Risk of primary and recurrent acute myocardial infarction from lipoprotein(a) in men and women.

Objectives: This study sought to examine whether lipoprotein(a) concentrations were risk factors for a first acute and recurrent myocardial infarction.

Background: There is conflicting evidence concerning the risk of acute myocardial infarction from lipoprotein(a). No studies have examined the risk of recurrent acute myocardial infarction from lipoprotein(a), and few have addressed the risk in women.

Methods: This was a population-based case-control study of 893 men and women 35 to 69 years old participating in the World Health Organization Monitoring Trends and Determinants in Cardiovascular Disease (MONICA) Project in Newcastle, Australia in 1993 to 1994. Case and control patients were classified into those with and without a previous myocardial infarction, and median lipoprotein(a) concentrations were compared after adjusting for other variables. Quintiles of lipoprotein(a) concentration were also examined.

Results: Compared with control subjects without a previous myocardial infarction, median lipoprotein(a) concentrations increased from case patients with a first myocardial infarction (15 mg/liter higher, 95% confidence interval [CI] -36 to 60) to control patients with a previous myocardial infarction (159 mg/ liter higher, 95% CI 40 to 278) and case patients with a previous myocardial infarction (60 mg/liter higher, 95% CI -16 to 136, p < 0.01, test for trend). Women had significantly higher lipoprotein(a) concentrations than men (median 71 mg/liter higher, 95% CI 23 to 118). The highest quintile of lipoprotein(a) (>550 mg/liter) was a significant risk factor for a first acute myocardial infarction (odds ratio [OR] 1.77, 95% CI 1.03 to 3.03); but in those with a previous myocardial infarction, the highest quintile was not associated with recurrent myocardial infarction (OR 0.84, 95% CI 0.30 to 2.37).

Conclusions: High lipoprotein(a) concentrations may be a marker of vascular or tissue injury or may be associated with other genetic or environmental factors that cause acute myocardial infarction. Currently, lipoprotein(a) measurement cannot be recommended for assessment of risk for acute myocardial infarction.