MYOCARDIAL INFARCTION (MI)

Subject: Emergency  & Critical care Nursing.

(For Diploma, B.Sc in Nursing , All Nursing Student). 

Definition

Myocardial infarction is the irreversible necrosis of myocardium occurring as a result of critical imbalance between the coronary blood supply and myocardial demand.

Or                                               

Myocardial infarction is the term applied to myocardial necrosis secondary to an acute interruption of the coronary blood supply.

Types of Myocardial Infarction

There are two basic types of acute myocardial infarction. This are-

  1. Transmural: involve the full thickness of ventricular wall. It is associated with atherosclerosis involving major coronary artery. It can be sub classified into anterior, posterior and inferior.
  2. Non Transmural: involves small area, only the endocardium and adjacent myocardium, in the subendocardial wall of the left ventricle, ventricular septum and papillary muscles.

Pathophysiology

Myocardial infarction refers to the process by which myocardial tissue is destroyed in regions of the heart that are derived of an adequate blood supply because of a reduced coronary blood flow. The cause of reduced blood flow is either a critical narrowing of a coronary artery due to atherosclerosis or a complete occlusion of an artery due to embolus and thrombus. Decreased coronary blood flow may also result from shock and hemorrhage, in each case, there is a profound imbalance between myocardial oxygen supply and demand.

“Coronary occlusion”, “heart attack” and “myocardial infarction” are all used synonymously, but the preferred term is myocardial infarction.

Etiology

It occurs usually due to formation of occlusive thrombus at a site of rupture of an atheromatous plaque in a coronary artery.

The risk factors for Myocardial Infarction are:

  • Intense exertion
  • Psychological stress
  • Physical exertion
  • Tobacco use
  • Diabetes Mellitus
  • Hyperlipidemia
  • Age, obesity, and
  • Sedentary life style

Others (Rarely):

  • Emboli that lodge in the coronary arteries
  • Spasm of coronary musculature
  • Myocardial bridges
  • Severe anaemia
  • Profoundly low blood pressure results in myocardial infarction
  • Coronary embolism

Clinical Features

Symptoms:

The onset of symptoms in myocardial infarction is usually gradual, over several minutes, and rarely instantaneous.

  1. Chest pain– is the most common symotom of acute myocardial infarction.
  • Site: central, retrosternal
  • Severity: very severe
  • Onset: sudden
  • Duration: prolonged
  • Character: tightness, heaviness
  • Radiation: Left shoulder, neck, jaw, left arm, epigastrium and back.
  • Relief: not by rest or vasodilator
  1. Associated symptoms:
  • Breathlessness/ shortness of breath
  • Restlessness
  • Anxiety ( fear of impending death)
  • Nausea and vomiting
  • Collapse/ Syncope

Physical signs:

  1. Signs of sympathetic activation
  • Pallor
  • Sweating
  • Tachycardia
  1. Signs of vagal activation
  • Vomiting
  • Bradycardia
  1. Signs of impaired myocardial function
  • Hypotension, oliguria, cold peripherals
  • Raised JVP ( Jugular venous pressure)
  • Lung crepitation
  1. Signs of tissue damage
  • Fever
  • High ESR
  1. Signs of complications
  • Pericarditis
  • Mitral regurgition
  • Arrhythmia
  • Pan systolic murmur

Investigations

  1. ECG:
  • S-T segment elevation
  • Pathological Q wave
  • Symmetrical T inversion
  1. Cardiac enzymes
  • Troponin I
  • CKMB
  • CPK
  1. X-ray chest P/A view: may be cardiomegally pre-existing myocardial damage, pulmonary oedema
  2. Echocardiography
  3. Others: Radionuclide scanning, coronary angiogram, blood sugar and serum lipid profile

Management of acute Myocardial Infarction (MI):

  1. Immediate hospitalization under coronary care unit (CCU).
  2. Rest: Absolute bed rest in propped up position for 2-3 weeks.
  3. Oxygen inhalation is to be given if arterial oxygen level reduced.
  4. Analgesic to relive pain: Sublingual nitroglycerine/ inj. Morphine sulphate or pethidine may be given.
  5. Diet: First 24 hours liquid diet is preferred, subsequently low calorie normal diet should be given.
  6. Thrombolytic therapy: Oral aspirin at least 4weeks. If patient comes within 6 hours of chest pain- inj. Streptokinase or Alteplase should be given.
  7. Bita- Adrenoceptor antagonist: inj, Atenolol or Metoprolol to relive pain, reduces arrhythmias.
  8. Monitoring of ECG
  9. Monitoring and management of potential complications.
  10. Monitoring vital sign, blood pressure, pulse, respiration and temperature.
  11. Maintain fluid volume and maintain intake-output chart

Patient education and home care considerations

The home health care programmes for the patient with myocardial infarction are given bellow:

  1. Avoid any activity that produces chest pain, dyspnoea or undue fatigue.
  2. Avoid extreme of heat, cold and walking against the wind.
  3. Losses weight if indicated.
  4. Stops smoking.
  5. Develop regular eating patterns
  • Avoid large meal and hurrying while eating.
  • Restricts caffeine containing beverages, because caffeine can affect heart rate, rhythm and blood pressure.
  • Complies with prescribed diet, modifying calories, fat and sodium as prescribed.
  1. Makes every effort to adhere to medical regimen, especially in taking medication.
  2. Pursues activities that afford release of tension.
  3. Patient undertakes an orderly program of exercise for long term rehabilitation.
  4. Avoid activities that tense the muscles e.g. heavy weight lifting.
  5. Manages occurrences of symptoms:
  • Reports to nearest emergency facility
  • Contacts with physician when any emergency arises.

