Regional hypoxic pulmonary vasoconstriction in dogs with asymptomatic dirofilariasis.
The pulmonary hemodynamic response to unilateral alveolar hypoxia was investigated in pentobarbital-anesthetized dogs with mild heartworm (HW) disease and in dogs free of HW (HWF). Left lung nitrogen ventilation in HWF dogs resulted in a decrease in the fraction of the cardiac output (QT) perfusing the left lung (QL) from 0.37 +/- 0.03 (SEM) to 0.20 +/- 0.02 (P less than 0.01). In contrast, dogs with mild HW disease did not develop a significant decrease in QL/QT which decreased from 0.38 +/- 0.02 to 0.33 +/- 0.02. This attenuated pulmonary vascular response to regional alveolar hypoxia in dogs with HW disease was associated with a normal pulmonary arterial pressure (14.8 +/- 1.5 mm of Hg) that was not different from that seen in HWF dogs (15.8 +/- 1.7 mm of Hg). These results indicate that mild HW disease interferes with the ability of hypoxic pulmonary vasoconstriction to redistribute pulmonary blood flow away from hypoxic regions of the lung.
D000818:Animals; D002302:Cardiac Output; D004184:Dirofilariasis / Q000503:physiopathology / Q000662:veterinary*; D004283:Dog Diseases / Q000503:physiopathology*; D004285:Dogs; D005260:Female; D008297:Male; D011651:Pulmonary Artery / Q000503:physiopathology; D011652:Pulmonary Circulation; D014661:Vasoconstriction