Heart attack (Myocardial infarction) - Symptoms, Causes, Treatment & Prevention

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Overview

A heart attack, medically known as myocardial infarction (MI), occurs when blood flow to a portion of the heart muscle is abruptly blocked, causing tissue damage or death. The blockage is most often the result of a blood clot forming on a ruptured atherosclerotic plaque within a coronary artery.

Who it affects: While anyone can experience an MI, the risk increases with age and is higher in men under 55 and women after menopause. In the United States, about 803,000 people have a heart attack each year, and roughly 1 in 5 deaths is due to coronary heart disease.<sup>1</sup>

Prevalence worldwide: According to the World Health Organization, ischemic heart disease (which includes MI) caused 9.0 million deaths globally in 2022, making it the leading cause of death worldwide.<sup>2</sup>

Symptoms

Symptoms can vary between individuals, between sexes, and depending on whether the infarction is “ST‑segment elevation” (STEMI) or “non‑ST‑segment elevation” (NSTEMI). Below is a comprehensive list:

• Chest discomfort – pressure, tightness, squeezing, or heaviness lasting 2–30 minutes, may radiate to the left arm, neck, jaw, or back.
• Shortness of breath – often accompanies chest pain, but can be the primary complaint, especially in women and older adults.
• Cold sweat – sudden onset of diaphoresis without obvious cause.
• Nausea or vomiting – more common in women.
• Dizziness or light‑headedness – can result from reduced cardiac output.
• Palpitations – irregular or rapid heartbeat.
• Feeling of impending doom – a vague sense of severe anxiety.
• Unusual fatigue – especially in women, diabetics, and elderly patients; may last days before the event.
• Indigestion‑like pain – burning sensation that mimics heartburn.

In silent myocardial infarctions, up to 45% of MIs are asymptomatic and only discovered on electrocardiogram (ECG) or imaging tests.<sup>3</sup>

Causes and Risk Factors

Primary cause

The underlying pathology is atherosclerosis – plaque buildup inside coronary arteries. Plaques can rupture, exposing the lipid core to blood, which triggers platelet aggregation and thrombus formation that blocks the artery.

Major risk factors

• Non‑modifiable
  • Age (men >45, women >55)
  • Male sex (higher incidence before menopause)
  • Family history of premature coronary artery disease (CAD)
  • Genetic lipid disorders (e.g., familial hypercholesterolemia)
• Modifiable
  • Smoking (including e‑cigarettes)
  • Hypertension
  • High LDL‑cholesterol or low HDL‑cholesterol
  • Type 2 diabetes mellitus
  • Obesity (BMI ≥30 kg/m²)
  • Physical inactivity
  • Unhealthy diet (high saturated fat, trans‑fat, salt, sugar)
  • Chronic stress & depression
  • Excessive alcohol use

Diagnosis

Rapid diagnosis saves heart muscle. Clinicians combine history, physical exam, and several key tests.

1. Electrocardiogram (ECG)

A 12‑lead ECG is performed within 10 minutes of arrival. It can show:

• ST‑segment elevation (STEMI)
• ST‑segment depression or T‑wave inversion (NSTEMI or unstable angina)
• New left bundle‑branch block (considered equivalent to STEMI)

2. Cardiac Biomarkers

Blood tests for cardiac‑specific proteins rise after myocardial injury:

• Troponin I/T – most sensitive and specific; levels >99th percentile indicate MI.
• CK‑MB – less specific, used when troponin unavailable.

3. Imaging

• Echocardiography – bedside ultrasound shows wall‑motion abnormalities and assesses pump function.
• Coronary angiography – invasive gold standard to visualize blockages; guides revascularization.
• CT coronary angiography – non‑invasive alternative in low‑risk patients.
• Cardiac MRI – precise quantification of infarct size, useful for prognosis.

4. Additional tests

Complete blood count, metabolic panel, lipid profile, HbA1c, and coagulation studies help identify contributing factors.

Treatment Options

Treatment occurs in three phases: acute, post‑acute (in‑hospital), and long‑term management.

Acute Phase (First 12 hours)

• Reperfusion therapy
  • Percutaneous coronary intervention (PCI) – primary angioplasty with stent placement; preferred when performed <12 minutes (door‑to‑balloon) after arrival.
  • Fibrinolytic therapy – IV alteplase, reteplase, or tenecteplase when PCI unavailable within 120 minutes.
• Antiplatelet agents – aspirin 162‑325 mg chewed immediately; P2Y12 inhibitors (clopidogrel, ticagrelor, prasugrel).
• Anticoagulants – unfractionated heparin, low‑molecular‑weight heparin, or direct thrombin inhibitors.
• Nitrates – sublingual or IV for chest pain relief.
• Beta‑blockers – reduce myocardial oxygen demand unless contraindicated.
• Oxygen therapy – given only if oxygen saturation <90%.
• Analgesia – IV morphine for refractory pain.

