Mayocardial infraction bsc nursing

Reading File

Finding Sources

Reading File

Finding Sources

Reading File

Finding Sources

Loading Image

Reading File

Loading Image

I now have all the material needed for a comprehensive BSc Nursing-level answer. Let me compose the full response.

Myocardial Infarction (MI) - BSc Nursing

Definition

Myocardial infarction (MI), commonly called a "heart attack," is necrosis (death) of heart muscle resulting from ischemia (inadequate blood supply). The 2018 joint U.S./European Cardiology task force defines it as "the presence of acute myocardial injury detected by abnormal cardiac biomarkers in the setting of evidence of acute myocardial ischemia."

Robbins & Kumar Basic Pathology, p. 353

Etiology and Risk Factors

The major underlying cause is atherosclerosis of the coronary arteries. Risk factors include:

Modifiable	Non-modifiable
Hypertension	Age (risk rises progressively)
Diabetes mellitus	Male sex (women protected pre-menopause)
Smoking	Family history
Dyslipidemia	Post-menopause (estrogen loss)
Obesity / Physical inactivity
Cocaine use

About 10% of MIs occur before age 40; 45% before age 65. Men are at greater risk, but the gap narrows with age.

Robbins & Kumar Basic Pathology, p. 353

Pathophysiology

Step-by-step Mechanism

An atheromatous plaque is disrupted by endothelial injury, intraplaque hemorrhage, or mechanical forces, exposing subendothelial collagen and necrotic contents to blood.
Platelets adhere, aggregate, and release thromboxane A2, ADP, and serotonin - triggering further aggregation and vasospasm.
Coagulation is activated by tissue factor exposure, building a growing thrombus.
Within minutes, the enlarging thrombus completely occludes the coronary artery lumen.
Angiography within 4 hours of MI shows coronary thrombosis in ~90% of cases.

In ~10% of MIs, transmural infarction occurs without occlusive atherosclerosis - attributed to coronary artery vasospasm or embolization (e.g., from atrial fibrillation or valve vegetations).

Robbins & Kumar Basic Pathology, p. 353-354

Cellular Response to Ischemia

Within seconds: aerobic metabolism stops; ATP falls; lactic acid accumulates.
Within minutes: contractility is lost (but still reversible).
After 20-40 minutes: irreversible damage and coagulative necrosis of myocytes begins.
The subendocardial zone is most vulnerable - it is farthest from epicardial blood supply and exposed to high intramural pressures.
In 80-90% of deaths from ischemia, the cause is ventricular fibrillation from myocardial irritability, not mechanical failure.

Progression of myocardial necrosis: zone at risk (0 hr), developing necrosis (2 hr), and completed infarct (24 hr)

Progression of myocardial necrosis after coronary artery occlusion - Robbins & Kumar Basic Pathology

Types / Patterns of MI

By Location of Vessel

Occluded Artery	% of MIs	Area Affected
Left Anterior Descending (LAD)	40-50%	Anterior LV wall, anterior 2/3 of septum, apex
Right Coronary Artery (RCA)	30-40%	Right ventricle, posterior LV, posterior septum
Left Circumflex (LCX)	15-20%	Lateral LV wall

By Depth (Transmural vs. Subendocardial)

Transmural infarction: Full thickness of the ventricular wall; caused by complete epicardial vessel occlusion with atherosclerosis + acute thrombus. Associated with ST-elevation MI (STEMI).
Subendocardial infarction: Limited to the inner 1/3 of myocardium; thrombus is lysed before necrosis becomes transmural. Associated with NSTEMI.
Microscopic infarcts: Small vessel occlusions (vasculitis, emboli, vasospasm); no diagnostic ECG changes.

Transmural vs. non-transmural infarction patterns based on coronary artery occlusion location

Patterns of transmural and nontransmural MI based on coronary artery involved - Robbins & Kumar Basic Pathology

Robbins & Kumar Basic Pathology, p. 354-356

Morphological Changes Over Time

Table (from Robbins & Kumar Basic Pathology, Table 9.2):

Time	Gross Features	Light Microscopic Findings
0-30 min	None	None (electron microscopy: mitochondrial swelling, glycogen loss)
30 min - 4 hr	None	Waviness of fibers at border
4-12 hr	Occasional dark mottling	Coagulation necrosis begins; edema; hemorrhage
12-24 hr	Dark mottling	Coagulation necrosis; pyknotic nuclei; hypereosinophilic myocytes; early neutrophil infiltrate
1-3 days	Yellow-tan center with mottling	Loss of nuclei and striations; increased neutrophils
3-7 days	Hyperemic border; central softening	Dead myofiber disintegration; macrophage phagocytosis begins
7-10 days	Yellow-tan, soft with depressed red-tan margins	Early granulation tissue formation
10-14 days	Red-gray depressed borders	Well-established granulation tissue
2-8 weeks	Gray-white	Progressive collagen deposition (fibrosis)
>2 months	White, dense scar	Dense collagenous scar

Key point for exams: MI less than 12 hours old is usually NOT grossly visible. Vital stains (triphenyl tetrazolium chloride) can reveal infarcts >3 hours old - necrotic areas stain pale (enzymes leak out), while healthy tissue stains red.

