Heart Attack (Myocardial Infarction)

Overview

A heart attack, medically known as myocardial infarction (MI), occurs when blood flow to a part of the heart muscle is severely reduced or blocked. This interruption in blood flow deprives the heart muscle of oxygen and nutrients, causing heart cells to die. Without immediate treatment, a heart attack can cause permanent heart damage or death.

Heart attacks are typically caused by coronary artery disease, where plaque buildup in the arteries narrows the blood vessels. When a plaque ruptures, a blood clot forms and can completely block blood flow. The longer the heart muscle goes without oxygen, the greater the damage. This is why immediate medical attention is crucial – time is muscle when it comes to heart attacks.

Each year, approximately 805,000 Americans experience a heart attack, with about 605,000 being first-time attacks. While heart attacks can be fatal, advances in emergency treatment have significantly improved survival rates. With prompt medical care and lifestyle changes, many heart attack survivors go on to live full, active lives.

Symptoms

Heart attack symptoms can vary significantly from person to person, and may differ between men and women. Some people experience intense symptoms, while others have mild discomfort. About 20% of heart attacks are "silent," occurring without obvious symptoms.

Classic Symptoms

Additional Symptoms

• Cold sweats or profuse sweating
• Heartburn or indigestion-like symptoms
• Pain in the jaw, neck, back, or stomach
• Irregular heartbeat or palpitations
• Lightheadedness or fainting
• Chest tightness or pressure
• Sudden extreme fatigue
• Anxiety or feeling of impending doom

Symptoms in Women

Women may experience different or additional symptoms:

• Unusual fatigue lasting for days
• Sleep disturbances
• Shortness of breath without chest pain
• Back or jaw pain
• Nausea or vomiting more commonly than men
• Lightheadedness or dizziness

Warning Signs (Prodromal Symptoms)

Some people experience warning signs hours, days, or weeks before a heart attack:

• Recurring chest discomfort that comes and goes
• Unusual fatigue
• Sleep problems
• Shortness of breath during normal activities
• Increased anxiety

Causes

Heart attacks occur when one or more coronary arteries become blocked, preventing oxygen-rich blood from reaching part of the heart muscle. Understanding the underlying causes helps in prevention and treatment.

Primary Causes

Coronary Artery Disease (CAD)

The most common cause of heart attacks is coronary artery disease, where:

• Fatty deposits (plaques) build up in coronary arteries
• Plaques narrow the arteries (atherosclerosis)
• A plaque ruptures, forming a blood clot
• The clot blocks blood flow to the heart muscle

Coronary Artery Spasm

A severe spasm of a coronary artery can temporarily cut off blood flow:

• Can occur in arteries without significant plaque buildup
• Often triggered by drug use (cocaine, amphetamines)
• May be caused by extreme stress or cold
• More common in younger people

Contributing Factors

• Blood clots: Form when plaques rupture
• Inflammation: Chronic inflammation damages artery walls
• Plaque instability: Vulnerable plaques more likely to rupture
• Oxygen supply-demand mismatch: Heart needs more oxygen than available

Less Common Causes

• Spontaneous coronary artery dissection (SCAD)
• Coronary embolism from another part of the body
• Certain infections affecting the heart
• Extreme physical or emotional stress (Takotsubo cardiomyopathy)
• Radiation therapy to the chest
• Congenital heart abnormalities

Risk Factors

Multiple factors can increase your risk of having a heart attack. Some are controllable through lifestyle changes and medical treatment, while others cannot be changed but should be monitored.

