Myocardial Infarction ( Heart Attack)

Introduction:

      Acute Myocardial Infarction (AMI), commonly known as a heart attack is the irreversible necrosis of heart muscle secondary to prolonged ischemia.
Results from an imbalance is oxygen supply and demand, 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.

Risk factors:

Non-modifiable risk factors:

1. Age.
2. Sex.
3. Genetic Influence.
4. Race.

Modifiable risk factors:

1. High Blood pressure.
2. Smoking.
3. High cholesterol.
4. Weight and inactivity.
5. Diabetes.

Causes:

1. Age: Individuals aged >40 years have 8 times greater risk for AMI.
2. Sex: Men- >55 years. Women- >65 years.
3. Smoking: Increases the risk by 4 times.
4. Obesity: people who have excess body fat especially at the waist are most likely to develop heart disease.
5. Lack of physical exercise: has been linked to 7- 12% of the cases.
6. Acute and prolonged intake of high quantity of alcohol: increases risk by 3-4 or more times.
7. Hypertension, dyslipidemia and diabetes.

Classification:

Based on pathology:

• Transmural Infarction: extends through the whole thickness of the heart muscle and usually the result of complete occlusion of heart's blood supply. Also called ST elevation MI.
• Sub- endocardial (nontransmural) Infarction: involves a small area in the subendocardinal wall of the left ventricle, ventricular septum or papillary muscle. Also known as non ST elevation MI.

Sign and Symptoms:

1. Retrosternal chest pain, sensation of chest tightness, pressure or squeezing, not relived by rest, position changes or nitrate administration.
2. pain radiates most often to the left arm, lower jaw, neck, right arm, back and upper abdomen where it may mimic heart burn.
3. Levine's sign: person localizes the chest pain by clenching fist over the sternum. In case of silent AMI 20-30% subjects don't have chest pain. Common in patients with DM, HTN, and elderly patients.
4. Diaphoresis.
5. Palpitation and light headedness.
6. Nausea and vomitting.
7. Shortness of breath (dyspnea).
8. Loss of consciousness.

Diagnosis:

1. Health History.
2. Physical Health Examination.
3. Electrocardiogram: shows ST elevation, T wave inversion, Q wave prominent.
4. Cardiac markers: CPKMB, Myoglobin, troponin, LDH.
5. Cardiac catheterization. (Angiogram of the coronary artery).

Management: 

       PNEUMONICS: ONAMBHAI

1. O- Oxygen.
2. N- Nitroglycerine.
3. A- Anti- platelet agents. like Aspirn.
4. M- Morphine.
5. B- Beta blockers.
6. H- Heparin.
7. A- Atrovastatin.
8. I- Inotropes. (dopamine, dobutamine).

Medical Management:

• Complete bed rest for atleast 24 hours.
• Administer high flow of oxygen in acute phase, then at the rate of 2-4 litres, through nasal cannula and maintain oxygen saturation.
• Administer Antiplatelet (aspirin, clopilet), initially 300mg loading dose and then continue to 75 to 150 mg.
• Nitroglycerine sublingually.
• Thrombolytic/ Fibrinolytic Therapy. Mostly Streptokinase (150,000 IU) is used by dissolving it in 1000ml NS over 30 to 60 mins.
• Administration of anti-coagulants like Heparin or low molecular weight heparin.
• Beta- blockers such as Propanolol,  Atenolol.
• Continuous monitoring of blood pressure and heart rate.
• Angiotensin converting enzyme (ACE) inhibitors like Captapril to prevent the conversion of Angiotension I into Angiotension II.
• Lipid lowering drugs.
• Antipyretics to reduce fever.

Surgical Management:

1. Percutaneous coronary intervension/ Percutaneous Tranluminal Coronary Angioplasty (PCI/ PCTA).
2. Coronary Artery Stents.
3. Coronary Artery Bypass Graft.

Nursing Management:

I) Assessment:

• Careful history taking.
• Assess for chest pain, discomfort, dyspnea, palpatation, unsual fatigue, faintness, sweating.
• Each symptoms should be evaluated with regard to time duration, factors that precipitate the symptoms and relive it.
• Vital signs.
• Assess for complications.

Nursing Diagnosis:

1. Acute pain related to mycoardial injury.
2. Ineffective cardiopulmonary tissue perfusion related to reduced coronary blood flow.
3. Ineffective tissue perfusion related to decreased cardiac output.
4. Anxiety related to fear of death/change in health status.

Prepared By: RN Anusha Shrestha.