Study of the presence and prevalence of systemic hypertension in dogs with heartworm (Dirofilaria immitis)

Abstract

Dirofilaria immitis is a parasite responsible of causing heartworm disease. This parasite causes serious physiopathology damages in multiple organs and systems being the cardiorespiratory system the most studied. The most common consequence of this disease is the pulmonary hypertension (PH) which can be measured by a transthoracic Doppler echocardiography and the severity by the Right Pulmonary Artery Distensibility Index. There are preliminary results that suggest that one of the consequences of PH could be the presence of systemic hypertension, which has not been studied with dogs with heartworm before. Therefore, the aim of this study was to determine the relationship between systemic hypertension and some clinical parameters of heartworm disease: pulmonary hypertension, parasite burden, presence of microfilariae and renal biomarkers. For this, 116 dogs infected by D. immitis were tested for microfilariae, had the systemic blood pressure tested, presence/absence of PH echocardiographically calculated and the parasite burden estimated. Of the 116 dogs, 36 had also renal parameters measured: urea, creatinine, UPC ratio, and SDMA. Furthermore, 55 dogs followed adulticide treatment and microfilaria, parasite burden, systemic and pulmonary pressures were also determined on day of discharge. Systolic and mean blood pressures showed a statistically significant difference regarding presence/absence of PH at the beginning of the study, but not after the adulticide treatment. No significant differences were found in systemic blood pressures regarding renal parameters. The results of this study show that a high percentage of dogs with heartworm present systemic hypertension being probably due to a chronicity of the infection, underlying diseases not diagnosed, high stress levels at the veterinary clinic or due to cardiorespiratory alterations. In order to clarify the origin and consequences of this clinical signs, as well as the usefulness of the measurement of systemic blood pressure, further studies must be carried out.