Impact of medical genetics on research and practices in the area of cardiovascular disease.

The evidence that genetic factors are of importance in the etiology of coronary heart disease (CHD) originates from several areas. Cases of premature CHD cluster in families in a way which indicates the importance of genetic factors, and having a first-degree relative who contracted CHD before the age of 50-55 is by itself a significant risk factor. Genes are of importance in determining the level of several established risk or "anti-risk" factors, and association between risk factor level and random genetic markers has been known for several years. The "candidate gene" approach was first applied in the 1970s, when a strong association between genetically determined Lp(a) lipoprotein and premature CHD was found, and associations between Ag allotypes and lipid levels were uncovered. The new DNA technology has greatly increased the potential of the "candidate gene" approach. Genes are of importance not only for the absolute risk factor level but also with respect to the amount of variation in risk factor level that any one person can have. Thus, in addition to traditional "level genes", new "variability genes" are being identified. Knowledge of genetic factors in the etiology of coronary heart disease has not so far been adequately utilized in attempts to combat premature CHD. The time has now come to utilize genetic information in a setting of family-oriented preventive medicine. This approach would greatly improve the efficiency of preventive efforts, utilizing predictive genetic testing and targeting counseling on those who need it most.