Clinical and electrocardiographic findings in suspected viral myocarditis of pups.

Surviving puppies from three separate litters in which deaths had occurred from suspected viral myocarditis were examined clinically and electrocardiographically. Of 11 puppies examined, 5 subsequently died or were euthanised within 11 days of initial examination. ECG changes present in these puppies for 1 to 11 days prior to death were small R waves (less than 0.4 mV in lead II), S-T segment elevation, QRS notching and paroxysmal ventricular tachycardia (PVT). No clinical signs referable to the ECG changes were present before the terminal episodes of apparent sudden death or death following a brief period of dyspnoea. Multifocial subacute myocarditis was present on post-mortem examination. A sixth puppy with small R waves remained clinically normal for a further 4 weeks. It then developed severe dyspnoea which persisted for 24 hours before euthanasia. Extensive fibrosis of the left ventricle was present on post-mortem examination.