A 61-year-old man presented to the Emergency Department after
receiving multiple shocks from his cardiac resynchronisation
therapy-defibrillator (CRT-D) device, implanted 2 months previously
for New York Heart Association (NYHA) class III heart failure and
left bundle branch block (LBBB). He had hiccoughs and was anxious,
but denied chest pain and dyspnoea. He had chronic
atrialfibrillation (AF). He was haemodynamically stable but
received several further unheralded shocks. The cardiac monitor
appeared to show AF and LBBB throughout. His presenting chest
radiograph is demonstrated in figure 1.
Fig 1. The ED chest radiograph.
Which of the following is the most likely cause for this
man's CRT-D firing?