Cardiac Magnetic Resonance Imaging Detects Myocardial Abnormalities in Naturally Infected Dogs with Chronic Asymptomatic Chagas Disease

SIMPLE SUMMARY: Trypanosoma cruzi infection causes Chagas disease in dogs and people by damaging the heart with inflammation and fibrosis, resulting in heart enlargement, abnormal function, and irregular heart rhythms. Cardiac magnetic resonance imaging can detect damage to the heart in people with Chagas disease even when other diagnostic tests cannot. The objectives of this study were to describe cardiac magnetic resonance imaging in naturally infected, asymptomatic dogs with chronic Chagas disease and the frequency of abnormalities for cardiac magnetic resonance imaging and other diagnostic tests, including cardiac ultrasound, electrocardiography, and the cardiac biomarker troponin I. In 10 chronically infected dogs. Abnormal findings were present most often with cardiac magnetic resonance imaging (seven dogs) followed by ultrasound (six dogs), electrocardiography (four dogs), and troponin (one dog). Cardiac magnetic resonance imaging abnormalities included increased fibrosis and abnormal wall motion of the heart. The results of this study suggest cardiac magnetic resonance imaging can provide useful information in dogs with T. cruzi infection and may support naturally infected dogs for future clinical investigation as an animal model for Chagas disease. ABSTRACT: Trypanosoma cruzi infection causes inflammation and fibrosis, resulting in cardiac damage in dogs. The objectives of this study were to describe cardiac magnetic resonance imaging (CMR) in naturally infected dogs with chronic Chagas disease and the frequency of abnormalities for CMR and cardiac diagnostic tests. Ten asymptomatic, client-owned dogs seropositive for T. cruzi were prospectively enrolled in an observational study evaluating echocardiography, ECG (standard and ambulatory), cardiac troponin I (cTnI), and CMR. Standard ECG measurements (3/10) and cTnI concentration (1/10) outside the reference range were uncommon. Ambulatory ECG abnormalities were documented more frequently (6/10 dogs) than with standard ECG and included ventricular arrhythmias (4), supraventricular premature beats (3), second-degree atrioventricular block (2), and sinus arrest (1). Echocardiographic abnormalities were documented in 6/10 dogs including mildly increased left ventricular internal dimension in diastole (1) and decreased right ventricular (RV) systolic function based on reductions in tricuspid annular plane systolic excursion (3) and RV S’ (4). Abnormalities were detected with CMR in 7/10 dogs including delayed myocardial enhancement in 5 of which 2 also had increased extracellular volume, abnormal wall motion in 5, and loss of apical compact myocardium in 1. In conclusion, CMR abnormalities were common, and the results of this study suggest CMR can provide useful information in dogs with T. cruzi infection and may support naturally infected dogs for future clinical investigation as an animal model for Chagas disease.