Pacemaker lead perforation of the right ventricle associated with Moraxella phenylpyruvica infection in a dog

Abstract

A 13-year-old neutered male Border Collie was presented with acute onset syncope, weakness and anorexia 10 months after transvenous pacemaker implantation. The patient was laterally recumbent, bradycardic (36 beats/min) and febrile (40.7°C) on presentation. An electrocardiogram (ECG) revealed recurrence of third-degree atrioventricular block with a ventricular escape rhythm. Fluoroscopy identified migration of the pacemaker tip through the apex of the right ventricle. Echocardiography failed to reveal any evidence of pericardial effusion or cardiac tamponade. Full postmortem was performed after euthanasia. The pacemaker lead had perforated the apex of the right ventricle and lodged in the right pleural space. Culture of blood (taken antemortem), pericardial sac, right ventricular wall (surrounding pacemaker lead), pacemaker lead tip and pericardial fluid revealed a pure growth of Moraxella phenylpyruvica. Bacteraemia associated with M. phenylpyruvica has never been reported in the dog, but sporadic cases are reported in humans. Infection could have resulted from either pre-existing myocarditis or opportunistic infection and bacteraemia post pacemaker implantation. Evaluation of the pacemaker function at regular intervals would allow early detection of poor pacemaker-to-myocardium contact, which would prompt further investigation of pacemaker lead abnormalities such as perforation.