Non-ischemic chest pain occurring after a patient has had a myocardial infarction, that typically worsens with deep breathing, improves while sitting up, and is aggravated by lying down. The patient may develop a low-grade fever, an elevated erythrocyte sedimentation rate, and elevated levels of anti-myocardial antibodies. The cause is unknown. Patients usually are treated with nonsteroidal anti-inflammatory drugs or corticosteroids. A similar syndrome occurs in some patients who have undergone cardiac surgery (post-pericardiotomy syndrome).