Secure pacemaker fixation critical for prevention of Twiddler's syndrome

A two year old, female spayed border collie presented three weeks after permanent pacemaker implantation for weakness, lethargy and collapse. Electrocardiogram documented complete (3^rd degree) atrioventricular (AV) block, the absence of pacing and a ventricular escape rhythm. Thoracic radiographs revealed retraction and dislodgement of the passive fixation lead from the right ventricular apex. During a procedure to reposition the lead, it was noted that lead retraction had resulted from rotation of the generator with twisting and entanglement of the lead on itself and around the generator, a complication recognized in human patients as “Twiddlers syndrome”. The pacemaker lead was removed, a new lead securely placed at the right ventricular apex, and the generator was secured into a revised subcutaneous pocket. Pacing was re-established and the Twiddler's syndrome has not reoccurred.     

Successful biphasic transthoracic defibrillation of a dog with prolonged, refractory ventricular fibrillation

Objective – To describe a case of spontaneous ventricular fibrillation in a dog in which biphasic defibrillation was life saving.
Case Summary – Ventricular fibrillation occurred in a 7-year-old female Australian Heeler during recovery from anesthesia following pacemaker implantation. Resuscitative efforts including immediate delivery of transthoracic monophasic defibrillation shocks of escalating energy and administration of vasopressors were unsuccessful. However, a single biphasic shock restored sinus rhythm despite prolonged duration of the arrhythmia.
New or Unique Information Provided – This case suggests greater efficacy of biphasic defibrillation compared with traditional monophasic defibrillation. In this dog the newer, biphasic technology was life saving after monophasic shocks failed repeatedly to terminate ventricular fibrillation.