Heart Attack

Definition and Medical Diagnosis

A heart attack, known in medical terms as an acute myocardial infarction, refers to the death of heart tissue following the rupture of atherosclerotic plaque in the wall of a coronary artery that causes a blood clot to block the flow of blood and supply of oxygen through the artery downstream to that area. The rupture of the atherosclerotic plaque is often triggered within a few hours by factors such as physical exertion (particularly for people not normally active), emotional stress, anger, and excitement. A heart attack can be life threatening, and typically requires hospitalization. Common symptoms of a heart attack include chest pain, sweating, and shortness of breath, although heart attacks can also occur without any symptoms (so-called “silent” heart attacks). A diagnosis of heart attack is made according to criteria of a positive history, electrocardiogram, and heart enzymes measured in the blood, as set out by the World Health Organization. “Probable” and “definite” diagnoses of a heart attack require that two and all three of these criteria are met, respectively.

Risk Factors

Established risk factors for coronary artery atherosclerosis (and thus heart attacks) include age, male gender, [Page 811]cigarette smoking, elevated low-density lipoprotein (LDL) cholesterol, low high-density lipoprotein (HDL) cholesterol, hypertension, diabetes, physical inactivity, obesity, and low socioeconomic status (as measured by income and education). Risk factors for which there is less consensus among scientists include novel markers of systemic inflammation such as C-reactive protein, elevated homocysteine and lipoprotein(a) levels, psychological factors such as depression and hostility, and physical and social environmental factors such as living in a poor neighborhood.

The average age at which a first heart attack occurs is 66 years in men and 70 years in women. In general, higher rates of a first heart attack occur among blacks than among those of other races/ethnicities. The average rates for a first heart attack per 1,000 population in nonblack women during the 1990s were estimated at 6.8, 14.2, and 33.2 for ages 65 to 74, 75 to 84, and 85 and older, respectively. Among black women, the average rates per 1,000 for these same age groups were higher at 8.6, 17.6, and 24.8, respectively. These discrepancies are in keeping with the higher prevalence of heart disease risk factors also found among blacks.

Based on a study spanning 52 countries, nine modifiable risk factors (including smoking, abnormal lipid levels, hypertension, and diabetes) account for more than 90 percent of the risk of a first heart attack. This suggests a tremendous potential to reduce heart attack risk and the burden of heart disease through these risk factors. The associations were consistent between men and women, between racial/ethnic groups, and across geographic regions, such that these findings should be applicable worldwide.

In recent years, research studies have increasingly explored associations between the socioeconomic environments of neighborhoods in which one lives and the risk of a heart attack. In a four-year follow-up study of the entire Swedish population aged 40 to 64 years, researchers looked at the relationship between the level of neighborhood socioeconomic deprivation and the risk of being admitted to hospital with a nonfatal heart attack, controlling for one's age and income. Both women and men living in the poorest versus richest neighborhoods

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