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 plateauEvery additional cigarette smoked increases

MI risk furtherReduces 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 startHowever much you smoke, smoke less.

Risk Factor: Hi LDL/ Lo HDL

Cholesterol:Vital component of cell wallsVital precursor to many hormonesHOWEVER, also major component of

atherosclerotic plaquesMade in the liver

LipoproteinsMake 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 (>70-100 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 consumptionCholesterol in food NOT strong link to

increased LDLLifestyle Changes:

Increase activityNot 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 factorsHigh LDLHypertensionDiabetes

Waist:Hip ratio0.9 for men0.85 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 genesFamily history increases risk of

Hypercholesterolemia (High LDL)HypertensionAtherosclerosis

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 MIPre-menopause: women at lower riskPost-menopause: women at same risk as

menMI 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 functionType I: genetic, no insulin producedType II: acquired with some genetic

predisposition, insulin resistanceIncreases risk of high LDL and high

blood pressureFurther 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 937 - 952, 11 September 2004

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. 210-214

Ardissino, et al, “Prothrombotic Genetic Risk Factors in Young Survivors of Myocardial Infarction,” Blood, 1999 94: 46-51