Non-Modifiable Risk Factors

• Age: Men over 45, women over 55
• Gender: Men at higher risk, women's risk increases after menopause
• Family history: Parent or sibling with early heart disease
• Race/ethnicity: Higher risk in African Americans, Mexican Americans, Native Americans
• Previous heart attack: Increases risk of another

Modifiable Risk Factors

• Smoking: Doubles heart attack risk
• High blood pressure: Damages arteries over time
• High cholesterol: Contributes to plaque buildup
• Diabetes: Significantly increases risk
• Obesity: Associated with multiple risk factors
• Physical inactivity: Weakens the heart
• Unhealthy diet: High in saturated fats, trans fats, salt
• Excessive alcohol: Can raise blood pressure
• Stress: Chronic stress affects heart health
• Sleep apnea: Stresses the cardiovascular system

Medical Conditions That Increase Risk

• Metabolic syndrome
• Chronic kidney disease
• Autoimmune conditions (rheumatoid arthritis, lupus)
• HIV/AIDS
• Preeclampsia during pregnancy
• Polycystic ovary syndrome (PCOS)

Medications and Substances

• Cocaine and amphetamines
• Some chemotherapy drugs
• Certain antipsychotics
• High doses of NSAIDs (in some people)

Diagnosis

Rapid and accurate diagnosis of a heart attack is crucial for effective treatment. Emergency medical personnel begin assessment immediately, and diagnosis continues in the hospital emergency department.

Initial Assessment

• Medical history: Symptoms, timing, risk factors
• Physical examination: Blood pressure, pulse, heart sounds
• Symptom evaluation: Type, location, duration of pain

Diagnostic Tests

Electrocardiogram (ECG/EKG)

• First test performed, results within minutes
• Shows electrical activity of the heart
• Can identify location and extent of damage
• Distinguishes between STEMI and NSTEMI heart attacks

Blood Tests

• Troponin: Most sensitive marker, peaks 12-24 hours after attack
• CK-MB: Another cardiac enzyme, less specific
• Myoglobin: Early marker but not specific to heart
• BNP: Indicates heart failure

Imaging Tests

• Chest X-ray: Shows heart size and lung fluid
• Echocardiogram: Ultrasound showing heart function
• Coronary angiography: Gold standard for viewing blockages
• CT coronary angiogram: Non-invasive artery imaging
• Nuclear stress test: Shows blood flow to heart

Types of Heart Attacks

• STEMI: ST-elevation myocardial infarction (complete blockage)
• NSTEMI: Non-ST-elevation myocardial infarction (partial blockage)
• Unstable angina: Severely reduced blood flow without permanent damage

Treatment Options

Heart attack treatment focuses on quickly restoring blood flow to prevent heart muscle death. The faster treatment begins, the less damage occurs. Treatment continues long-term to prevent future heart attacks.

Emergency Treatment

Immediate Medications

• Aspirin: Prevents further clotting
• Nitroglycerin: Improves blood flow
• Oxygen therapy: If blood oxygen is low
• Morphine: For severe pain
• Beta-blockers: Reduce heart workload

Clot-Busting Medications (Thrombolytics)

• Given within 3-4 hours of symptom onset
• Dissolve blood clots blocking arteries
• Include alteplase, reteplase, tenecteplase
• Most effective when given early

Procedures to Restore Blood Flow

Percutaneous Coronary Intervention (PCI/Angioplasty)

• Preferred treatment if available within 90 minutes
• Catheter inserted through artery to heart
• Balloon inflated to open blocked artery
• Stent usually placed to keep artery open
• Drug-eluting stents reduce re-blockage risk

Coronary Artery Bypass Grafting (CABG)

• Surgery for multiple or complex blockages
• Healthy blood vessel grafted to bypass blockage
• May be done emergently or after stabilization
• Longer recovery but durable results

Long-Term Medications

• Dual antiplatelet therapy: Aspirin plus clopidogrel/ticagrelor
• ACE inhibitors or ARBs: Protect heart function
• Beta-blockers: Reduce heart rate and blood pressure
• Statins: Lower cholesterol aggressively
• Aldosterone antagonists: For heart failure prevention

Cardiac Rehabilitation

• Medically supervised exercise program
• Education on heart-healthy living
• Nutritional counseling
• Stress management techniques
• Smoking cessation support
• Psychological support

Prevention

Most heart attacks can be prevented through lifestyle changes and managing risk factors. Prevention is especially important for those with existing heart disease or multiple risk factors.

