Myocardial Infarction (MI) Nursing Care and Medical Management

Cardiovascular disease is the leading cause of death in the United States; approximately 1.5 million cases of myocardial infarction occur annually in the United States. MI, colloquially known as “heart attack” is caused by decreased or complete cessation of blood flow to a portion of the myocardium. Acute MI is associated with a 30% mortality rate and an additional 5 to 10% of survivors die within the first year after their MI.

Definition

Myocardial infarction (MI) is the irreversible necrosis of heart muscle secondary to prolonged ischemia. This usually results from an imbalance in oxygen supply and demand, which is most often caused by plaque rupture with thrombus formation in a coronary vessel, resulting in an acute reduction of blood supply to a portion of the myocardium. MI may be “silent” and go undetected, or it could be a catastrophic event leading to hemodynamic deterioration and sudden death.

MI is considered part of a spectrum referred to as acute coronary syndrome (ACS). The ACS continuum representing ongoing myocardial ischemia or injury consists of unstable angina, non-ST-segment elevation MI (NSTEMI), and ST-segment elevation MI (STEMI).

Risk Factors/Etiology

MI is closely associated with coronary artery disease (CAD). INTERHEART is an international multi-center case-control study that delineated the following modifiable risk factors for coronary artery disease:

• Smoking. The use of inhaled tobacco products is a strong risk factor for CAD, MI, and mortality. A combination of endothelial dysfunction, increased myocardial oxygen demand, and heightened risk of thrombosis are all believed to contribute to this pathophysiology.
• Abnormal lipid profile. CAD has been directly linked to hypercholesterolemia, particularly elevated plasma levels of cholesterol in low-density lipoproteins (LDL-C). Increased risk of MI has been seen in clients with low plasma levels of high-density lipoprotein (HDL-C) cholesterol.
• Hypertension. Hypertension is a risk factor for coronary heart disease. The pathophysiology includes left ventricular hypertrophy, coronary endothelial dysfunction, accelerated coronary atherosclerosis, abnormal coronary artery remodeling, coronary microvascular dysfunction, and epicardial fat .
• Diabetes mellitus (DM). Diabetes mellitus is a risk factor for cardiovascular disease and has been associated with 2- to 4-fold mortality. MI is the leading cause of death among individuals with DM.
• Abdominal obesity. High waist circumference (WC) even in individuals with normal weight may unmask higher CVD risk because WC is an indicator of abdominal body fat, which is associated with cardiometabolic disease and CVD and is predictive of mortality. WC as a measure of abdominal obesity provides an indicator of body composition and adds critical information along with BMI.
• Psychosocial factors. Psychosocial factors such as depression, loss of locus of control, global stress, financial stress, and life events including marital separation, job loss, and family conflicts may contribute to the development of MI.
• Lack of daily consumption of fruits and vegetables. Studies have reported that one-third of the population’s risk for acute MI can be attributed to eating unhealthy foods, such as excessive meat, eggs, and salty snacks. Consumption of foods high in fat and other dietary habits in the West has a significant association with the risk of CAD.
• Lack of physical activity. Sedentary behavior and physical inactivity are among the leading modifiable risk factors worldwide for CVS and all-cause mortality. The promotion of physical activity and exercise training leading to improved levels of cardiorespiratory fitness is needed in all age groups, races, ethnicities, and both sexes to prevent many chronic diseases, especially CVD.
• Alcohol consumption. Some studies have shown that heavy drinking, as well as binge drinking, can lead to acute MI, especially among older adults, according to an INTERHEART study.

Epidemiology

The most common cause of death and disability in the Western world and worldwide is CAD. Based on 2015 mortality data from the National Health Interview Survey (NHIS-CDC), MI mortality was 114,023, and MI any-mention mortality was 151,863. An estimated 16.5 million Americans older than 20 years of age have CAD, and the prevalence was higher in males than females for all ages.

Pathophysiology

Atherosclerotic rupture leads to an inflammatory cascade of monocytes and macrophages, thrombus formation, and platelet aggregation. This leads to decreased oxygen delivery through the coronary artery resulting in decreased oxygenation of the myocardium. The inability to produce ATP in the mitochondria leads to an ischemic cascade, and therefore apoptosis (cell death) of the endocardium or myocardial infarction.

Presentation

Clients with typical MI may have the following prodromal symptoms in the days preceding the event.

• Fatigue/malaise. Clients with ongoing symptoms usually lie quietly in bed and appear pale and diaphoretic. Older adult clients and those with diabetes may have particularly subtle presentations and may complain of fatigue, syncope, or weakness.
• Chest pain/discomfort. Typical chest pain is intense and unremitting for 30 to 60 minutes. The pain may occur retrosternal and often radiates up to the neck, shoulders, and jaw and down to the ulnar aspect of the left arm. It may also be described as a substernal pressure sensation or as an epigastric pain with a feeling of indigestion or of fullness and gas.
• Tachycardia. The client’s heart rate is often increased secondary to sympathoadrenal discharge.
• Irregular pulse. The pulse may be irregular because of ventricular ectopy, an accelerated idioventricular rhythm, ventricular tachycardia, atrial fibrillation or flutter, or other supraventricular arrhythmias.
• Hypertension/hypotension. In general, the client’s blood pressure is initially elevated because of peripheral arterial vasoconstriction resulting from an adrenergic response to pain and ventricular dysfunction. However, with right ventricular MI or severe left ventricular dysfunction, hypotension is seen.
• Tachypnea. The respiratory rate may be increased in response to pulmonary congestion or anxiety.
• Fever. Fever is usually present within 24 to 48 hours, with the temperature curve generally parallel to the time course of elevations of creatinine kinase levels in the blood.

