left ventricle (LV), where it was demonstrated to be highly dependent of preload, but independent of afterload. Load dependence of right ventricular (RV) dP/dtmax is assumed to be similar to (LV)dP/dtmax, although this issue has not yet been investigated in detail. In the current study, we evaluated acute afterload dependence of dP/dtmax in both ventricles in rats.


RESULTS
Adult Wistar rats (n = 8) were instrumented to record RV and LV pressures and septal-free wall diameters. RV and LV afterload elevations were performed by beat-to-beat graded constrictions of the pulmonary trunk or aortic root, respectively. Control cycles and low, moderate and high (isovolumetric) afterload levels were analysed. In both ventricles, afterload modulation of dP/dt was assessed by dP/dtmax normalized for end-diastolic dimensions (dP/dtmax/EDD) and by peak and mean accelerations of pressure rise. RV afterload elevation increased dP/dtmax, dP/dtmax/EDD, peak and mean acceleration of RV pressure rise, without changing the time from end-diastole to dP/dtmax. LV afterload elevations did not significantly change the corresponding left-sided parameters.


CONCLUSIONS
In this study we demonstrated that, in contrast to the left ventricle, right ventricular dP/dtmax and dP/dtmax/EDD relation are significantly afterload sensitive. This should be taken into account for its application in the haemodynamic evaluation of cardiac function in experimental and clinical settings.
Correia-Pinto
Jorge
J
Department of Physiology, Faculty of Medicine, University of Porto, Portugal.
Leite-Moreira
Adelino F
AF
Henriques-Coelho
Tiago
T
Magalhaes
Sónia
S
Gillebert
Thierry C
TC
D000818:Animals; D006439:Hemodynamics; D008297:Male; D009200:Myocardial Contraction / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D016277:Ventricular Function, Left / Q000502:physiology*; D016278:Ventricular Function, Right / Q000502:physiology*; D017725:Ventricular Pressure