What Happens During a Heart Attack? Symptoms and Timeline

Every 40 seconds, someone in the U.S. has a heart attack—but what actually happens inside the body during this life-threatening event?

Heart attacks, also known as myocardial infarctions (MI), occur when blood flow to a part of the heart muscle becomes suddenly blocked. Without oxygen-rich blood, the heart muscle begins to die, potentially within minutes. This article walks through the anatomy of a heart attack, what happens during and after the event, and how early recognition and prevention can save lives.

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The Anatomy of a Heart Attack

Before diving into the symptoms and treatments, it's helpful to understand what a heart attack is and how it differs from other cardiac events.

What is a Heart Attack?

A heart attack, or myocardial infarction, occurs when blood flow to a portion of the heart muscle becomes suddenly blocked. In most cases, this happens when a fatty plaque inside a coronary artery ruptures, triggering the formation of a blood clot. If the clot significantly or completely obstructs the artery, the affected part of the heart may be deprived of oxygen, which can lead to tissue damage or death.

It's important to understand the difference between a heart attack and cardiac arrest, as they are often confused:

• A heart attack is a circulation problem: Blood can’t reach the heart muscle due to a blocked artery.
• Cardiac arrest is an electrical problem: The heart suddenly stops beating due to an abnormal rhythm.

Although a heart attack can lead to cardiac arrest, they are not the same event.

The Heart’s Blood Supply

The heart receives oxygen and nutrients through blood vessels called the coronary arteries, which wrap around the surface of the heart.

Over time, these arteries can become narrowed by atherosclerosis, a buildup of fatty deposits (plaques) along the artery walls. If a plaque ruptures, the body may respond by forming a clot at the site, which can block blood flow entirely, resulting in a heart attack.

What Happens Inside the Heart

Understanding what occurs inside the heart during a heart attack helps explain why rapid treatment is essential.

The Trigger Event

Most heart attacks begin with the rupture of a plaque in a coronary artery. This rupture signals the body to form a clot, which can either partially or completely block the artery.

• Complete blockage stops blood flow and oxygen delivery.
• Partial blockage may cause milder symptoms or unstable angina.
  

Oxygen Deprivation and Cell Death

Without oxygen, the heart muscle starts to suffer damage within 10 to 15 minutes. If blood flow isn’t restored quickly, parts of the heart muscle begin to die.

This process is progressive:

• 0–30 minutes: oxygen starvation begins.
• 30–60 minutes: heart muscle injury worsens.
• 1–6 hours: irreversible damage occurs.

In many cases, earlier treatment results in greater preservation of the heart muscle. 

Electrical Malfunctions

A heart attack can disrupt the heart's normal rhythm. Arrhythmias, like ventricular fibrillation, can cause the heart to quiver instead of pump, leading to sudden cardiac arrest. These electrical problems are a major cause of death in the first hour of a heart attack.

Recognizing a Heart Attack

Prompt recognition of symptoms can lead to quicker treatment and better outcomes.

Classic Symptoms

Common signs of a heart attack include:

• Chest pain or pressure (“like an elephant sitting on the chest” or “squeezing”), typically in the center or left side of the chest
• Shortness of breath
• Nausea or vomiting
• Pain radiating to the jaw, arm, back, or stomach
• Suddenly breaking into a cold sweat
• Men often report classic symptoms like chest pain.
• Women may experience more subtle signs such as fatigue, back pain, or lightheadedness.

Atypical Presentations

Some people—especially those who are older or have diabetes—may have “silent” heart attacks, with minimal or unusual symptoms.

Atypical symptoms may include:

• Mild indigestion or upper abdominal discomfort
• Weakness or fatigue
• Confusion or dizziness

Even without chest pain, seek immediate medical attention if you experience any of these symptoms.

Immediate Response and Emergency Treatment

Recognizing a heart attack and responding quickly is critical. Every minute counts—because the longer the heart goes without oxygen, the more damage occurs.

What to Do First

If someone may be having a heart attack:

• Call 911 immediately. Emergency medical services (EMS) can begin treatment on the way to the hospital and are trained to handle cardiac emergencies.
• Do not drive yourself or a loved one to the hospital unless absolutely necessary. Driving can delay critical treatment and is unsafe if the person’s condition worsens en route.
• Chewing one regular aspirin (325 mg) may help reduce clot formation, but only do so if advised by a healthcare provider and you have no known allergies or bleeding disorders
• Take prescribed nitroglycerin if available. This medication helps open blood vessels to improve blood flow to the heart.
• Stay calm and sit or lie down while waiting for emergency responders.

In-Hospital Treatments

Once in the emergency room, a patient suspected of having a heart attack will undergo several rapid assessments and interventions:

• Electrocardiogram (EKG): A quick and painless test that records the heart’s electrical activity to detect signs of a heart attack.
• Blood tests: 
  
  • Troponin - detects heart muscle damage.  Levels typically elevate within 3-6 hours of a heart attack and remain elevated for about 7-10 days.  Readily available in most ERs.
  • Creatine Kinase-MB (CK-MB) - Usually rises within 3-6 hours after a heart attack, peaks at 12-24 hours, and returns to normal within 2-3 days. Used when troponin testing is not available or for select clinical scenarios.
  • Myoglobin - a protein that is released about 1-2 hours after heart muscle injury occurs.  It is not specific to the heart; levels may rise with any muscle injury.  Often used in conjunction with other tests.
  • Chemistry Panel - This includes electrolytes, kidney function, and glucose.
• Chest X-ray or other imaging tests may be done to rule out other causes of symptoms.
  

