A heart attack happens when blood flow to part of the heart muscle gets cut off, starving those cells of oxygen. The most common cause is a buildup of fatty deposits inside a coronary artery that suddenly ruptures and triggers a blood clot. But that’s not the only way it happens. Arteries can spasm shut, tear from the inside, or become overwhelmed by extreme physical stress. Understanding these different pathways helps explain why heart attacks strike people of all ages and fitness levels.
The Most Common Cause: Plaque Rupture
Most heart attacks follow years of gradual cholesterol buildup inside the coronary arteries, the small blood vessels that feed the heart itself. Over time, fatty material collects beneath the artery lining and forms a deposit called plaque. This process, atherosclerosis, often produces no symptoms for decades.
The danger isn’t necessarily the size of the plaque. It’s the stability. Each plaque has a fibrous cap holding it together. When that cap becomes extremely thin, the plaque can crack open. Once it ruptures, it exposes the material inside to the bloodstream. The body treats this like a wound and rushes to form a clot. That clot can partially or completely block blood flow through the artery in minutes.
Chronic inflammation plays a central role in weakening these caps. Inflammation is involved in every phase of heart disease, from the initial formation of plaque to the acute rupture that causes a heart attack. Activation of the sympathetic nervous system (your body’s “fight or flight” response) can also trigger rupture by increasing blood pressure, making blood more likely to clot, and ramping up platelet activity, all at once.
What Happens to the Heart Muscle
Once blood flow stops, heart muscle cells begin dying, and the damage accelerates with every passing hour. In patients treated within three hours, the final area of dead tissue averages about 21% of what could have been affected. Between three and six hours, that jumps to 38%. By six to nine hours it reaches 66%, and beyond nine hours it climbs to 77%. This is why emergency medicine treats heart attacks as a race against the clock. The phrase “time is muscle” exists for a reason.
Dead heart muscle can’t regenerate. It’s replaced by scar tissue that doesn’t contract, which permanently weakens the heart’s pumping ability. The faster blood flow is restored, the more muscle survives and the better the long-term outcome.
Heart Attacks Without Plaque Buildup
Not every heart attack involves clogged arteries. In some cases, a coronary artery suddenly spasms shut, temporarily blocking blood flow even though no significant plaque is present. This happens when the muscle cells in the artery wall become hyperreactive to signals that cause constriction. The artery essentially squeezes itself closed.
Triggers for coronary artery spasm include surges of stress hormones, extreme cold, and stimulant drugs. Cocaine and amphetamines are particularly dangerous because they both activate the sympathetic nervous system and make artery walls more sensitive to constriction signals. Even parasympathetic (rest-and-digest) nerve activity can trigger spasm in a susceptible artery.
Spontaneous Coronary Artery Dissection
Another lesser-known cause is spontaneous coronary artery dissection, or SCAD, where the inner lining of a coronary artery tears and blood collects within the artery wall. This pocket of trapped blood compresses the artery from the outside, choking off flow. SCAD has nothing to do with cholesterol or traditional risk factors.
SCAD overwhelmingly affects women. It may account for up to 35% of heart attacks in women aged 50 and younger and is the most common cause of heart attacks related to pregnancy, responsible for about 43% of those cases. The average age of women with SCAD ranges from 45 to 53, though it has been reported across all decades of adult life. Because it strikes people with few conventional risk factors, it’s often missed or misdiagnosed.
External Triggers That Push the Heart Over the Edge
Even when underlying artery disease is already present, a specific event often tips the balance. Cold weather is a well-documented trigger. When you’re exposed to cold, your blood vessels narrow to conserve body heat, which forces the heart to pump harder against increased resistance. Blood also becomes slightly thicker and more prone to clotting in cold conditions. Combine that with sudden physical exertion, like shoveling snow, and you’ve created a perfect storm: higher oxygen demand from the muscles, higher blood pressure from the cold, and a greater tendency to clot.
Intense emotional stress works through a similar pathway. A surge of adrenaline raises heart rate and blood pressure, can destabilize vulnerable plaque, and increases the blood’s clotting tendency, all simultaneously. This is why heart attacks sometimes cluster after natural disasters, major sporting events, or personal crises.
The Major Risk Factors
Three conditions stand above the rest as drivers of heart attack risk: high blood pressure, high blood cholesterol, and smoking. High blood pressure damages artery walls over time, creating sites where plaque can take hold. High cholesterol supplies the raw material for those deposits. Smoking accelerates both processes while also promoting clot formation and reducing the blood’s oxygen-carrying capacity.
Diabetes significantly compounds the risk because chronically elevated blood sugar damages blood vessel linings and promotes inflammation. Obesity, physical inactivity, and a family history of early heart disease also raise the likelihood. Most heart attacks result from a combination of these factors building silently over years, not from any single cause.
Silent Heart Attacks
Not all heart attacks announce themselves with crushing chest pain. A study tracking nearly 2,000 adults over 10 years found that 8% developed scarring on the heart consistent with a heart attack. Of those, 80% had no idea it had happened. These silent heart attacks cause the same kind of muscle damage but produce symptoms so mild they get attributed to fatigue, indigestion, or just getting older.
People experiencing a silent heart attack might feel vague discomfort in the center of the chest rather than sharp pain on the left side. Some notice mild throat or chest pressure they mistake for heartburn. Others feel nothing unusual at all, during or after. The damage only shows up later on imaging or when the weakened heart starts causing other problems.
How Symptoms Differ Between Men and Women
The classic image of a heart attack, a person clutching the left side of their chest, more closely matches how men typically experience it. Women often present differently. Chest pain or pressure may not be the most prominent symptom, or it may be absent entirely.
Women are more likely to experience sweating, nausea, dizziness, and unusual fatigue, sometimes while resting or even asleep. Shortness of breath, vomiting, back pain, jaw pain, and discomfort in the upper abdomen are all common. Because these symptoms are vague and overlap with many less serious conditions, women’s heart attacks are more frequently dismissed or delayed in diagnosis. Discomfort in the center of the chest that lasts several minutes (or comes and goes), pain radiating to the arms, back, neck, jaw, or stomach, and unexplained shortness of breath all warrant emergency evaluation regardless of how “typical” they seem.