Clinical Features / Signs and Symptoms

Classic Presentation

Chest pain: Sudden onset, severe, crushing/squeezing, substernal, radiates to left arm, jaw, neck, back
Diaphoresis (profuse sweating)
Dyspnea (shortness of breath)
Nausea and vomiting
Sense of impending doom / anxiety
Pallor, cold clammy skin
Tachycardia or bradycardia
Hypotension (in severe cases)

Atypical Presentation (common in women, elderly, diabetics)

Epigastric pain / indigestion-like symptoms
Fatigue, weakness
Silent MI (no pain - especially in diabetics due to neuropathy)

Diagnosis

1. ECG (Electrocardiogram)

The hallmark of acute MI is ST-segment elevation in leads overlying the area of infarction.

Three electrical abnormalities cause ECG changes:

Defect in Infarcted Cells	Current Flow	ECG Change
Rapid repolarization	Out of infarct	ST segment elevation
Decreased resting membrane potential	Into infarct	TQ depression (seen as ST elevation)
Delayed depolarization	Out of infarct	ST segment elevation

After days to weeks, the infarcted zone becomes electrically silent, and pathological Q waves appear - the permanent marker of a completed MI.

Serial ECG patterns in anterior MI: (A) Normal, (B) Early ST elevation, (C) Q waves developing, (D) Deep Q waves, (E) Partial recovery

Serial ECG changes in anterior MI - Ganong's Review of Medical Physiology

STEMI: ST elevation + Q waves (transmural)
NSTEMI: No ST elevation; ST depression or T-wave inversion (subendocardial)

2. Cardiac Biomarkers

Biomarker	Rises	Peaks	Returns to Normal	Notes
Troponin I / T	3-6 hr	24-48 hr	7-10 days	Most specific and sensitive; gold standard
CK-MB	3-6 hr	12-24 hr	48-72 hr	Useful for reinfarction detection
Myoglobin	1-2 hr	4-8 hr	24 hr	First to rise; less specific
LDH	24-48 hr	3-6 days	8-14 days	Older marker

Troponin I and T are the gold standard markers - they are highly specific for myocardial injury.

3. Other Diagnostic Tests

Echocardiography: Wall motion abnormalities, ejection fraction assessment
Coronary angiography: Definitive identification of the blocked vessel
Chest X-ray: Pulmonary edema, cardiomegaly
CBC: Leukocytosis (inflammatory response)
Serum lipids, blood glucose

Management / Treatment

Immediate (Emergency) Management - "MONA" (or Modified)

Drug/Action	Purpose
Morphine 2-4 mg IV (every 5 min)	Pain relief; reduces anxiety and preload
Oxygen (if SpO2 <90%)	Correct hypoxemia; not given if O2 saturation is normal
Nitroglycerin 0.4 mg sublingual (up to 3 doses, 5 min apart)	Reduces preload; dilates coronary vessels
Aspirin 160-325 mg chewed	Inhibits COX-1; reduces thromboxane A2; prevents further platelet aggregation

Harrison's Principles of Internal Medicine 22E, 2025

Reperfusion Therapy (Most Critical)

"Time is muscle" - the goal is restoring blood flow as fast as possible.

Primary PCI (Percutaneous Coronary Intervention): Preferred for STEMI if available. Goal: balloon inflation within 90 minutes of first medical contact (or 120 min if transfer required). More effective than thrombolysis.
Thrombolysis (fibrinolytic therapy): Used when PCI is not available within the recommended time. Agents: streptokinase, alteplase (tPA), reteplase, tenecteplase. Effective if given within 12 hours of symptom onset.

Antiplatelet and Anticoagulation Therapy

Clopidogrel / Prasugrel / Ticagrelor (P2Y12 inhibitors): Added to aspirin; reduces reocclusion risk
Unfractionated Heparin (UFH): IV bolus 60 U/kg then infusion; maintains artery patency after thrombolysis or PCI
Enoxaparin (LMWH): Subcutaneous alternative; better bioavailability

Beta-Blockers

Metoprolol 5 mg IV (every 2-5 min, up to 3 doses) if HR >60, SBP >100 mmHg
Reduce myocardial O2 demand
Reduce risk of reinfarction and ventricular fibrillation
Contraindicated in acute decompensated HF, bradycardia, heart block

ACE Inhibitors / ARBs

Started within 24 hours, especially for anterior MI with reduced EF
Reduce ventricular remodeling
Prevent HF progression

Statins

High-intensity statin (e.g., atorvastatin 80 mg) started early and continued long-term
Stabilize plaques, reduce inflammation and LDL

Complications

From Robbins & Kumar Basic Pathology:

