Complete Heart Block after Sublingual Nitroglycerin

A 62-year-old man who was under observation following an episode of severe chest pain developed complete heart block and hypotension after receiving sublingual nitroglycerin. The reaction occurred while the patient was receiving an intravenous maintenance infusion of lidocaine but did not occur in response to either nitroglycerin alone or lidocaine alone. There was no evidence of acute cardiac ischemia nor of clinically significant underlying heart disease. Complete heart block after sublingual nitroglycerin in the absence of significant cardiac disease is an exceedingly rare phenomenon.