The symptoms of a 72-year-old man with persistent systolic congestive heart failure have gotten worse, so he is admitted to the hospital.
He initially appears to be in good health, but on the second day of his hospital stay, he suddenly starts to have chest pain, a cough that gets worse, and rapidly deteriorating shortness of breath.
An abrupt ST-segment elevation myocardial infarction on the left side is seen on an ECG.
What is the most likely reason for his breathing difficulties?