Diagnostic Considerations

The three components in the evaluation of MI are clinical features, ECG findings, and cardiac biomarkers.

• ECG. the resting 12 lead ECG is the first-line diagnostic tool for the diagnosis of acute coronary syndrome (ACS). It should be obtained within 10 minutes of the client’s arrival in the emergency department. ECG findings suggestive of ongoing coronary artery occlusion include ST-segment elevation in two contiguous lead and ST-segment depression and T-wave changes. Serial or continuous ECG recordings may help determine reperfusion or re-occlusion status.
• Cardiac biomarkers. Cardiac troponins I and T are components of the contractile apparatus of myocardial cells and are expressed almost exclusively in the heart. Elevated serum levels of cardiac troponin are not specific to the underlying mode of injury (ischemic vs. tension). The  rising and/or falling patterns of cardiac troponin values with at least one value above the 99 percentile of the upper reference limit associated with symptoms of myocardial ischemia would indicate an acute MI.
• Imaging. Some imaging modalities that can be used are echocardiography, radionuclide imaging, and cardiac magnetic resonance imaging (cardiac MRI). Regional wall motion abnormalities induced by ischemia can be detected by echocardiography. Cardiac MI provides an accurate assessment of myocardial structure and function.

Medical Management

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

• Supplemental oxygen. Pulse oximetry should be performed, and appropriate supplemental oxygen should be given (maintain oxygen saturation >90%) to prevent hypoxemia. High concentrations may be counterproductive because of vasoconstriction and the lack of augmented myocardial oxygen delivery in normoxic clients.
• Nitroglycerin. Nitroglycerin is given for active chest pain, either sublingually or by spray. If pain persists, 2 additional doses of nitroglycerin may be administered at 5-minute intervals. Vasodilators such as this drug relieve chest discomfort by improving myocardial oxygen supply, which in turn dilates epicardial and collateral vessels, improving blood supply to the ischemic myocardium.
• Morphine. Morphine is the drug of choice to reduce pain and anxiety. It also reduces preload and afterload, decreasing the work of the heart. The response to morphine is monitored carefully to assess for hypotension or decreased respiratory rate.
• Aspirin. All clients suspected of MI should be given chewable aspirin, 160 to 325 mg unless they have a documented allergy to aspirin. Early administration of aspirin in clients with acute MI has been shown to reduce cardiac mortality by 23% in the first month.
• Beta-blocker. A beta-blocker may be used if dysrhythmias occur. If a beta-blocker is not needed in the initial management period, it should be introduced within 24 hours of admission, once hemodynamics have stabilized and it is confirmed that the client has no contraindications.
• ACE inhibitors. ACE inhibitors may prevent the conversion of angiotensin I to angiotensin II, a potent vasoconstrictor, resulting in lower aldosterone secretion. These drugs reduce mortality rates after MI. Administer captopril or enalapril as soon as possible as long as the client has no contraindications and remains in a stable condition.
• Anticoagulants. Unfractionated heparin or low-molecular weight heparin (LMWH) may also be prescribed along with platelet-inhibiting agents to prevent further clot formation.
• Percutaneous coronary intervention (PCI). A client with STEMI is taken directly to the cardiac catheterization laboratory for an immediate PCI. The procedure is used to open the occluded coronary artery and promote reperfusion to the area that has been deprived of oxygen.
• Thrombolytics. Thrombolytic therapy is initiated when primary PCI is not available or the transport time to a PCI-capable hospital is too long. These agents are administered IV according to specific protocols, and those used most often are alteplase, reteplase, and tenecteplase. The purpose of thrombolytics is to dissolve the thrombus in a coronary artery, allowing the blood to flow through the coronary artery again, minimizing the size of the infarction and preserving ventricular function.
• Cardiac rehabilitation. Cardiac rehabilitation is a long-term program of medical evaluation, exercise, risk factor modification, education, and counseling designed to limit the physical and psychological effects of cardiac illness and improve the person’s quality of life.

Nursing Management

Health promotion, assessment, nursing diagnoses, and interventions for the lenient with ACS are similar to those identified for people with acute MI and angina. Nursing care of the client with acute MI focuses on reducing cardiac work, identifying and treating complications in a timely manner, and preparing for rehabilitation.

Nursing Assessment

Nursing assessment for a client with MI must be both timely and ongoing. Assessment data must include the client’s health history and physical examination.