Treatment Options

Immediate interventions include:

• Oxygen therapy may be used if blood oxygen levels are low.
• Nitroglycerin and pain relief are often given for chest pain.
• Antiplatelet and anticoagulant medications may be administered to prevent further clot formation.
• Coronary angiography may be performed, using a catheter to examine the patency of the arteries.

If a blockage is found, therapeutic options include:

• Percutaneous coronary intervention (PCI), commonly called angioplasty, may be performed. A small balloon is inflated to open the artery, and a cardiac stent is placed to keep it open.
• If PCI isn’t available or appropriate, thrombolytic (clot-busting) drugs may be used, especially in rural or time-sensitive settings.
• In some cases, surgical intervention, such as a coronary artery bypass surgery (CABG) may be needed, particularly for multiple blockages.

Long-Term Recovery and Complications

Recovery from a heart attack extends beyond the hospital. How a person heals and adapts afterward can affect future heart health and quality of life.

Healing and Scar Tissue Formation

Once blood flow is restored, the damaged part of the heart begins to heal. However, the heart muscle does not typically regenerate; instead, it forms scar tissue. This area may not contract as strongly as before, potentially reducing the heart’s overall function.

Recovery can take several weeks, depending on the severity of the heart attack. Most patients benefit from a structured cardiac rehabilitation program, which typically includes:

• Supervised exercise to strengthen the heart safely
• Nutrition counseling to support heart health
• Education on medications and lifestyle changes
• Stress reduction techniques and emotional support

Post-Heart Attack Medications

After a heart attack, medications are prescribed to reduce the risk of future events, improve heart function, and support long-term recovery. These medications are often taken together in a comprehensive secondary prevention plan. Commonly prescribed medications include: 

Antiplatelet Agents

• Examples: Aspirin, Clopidogrel (Plavix), Ticagrelor (Brilinta), Prasugrel (Effient)
• Prevent blood clots from forming or getting larger by reducing platelet aggregation.
• Dual antiplatelet therapy (DAPT) may be prescribed after stent placement (aspirin + another antiplatelet).

Beta Blockers

• Examples: Metoprolol, Carvedilol, Atenolol
• Reduce the heart’s workload and oxygen demand by slowing the heart rate and lowering blood pressure.
• May help prevent arrhythmias and reduce the risk of repeat heart attacks.

ACE Inhibitors 

• Examples (ACE inhibitors): Lisinopril, Ramipril, Enalapril
• Lower blood pressure and reduce strain on the heart.
• Help prevent heart failure and slow the progression of heart damage.

Statins (Cholesterol-Lowering Medications)

• Examples: Atorvastatin (Lipitor), Rosuvastatin (Crestor), Simvastatin
• Reduce LDL ("bad") cholesterol and stabilize plaque in the arteries.
• Recommended even if cholesterol levels are normal.

Nitroglycerin (as needed)

• Forms: Sublingual tablets or sprays
• Quickly relieves chest pain (angina) by dilating the coronary arteries.
• Usually prescribed for use only if chest discomfort recurs.

Medication regimens are personalized based on the patient’s heart function, kidney function, blood pressure, presence of stents, and other medical conditions. Medications should only be started or adjusted under the supervision of a healthcare provider.

Common Complications

Complications may occur, especially if large areas of the heart were damaged or treatment was delayed. These can include:

• Arrhythmias: Abnormal heart rhythms that may feel like fluttering, skipping, or pounding. Some are harmless, but others may require medication or devices like pacemakers or defibrillators.
• Heart failure: When the heart can’t pump blood effectively, leading to fatigue, shortness of breath, and swelling in the legs.
• Cardiogenic shock: A rare but serious condition where the heart suddenly can’t supply enough blood to the organs.
• Mental health challenges: Anxiety, depression, and post-traumatic stress may occur after a heart attack. Emotional recovery is just as important as physical healing.

Follow-up care is essential. Routine checkups, lab work, imaging tests, and medication adjustments are part of managing recovery and reducing the risk of a second heart attack.

Prevention and Risk Management

The risk of a future heart attack can be reduced with the right combination of lifestyle and medical care.

Modifiable Risk Factors

• Quit smoking
• Eat a heart-healthy diet (low in saturated fat and sodium)
• Exercise regularly (under a healthcare provider’s guidance)
• Maintain a healthy weight
• Control high blood pressure, diabetes, and cholesterol

Medical and Lifestyle Support

• Take medications as prescribed 
• Attend all follow-up appointments
• Participate in cardiac rehabilitation programs 
• Monitor mental health and seek counseling if needed

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Key Takeaways

• A heart attack (myocardial infarction) occurs when blood flow to part of the heart muscle is suddenly blocked, typically due to a ruptured plaque and clot in a coronary artery.
• Time is critical: Heart muscle begins to die within minutes of oxygen deprivation, which can lead to irreversible damage or death if not treated quickly.
• Symptoms vary: Classic signs include chest pain, shortness of breath, and nausea, but women, older adults, and people with diabetes may have atypical or silent symptoms.
• Immediate action saves lives: Call 911, take aspirin (if advised), and use prescribed nitroglycerin while waiting for emergency help—never attempt to drive yourself to the hospital.
• Emergency treatment includes EKG, blood tests (troponin), angioplasty with stenting, or clot-busting medications to restore blood flow and minimize heart damage.
• Recovery involves healing and lifestyle change: Scar tissue replaces damaged heart muscle, and cardiac rehabilitation helps improve physical and emotional health.
• Prevention is possible: Managing risk factors like smoking, high blood pressure, diabetes, and cholesterol, along with diet, exercise, and regular checkups, can significantly reduce the risk of a first or repeat heart attack.