Robert is a 68-year-old male admitted to the hospital for monitoring overnight

Robert is a 68-year-old male admitted to the hospital for monitoring overnight after an elective Permanent Pacemaker (PPM) insertion for tachycardia-bradycardia syndrome.

Several hours after admission, he begins to complain of shortness of breath and sharp chest pain, worse on inspiration.

He denies any palpitations. His past medical history includes a deep vein thrombosis 2 months ago, for which he is on apixaban 10mg bd. He remains conscious throughout the episode.

Which of the following is the most likely cause of Robert’s symptoms?