MI: Risk Factors and Primary Prevention

Risk Factors Factors that appear to increase the general population’s chances of experiencing a health problem Not a guarantee that any one individual will have the problem, but useful when applied to entire patient population

How are Risk Factors Determined? Show a causal relationship between the risk factor and the disease through careful study Association studied should have, if possible: Strength Consistency Specificity Proper Time Sequence A Potential Biological Explanation and/or Analogy A Dose-Response Relationship A large Testable Population

MI Risk Factors Many can be reduced or avoided through Primary Prevention

Preventable Risk Factors and MI Up to 90% of myocardial infarction risk comes from factors that can be changed long before MI occurs (Lancet, Sept. 2004) Primary prevention: actions that stop the development of a disease before it even starts

Risk Factor: Smoking Dose-response relationship without plateau Every additional cigarette smoked increases MI risk further Reduces body’s ability to signal for production of tPA, a natural clot-busting protein Women smokers at further elevated risk

Primary Prevention: Smoking Don’t start However much you smoke, smoke less.

Risk Factor: Hi LDL/ Lo HDL Cholesterol: Vital component of cell walls Vital precursor to many hormones HOWEVER, also major component of atherosclerotic plaques Made in the liver Lipoproteins Make fat and cholesterol soluble in the blood

Risk Factor: Hi LDL/ Lo HDL Low Density Lipoprotein Carries cholesterol from liver to body for use “Bad” cholesterol High plasma LDL (> mg/dL) = more atherosclerosis, MI High Density Lipoprotein Carries cholesterol from body to the liver for elimination “Good” cholesterol Low plasma HDL (<40mg/dL) = more atherosclerosis, MI

Primary Prevention: Hi LDL/ Lo HDL Dietary Changes: Decrease saturated fat consumption (<7%) Eliminate trans fat consumption Cholesterol in food NOT strong link to increased LDL Lifestyle Changes: Increase activity Not always possible

Risk Factor: Chronic Hypertension Continuously High Blood Pressure Systolic > 140 mmHg Linked to ¼ of MI cases Strongly linked to arteriosclerosis and CVD

Primary Prevention: Hypertension Dietary Changes: Reduce sodium intake Reduce simple sugar intake Get daily doses of Potassium and Calcium Lifestyle changes Get more exercise, keep HR elevated for longer Decrease body fat Avoid stress Again, not always possible

Abdominal Obesity and Diet Obesity from excessive fat around the abdomen is a strong predictor of many other risk factors High LDL Hypertension Diabetes Waist:Hip ratio 0.9 for men 0.85 for women

Abdominal Obesity and Diet However, poor diet can lead to all of those even without obesity Eat fruits and vegetables Avoid saturated fats and trans fats Get >25g dietary fiber per day

Unavoidable MI Risk Factors

Genetics and MI risk factors All previously mentioned risk factors can also be influenced by genes Family history increases risk of Hypercholesterolemia (High LDL) Hypertension Atherosclerosis As genetics advances, we can separate “nature” from “nurture” Specific genes and mutations shown to increase clotting risk, LDL, etc.

Gender Estrogen linked to lower risk of MI Pre-menopause: women at lower risk Post-menopause: women at same risk as men MI leading cause of death for both men and women

Aging Some degree of atherosclerosis inevitable with age Even with perfect health, risk of MI increases in old age

Diabetes Failure of normal insulin function Type I: genetic, no insulin produced Type II: acquired with some genetic predisposition, insulin resistance Increases risk of high LDL and high blood pressure Further increases the risk of MI, possibly due to damage caused by poorly controlled blood sugar

Recap If a patient doesn’t think they can quit smoking, is there any use to trying to get them to smoke less? True or false: only overweight patients have high blood pressure. Which item should you leave out of your breakfast if you want to improve your LDL:HDL ratio the most: eggs, bacon, or milk?

Sources Yusuf, et al, “Effect of potentially modifiable risk factors associated with myocardial infarction in 52 countries (the INTERHEART study): case- control study,” The Lancet, Volume 364, Issue 9438, Pages , 11 September 2004Volume 364, Issue 9438 Chobanian, et al, “Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure,” Hypertension. 2003;42:1206 Ulrich, et al, “A comprehensive linkage analysis for myocardial infarction and its related risk factors,” Nature Genetics, 2002, vol. 30, no2, pp Ardissino, et al, “Prothrombotic Genetic Risk Factors in Young Survivors of Myocardial Infarction,” Blood, : 46-51