Ischemic heart disease can vary substantially in its clinical presentation. Some patients have acute myocardial infarction (MI) without any previous signs of myocardial ischemia, whereas other patients may have stable angina pectoris for years without periods of acute unstability. This study compared baseline risk factors between subjects in whom stable angina pectoris developed and subjects in whom unheralded fatal or nonfatal MI developed during the follow-up period.

In 1970 to 1973, all 50-year-old men in Uppsala, Sweden, were invited to participate in a health survey aimed at identifying risk factors for cardiovascular disease. The present study is a nested case-control study of subjects who were free of coronary heart disease (CHD) at baseline and who then underwent revascularization (percutaneous transluminal coronary angioplasty or coronary artery bypass grafting) because of angina pectoris without preceding MI (n = 70) or in whom fatal or nonfatal MI developed without prior known CHD (n = 372) during the period until 1998.

In multivariate Cox proportional hazard models, low-density lipoprotein and high-density lipoprotein levels (protective) were significant independent risk factors for stable angina pectoris demanding revascularization, whereas smoking, diastolic blood pressure, serum proinsulin levels, and serum lipid levels were significant independent predictors of subsequent unheralded MI. When comparing hazard ratios (HR), significantly higher HR for diastolic blood pressure (1.40 vs 1.00, for 1 SD increase) and serum proinsulin (1.82 vs1.20, for 1 SD increase) were found in the group in which unheralded MI developed than in the group with stable angina pectoris.

Serum lipid levels were important risk factors for the development of both stable and acute coronary heart disease. In addition, proinsulin levels and blood pressure were independent predictors of unheralded MI only, which suggests that these factors are involved in thrombosis, plaque rupture, or both.