Significance of right atrial function during right sided inotropic stimulation of pig hearts in situ.
Cardiac adjustments to inotropic stimulation of the right side of the heart were examined in anaesthetised, open chest pigs by calcium chloride infusion (80 mumol.min-1) into the right coronary artery. At stable haemodynamic conditions and at constant heart rate, right ventricular (RV) pre-ejection segment length increased by 4.6 (2.7-7.2) % (median, 95 % confidence interval) (p less than 0.01), RV end diastolic pressure rose from 5.3 (3.4-7.7) to 6.0 (3.6-8.8) mm Hg (p less than 0.05), and stroke volume rose by 6.8 (4.2-10.8) % (p less than 0.001). When the effect of right atrial contraction on RV filling was excluded by simultaneous pacing of atria and ventricles, the RV pre-ejection segment length no longer increased, and stroke volume rose by only 3.5 (0.1-9.5) % (p less than 0.05) during right side inotropic stimulation. Right atrial inotropic stimulation improves right ventricular filling, and may cause redistribution of blood from the systemic to the pulmonary circulation. This redistribution would raise the pulmonary vascular pressures, and thereby also improve left ventricular filling. The improved right ventricular filling partly accounts for the rise in RV output.
Vengen
O A
OA
Institute for Experimental Medical Research, Ullevaal Hospital, Oslo, Norway.
Ellingsen
O
O
Lande
K
K
Ilebekk
A
A
D000818:Animals; D016275:Atrial Function; D002122:Calcium Chloride / Q000494:pharmacology*; D002304:Cardiac Pacing, Artificial; D005260:Female; D006321:Heart / Q000502:physiology*; D006439:Hemodynamics / Q000187:drug effects; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D013268:Stimulation, Chemical; D013552:Swine
D002122:Calcium Chloride