Tests for rheumatoid factor after myocardial infarction.

An investigation was carried out into the occurrence of positive tests for rheumatoid factor after myocardial infarction. Fifty-five patients, 41 males and 14 females, were studied in 56 separate admissions for acute myocardial infarction. Tests for thyroid antibodies were also performed on all patients. In 16 patients a positive rheumatoid factor test was obtained in the post-infarction period on at least one occasion. The reaction was usually a weak positive one, and in most cases had disappeared on discharge from hospital. Transient false positive tests for thyroid complement-fixing antibody were obtained in seven male patients.Positive tests tended to occur in older patients, with a previous history of infarction, and usually with more severe infarcts, as judged from the maximum level of serum glutamic oxaloacetic transaminase obtained in the first 48 hours after infarction, and the occurrence of clinical cardiac failure. This is probably a relatively non-specific manifestation of tissue damage, the clinical importance of which is unknown.