Complication	Time of Occurrence	Notes
Arrhythmias	Immediate/Early	Most common; VF is most lethal; seen in 3 phases (0-30 min, 12 hr, 3 days-weeks)
Cardiogenic shock	Early	Pump failure; >40% LV damage
Ventricular free wall rupture	3-7 days	Cardiac tamponade; often fatal
Interventricular septal rupture	3-7 days	New loud systolic murmur; VSD
Papillary muscle rupture	3-7 days	Acute mitral regurgitation
Pericarditis (Dressler syndrome)	Days to weeks	Fibrinous inflammation over infarcted area
Mural thrombus	Days to weeks	Embolism risk; anticoagulation needed
Ventricular aneurysm	Weeks to months	Paradoxical wall motion; late complication
Heart failure	Any time	Due to loss of contractile mass

Nursing Assessment

A nurse should assess for:

Vital signs: HR, BP, RR, SpO2, temperature
Pain: Onset, character, location, radiation, severity (0-10 scale), duration
Skin: Pallor, cyanosis, diaphoresis, coolness, capillary refill
Level of consciousness: Confusion, restlessness
Lung sounds: Crackles (pulmonary edema), S3/S4 heart sounds
Urine output: Oliguria suggests reduced cardiac output
Peripheral pulses: Strength and regularity
JVP (jugular venous pressure): Elevated in right heart failure

Nursing Diagnoses (NANDA)

Acute pain related to myocardial ischemia
Decreased cardiac output related to myocardial damage
Activity intolerance related to reduced cardiac reserve
Anxiety / Fear related to severity of illness and perceived threat of death
Ineffective tissue perfusion (cardiopulmonary) related to coronary artery occlusion
Risk for arrhythmia related to ischemia and electrolyte imbalance
Deficient knowledge related to disease, treatment, and lifestyle modifications

Nursing Interventions

Immediate (Acute Phase)

Admit to CCU / ICU; continuous ECG monitoring
Establish IV access; administer medications as prescribed
Administer supplemental oxygen (if SpO2 <90%)
Relieve pain: Administer morphine/nitrates as ordered; reassess pain
Complete bed rest to minimize myocardial oxygen demand
Monitor vital signs every 15-30 minutes
Monitor cardiac biomarkers (Troponin, CK-MB) serially
Prepare patient for PCI/thrombolysis as indicated
Keep defibrillator and crash cart at bedside

Ongoing Care

Monitor for complications: arrhythmias, signs of heart failure, hypotension
Fluid management: Strict input/output recording
Psychological support: Calm environment; address patient and family anxiety
Nutrition: Low-sodium, low-fat diet; restrict caffeine and stimulants
Bowel care: Prevent straining (Valsalva increases cardiac workload) - stool softeners
Leg exercises: Prevent DVT; graduated mobility

Rehabilitation / Discharge Teaching

Medication adherence: Aspirin, beta-blockers, ACE inhibitors, statins (explain purpose and side effects)
Activity progression: Gradual increase; cardiac rehabilitation referral
Diet modification: Heart-healthy diet (DASH diet principles)
Smoking cessation: Complete and permanent
Risk factor control: BP, diabetes, cholesterol management
When to seek emergency care: Recurrent chest pain, dyspnea, palpitations
Psychological support: Depression is common post-MI; screen and refer

Prevention

Primary Prevention (Before MI)

Control hypertension, diabetes, and dyslipidemia
Smoking cessation
Regular physical exercise (150 min/week moderate activity)
Heart-healthy diet
Weight management

Secondary Prevention (After MI)

DAPT (dual antiplatelet therapy) for at least 12 months
Statin therapy indefinitely
Beta-blocker (at least 1 year post-MI)
ACE inhibitor/ARB for reduced EF
Cardiac rehabilitation

Key Points Summary for Exam

Topic	Key Fact
Most common cause	Atherosclerosis with plaque disruption + thrombosis
Most common occluded vessel	LAD artery (40-50% of MIs)
Irreversible damage begins	After 20-40 minutes of ischemia
Time for full infarct	3-6 hours without intervention
Gold standard biomarker	Cardiac Troponin I/T
Earliest biomarker	Myoglobin (rises in 1-2 hr)
ECG hallmark of STEMI	ST segment elevation
ECG permanent marker	Pathological Q waves
Most common cause of death	Ventricular fibrillation (80-90% of cardiac deaths)
Most lethal complication	Ventricular rupture (3-7 days)
Preferred reperfusion therapy	Primary PCI within 90 min
Nursing priority #1	Pain relief + continuous ECG monitoring

Sources:

Robbins & Kumar Basic Pathology - Myocardial Infarction section, pp. 353-358
Ganong's Review of Medical Physiology, 26th Edition - ECG changes in MI, p. 534
Harrison's Principles of Internal Medicine, 22nd Edition (2025) - STEMI management
Guyton and Hall Textbook of Medical Physiology - Myocardial Infarction

This is a shared conversation. Sign in to Orris to start your own chat.