A 44 year old man presents with chest discomfort and dyspnea for 2 weeks; these symptoms have markedly worsened over the last 4 days.
He is otherwise asymptomatic, with no history of paroxysmal nocturnal dyspnea or orthopnea. His medical, surgical, and family histories are unremarkable.
He only drinks socially, and has never smoked before.
An urgent 12-lead ECG reveals a rate of 106 bpm, with a regular rhythm. All leads show low voltage QRS complexes with electrical alternans.