Forward diastolic flow in pulmonary artery induced by right atrial contraction of pig hearts.
To study whether right atrial contraction can forward blood into the pulmonary artery during diastole, blood volume was expanded in anesthetized open-chest pigs until mean right atrial pressure was 13-20 mmHg (range). In the control situation, blood flow in the pulmonary artery was only observed during ventricular systole. Forward diastolic pulmonary artery flow, coinciding with right atrial contraction, was observed when diastolic pulmonary artery pressure was reduced during selectively increased left-side contractility, during bradycardia after propranolol injection (0.5 mg/kg body wt iv), and during the prolonged diastolic interval after spontaneously occurring atrial extrasystoles. The prolongation of the diastolic interval in all three series caused the diastolic pulmonary artery pressure to decline and the filling of the right atrium to increase, thus further stimulating the right atrial Frank-Starling mechanism. The diastolic blood flow in the pulmonary artery constituted 11% of the stroke volume during increased left-side inotropic stimulation, 8% during bradycardia, and 6% in beats preceded by a prolonged diastolic interval. Thus, in the normal heart, blood can be ejected into the pulmonary artery during right atrial contraction.
Vengen
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OA
Institute for Experimental Medical Research, Ullevaal Hospital, University of Oslo, Norway.
Ellingsen
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O
Ilebekk
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D000818:Animals; D016275:Atrial Function; D001794:Blood Pressure; D002122:Calcium Chloride / Q000494:pharmacology; D003971:Diastole; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D011433:Propranolol / Q000494:pharmacology; D011651:Pulmonary Artery / Q000502:physiology*; D011652:Pulmonary Circulation; D012016:Reference Values; D012039:Regional Blood Flow; D013552:Swine
D011433:Propranolol; D007545:Isoproterenol; D002122:Calcium Chloride