Myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow to part of the heart muscle is severely reduced or blocked, causing damage to the heart muscle.
This article provides nurses and nursing students an extensive overview of MI including pathophysiology, causes, risk factors, signs and symptoms, diagnosis, complications, treatment, nursing care, and considerations for the NCLEX exam.
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Pathophysiology of Myocardial Infarction
The heart muscle requires a constant supply of oxygen and nutrients from the coronary arteries. Atherosclerosis causes fatty deposits called plaque to build up inside the artery walls over time. This plaque narrows the coronary arteries, restricting blood flow to the heart muscle .
An MI occurs when a plaque ruptures, causing a blood clot to quickly form at the site. This blood clot can block the coronary artery, severely reducing or stopping blood flow. Without oxygen, heart muscle cells begin to die within minutes. The longer blood flow is blocked, the more damage occurs . As heart cells die, enzymes like troponin are released into the bloodstream. Troponin levels help determine the extent of damage to the heart . The affected area develops necrosis and scar tissue, impairing the heart’s pumping ability.
Causes and Risk Factors for Myocardial Infarction
The most common cause of MI is atherosclerotic coronary artery disease. Less common causes include :
- Coronary artery spasm
- Coronary embolism
- Spontaneous coronary artery dissection
- Hypercoagulable states
- Trauma
- Vasculitis
Modifiable risk factors that can be managed to reduce MI risk include :
- Cigarette smoking
- High blood pressure
- High LDL cholesterol
- Diabetes
- Obesity
- Physical inactivity
- Unhealthy diet
Non-modifiable risk factors include:
- Family history of early heart disease
- Age – Risk increases after age 45 for men and age 55 for women
- Gender – Men have a greater risk than women
Signs and Symptoms of Myocardial Infarction
Classic signs and symptoms of MI include :
- Chest pain – Often described as pressure, squeezing, fullness or pain in the center or left side of chest. May radiate to jaw, neck, shoulders, arms or back.
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- Shortness of breath
- Nausea, vomiting, dizziness
- Sweating and anxiety
- Irregular heartbeat
Atypical symptoms are more common in women, elderly adults, and diabetics. These may include :
- Epigastric pain
- Fatigue
- Palpitations
- Syncope
Silent MIs have no symptoms but are detected by ECG changes or elevated cardiac enzymes.
Diagnosing Myocardial Infarction
An MI is typically diagnosed in the emergency department using :
- Medical history – Details about symptoms, risk factors, and family history.
- Physical exam – Listening to heart and lung sounds, checking blood pressure, pulse, oxygen levels.
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- Electrocardiogram (ECG) – Records electrical signals in the heart. ST segment changes can indicate blocked arteries and heart muscle damage.
- Cardiac enzyme blood tests – Troponin and CK-MB levels help confirm heart muscle injury. Levels begin to rise 2-4 hours after an MI and remain elevated for days to weeks.
- Imaging tests – Echocardiography and radionuclide scanning check heart function. Coronary angiography visualizes blockages in arteries.
Types of Myocardial Infarction
MIs are classified by ECG and cardiac enzymes :
- STEMI – ST segment elevation on ECG plus elevated cardiac enzymes indicates full thickness heart muscle damage. This is the most serious type.
- NSTEMI – No ST elevation on ECG but elevated cardiac enzymes indicates partial thickness heart muscle damage.
Location of MI refers to the affected area of heart muscle:
- Anterior wall MI – Significant left ventricular damage
- Inferior wall MI
- Lateral wall MI
- Posterior wall MI
Complications of Myocardial Infarction
Potential complications after an MI include :
- Arrhythmias – Irregular heart rhythms like ventricular tachycardia or ventricular fibrillation. These can decrease heart function.
- Cardiogenic shock – Condition where extensive heart muscle damage impairs the heart’s ability to pump enough blood to organs.
- Heart failure – Condition where the weakened heart cannot pump adequately to meet the body’s needs.
- Heart rupture – Rupture of the ventricular wall, septum, papillary muscle or valve. This is often fatal.
Medical Management of Myocardial Infarction
Immediate treatment focuses on restoring blood flow and limiting heart muscle damage .
This may include:
- Oxygen – Improves oxygen delivery to ischemic heart muscle
- Aspirin – Antiplatelet agent to prevent further clotting
- Nitroglycerin – Vasodilator to improve blood flow
- Pain medication – To decrease cardiac workload
- Thrombolytic therapy – Clot-busting drugs like tPA to dissolve clots
- PCI – Cardiac catheterization with balloon angioplasty and stent placement to open blocked arteries
- CABG – Coronary artery bypass surgery to reroute blood flow around blocked arteries
After an MI, medications help prevent future heart attacks and manage complications:
- Antiplatelets – Prevent clot formation and support stent patency
- ACE inhibitors – Reduce workload on heart, lower blood pressure
- Beta blockers – Slow heart rate, lower blood pressure, reduce workload
- Statins – Lower cholesterol levels in blood
Nursing Care for Myocardial Infarction
Nursing care for MI focuses on:
Assessment
- Obtain thorough history – Note risk factors, symptoms
- Complete physical exam – Check vital signs, heart and lung sounds, peripheral pulses
- Monitor cardiac rhythm
- Draw cardiac enzyme blood tests
- Evaluate diagnostic tests – ECG, echocardiography findings
Pain Management
- Administer oxygen, nitrates, morphine
- Teach relaxation techniques
- Provide comfort measures
Prevent Complications
- Monitor vital signs and cardiac rhythm
- Administer antiplatelet, thrombolytic, or anticoagulant therapy
- Prepare for procedures like PCI or CABG
Educate on Lifestyle Changes
- Smoking cessation
- Heart healthy diet
- Stress management
- Medication adherence
- Activity recommendations
Discharge Planning
- Schedule follow-up care
- Discuss cardiac rehabilitation programs
- Review medication, diet and activity guidelines
NCLEX Questions for Myocardial Infarction
Here are some practice questions nurses should know relevant to caring for MI patients :
- Where does the most significant damage occur with an anterior wall MI?
A. Left ventricle
B. Right ventricle
C. Intraventricular septum
D. Papillary muscles
Answer: A
- A patient recovering from MI is scheduled to start cardiac rehabilitation. What is the priority goal of this program?
A. Strengthen cardiac muscle
B. Lower cholesterol
C. Reduce risk of future heart attacks
D. Improve balance
Answer: C
- Which finding indicates the patient is bleeding excessively from their arterial access site after a cardiac catheterization post-MI?
A. Hemoglobin 12 g/dL
B. Platelets 98,000/mm3
C. PTT 52 seconds
D. INR 5.2
Answer: D
Conclusion
Myocardial infarction is a serious medical condition requiring prompt assessment and treatment to restore blood flow and prevent extensive damage to the heart muscle.
Knowledge of MI pathophysiology, risk factors, diagnosis, and management is essential for nurses and nursing students to provide optimal care for these patients. Appropriate nursing care helps prevent complications and supports positive outcomes after an MI occurs.
