Symptom and clinical finding	Acute pericarditis	Myocardial ischemia or infarction	Pulmonary embolism
Chest pain
Location	Retrosternal	Retrosternal	Anterior, posterior or lateral
Duration	Hours to days	Minutes (ischemia); hours (infarction)	Hours to days
Character	Sharp, stabbing, occasionally dull	Pressure-like, heavy, squeezing	Sharp, stabbing
Change with position	Worse when patient is supine, improved when sitting up or leaning forward	No	No
Change with respiration	Worsened with inspiration	No	In phase with respiration (absent when the patient is apneic)
Radiation	Jaw, neck, shoulder, one or both arms, trapezius ridge	Jaw, neck, shoulder, one or both arms	Shoulder
Response to nitroglycerin	No change	Improved	No change
Physical examination
Friction rub	Present (in 85% of patients)	Absent (unless pericarditis is present)	Rare; a pleural friction rub is present in 3% of patients
S3 sound, pulmonary congestion	Absent	May be present	Absent