AJP - Heart and Circulatory Physiology, Vol 246, Issue 3 339-H343, Copyright © 1984 by American Physiological Society
Effect of increased pulmonary vascular resistance on right ventricular systolic performance in dogs
M. Ghignone, L. Girling and R. M. Prewitt
We tested the possibility that for a given contractile state and right
ventricular systolic pressure (RVSP), rate and extent of ventricular
shortening would be reduced as resistance to ejection increased. In eight
anesthetized, ventilated dogs, we measured RV and pulmonary artery pressure
(Ppa), blood pressure, heart rate, cardiac output (CO), and RV dP/dt before
(condition 1) and after (condition 2) pulmonary vascular resistance (PVR)
was increased by injection of small (80 micron) glass beads. Glass beads
caused a large increase (P less than 0.001) in Ppa and in RVSP and, despite
increased RV end-diastolic pressure (EDP), CO and stroke volume (SV) were
reduced. A third set of measurements was obtained following a further
increase in resistance (condition 3). A comparison of condition 2 with
condition 3, despite constant RVSP, constant mean Ppa, and increased EDP,
showed a marked fall in CO and SV (P less than 0.001) when glass bead
injection increased calculated resistance from 21 (condition 2) to 34
(condition 3) mmHg X 1(-1) X min. RV contractility, as assessed by Vmax and
peak dP/dt was similar in both conditions. In five additional dogs, we
measured the same parameters as before plus instantaneous pulmonary artery
flow in all conditions. In a comparison of conditions 2 and 3, despite
constant RVSP and increased EDP, peak and total flow (P less than 0.05)
were reduced as resistance to RV ejection increased. We conclude that the
right ventricle shortens more slowly and to a smaller extent against the
same systolic pressure when its resistive afterload increases.
