Echocardiographic Evaluation of Pulmonary Hypertension in Dogs with Heartworm Disease Using the Pulmonary Vein to Pulmonary Artery Ratio

Abstract

Dirofilaria immitis is a nematode that produces proliferative pulmonary endarteritis in dogs due to direct contact of the adult parasites with the intima layer of the pulmonary arteries. The vascular lesions lead to an irreversible structural damage and a sustained pulmonary hypertension which can produce dyspnoea, exercise intolerance, cough, or even right heart failure. The purpose of this study was to assess the diagnostic value of the pulmonary vein to pulmonary artery ratio (PV:PA ratio) measure obtained by echocardiography to determine moderate or severe pulmonary hypertension (PH) (>55mmhg) in dogs with heartworm disease. 29 heartworm-infected dogs and 11 healthy dogs were included in the study. Based on the Right Pulmonary Artery Distensibility index, PH was present in 58.6% of dogs infected by Dirofilaria immitis. The PV:PA ratio was measured by M mode and 2D (or B) mode, and compared with the right pulmonary artery distensitivity index (RPAD index), the Gold Standard, and with other alternative measures for estimation of PH (Main pulmonary Artery to Aorta ratio or MAP:Ao, parasitic burden and the PV:PA ratio via thoracic radiology) to value their sensitivity and specificity in the detection of PH. The statistical study of the results showed a high positive correlation between RPAD index and PV:PA ratio, with a sensitivity and specificity of 1.00. The PV:PA ratio may be useful as a complementary diagnostic method for the determination of moderate or severe PH in dogs with Dirofilaria immitis, when the measure is ≤ 0.615 measured as M mode and 2D Mode. However, further research with a greater number of dogs must be carried out to confirm these results.