Rapid in vivo determinations of instantaneous right ventricular pressure and volume in dogs.
We have developed a method for measuring in vivo canine right ventricular (RV) volume at a frequency of 60 Hz. In six dogs (17-22 kg), under pentobarbital anesthesia, 18 radiopaque markers were surgically implanted in the RV myocardium to maximally represent the RV shell. The xyz-coordinates of the markers were obtained from biplane cineradiographic recordings. RV volume was calculated from the polyhedron created by the markers by decomposing the polyhedron into 24 tetrahedrons, each of whose volumes could be solved from the xyz-coordinates of markers. RV volume was obtained each 16.7 ms, permitting detailed representation if RV volume dynamics. RV end-diastolic volume, end-systolic volume, and ejection fraction averaged 41.3 +/- 10.9, 23.0 +/- 5.8, and 0.44 +/- 0.05 ml, respectively. By simultaneously measuring RV pressure, RV pressure-volume loops were constructed that demonstrated that RV ejection occurred without significant isovolumic contraction, although isovolumic relaxation occurred at end systole. RV systolic elastance was determined in two dogs by imposing four levels of RV afterload. Maximal systolic elastance averaged 4.14 mmHg/ml under control conditions and 9.20 mmHg/ml during dobutamine infusion.
Schwiep
F
F
Department of Internal Medicine, Southwestern Medical School, University of Texas Health Science Center, Dallas 75235.
Cassidy
S S
SS
Ramanathan
M
M
Johnson
R L
RL
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002302:Cardiac Output; D004280:Dobutamine / Q000494:pharmacology; D004285:Dogs / Q000502:physiology*; D006339:Heart Rate; D008433:Mathematics; D008954:Models, Biological; D013318:Stroke Volume / Q000187:drug effects; D016276:Ventricular Function
D004280:Dobutamine