Myocardial Infarction: Nursing Care Management and Study Guide

Time is muscle. An MI is dying myocardium, and every minute of delayed reperfusion costs the patient more functioning heart. Your job is to recognize it fast, get oxygen and reperfusion therapy moving, control pain and workload, and watch relentlessly for the dysrhythmias and pump failure that kill in the first hours.

What is Myocardial Infarction?

Myocardial infarction (MI) is used synonymously with coronary occlusion and heart attack, but MI is the preferred term because myocardial ischemia drives the acute coronary syndrome (ACS) that ends in myocardial death. In an MI, an area of myocardium is permanently destroyed: plaque ruptures, a thrombus forms, and the artery occludes completely. The ACS spectrum runs from unstable angina to non-ST-segment elevation MI (NSTEMI) to ST-segment elevation MI (STEMI).

Pathophysiology

Every MI is a profound imbalance between myocardial oxygen supply and demand. In unstable angina, an atherosclerotic plaque ruptures and blood flow drops, but the artery is not fully occluded. When occlusion is complete, the deprived cells move from ischemia to cellular injury to infarction, the death of the muscle.

Statistics and Epidemiology

Each year in the United States, nearly 1 million people have acute MIs. One fourth of them die of the MI, and half of those who die never reach the hospital. That prehospital mortality is why speed and early recognition matter more than anything you do later.

Causes

MI originates in the vascular system. Vasospasm, the sudden constriction of a coronary artery, can occlude flow. Oxygen supply falls with acute blood loss, anemia, or low blood pressure. Demand climbs with a rapid heart rate, thyrotoxicosis, or cocaine ingestion. Any of these, alone or stacked, can tip an at-risk vessel into infarction.

Clinical Manifestations

About half of patients have prodromal symptoms or known CAD; the other half report nothing beforehand. The cardinal sign is chest pain: persistent, crushing, substernal, often radiating to the left arm, jaw, neck, or shoulder blades, described as heavy or squeezing, and it may persist for 12 hours or more. Expect shortness of breath as oxygen demand outruns supply, indigestion from sympathetic stimulation, and tachycardia and tachypnea as the body compensates. Catecholamine release shows up as cool extremities, diaphoresis, anxiety, and restlessness. Fever is uncommon at onset, but a low-grade temperature may develop over the next few days.

Prevention

A healthy lifestyle lowers MI risk. Exercising at least three times a week helps lower the cholesterol that drives vasoconstriction. A balanced diet with fruits, vegetables, meat, and fish supplies the nutrients the patient needs. Smoking cessation matters because nicotine causes vasoconstriction, raising blood pressure and MI risk.

Assessment and Diagnostic Findings

Diagnosis rests on the presenting symptoms backed by serial markers and imaging.

• Patient history. Presenting symptoms, prior cardiac and other illnesses, and family history of heart disease.
• ECG. ST elevation signifies ischemia; peaked or inverted T waves indicate injury; Q waves signify prolonged ischemia or necrosis.
• CPK-MB (cardiac muscle isoenzyme): elevates within 4 to 8 hr, peaks in 12 to 20 hr, returns to normal in 48 to 72 hr.
• LDH. Elevates within 8 to 24 hr, peaks within 72 to 144 hr, and may take as long as 14 days to normalize. An LDH1 greater than LDH2 (flipped ratio) helps confirm MI not caught in the acute phase.
• Troponins. Troponin I (cTnI) and troponin T (cTnT) elevate at 4 to 6 hr, peak at 14 to 18 hr, and return to baseline over 6 to 7 days. They are more specific for necrosis, which makes them useful for diagnosing postoperative MI when MB-CPK may be elevated from skeletal trauma.
• Myoglobin. A small heme protein released rapidly from damaged muscle, elevating within 2 hr of an acute MI with peak levels at 3 to 15 hr.
• Electrolytes. Sodium and potassium imbalances alter conduction and compromise contractility.
• WBC. Leukocytosis (10,000 to 20,000) usually appears on the second day after MI from the inflammatory process.
• ESR. Rises on the second or third day, reflecting the inflammatory response.
• Chemistry profiles. May be abnormal depending on acute or chronic organ function and perfusion.
• ABGs/pulse oximetry. May show hypoxia or underlying lung disease.
• Lipids (total lipids, HDL, LDL, VLDL, total cholesterol, triglycerides, phospholipids). Elevations point to arteriosclerosis as a cause of coronary narrowing or spasm.
• Chest x-ray. May be normal or show an enlarged cardiac shadow suggesting HF or ventricular aneurysm.
• Two-dimensional echocardiogram. Defines chamber dimensions, septal and ventricular wall motion, ejection fraction, and valve function.
• Nuclear imaging (Persantine or Thallium). Evaluates myocardial blood flow and cell status, including location and extent of acute or previous MI.
• Cardiac blood imaging/MUGA. Evaluates ventricular performance, regional wall motion, and ejection fraction.
• Technetium. Accumulates in ischemic cells, outlining the necrotic area.
• Coronary angiography. Visualizes coronary narrowing or occlusion with chamber pressures and left ventricular function (ejection fraction). It is not usually done in the acute phase unless angioplasty or emergency surgery is imminent.
• Digital subtraction angiography (DSA). Visualizes arterial bypass grafts and detects peripheral artery disease.
• MRI. Visualizes blood flow, chambers, intraventricular septum, valves, vascular lesions, plaque, necrosis or infarction, and blood clots.
• Exercise stress test. Determines cardiovascular response to activity, often paired with thallium imaging in recovery.

