Virtual Medical Centre

Heart Attack (Myocardial Infarction)

• What is Heart Attack?
• Who gets Heart Attack?
• Predisposing Factors
• Progression
• Probable Outcomes
• How is Heart Attack Diagnosed?
• How is Heart Attack treated?
• Heart Attack References
• Drugs/Products Associated with Heart Attack

What is Heart Attack?

3D Animation on
Myocardial Infarction

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This animation brought to you by Blausen Medical Communications.
Contact Andrew Walbank.

Who gets Heart Attack?

Coronary artery disease is the most common cause of death in the Western world, and most of these deaths are due to myocardial infarction (heart attack). In Australia, approximately 21% of all deaths are due to coronary heart disease, and there are 605 coronary events per 100,000 people aged 40-90 years.

Myocardial infarction is a common condition. There are thousands of new cases every year. It is a serious and life-threatening condition.  Around one quarter of patients die from the acute event, half of these before the hospital is reached. Survivors have a higher risk of recurrent heart attacks or cardiac death, and a further 10% die within two years. Only 50% of initial survivors are alive at 10 years.

Men

Men have a higher risk of heart attacks and other acute coronary events, and males are more likely to be affected at a younger age. Around three quarters of heart attacks are in male patients. Males and females older than 70 years of age are equally affected.

Women

Women before menopause have lower rates of heart attack, which may be due to the effects of oestrogen (oestrogen reduces the build up of plaques in blood vessels). However, the incidence of heart attacks increases dramatically in women aged 60-70 years to match that of men.

Women have higher mortality and hospitalisation rates from heart attacks, perhaps partly because women receive less aggressive in-hospital therapy for acute myocardial infarction than men. The reasons for this are not clear, but may be due to poor diagnosis and lack of knowledge about the benefits of treatment in women.

Predisposing Factors

3D Animation on Plaque Rupture This animation brought to you by Blausen Medical Communications. Contact Andrew Walbank. Coronary atherosclerosis is the main process causing myocardial ischaemia (restriction in blood supply to heart muscles) and infarction (death of heart muscle tissue). Fatty plaques (cholesterol is a kind of fat) develop on the inside of the coronary arteries. The diameter of the arteries is reduced, inhibiting blood flow to the heart muscle. Eventually the plaques rupture. When this happens, blood starts to clot around the ruptured plaque. Eventually either a piece of clot or a piece of plaque breaks off and blocks a smaller downstream artery, causing a heart attack.

 

There are many risk factors for coronary artery disease:

• Hypercholesterolaemia (elevated levels of cholesterol in the blood) plays a central role in the development of plaques.
• Increased age and male gender.
• Family history of coronary artery disease.
• Smoking: Risk is directly related to the number of cigarettes smoked.
• Diabetes mellitus: Abnormal blood sugar levels promote vascular damage and the development of plaques.
• Hypertension: High blood pressure promotes artery damage, which may initiate or exacerbate atherosclerosis, causing plaque rupture.

Other, less important risk factors (so-called soft factors) include:

• Stress/anxious personality
• Obesity
• Alcohol consumption

General Cardiovascular Disease 10-Year Risk Calculator

This risk assessment tool is based on data from the Framingham Heart Study to estimate 10-year risk for general cardiovascular disease outcomes (coronary death, myocardial infarction, coronary insufficiency, angina, ischaemic stroke, haemorrhagic stroke, transient ischaemic attack, peripheral artery disease, heart failure). This tool is designed to estimate risk in adults aged 30-74 years of age without CVD at baseline examination. Use the calculator below to estimate 10-year risk.

Predictors

Age		years
		Male	Female
Gender
		Yes	No
Have you been diagnosed with Type II diabetes?
Are you a smoker?*
Are you prescribed medication to lower your blood pressure?
If you do not know the following blood pressure and cholesterol parameters ask your General Practitioner on your next visit.
Systolic blood pressure**		mmHg
Total cholesterol***	mmol/L      OR	mg/dl
HDL cholesterol****	mmol/L      OR	mg/dl

Results

Significant (> 20%)
Elevated (10–20%)
Mild risk (< 10%)
You have a significant risk of future cardiovascular disease requiring aggressive risk factor modification. You should see a health professional to ensure appropriate management.

• If diabetic, your sugar levels should be well controlled.
• Continue to avoid tobacco use or if you are a smoker, consider stopping this is something your General Practitioner can help you with.
• Blood pressure should be monitored closely. If elevated you should consider either lifestyle modification or appropriate medication. Your general Practitioner can advise you on this.
• Cholesterol levels should be assessed at least annually. Depending on your level, you might be advised to commence lifestyle changes or medication.

Significant (> 20%)
Elevated (10–20%)
Mild risk (< 10%)
You have an elevated risk of future cardiovascular disease requiring risk factor modification. You should see a health professional to ensure appropriate management.

• If diabetic, you should aim for your sugar levels to be well controlled.
• Continue to avoid tobacco use or if a smoker, consider stopping this is something your general practitioner can help you with.
• Blood pressure should be monitored closely. If elevated you should consider either lifestyle modification or appropriate medication. Your general Practitioner can advise you on this.
• Cholesterol levels should be assessed at least annually. Depending on your level you might be advised to commence lifestyle changes or medication.

Significant (> 20%)
Elevated (10–20%)
Mild risk (< 10%)
You have a mild risk of future cardiovascular disease, consider risk factor modification. You may like to see a health professional to ensure appropriate management.

• If diabetic, you should aim for your sugar levels to be well controlled.
• Continue to avoid tobacco use or if a smoker, consider stopping this is something your general practitioner can help you with.
• Blood pressure should be monitored closely. If elevated you should consider either lifestyle modification or appropriate medication. Your general Practitioner can advise you on this.
• Cholesterol levels should be assessed at least annually. Depending on your level you might be advised to commence lifestyle changes or medication.

^*For these purposes "smoker" means any cigarette smoking in the past month.
^**Use current blood pressure, regardless of whether the person is on antihypertensive therapy.
^***Total cholesterol values should be the average of at least two measurements obtained from lipoprotein analysis.
^****HDL cholesterol values should be the average of at least two measurements obtained from lipoprotein analysis.

References:

1. D'Agostino RB, Vasan RS, Pencina MJ, Wolf PA, Cobain M, Massaro JM, Kannel WB. General cardiovascular risk profile for use in primary care: the Framingham Heart Study. Circulation 2008; 117: 743-753.
2. National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III). Third Report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III) final report. Circulation 2002; 106: 31433421.
3. Stancoven A, McGuire DK. Preventing macrovascular complications in Type 2 Diabetes Mellitus: glucose control and beyond. American Journal of Cardiology 2007; 99: 5H-11H.

Progression

Coronary atherosclerosis leads to narrowing of the arteries and impairment of blood supply to the heart muscle. Early in the disease process, this causes angina pectoris, or chest pain experienced when the heart muscle's demand for blood is increased (e.g. during exercise). Later in the disease process, the artery may become completely blocked, usually due to a piece of plaque breaking off, moving downstream and obstructing a smaller artery. This causes myocardial infarction and results in permanent damage to the heart muscle. Even if blood flow to the heart muscle is not physically impaired, ischaemia can still occur when, for example, the blood's ability to carry oxygen is impaired (e.g. anaemia) or when the heart's requirements are significantly increased (e.g. during exercise and ventricular hypertrophy).