Myocardial infarction

What happens during a heart attack

The heart muscle (myocardium) receives its blood from the coronary arteries. In most cases one of them has carried an atherosclerotic plaque for years, a deposit of fat, inflammation and calcium in the artery wall. When this plaque ruptures or erodes, the body treats it like a wound and forms a blood clot (thrombus) on top of it. If the clot blocks the artery, the part of the muscle it supplied receives no oxygen and its cells begin to die. After roughly 20–30 minutes the damage becomes irreversible in the most affected areas, and it spreads over the following hours.

That is why doctors say “time is muscle”: the sooner the artery is opened, the less heart muscle is lost and the better the heart works afterward. A heart attack treated early may leave minor consequences; one treated late can lead to heart failure, dangerous arrhythmias or sudden death.

Less often a heart attack occurs without a large plaque: from an artery spasm, a tear in the artery wall (spontaneous coronary artery dissection, which more often affects younger women) or clots that travel from elsewhere. The doctor considers these possibilities when the case does not look typical.

Doctors divide heart attacks into two broad forms according to the ECG. In ST-elevation myocardial infarction (STEMI) the artery is usually completely blocked and urgent reopening is needed. In non-ST-elevation myocardial infarction (NSTEMI) the blockage is partial or temporary; it is just as serious, but the timing and approach to coronary angiography are set according to the patient’s risk.

Warning signs

The classic sign is pressure, tightness or heaviness in the middle of the chest lasting more than a few minutes, or one that goes away and comes back. Patients often describe it as “a stone on the chest” or “a band squeezing.” The pain may spread to:

• the left arm, less often both arms or the right arm;
• the shoulder, neck, jaw or teeth;
• the back, between the shoulder blades, or the upper abdomen, which is sometimes mistaken for gastritis.

The pain is often accompanied by cold sweats, shortness of breath, nausea or vomiting, sudden weakness, light-headedness or an unexplained sense of dread.

Not every heart attack begins with severe pain. Women, older adults and people with diabetes may have only shortness of breath, unusual fatigue, nausea, or pain in the back or jaw. Chest pain is still the most common symptom in women too, but the absence of severe pain does not rule out a heart attack. Some people noticed a “warning” days or weeks earlier: chest pain on exertion that was new or milder before (coronary artery disease and angina).

Pain that changes with breathing, with arm movement, or that can be reproduced by pressing a finger on one spot of the chest wall is less typical of a heart attack, but that alone is not enough to rule it out. When in doubt, no one should make the diagnosis at home.

What to do right away

1. Call 127. The operator guides you step by step and sends the emergency team, who can record an ECG on the way and alert the hospital.
2. Sit or lie in a comfortable position and stay calm; avoid any exertion.
3. Aspirin: follow the operator’s instructions. In most cases chewing one aspirin tablet is recommended, but tell them if you are allergic, have an ulcer or known bleeding, or take anticoagulants.
4. Do not drive yourself and do not waste time looking for medicines or waiting for symptoms to pass. Waiting is the most common cause of delay.

If the person loses consciousness and is not breathing normally, this is cardiac arrest. Call 127, start chest compressions in the center of the chest, fast and hard, as the operator instructs, and use an automated external defibrillator (AED) as soon as one is available. Many arrests caused by a heart attack have a rhythm that can be corrected with an electric shock, and every minute without intervention lowers the chance of survival.

How it is diagnosed in hospital

In hospital the diagnosis rests on three elements that complement each other:

• the ECG, done within the first minutes of arrival (or already in the ambulance). It shows whether there is ST elevation and in which area of the heart the problem lies.
• Cardiac troponin, a blood test that detects damage to the heart muscle. It rises with a delay of a few hours, so it is often repeated; for this reason a very early test or a single normal ECG does not always rule out a heart attack.
• the clinical history: how the pain started, how long it lasted, which risk factors you have.

Coronary angiography shows the blocked artery itself and decides whether it can be opened with a stent. Echocardiography assesses how damaged the pumping function is and whether the valves are affected. If these tests point to another cause of chest pain, such as pericarditis, pulmonary embolism, aortic dissection or gastric causes, the hospital treats that instead. This distinction is exactly why chest pain should be assessed in a hospital and not at home.

Acute treatment

The aim is the same in every case: reopening the artery as quickly as possible. The main tool is coronary angioplasty with a stent: through an artery in the wrist or groin, the interventional cardiologist guides a catheter to the blockage, inflates a tiny balloon and leaves a thin metal mesh (stent) that keeps the artery open. In STEMI the goal is for this to be done as soon as possible after first contact with the health service.

Medicines accompany the procedure: antiplatelet drugs (aspirin and a second drug that prevents platelets from sticking together) and anticoagulants during the intervention. When angioplasty cannot be performed in an acceptable time, thrombolysis, drugs that dissolve the clot, may be used, usually followed by transfer for angiography. In certain cases, when many arteries are affected or the anatomy does not allow a stent, coronary bypass surgery is recommended. The patient is monitored in a coronary care unit for arrhythmias and any complications.

Possible complications are ventricular arrhythmias in the first hours, heart failure, damaged valves (especially mitral regurgitation) and, more rarely, rupture of the muscle. The team watches for these and adjusts treatment.

After a heart attack: preventing a second one

The phase after leaving hospital is as important as the acute treatment, because other arteries may also have plaques and atherosclerosis continues if it is not controlled. This is the usual program:

• Daily medicines: a statin (sometimes with ezetimibe) to lower LDL cholesterol, antiplatelet drugs, often a beta-blocker and an ACE inhibitor or ARB, depending on heart function and blood pressure. Never stop antiplatelet drugs on your own, especially after a stent: early discontinuation raises the risk of stent thrombosis, which can cause a new heart attack.
• Cardiac rehabilitation: a supervised program of exercise and education that lowers the risk of another heart attack and improves quality of life.
• Complete smoking cessation, the intervention with the greatest benefit after a heart attack.
• Control of risk factors: blood pressure, diabetes, weight, and LDL cholesterol (the target after a heart attack is usually below 55 mg/dL, per European guidelines; see dyslipidemia).
• Regular cardiology follow-up with ECG and echocardiography to track heart function.

Returning to work, travel, physical activity and intimate life is adapted to your progress and your cardiologist’s advice; most patients return to a full life. It is normal to feel frightened or low in the first months; talk to your doctor, because this too has treatment and affects recovery.

How to prevent it

Most heart attacks are linked to factors that can be controlled: smoking, hypertension, high cholesterol, diabetes, excess weight, inactivity and constant stress. Timely blood pressure checks, a lipid profile and blood glucose, a balanced diet (vegetables, fruit, legumes, olive oil, fish) and 150 minutes of moderate activity a week are the measures with the strongest evidence. If you have a family history of early heart attack or symptoms that worry you, a cardiology consultation can assess your risk.

This information is educational and does not replace a medical visit.