Introduction

The adult parasites of Dirofilaria immitis lodge in the pulmonary arteries and right cardiac chambers of the dogs, chronically causing proliferative endarteritis, pulmonary hypertension (PH) and cardiac failure.

Objectives

The aim was to assess the utility of thoracic radiology and echocardiography in the classification of the severity of the disease.

Methods

Twenty-one (21) heartworm-infected dogs were classified in 2 groups based on the symptomatology, color intensity of the antigens test, presence/absence of parasites in echocardiographic exam and subjective evaluation of the thoracic radiography. For this study, the vertebral heart score (VHS) and ratio for the right cranial pulmonary artery to the fourth rib (RCrPa/4R) were measured in thoracic radiographies. The right pulmonary artery distensibility index (RPAD index) was echocardiographically assessed to evaluate the presence or absence of PH.

Results

Mildly-diseased dogs (n=14) presented VHS of 10.25 and RCrPa/4R ratio of 1.29. The RPAD index was 31.84%. Severely-diseased dogs (n=7) had a VHS of 10.85, RCrPa/4R ratio of 2.15 and the RPAD index was 25.68%. Significant differences were observed in RCrPa/4R and RPAD index between both groups (p<0.05).

Conclusions

VHS and RCrPa/4R were increased in all animals, especially in severely-diseased dogs. The RPAD index showed presence of PH in all dogs, being greater in the severely-diseased animals. The diagnostic imaging may be useful in the objective establishment of the severity of the disease in dogs with heartworm and further research may allow the establishment of reference values to objectively classify the severity of heartworm disease in dogs.