Intrapulmonary arteriovenous anastomoses in healthy dogs assessed using saline contrast echocardiography and response to oxygen therapy.

Abstract

BACKGROUND: Intrapulmonary arteriovenous anastomoses (IPAVAs) are physiological pulmonary right-to-left shunts reported in both humans and dogs but their clinical relevance remains uncertain. HYPOTHESIS/OBJECTIVES: Intrapulmonary arteriovenous anastomoses frequently are present in healthy dogs at rest and oxygen therapy will decrease IPAVA flow. We aimed to determine the prevalence of IPAVAs in clinically healthy dogs and to assess the effect of oxygen supplementation on shunt flow. ANIMALS: Fifty-three client-owned dogs undergoing routine cardiac screening at the Jeonbuk National University Animal Medical Center. METHODS: Prospective study. Clinically healthy dogs underwent agitated saline contrast echocardiography to detect IPAVAs at rest. The IPAVAs were identified by delayed microbubble appearance in the left ventricle (&#x2265;3 cardiac cycles after right ventricular opacification). Dogs with confirmed IPAVAs received oxygen therapy (FiO&#x2082;&#xa0;=&#xa0;0.4) for 5&#xa0;min, and bubble scores were compared before and after oxygen supplementation. RESULTS: Of the 53 clinically healthy dogs, IPAVAs were observed in 24 (45.3%). Among 20 IPAVA-positive dogs that received oxygen therapy, bubble scores significantly decreased (P&#xa0;<&#xa0;.01), with complete resolution of shunting in 8 dogs. CONCLUSIONS AND CLINICAL IMPORTANCE: Intrapulmonary arteriovenous anastomoses are common in clinically healthy dogs and may cause delayed left ventricular microbubble appearance during saline contrast echocardiography, potentially mimicking intracardiac right-to-left shunts. Oxygen supplementation significantly decreased IPAVA flow, suggesting that these physiological shunts may be dynamically regulated by inspired oxygen levels.