Post‑Acute (In‑hospital) Care

• Continue dual antiplatelet therapy (DAPT) for ≥12 months.
• High‑intensity statin (e.g., atorvastatin 40‑80 mg) regardless of baseline LDL.
• ACE inhibitor or ARB for left‑ventricular dysfunction, hypertension, or diabetes.
• Early cardiac rehabilitation referral (within 2‑4 weeks).

Long‑Term Management

• Life‑long antiplatelet therapy (aspirin + P2Y12 inhibitor for at least 1 year, then aspirin alone).
• Statin therapy targeting LDL <70 mg/dL (or <55 mg/dL for very high risk).
• Blood pressure control <130/80 mmHg.
• Diabetes management (HbA1c <7%).
• Weight management, smoking cessation, and regular physical activity.
• Periodic stress testing or imaging to monitor graft/ stent patency.

Living with Heart Attack (Myocardial Infarction)

Survival rates have improved dramatically, but lifestyle adaptation is essential to prevent recurrence.

Daily Management Tips

• Medication adherence – use pill organizers or smartphone reminders; never stop a drug without consulting your doctor.
• Blood pressure & cholesterol monitoring – check at home or at a pharmacy weekly for BP; schedule lipid panels every 3–6 months.
• Heart‑healthy diet – adopt a Mediterranean or DASH eating plan: plenty of vegetables, fruits, whole grains, fish, nuts; limit red meat, processed foods, sugary drinks.
• Physical activity – aim for ≥150 minutes of moderate aerobic exercise per week (e.g., brisk walking) plus two strength‑training sessions.
• Weight control – maintain BMI 18.5‑24.9 kg/m²; lose 5‑10% of body weight if overweight.
• Stress reduction – mindfulness, yoga, or counseling; chronic stress raises cortisol and can trigger arrhythmias.
• Vaccinations – annual flu shot and COVID‑19 vaccine reduce cardiovascular complications.
• Regular follow‑up – cardiology visits every 3–6 months in the first year, then annually.
• Know your “code” – keep a written list of current medications, allergies, and emergency contacts.

Prevention

Primary and secondary prevention share many strategies.

Evidence‑based measures

1. Quit smoking – behavioral counseling + nicotine replacement or varenicline reduces MI risk by 30‑50% within 1 year.<sup>4</sup>
2. Control blood pressure – every 10 mmHg systolic reduction cuts stroke risk by 40% and MI risk by 20%.
3. Manage lipids – high‑intensity statins lower major vascular events by ~25% per 1 mmol/L LDL reduction.
4. Diabetes care – intensive glycemic control plus SGLT2 inhibitors or GLP‑1 receptor agonists reduces cardiovascular death.
5. Regular exercise – 30 minutes of moderate activity 5 days/week decreases MI risk by ~20%.
6. Healthy diet – high fiber, low saturated fat diet linked to 30% lower coronary events.
7. Limit alcohol – ≤2 drinks/day for men, ≤1 for women; excess intake raises blood pressure and triglycerides.

Complications

If the infarcted area is large or treatment is delayed, several serious complications can arise:

• Heart failure – reduced ejection fraction; may require ACE inhibitors, beta‑blockers, or devices (ICD, CRT).
• Cardiac arrhythmias – ventricular tachycardia/fibrillation, atrial fibrillation; can be life‑threatening.
• Cardiogenic shock – severe pump failure, requiring inotropes, intra‑aortic balloon pump, or ECMO.
• Mechanical complications
  • Ventricular septal rupture
  • Papillary muscle rupture → acute mitral regurgitation
  • Free‑wall rupture → cardiac tamponade
• Pericarditis – inflammation of the lining around the heart, usually 2‑4 days post‑MI.
• Thromboembolism – left‑ventricular thrombus can embolize to the brain or limbs.

Early reperfusion dramatically reduces the incidence of these complications. For instance, primary PCI lowers the risk of cardiogenic shock from >10% (with fibrinolysis) to <5%.<sup>5</sup>

When to Seek Emergency Care

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References

1. Centers for Disease Control and Prevention. Heart Attack. Updated 2023.
2. World Health Organization. Cardiovascular diseases (CVDs) fact sheet. 2022.
3. Thygesen K, et al. “Silent myocardial infarction: clinical implications.” J Am Coll Cardiol. 2020;75(23):3033‑3044.
4. U.S. Department of Health and Human Services. “Smoking Cessation: A Report of the Surgeon General.” 2020.
5. O’Gara PT, et al. “2013 ACCF/AHA Guideline for the Management of ST‑Elevation Myocardial Infarction.” Circulation. 2013;127:e362‑e425.

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