Cardiopulmonary and inflammatory biomarkers in the assessment of the severity of canine dirofilariosis

Abstract

The prognosis and success of adulticide treatment depends on the baseline severity of infection with Dirofilaria immitis in dogs and can influence the therapeutic protocol to choose. A study was conducted to assess the utility of the cardiopulmonary biomarkers N-terminal of the prohormone brain natriuretic peptide (NT-proBNP), cardiac troponin I (cTnI), myoglobin, and D-dimer, as well as the biomarker of inflammation C-reactive protein (CRP) to evaluate the severity of canine heartworm disease in different stages. Serum samples were collected from 20 heartworm-infected dogs for measurement of these biomarkers. Dogs were assigned to four groups (n = 5/group) according to the severity of the disease: Class I and Class II dogs showed concentrations of biomarkers generally within normal ranges for healthy dogs, except CRP in dogs classified as Class II, which showed values slightly above laboratory reference values (19.46 ± 5.69 mg/l). Dogs of Class III showed elevated levels of NT-proBNP (1220.12 ± 465.18 pmol/l) (p < 0.05), cTnI (0.99 ± 0.39 ng/ml), CRP (33.98 ± 7.99 mg/l) (p < 0.05), and 40% of these dogs (2/5) presented pathological values of D-dimer and myoglobin (p < 0.05). Dogs of Class IV (caval syndrome) presented elevated levels of NT-proBNP (>2530.8 pmol/l), cTnI (1.99 ± 0.32 ng/ml), and CRP (80.24 ± 47.69 mg/l); all Class IV dogs showed pathological elevations of D-dimer (0.81 ± 0.46 ng/ml), and 60% (3/5) of these dogs showed pathological elevations of myoglobin (significant elevations [p < 0.05] for all biomarkers with respect to reference values and values for dogs in Classes I, II, and III). In canine heartworm disease, chronic presence of D. immitis causes a proliferative endoarteritis, thromboembolisms, pulmonary hypertension, and right-sided congestive heart failure. As the severity of the disease worsens, serum values of cTnI, myoglobin, and NT-proBNP increase, indicating significant cardiac damage. The finding of pathological concentrations of D-dimer suggests the presence of thromboembolism and/or disseminated intravascular coagulation. CRP increases according to the severity of the disease, indicating inflammatory processes that could contribute to the progression of the disease. These preliminary results demonstrate the utility of cardiopulmonary and inflammation biomarkers to assist in the establishment of the severity of canine heartworm disease.