Cardiac histopathology and electrocardiographic changes in canine babesiosis

Abstract

Electrocardiographic (ECG) changes have never been reported in canine babesiosis. Based on the metabolic, electrolyte, and myocardial alterations described for the disease, such changes are to be expected. The purpose of this study was to describe ECG changes in canine babesiosis, and to correlate those changes to clinical severity, outcome and cardiac histopathological changes. Four groups of dogs with babesiosis were studied: mild to moderate anaemia (n=40), severe anaemia (n=35), concurrent immune-mediated haemolytic anaemia (n=18) and complicated (n=28). Lead II ECG was recorded at admission for 1 minute in all dogs, and repeated after 24 hours in admitted dogs (groups II – IV). Six lead ECG was recorded in 88 dogs. Full necropsy was performed between 30-60 minutes after death on 16 dogs (5 died on arrival, 11 had ECG recording). Gross cardiac pathology was recorded and histopathology of myocardial sections from ventricles, atria, apex and interventricular septa was evaluated, using a scoring system for haemorrhages, necrosis, inflammatory infiltrate and fibrin microthrombi. The following ECG changes were recorded: sinoatrial (7%) and atrioventricular blocks (4%), ventricular premature complexes (7%), low R-amplitude (23%), prominent Q (33%), axis deviations (40%), prolonged QRS (32%), ST depression and coving (28%), large T (42%), and notched R (28%). Differences between groups were minor and inconsistent. Gross pathological changes were pericardial effusion (25%) and subepicardial (56%) and subendocardial haemorrhages (63%). Histological changes were haemorrhages (69%), necrosis (50%), inflammation (63%) and fibrin microthrombi (75%). The only correlation between pathology and ECG was low R-amplitude and pericardial effusion. There was a significantly higher prevalence of sinus bradycardia and irregular sinus rhythm in the non-survivors. Both ECG and pathological changes were non-specific, but there were similarities to the pattern of changes that have been described for myocarditis and myocardial ischaemia. Antiarrhythmic treatment was only required in 1 dog. Thus, the clinical application of the ECG changes found in this study was limited. It was concluded that the heart suffers from the same pathological processes described in other organs in canine babesiosis, namely inflammation and hypoxia. Cardiovascular management, if necessary, should be based on functional monitoring rather than ECG.