Recruitment of arteriovenous pulmonary shunts may attenuate the development of pulmonary hypertension in dogs experimentally infected with Angiostrongylus vasorum.

OBJECTIVES: The purposes of this study were to evaluate if (1) Angiostrongylus vasorum-infected dogs recruit pulmonary arteriovenous (AV) shunts attenuating the development of pulmonary hypertension (PH), detectable using saline contrast echocardiography, (2) anthelmintic therapy causes an acute increase in pulmonary arterial pressure (PAP), (3) Tissue Doppler Imaging (TDI) allows detection of mild changes in right ventricular function secondary to pulmonary (vascular) disease. ANIMALS: 6 healthy Beagle dogs, each infected with 200 A. vasorum larvae.
METHODS: Conventional, TDI and contrast echocardiography, invasive PAP measurements before (T0), 7-12 weeks post infection (wpi, T1), and 1-5 days post therapy (dpt, T2).
RESULTS: All dogs had patent infections 7-8 wpi and respiratory signs 6-9 wpi. PAP was mildly but significantly increased at T2. Saline contrast echo was positive in 3/6 dogs at T1 and 4/6 dogs at T2. Pulmonary transit time did not change. Of all numeric echocardiographic parameters, only a non-significant decrease in the E' wave and inversion of E'/A' ratio in 3 dogs at T2 could be observed. Two of these had mild PH and negative saline contrast echocardiography.
CONCLUSION: A. vasorum infection causes only a mild increase in PAP following inoculation and anthelmintic therapy. The absence of important PH may in part be explained by the recruitment of AV shunts in the presence of vascular obstructive disease. TDI echocardiographic parameters may be more sensitive to detect mild changes in RV function than conventional parameters.