Myocardial infarction or heart attack is an interruption of blood supply to a part of the heart, causing heart cells to die due to a lack of oxygen. Oxygenated blood flow that is supplied to the heart by the coronary arteries becomes blocked by atheromatous plaques, that rupture and form a thrombus (blood clot) around them.
Without a blood supply, as any living tissue, the heart muscle dies. If a large area of the myocardium is affected, death is very probable. The area most commonly affected is the left ventricle
The outcome depends on the coronary artery that is affected. The earlier the person enters the healthcare system the better the prognosis is because emergency measures will be available for otherwise fatal arrhythmias. There is a better outcome for patients who receive adequate medical attention and make appropriate lifestyle changes post-myocardial infarction. Cardiac rehabilitation can help patients make these changes safely
- Age: Men acquire an independent risk factor at age 45, Women acquire an independent risk factor at age 55; in addition, individuals acquire another independent risk factor if they have a first-degree male relative (brother, father) who suffered a coronary vascular event at or before age 55. Another independent risk factor is acquired if one has a first-degree female relative (mother, sister) who suffered a coronary vascular event at age 65 or younger.
- Males are more at risk than females.
- Family history/race: A family history of heart disease increases the risk of coronary artery disease and myocardial infarction.
- Smoking: Cigarette smokers are twice as likely to experience myocardial infarction compared to non-smokers. Smokers also have a two to a four-time higher risk of sudden cardiac death (within an hour of a heart attack).
- Alcohol: Studies show that prolonged exposure to high quantities of alcohol can increase the risk of heart attack
- High blood pressure (hypertension): Alone or in association with obesity, smoking, high blood cholesterol levels or diabetes, high blood pressure increases the risk of myocardial infarction and stroke.
- High blood cholesterol: High total and low-density lipoprotein (LDL cholesterol) levels and low HDL cholesterol levels increase the risk of myocardial infarction
- Obesity: Obesity increases coronary artery disease, myocardial infarction, and stroke risk. Obesity increases strain on the heart, raises blood pressure and cholesterol, and increases diabetes risk.
- Diabetes: Approximately two-thirds of patients with diabetes die from heart or blood vessel disease. Adults with diabetes are three to seven times more likely to develop heart disease.
- Lack of physical activity: Regular exercise reduces the risk of coronary artery disease and myocardial infarction by controlling blood cholesterol levels, decreasing the risk of obesity or diabetes, and lowering blood pressure levels in some patients.
- Stress: Research indicates a possible relationship between stress and coronary artery disease, which may lead to myocardial infarction Hypertension (high blood pressure) and high cholesterol are associated with stress, as are increased tendencies to smoke, gain weight and/or decrease physical activity.
SIGNS AND SYMPTOMS
- Chest pain that is unrelieved by rest or nitroglycerin, unlike angina
- Pain that radiates to arms, jaw, back and/or neck
- Shortness of breath, especially in the elderly or women
- Nausea or vomiting possible
- Maybe asymptomatic known as a silent Ml, which is more common in diabetic patients
- Heart rate >100 (tachycardia) because of sympathetic stimulation. pain, or low cardiac output
- Variable blood pressure
- Feeling of impending doom
- Pale, cool, clammy skin, sweating (diaphoresis)
- Sudden death due to arrhythmia usually occurs within the first hour
- T-wave inversion—sign of ischemia
- ST-segment elevated or depressed sign of injury
- Significant Q—waves—sign of infarction.
- Decreased pulse pressure; because of diminished cardiac output.
- Increased white blood count (WBC) due to inflammatory response to injury.
- Elevated creatine kinase MB (CK—MB)—usually done serially. The numbers will rise along at a predetermined curve to signify myocardial damage and resolution.
- Elevated troponin I- and troponin T—proteins elevated within one hour of myocardial damage.
- Less than 25 ml/hr of urine output due to lack of renal blood flow.
Treatment is focused on reversing and preventing further damage to the myocardium. Early intervention is needed to have the best possible outcome; Thrombolytic therapy is instrumental in reducing mortality. A three—hour time window is ideal for maximizing benefit. Medications are used to enhance blood flow to the heart muscle while reducing the workload of the heart. Supplemental oxygen is used to help meet myocardial oxygen demand. Data from coronary angioplasty and percutaneous coronary intervention (stenting) of an occluded artery have been impressive. Following the acute management. the patient will have to make lifestyle changes—altering diet and exercise, stopping smoking, and so on.
- Administer oxygen, aspirin.
- Administer antiarrhythmics because arrhythmias are common as are conduction disturbances.
- Electrical cardioversion for unstable ventricular tachycardia. In cardioversion,an initial shock is administered to the heart to re-establish sinus rhythm.
- Administer antihypertensive to keep blood pressure low.
- Percutaneous revascularization.
- Administer thrombolytic therapy within 3 to 12 hours of onset because it can re-establish blood flow in an occluded artery, reduce mortality, and halt the size of the infarction.
- Heparin following thrombolytic therapy.
- Administer calcium channel blockers as they appear to prevent reinfarction and ischemia, only in non—Q—wave infarctions.
- Administer beta-adrenergic blockers because they reduce the duration of ischemic pain and the incidence of ventricular fibrillation; decreases mortality.
- Administer analgesics to relieve pain, reduce pulmonary congestion, and decrease myocardial oxygen consumption.
- Administer nitrates to reduce ischemic pain by dilation of blood vessels; helps to lower BP.
- No bathroom privileges. Bedside commode only.
- Low—fat, low—caloric, low—cholesterol diet.
- Ineffective tissue perfusion
- Decrease cardiac output
- Monitor and record ECG readings, blood pressure, temperature, and heart and breath sounds.
- Assess pain and administer analgesics, as ordered. Always record the severity and duration of pain. Don’t give I.M. injections because absorption from the muscle is unpredictable. Also, muscle damage Increases CK, myoglobin, and LD levels, making the diagnosis of MI more difficult.
- Check the patient’s blood pressure alter giving nitroglycerin, especially the first dose.
- Frequently monitor the ECG to detect rate changes or arrhythmias.
- During episodes of chest pain, obtain ECG, blood pressure, and pulmonary artery catheter measurements to determine changes.
- Watch for signs and symptoms of fluid retention(crackles, cough, tachypnea, and edema), which may indicate impending heart failure. Carefully monitor daily weight, Intake and output, respirations, serum enzyme levels, and blood pressure. Auscultate for adventitious breath sounds periodically (patients on bed rest commonly have atelectatic crackles) and for S3 or S4 gallops.
- Organize patient care activities to maximize periods of uninterrupted rest.
- Provide a stool softener to prevent straining, which causes vagal stimulation and may slow heart rate. Allow the patient to use a bedside commode, and provide as much privacy as possible.
- Administer a histamine2 receptor blocker to help prevent stress ulcers from forming.
- Assist with ROM exercises and ambulation as allowed. If the patient is completely immobilized by a severe MI, tum him often. Anti-embolism stockings help prevent venostassis and thrombophlebitis in patients on prolonged bed rest.
- Provide emotional support, and help reduce stress and anxiety; administer tranquilizers, as needed. Involve his family as much as possible in his care.
- Evaluate the patient. When assessing treatment outcomes, look for clear breath sounds; normal heart sounds and blood pressure; absence of arrhythmias, chest pain, shortness of breath, fatigue, and edema; and evidence of ability to tolerate exercise.