Subjective Cues

• History of sedentary lifestyle
• Weakness, fatigue, activity intolerance
• History of previous CVD
• Syncopal events
• Nausea, vomiting
• Dizziness, fainting spells
• Sudden onset of chest pain unrelieved by rest or nitroglycerin
• Pain between shoulder blades, back pain, tiredness
• Recent history of dyspnea with or without exertion
• Recent history of cough with or without sputum production
• History of smoking

Objective Cues

• Chest pain with activity or rest
• Tachycardia
• Dyspnea with rest or activity
• Fatigue with normal daily activities
• Pallor or cyanosis
• Hypertension or hypotension
• Dysrhythmias
• Heart murmurs or friction rubs
• Jugular vein distention
• Peripheral or dependent edema
• Irritability, anger, restlessness
• Normal or decreased bowel sounds
• Altered mental status such as disorientation or confusion
• Vomiting
• Decreased urine output
• Motor weakness, unsteady gait

Nursing Diagnoses

• Acute pain related to increased myocardial oxygen demand and decreased myocardial oxygen supply
• Risk for decreased cardiac tissue perfusion related to reduced coronary blood flow
• Risk for imbalanced fluid volume related to decreased organ perfusion
• Risk for ineffective peripheral tissue perfusion related to decreased cardiac output from left ventricular dysfunction
• Anxiety related to cardiac event and possible death
• Deficient knowledge related to post-ACS self-care
• Activity intolerance related to general weakness and fatigue
• Ineffective role performance related to health crisis
• Ineffective coping related to a life-threatening event or acute changes in health

Nursing Desired Outcomes

• The client will verbalize relief from pain and discomfort.
• The client will demonstrate measures that reduce myocardial workload.
• The client will display reduced tension, a relaxed manner, and ease of movement.
• The client will demonstrate a measurable, progressive increase in tolerance to activity.
• The client will report the absence of angina with activity.
• The client will recognize and verbalize feelings.
• The client will demonstrate positive problem-solving skills and coping mechanisms.
• The client will maintain hemodynamic stability.
• The client will demonstrate adequate perfusion as individually appropriate.
• The client will maintain fluid balance as evidenced by BP within the client’s normal limits.
• The client will verbalize understanding of the disease process, potential complications, and treatment regimen.

Nursing Interventions

• Relieve pain and other signs and symptoms of ischemia. Administer oxygen at 2 to 5 L/minute per nasal prong to increase oxygen supply to the myocardium. Promote physical and psychological rest to decrease cardiac workload and sympathetic nervous system stimulation. Administer nitrates to relieve chest pain and maintain a systolic blood pressure greater than 100 mm Hg. Administer morphine by an intravenous push for chest pain as needed. Morphine is an effective narcotic analgesic for chest pain.
• Improve respiratory function. Regular and careful assessment of respiratory function detects early signs of pulmonary complications. The nurse should monitor fluid volume status to prevent fluid overload and encourage the client to breathe deeply and change position frequently to maintain effective ventilation throughout the lungs.
• Promote adequate tissue perfusion. Monitor oxygen saturation levels and administer oxygen as ordered. Oxygen saturation is an indicator of gas exchange, tissue perfusion, and the effectiveness of oxygen therapy. Obtain and assess ABGs as indicated because they provide a more precise measurement of acid-base balance. Administer antiarrhythmics as needed because arrhythmias affect tissue perfusion by altering the cardiac output. Obtain cardiac markers to correlate with the extent of myocardial damage. Plan for invasive hemodynamic monitoring to facilitate MI management through assessing pressures in the systemic and pulmonary arteries, the relationship of oxygen supply and demand, cardiac output, and cardiac index.
• Reduce anxiety. Acknowledge the client’s situation and allow them to verbalize their concerns. A sudden change in health status causes anxiety and fear of the unknown. Verbalizing these fears may help the client cope with the changes. Encourage the client to ask questions, then provide consistent, honest answers. Honest explanations help strengthen the client-nurse relationship and help the client develop realistic expectations. Encourage self-care, and allow the client to make decisions about the plan of care to promote personal responsibility for health and allow control over the situation.
• Promote effective coping. Accept the client’s denial as a coping mechanism, but do not reinforce it. Denial may initially help by diminishing the psychological threat to health, therefore decreasing anxiety. However, prolonged use can interfere with the acceptance of reality and cooperation. Help the client identify positive coping skills instead, such as problem-solving skills, verbalization of feelings, or asking for help. Reinforcing the use of these positive coping skills can help the client deal with the current situation.
• Monitor and manage potential complications. The nurse should monitor the client closely for changes in cardiac rate and rhythm, heart sounds, blood pressure, chest pain, respiratory status, urinary output, skin color and temperature, mental status, ECG changes, and laboratory values. Any changes in the client’s condition must be reported promptly to the healthcare provider and emergency measures instituted when necessary.
• Educate about self-care. The most effective way to increase the probability that the client will implement a self-care regimen after discharge is to identify the client’s priorities, provide adequate education about heart-healthy living, and facilitate the client’s involvement in a cardiac rehabilitation program.

Nursing Evaluation

• The client reports relief of angina.
• The client has a stable cardiac and respiratory status.
• The client maintains adequate tissue perfusion.
• The client exhibits decreased anxiety or fear.
• The client adheres to a self-care program.
• The client develops no complications.

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