Lifestyle Modifications

Heart-Healthy Diet

• Emphasize fruits, vegetables, whole grains
• Choose lean proteins (fish, poultry, legumes)
• Limit saturated and trans fats
• Reduce sodium to less than 2,300mg daily
• Limit added sugars and processed foods
• Mediterranean or DASH diet patterns recommended

Regular Physical Activity

• At least 150 minutes moderate exercise weekly
• Or 75 minutes vigorous exercise weekly
• Include strength training twice weekly
• Start slowly and gradually increase
• Any activity better than none

Smoking Cessation

• Quitting immediately reduces heart attack risk
• Risk drops 50% after one year
• Multiple cessation aids available
• Avoid secondhand smoke exposure

Medical Management

• Control blood pressure: Target below 130/80 mmHg
• Manage cholesterol: LDL goals based on risk
• Diabetes control: Keep A1C below 7% for most
• Weight management: BMI 18.5-24.9 ideal
• Regular check-ups: Monitor risk factors

Medications for Prevention

• Aspirin: For those at high risk (consult doctor)
• Statins: For high cholesterol or diabetes
• Blood pressure medications: As prescribed
• Diabetes medications: To control blood sugar

Stress Management

• Practice relaxation techniques
• Regular exercise for stress relief
• Adequate sleep (7-9 hours)
• Social connections and support
• Professional help for anxiety/depression

Emergency Response

A heart attack is a medical emergency requiring immediate action. Every minute counts – rapid treatment can save lives and prevent permanent heart damage.

Call 911 Immediately If You Experience:

• Chest pain or pressure lasting more than a few minutes
• Pain spreading to arm, jaw, neck, back, or stomach
• Shortness of breath with or without chest pain
• Breaking out in cold sweat, nausea, or lightheadedness
• Sudden extreme fatigue or weakness

What to Do While Waiting for Help

1. Stop all activity and sit or lie down
2. Chew aspirin (325mg) if not allergic
3. Take nitroglycerin if prescribed
4. Unlock doors for emergency personnel
5. Have medications list ready
6. Stay calm and try to relax

Do NOT:

• Drive yourself to the hospital
• Wait to see if symptoms go away
• Take someone else's heart medications
• Ignore "mild" symptoms

For Bystanders: CPR

If someone is unconscious and not breathing:

1. Call 911 immediately
2. Begin chest compressions (100-120/minute)
3. Push hard and fast in center of chest
4. Use AED if available
5. Continue until help arrives

Warning: Time Is Critical

The first hour after heart attack symptoms begin is called the "golden hour." Treatment within this time can:

• Stop the heart attack
• Minimize heart damage
• Save your life
• Preserve heart function

Related Conditions

Heart attacks are often associated with other cardiovascular conditions and risk factors that require management:

Other Related Conditions

• Diabetes - Significantly increases heart attack risk
• High cholesterol - Contributes to artery blockages
• Obesity - Associated with multiple cardiac risk factors
• Peripheral artery disease - Often coexists with coronary disease
• Kidney disease - Increases cardiovascular risk
• Sleep apnea - Stresses the cardiovascular system

Complications After Heart Attack

• Cardiogenic shock
• Ventricular rupture
• Pericarditis
• Blood clots
• Valve problems

Frequently Asked Questions

References

1. American Heart Association. Heart Attack (Myocardial Infarction). AHA. 2024.
2. Thygesen K, et al. Fourth Universal Definition of Myocardial Infarction. Circulation. 2018.
3. O'Gara PT, et al. 2013 ACCF/AHA Guideline for the Management of ST-Elevation Myocardial Infarction. Circulation. 2013.
4. Amsterdam EA, et al. 2014 AHA/ACC Guideline for the Management of Patients With Non-ST-Elevation Acute Coronary Syndromes. Circulation. 2014.
5. Virani SS, et al. Heart Disease and Stroke Statistics—2024 Update. Circulation. 2024.
6. National Heart, Lung, and Blood Institute. Heart Attack. NHLBI. 2024.