Medical Management

The goals are to minimize myocardial damage, preserve myocardial function, and prevent complications.

Pharmacologic Therapy

Morphine in IV boluses reduces pain and anxiety. ACE inhibitors block conversion of angiotensin I to angiotensin II, lowering blood pressure and prompting the kidneys to shed sodium and fluid, which cuts cardiac oxygen demand. Thrombolytics dissolve the coronary thrombus, restore flow, limit infarct size, and preserve ventricular function.

Emergent Percutaneous Coronary Intervention

PCI opens the occluded artery and reperfuses the deprived myocardium. It is also indicated in unstable angina and NSTEMI for high-risk patients with persistent ischemia.

Nursing Management

Care of the MI patient is critical, systematic, and time-sensitive.

Nursing Assessment

Assessment drives everything. Assess chest pain not relieved by rest or medication. Monitor vital signs, especially blood pressure and pulse. Watch for shortness of breath, dyspnea, tachypnea, and crackles. Assess for nausea and vomiting, decreased urinary output, and a history of illnesses. Do a precise, complete physical exam to catch complications and status changes, and check IV sites frequently.

Diagnosis

• Ineffective cardiac tissue perfusion related to reduced coronary blood flow.
• Risk for ineffective peripheral tissue perfusion related to decreased cardiac output from left ventricular dysfunction.
• Deficient knowledge related to post-MI self-care.

Planning and Goals

Goals center on relieving pain and ischemic signs, preventing myocardial damage, keeping respiratory function intact, maintaining adequate tissue perfusion, and reducing anxiety. The heart rate and rhythm should sustain adequate cardiac output, the patient should reach an activity level sufficient for basic self-care, and the patient should understand the disease process, treatment plan, and prognosis with a plan in place to meet needs after discharge.

Nursing Priorities

Relieve pain and anxiety, reduce myocardial workload, prevent or detect and help treat life-threatening dysrhythmias and complications, and promote cardiac health and self-care.

Nursing Interventions

Interventions follow the care plan goals. Give oxygen alongside drug therapy to relieve symptoms. Keep the patient on bed rest with the back rest elevated to ease chest discomfort and dyspnea. Reposition frequently to keep fluid from pooling in the lung bases. Check skin temperature and peripheral pulses often to gauge tissue perfusion. Give information honestly and supportively. Monitor closely for changes in cardiac rate and rhythm, heart sounds, blood pressure, chest pain, respiratory status, urinary output, skin color, and lab values.

Evaluation

Confirm the goals were met: pain and ischemic signs are absent, myocardial damage was prevented, respiratory function is intact, tissue perfusion is adequate, and anxiety is reduced.

Discharge and Home Care Guidelines

The best way to get a patient to follow a self-care regimen is to identify the patient's own priorities first. Teach heart-healthy living. The home care nurse helps the patient schedule and keep followup appointments and adhere to prescribed cardiac rehabilitation. The patient may need reminders about followup monitoring, including periodic lab testing, ECGs, and general health screening. Monitor adherence to dietary restrictions and prescribed medications.

Documentation Guidelines

Document individual findings; vital signs, cardiac rhythm, and any dysrhythmias; the plan of care and who was involved in planning; the teaching plan; response to interventions, teaching, and actions performed; attainment or progress toward desired outcomes; and any modifications to the plan of care.