Anti-cardiolipin antibodies in ischaemic heart disease.

IgG and IgM anti-cardiolipin antibodies (ACA) were assayed by an ELISA technique in 86 patients with ischaemic heart disease (IHD) and compared to 124 healthy controls and to 62 patients with rheumatoid arthritis (RA) and 20 with tuberculosis (TB). IgG ACA levels in IHD, RA and TB were comparable and significantly higher than in controls (P less than 0.0001). IgM ACA was significantly higher in IHD and RA than controls (P less than 0.0001) but not TB (P = 0.045). The number of IHD patients with raised ACA (IgG and/or IgM) was significantly greater than in RA or TB. (chi 2 = 30.77, P less than 0.0001). ACA were raised in 80.2% IHD patients on one or more occasions during a 1-11 day (mean 4.7) hospital admission. There was no difference in either ACA levels or in the frequency of ACA elevation in patients with stable or unstable angina pectoris or myocardial infarction. We conclude that there is a strong association between IHD and ACA with potentially important therapeutic implications.