Objective: To determine if the pulmonary to systemic flow ratio (Qp/Qs) could be assessed in healthy awake dogs using Doppler echocardiography.
Background: Qp/Qs could provide reliable information in assessing the severity of intracardiac shunts (ICS) by quantifying pulmonary overcirculation. Qp/Qs has been validated against electromagnetic flowmeter methods in experimental canine models. However, its clinical applicability in awake dogs has never been assessed.
Animals, materials and methods: Six healthy dogs were used to determine the repeatability and reproducibility of the technique (Study 1); Qp/Qs was then prospectively assessed in 50 healthy dogs (Study 2). In both studies Qp/Qs was calculated in awake animals using a standardized Doppler echocardiographic method.
Results: Within- and between-day coefficients of variation for Qp/Qs were <10% (Study 1). For Study 2, a relatively wide range of Qp/Qs was found (reference range=0.71-1.29; mean+/-SD=1.00+/-0.15).
Conclusions: Qp/Qs can be assessed with good repeatability and reproducibility in healthy dogs. However, the wide range of Qp/Qs obtained in the healthy population may suggest a limited usefulness of this variable for accurately assessing ICS severity in diseased animals. This needs to be assessed in further prospective and longitudinal studies including a large number of animals with ICS of various grades.