Heart Attack (Myocardial Infarction)

What is Heart Attack?

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A heart attack, also known as a myocardial infarction or MI, occurs when an area of heart muscle dies or is permanently damaged because of an inadequate supply of oxygen to that area.

Statistics on 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.

Risk Factors for Heart Attack

3D Animation on
Plaque Rupture

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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

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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:

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.
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.
Stancoven A, McGuire DK. Preventing macrovascular complications in Type 2 Diabetes Mellitus: glucose control and beyond. American Journal of Cardiology 2007; 99: 5H-11H.

This tool needs javascript enabled to work.Male risk estimate

Points

Age

HDL

Total Cholesterol

SBP Not Treated

SBP Treated

Smoker

Diabetic

-2

60+

<120

-1

50-59

30-34

45-49

<160

120-129

<120

35-44

160-199

130-139

35-39

<35

200-239

140-159

120-129

240-279

160+

130-139

Yes

280+

140-159

Yes

40-44

160+

45-49

50-54

55-59

60-64

65-69

70-74

75+

Points

CVD risk

Heart age (years)

-3 or less

Below 1%

< 30

-2

1.1%

< 30

-1

1.4%

< 30

1.6%

1.9%

2.3%

2.8%

3.3%

3.9%

4.7%

5.6%

6.7%

7.9%

9.4%

11.2%

13.2%

15.6%

18.4%

21.6%

25.3%

29.4%

> 80

18 +

> 30%

> 80

Female risk estimate

Points

Age

HDL

Total Cholesterol

SBP Not Treated

SBP Treated

Smoker

Diabetic

<-3

<120

-2

60+

-1

50-59

<120

30-34

45-49

<160

120-129

35-44

160-199

130-139

35-39

<35

140-149

120-129

200-239

130-139

Yes

40-44

240-279

150-159

Yes

45-49

280+

160+

140-149

150-159

50-54

160+

55-59

60-64

65-69

70-74

75+

Points

CVD risk

Heart age (years)

-2 or less

<1%

<30

-1

1.0%

<30

1.2%

<30

1.5%

1.7%

2.0%

2.4%

2.8%

3.3%

3.9%

4.5%

5.3%

6.3%

7.3%

8.6%

10.0%

11.7%

13.7%

>80

15.9%

>80

18.5%

>80

21.5%

>80

24.8%

>80

28.5%

>80

21+

>30%

>80

More than 20 points

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.

10 to 20 points

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.

Less than 10 points

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.

This information will be collected for educational purposes, however it will remain anonymous.

Progression of Heart Attack

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).

How is Heart Attack Diagnosed?

ECG
Chest x-ray
Blood tests to assess kidney function should be carried out

Prognosis of Heart Attack

Myocardial infarctions (heart attacks) are a serious event: approximately 25% of patients die from the initial event - that is, they may die before reaching hospital, or in the first day or so. Of the rest, 25% will die within the next two years, usually due to recurrent MI or complications. About 50% of the initial survivors are alive after 10 years. The prognosis is better for younger patients with less concurrent medical problems.

How is Heart Attack Treated?

Management is on a coronary care unit.
Aspirin 300mg is given.
High flow oxygen.
Pain management with morphine.
Heart rate is controlled using a beta-blocker (if no signs of heart failure or heart block).
If within 12 hours and no contraindications (stroke or active bleeding in the last two months) thrombolytic therapy or angiography with angioplasty may be considered.
Management of common complications of MI such as heart failure, pericarditis and arrhythmias.

Long term management is similar to that for angina (if not already instigated). This includes aspirin therapy, beta-blockers, and cholesterol lowering if required. Maintaining a healthy diet, quitting smoking, exercise and weight reduction (if overweight) are important aspects of long-term treatment to reduce the risk of recurrent heart attack.

Heart Attack References

Clarke K, Gray D, Keating N, Hampton J. Do women with acute myocardial infarction receive the same treatment as men? BMJ 1994; 309: 563-6.
Fenton D, Stahmer S. Myocardial Infarction, eMedicine, Web MD, 2006. Available from URL: http://www.emedicine.com/emerg/topic327.htm.
Gan S, Beaver S, Houck P, MacLehose R, Lawson H, Chan L. Treatment of acute myocardial infarction and 30-day mortality among women and men. NEJM 2000; 343(1): 8-15.
Garas S, Zafari A, Myocardial Infarction, eMedicine, Web MD, 2006. Available from URL: http://www.emedicine.com/med/topic1567.htm.
Hurst's The Heart 8th Edition, McGraw Hill, 1994.
Kumar and Clark. Clinical Medicine 4th Edition, W.B Saunders, 1998.
Martur S, Epidemic of coronary heart disease and its treatment in Australia, AIHW 2002, cat. no. CVD 21.
Mehta S, Eagle K. Secondary prevention in acute myocardial infarction. BMJ 1998; 316: 838-42.