A young,
overweight dog presented with sudden onset
lethargy and collapse following exercise in warm environmental conditions. Investigations revealed systolic
hypotension, multiform
ventricular premature complexes, irregular myocardial echogenicity with poor left ventricular systolic function and a markedly elevated
troponin cTnI (180ng/mL, reference range <0.3ng/mL) consistent with severe myocyte damage. Infectious causes of
myocarditis were ruled out on the basis of serological and polymerase chain reaction blood tests. Exercise-induced
malignant hyperthermia was excluded from the history, an exercise tolerance test and genetic testing for the
RYR1 V547A mutation. The diagnosis was myocardial damage secondary to suspected exertional
heatstroke, from which the dog recovered uneventfully over a number of weeks and serum
troponin normalised. This is the first case report in any species including man, documenting high
troponin as a marker of severe myocardial damage following suspected
heatstroke.