Heart attacks remain a leading cause of death worldwide, primarily due to the sudden blockage of blood flow to the heart muscle. The risk of heart attack increases with age, particularly in men over 45 and women over 55, and is influenced by a combination of genetic, lifestyle, and medical factors1 2. Understanding the underlying causes and risk factors is essential for prevention and timely treatment.
Understanding Atherosclerosis
Atherosclerosis is the most common cause of heart attacks. It involves the buildup of fatty deposits, cholesterol, and other substances on the walls of coronary arteries, forming plaques that narrow these vessels and reduce blood flow to the heart muscle1 . Over time, these plaques can rupture, triggering the formation of blood clots that may completely block the artery, leading to a heart attack1 .
This process, known as coronary artery disease, develops gradually and may cause symptoms like chest pain (angina) before a heart attack occurs. The blockage deprives the heart muscle of oxygen-rich blood, causing tissue damage or death if not promptly treated1 .
- Atherosclerosis leads to plaque buildup that narrows coronary arteries1 .
- Plaque rupture causes clot formation, blocking blood flow1 .
- Coronary artery thrombosis is a primary cause of myocardial infarction1 .
Heart Attack from Blood Clots
Blood clots can cause heart attacks by obstructing coronary arteries. These clots may form directly on ruptured plaques within the arteries or travel from other parts of the body, such as the legs, to the heart3 . Several conditions increase the risk of clot formation in the heart:
- Atrial fibrillation, an irregular heartbeat, promotes clot formation3 .
- Cardiomyopathy, a disease of the heart muscle, raises clot risk3 .
- Endocarditis, an infection of heart chambers or valves, can lead to clots3 .
- Deep vein thrombosis (DVT) in the legs may embolize to coronary arteries3 .
When a clot blocks a coronary artery, blood flow is interrupted, causing damage to the heart muscle and triggering a heart attack3 .
Spontaneous Coronary Artery Dissection
Spontaneous coronary artery dissection (SCAD) is an uncommon but important cause of heart attacks, especially in younger women under 50 years old4 . SCAD occurs when a tear forms spontaneously in the coronary artery wall, leading to bleeding within the artery wall (intramural hematoma) 4. This hematoma compresses the true lumen of the artery, restricting blood flow and causing ischemia (oxygen deprivation) to the heart muscle4 .
SCAD accounts for approximately 1-4% of all acute coronary syndrome cases and is implicated in 25-35% of myocardial infarctions in women under 504 .
- SCAD involves a spontaneous tear in the coronary artery wall4 .
- Intramural hematoma compresses the artery lumen, blocking blood flow4 .
- SCAD is a significant cause of heart attacks in younger women4 .
Coronary Artery Spasms
Coronary artery spasms are sudden, severe narrowing or tightening of the coronary arteries that can block blood flow to the heart muscle even in the absence of atherosclerosis1 5. These spasms may be triggered by factors such as smoking, extreme cold, stress, or drug use (e.g., cocaine) 5. The spasm causes temporary ischemia, which can lead to chest pain or a heart attack if prolonged5 .
Coronary Microvascular Disease
Beyond the large coronary arteries, the heart is supplied by a network of smaller vessels known as the microvascular circulation. Coronary microvascular dysfunction (CMD) refers to problems in these small vessels that impair blood flow to the heart muscle6 . CMD is increasingly recognized as a cause of heart attacks, particularly in patients with normal coronary angiograms and in women6 .
- CMD affects the small arteries supplying the heart muscle6 .
- Dysfunction in these vessels can cause ischemia and heart attacks6 .
Genetic Heart Attack Risk
Genetics play a significant role in heart attack risk. Some conditions, such as familial hypercholesterolemia, are inherited in an autosomal dominant pattern, meaning a child has a 25% chance of inheriting the gene if one parent carries it7 . Early-onset familial myocardial infarction increases the risk for first-degree relatives7 . Genetic predisposition can interact with lifestyle and other risk factors to influence the likelihood of a heart attack7 .
“If only we correct our eating habits. Then not only we would have perfect body weight, but also we can get rid of most of the diseases.”
— Subodh Gupta8
Heart Attack Demographics
Heart attack incidence varies by age, sex, and ethnicity. Men over 45 and women over 55 are at increased risk, with women’s risk rising after menopause2 9. Certain ethnic groups, including American Indian, Alaska Native, and Black populations, experience higher rates of heart disease and cardiovascular mortality2 . Social determinants such as access to healthcare and lifestyle factors contribute to these disparities2 .
- Older adults have higher heart attack risk2 .
- Men have earlier onset compared to women2 .
- Ethnic disparities affect heart disease prevalence and outcomes2 .
Heart Attack Risk Factors
Heart attack risk factors are classified as modifiable and non-modifiable. Modifiable factors include lifestyle habits and medical conditions that can be managed or changed to reduce risk. Non-modifiable factors include age, sex, and genetics.
High Blood Pressure
Hypertension (high blood pressure) is a major risk factor for heart attacks. It increases the workload on the heart and damages artery walls, promoting atherosclerosis10 . Hypertension often has no symptoms, making regular screening essential10 . When combined with other conditions like obesity, diabetes, or high cholesterol, the risk of myocardial infarction increases further10 .
Abnormal Cholesterol
Dyslipidemia, characterized by abnormal levels of blood lipids, contributes to plaque formation in arteries10 . Elevated low-density lipoprotein (LDL) cholesterol is causally linked to coronary artery disease10 . Lipid profile testing measures cholesterol fractions to assess cardiovascular risk10 . Maintaining healthy cholesterol levels reduces the risk of heart attacks.
Diabetes
Diabetes mellitus significantly increases the risk of coronary artery disease and heart attacks. High blood sugar damages blood vessels and accelerates atherosclerosis10 . Adults with diabetes have approximately double the risk of cardiovascular events compared to non-diabetics10 .
Lifestyle Habits
“Reading a technically poor echocardiogram is like looking at a polar bear in a snow storm.”
— Steven E. Nissen11
Lifestyle choices play a critical role in heart attack risk. Smoking, poor diet, physical inactivity, and excessive alcohol consumption increase the likelihood of myocardial infarction10 9. Healthy lifestyle habits such as a balanced diet, regular exercise, quitting smoking, and managing stress can reduce risk9 .
- Smoking increases clot formation and artery damage3 9.
- Unhealthy diet high in saturated fats and sodium raises risk10 9.
- Physical inactivity contributes to obesity and metabolic syndrome10 9.
- Stress and drug use can trigger heart attacks9 .
Summary of Heart Attack Causes
Heart attacks result primarily from obstruction of coronary blood flow. The most common cause is atherosclerosis, where plaque buildup narrows arteries and can rupture, causing clots that block blood flow1 . Other causes include coronary artery spasms, spontaneous coronary artery dissection, and microvascular dysfunction4 61. Blood clots originating elsewhere in the body can also lodge in coronary arteries, triggering heart attacks3 .
Risk factors include both modifiable elements such as hypertension, abnormal cholesterol, diabetes, and lifestyle habits, and non-modifiable factors like age, sex, and genetics10 27. Understanding these causes and risk factors is essential for prevention, early detection, and treatment.
