Primary Risk Factors for M.I / Atherosclerosis

High blood concentrations of cholesterol and certain lipids (LDL: Low Density Lipoprotein, the most atherogenic of the lipids), high blood pressure, smoking, obesity, sedentary lifestyle, diabetes. People who have stenosis of greater than 80 degrees have a very high chance of developing M.I., and are usually candidates for bypass surgery. Multiple risk factors can change the physician’s plan of attack—when multiple risk factors are present, the MD tries to get the LDL under 100 mg/dL. If no other risk factors are present the LDL can be as high as 160. This is called stratification, the doctor must decide which level he is aiming at depending on the presence of risk factors.

In a normal healthy individual we see an intact artery. After a variety of insults (including diet, smoking, lipid) there is injury to the endothelium, which leads to foam cell formation and the formation of a plaque.

If a plaque ruptures it becomes a thrombotic plaque. Statins are good drugs because they lower lipid levels and stabilize the plaques which are already present, to prevent them from rupturing and forming thrombi.

If someone has a diet rich in fats, its bad (about 50% of Americans’ calories are from fat, the American Heart Association would like to lower that to about 25%-- “but you’d be eating broccoli and celery and lettuce, you would not be eating the nice pizzas and treats that we have down in the Café Pacific”). In societies with low fat diets, longevity of life is much increased. The weight to height ratio or BMI (Body Mass Index) is a good clue as to whether a person is obese, and hence if they are at risk for heart attacks. Alcohol consumption is controversial—2 ounces of alcohol is good and reduces the chances of an M.I., but more alcohol is bad for you. The “French Paradox” refers to the fact that the French have a very high lipid diet, but a low rate of myocardial infarction, perhaps due to their red wine consumption. Race can be a factor affecting lipoprotein concentration, African Americans tend to have a higher risk. Gender plays a part in that pre-menopausal women have a lower risk than do men, but post-menopausal women tend to have about the same rate of M.I./ strokes. This variation is most likely due to estrogen levels, and leads some to consider hormone therapies as important for post-menopausal females. Diabetics are at a much higher risk of M.I./ stroke.

Category: Pharmacology Notes