Nursing Management of myocardial Infarction

  1. Nursing Assessment

Subject data– The subjective data includes the perception of patient about cardiac pain and feelings of both patient and family about patient’s condition during the acute phase of myocardial infarction.

  1. Patient’s perception of pain-
  • Location, sites, and radiation
  • Types of pain
  • Onset and duration
  • Associated factors
  • Relieving factors
  1. Presence of associated symptoms such as sweating, dyspnoea, nausea, dizziness, weakness etc.
  • Feelings of patients and family such as fear, death, depression.

Objective data-

  1. Signs of anxiety
  2. Changes of vital signs
  • Increased pulse rate
  • Decreased blood pressure
  • Diaporesis, vomiting, sudden arrhythmias.
  1. Breath sounds, presence of rhonchi
  2. Serum enzyme levels.
  3. Nursing Diagnosis
  4. Acute chest pain related to ischemia of myocardial tissue.
  5. Anxiety related to threat of death, uncertain prognosis and threatening environment.
  • Decreased cardiac output related to reduce preload, after load, contractility and heart rate secondary to hemodynamic effects of drug therapy.
  1. Alteration in nutrition less than body requirements.
  2. Nursing Interventions
  3. To reduce chest pain

Assess causative factors of pain.

  • Monitor and record pattern of pain including time of onset, duration, location and radiation and intensity.
  • Place the patient in comfortable position and maintain complete bed rest.
  • Evaluate cardiopulmonary status through cardiac monitor and ECG.
  • Give oxygen inhalation.
  • Administer thrombolytic therapy and nitroglycerine as per prescription and also administer other medications as per prescription.
  • Monitor ECG and vital signs strictly throughout the thrombolytic therapy.
  • Monitor and maintain intake and output.
  • Provide emotional support to the patients and his/her family.

2.To reduce anxiety

  • Assess for level of anxiety.
  • Assist the patient to identify and reduce or remove stressors.
  • Establishing a trusting relationship that encourages the patient to express feeling and needs.
  • Encourage patient to verbalize fears.
  • Administer anti-anxiety drugs as per prescription.
  • To maintain cardiac output
  • Provide bed rest to reduce myocardial oxygen demand.
  • Monitor carefully the patient’s response to drug therapy.
  • Monitor vital signs and record it.
  • Monitor ECG continuously.
  • Evaluate for development of heart failure.
  • Administer medication to relieve headache.

3.To promote nutritional status

  • Maintain fluid balance.
  • Regular diet with low cholesterol and low calorie intake if paitent has signs of heart failure.
  • Avoid hot and cold foods.
  • Avoid extra salt.
  • Provide small frequent feeding.
  1. Evaluation-
  2. Patient is free from chest pain.
  3. Patient appears relaxed and expresses a sense of calm and anxiety is improved.
  • Cardiac output is improved.
  1. Nutritional status is promoted

Nursing care client with mechanical ventilation

In the ventilator setting the patient has life threatening health problems that requires comprehensive care, continuous monitoring to prevent complications and to restore health. So the nurse must be able to perform the following measures:-

  1. Assess the patient for adequate chest movement and ensure the ventilator functioning properly.
  2. Make sure the ventilator alarms are on at all times to alert you to potentially hazards condition and changes in the patient’s status.
  3. Assess cardiopulmonary status frequently, at least every 2 to 4 hours or more often if indicated.
  4. Monitor pulse oxymetry and hemodynamic parameters.
  5. Monitor intake and output and assess for fluid volume excess or dehydration.
  6. Assess vital signs and auscultate breath sound.
  7. Unless contraindicated, turn the patient from side to side every 1 to 2 hours to aid lung expansion and removal of secretions.
  8. Perform active or passive range of motion exercises for all extremities.
  9. Place the call bell within the patient’s reached and establish a method of communication.
  10. Administer a sedative or neuromuscular blocking agent as ordered.
  11. Make sure emergency equipment is readily available in case the ventilator malfunction or the patient is extubated accidently.
  12. Monitor for pulmonary infection by sending the tracheal secretion for culture and sensitivity test and monitor for sign and symptoms of pulmonary infection.
  13. Monitor and maintain GI function and nutritional status.
  14. Provide total patient care like maintaining personal hygiene (mouth care, back care, ensure regular bowel movement etc), prevent from infection and maintain quiet and restful environment.

Lecture By-

Baby Kirttania,

Ex- Lecturer ( TMMCNC )  

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