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

Keywords: Trypanosoma cruzi; cardiomyopathy; echocardiography; myocarditis; troponin.

Figure 1

Classification of abnormalities by diagnostic tests including CMR (n = 7), echocardiography (n = 6), ambulatory ECG (n = 6), and cTnI (n = 1) in 10 naturally infected dogs with chronic Chagas disease. CMR, cardiac magnetic resonance imaging; cTnI, cardiac troponin I.

Figure 2

Cardiac magnetic resonance images from two dogs with chronic Chagas disease. In Panel (A), delayed myocardial enhancement (arrows) is demonstrated in the left ventricular (LV) apex compared to a dog without DME (Panel (B)). Panel (C) is a FLASH Cine image three-chamber view in the same dog as panel (A) with DME that demonstrates loss of myocardial compaction at the LV apex (arrows). LA, left atrium.