Cardiac diagnostic test results and outcomes in 44 dogs naturally infected with Trypanosoma cruzi

Abstract

Background: The protozoal parasite Trypanosoma cruzi causes myocarditis in dogs.

Objectives: To describe the cardiac diagnostic test results and outcomes of dogs naturally infected with T. cruzi.

Animals: Forty-four client-owned dogs.

Methods: Medical records were retrospectively reviewed to identify dogs with an indirect fluorescent antibody test result for T. cruzi ≥1 : 80. Data collected included signalment, cardiac diagnostic test results (ECG, echocardiography, cardiac troponin I) and outcome. Outcomes were categorized as alive, dead (cardiac or noncardiac) or lost to follow up.

Results: ECG abnormalities were present in 41 dogs with ventricular arrhythmias (n = 28) and atrioventricular block (AVB) (n = 15) most commonly identified. Echocardiographic chamber enlargement was present in 28 dogs and most often included the right ventricle (RV) (n = 15) and left atrium (n = 12). Troponin was ≥2 times the reference range in 20/36 (56%) dogs. In univariate analysis using nonparametric Kaplan-Meier, ventricular arrhythmias with a modified Lown score ≥2 (P = .02), presence of AVB (P = .04), and RV enlargement (P = .006) were associated with decreased survival times. Right ventricular enlargement (HR 3.6; 95% confidence interval [CI] 1.4-9.3; P = .007) and higher body weight at presentation (HR 1.0; 95% CI 1.0-1.1; P = .04) were associated with decreased time to death in the final explanatory multivariable model.

Conclusions and clinical importance: Cardiac abnormalities were common and variable, and RV enlargement was associated with shorter survival time. A diagnostic evaluation that includes screening for arrhythmias, echocardiography, and cTnI can provide useful information related to the characterization of heart disease in dogs seropositive for T. cruzi.

Keywords: Chagas disease; canine; echocardiography; heart; myocarditis; troponin.

FIGURE 1

Kaplan‐Meier survival curves for dogs seropositive for Trypanosoma cruzi. Each cross represents when a dog was censored and days are measured from first exam at a veterinary medical teaching hospital. Variables measured include, A, presence or absence of AV block, B, ventricular arrhythmias with modified Lown score (MLS) categorized as <2 or ≥2, and C, presence or absence of right ventricular (RV) enlargement. Only significant variables are shown