Heart attacks are usually caused by plaque buildup in the coronary arteries, but conditions like smoking, high blood pressure, and infections can also trigger them, especially in younger adults.
A heart attack usually brings one image to mind: a blocked artery choked with plaque. And that’s true for many cases — but not all of them. The classic scenario of fatty deposits narrowing your arteries over decades is only part of the story.
The reality is that heart attacks can have several triggers, and some don’t involve the typical plaque buildup at all. Understanding what can cause a heart attack means looking beyond the cholesterol narrative. The causes range from well-known lifestyle factors to less obvious medical stressors that can catch even seemingly healthy people off guard.
The Classic Plaque Blockage
The most common cause of a heart attack is coronary artery disease. Plaque — a mix of fat, cholesterol, and other substances — builds up inside the arteries that supply blood to your heart muscle. Over time, that buildup can narrow the passageway.
If the plaque ruptures, your body responds by forming a blood clot around the rupture. That clot can block blood flow entirely, starving part of the heart of oxygen. This type of blockage is what doctors call a STEMI, a severe heart attack that requires immediate treatment to minimize damage.
Nearly 99% of heart attacks are linked to known, modifiable risk factors, according to research from multiple health organizations. That means most cases are connected to things you can actively manage — not just random bad luck.
Why The Typical Risk Factors Matter
You’ve heard the term “risk factors” before, but it’s easy to assume they only apply to older adults or people with obvious health problems. The truth is that these factors add up quietly over time, and they affect younger people too.
- Smoking: Smokers have more than twice the risk of developing cardiovascular disease compared to non-smokers. Nicotine damages the cells lining the coronary arteries and raises blood pressure, putting extra stress on your heart.
- High blood pressure: Uncontrolled hypertension forces your heart to work harder and can damage artery walls, making plaque buildup more likely over time.
- High cholesterol: Excess LDL cholesterol contributes directly to plaque formation. The CDC lists high cholesterol as one of the three key risk factors for heart disease.
- Diabetes: High blood sugar can damage blood vessels and accelerate atherosclerosis, raising heart attack risk even when glucose levels are reasonably managed.
- Physical inactivity and poor diet: A sedentary lifestyle and a diet high in saturated fats, sodium, and processed foods contribute to multiple risk factors simultaneously.
A study in the Journal of the American College of Cardiology found that these same modifiable factors — smoking, hypertension, and high cholesterol — are common in young adults experiencing their first heart attack. So age doesn’t offer a free pass.
Surprising Triggers and Hidden Causes
Plaque isn’t the only way a heart attack can happen. A 2025 Mayo Clinic study found that atherosclerosis accounted for only 47% of heart attacks in younger adults. The rest were tied to less obvious triggers. The Iowa HHS includes physical inactivity, poor diet, and diabetes in its list of Iowa risk factors, but the research points to additional mechanisms as well.
| Cause Type | Examples | Notes |
|---|---|---|
| Traditional plaque buildup | Atherosclerosis, coronary artery disease | Still the most common overall cause |
| Anemia | Severe iron deficiency or chronic blood loss | Can deprive heart of oxygen; second-most common hidden cause |
| Infection | Sepsis, severe pneumonia, COVID-19 | Body’s inflammatory response can stress the heart |
| Stress triggers | Major surgery, emotional trauma, extreme physical exertion | Can spike blood pressure or cause arrhythmias |
| Heavy meal | Very fatty meal causing a sudden jump in blood lipids | Temporarily damages blood vessels in some people |
Interestingly, the Mayo study noted that heart attacks caused by these hidden triggers were the deadliest, with a higher five-year mortality rate than those from classic plaque buildup. That’s a reminder that a heart attack can happen even without obvious artery disease.
How Smoking Damages Your Heart
Smoking deserves special attention because it’s the most preventable cause of heart disease. It doesn’t just raise your risk — it actively damages your cardiovascular system in several ways.
- Destroys arterial lining: Nicotine directly attacks the endothelial cells that line your coronary arteries, making them more susceptible to plaque formation and clot development.
- Raises blood pressure: Nicotine causes blood vessels to constrict, which increases blood pressure and forces the heart to pump harder.
- Reduces oxygen in the blood: Carbon monoxide from cigarette smoke binds to hemoglobin more readily than oxygen does, lowering the amount of oxygen that reaches your heart muscle.
- Increases clotting risk: Smoking makes blood platelets stickier, raising the chances that a clot will form and block a narrowed artery.
- Compounds with other risk factors: Smokers who also have high blood pressure or diabetes face a dramatically amplified risk — the factors multiply, not just add.
On average, smoking costs about 13 years of life expectancy due to its cardiovascular impact. Quitting at any age lowers risk significantly within the first year.
What the Experts Recommend
Preventing a heart attack often comes down to managing the major modifiable risk factors. Per the NHS heart attack causes, smoking, high blood pressure, and diabetes are major contributing factors. Here’s a quick look at what the guidelines suggest for reducing risk.
| Risk Factor | Target or Recommendation |
|---|---|
| Blood pressure | Aim for less than 130/80 mmHg under current guidelines |
| LDL cholesterol | Individual targets vary; discuss with your doctor |
| Smoking | Complete cessation – any reduction is helpful |
| Diabetes | Maintain HbA1c within your doctor’s recommended range |
While no plan is one-size-fits-all, the research is clear that controlling these factors dramatically lowers heart attack risk. Small changes — like adding regular walks to your day or switching to a more plant-focused diet — can shift your numbers over time.
The Bottom Line
Heart attacks are rarely random. In most cases, they’re linked to a combination of lifestyle factors and underlying health conditions that build up over years. The good news is that many of those factors are modifiable: quitting smoking, managing blood pressure, keeping cholesterol in check, and staying physically active all reduce risk.
If several of these risk factors apply to you — or if your numbers have crept up — a conversation with your primary care provider or cardiologist can help you set a personalized plan. A quick blood pressure check and a lipid panel give you a solid starting point for understanding where you stand.
References & Sources
- Iowa HHS. “Heart Attacks” The Iowa Department of Health and Human Services lists high blood cholesterol, high blood pressure, diabetes, smoking, poor diet, and physical inactivity as key risk factors.
- NHS. “Heart Attack” The NHS lists smoking, high blood pressure, and diabetes as major factors that increase the likelihood of a heart attack.