Electrocardiogram

Myocardial Infarction, also known as heart attack, coronary thrombosis, or coronary occlusion is the sudden blocking of one or more of the coronary arteries. If the blocked artery involves an extensive area, the person may die. If not, there will still be necrosis of heart tissue and scarring, but other vessels may be able to take over for the damaged areas.
INTRODUCTION
Myocardial Infarction, also known as heart attack, coronary thrombosis, or coronary occlusion is the major cause of death in industrialized countries. The vessels that supply blood to the heart muscle may become occluded by atherosclerosis or a blood clot, shutting off the blood supply to a portion of the myocardium. When the blood supply to part of the myocardium is interrupted, there are profound changes in the myocardium that lead to irreversible changes and death of muscle cells. If a heart suddenly becomes severely damaged, as in a myocardial infarction (MI), the pumping activity of the heart is immediately depressed.
MI has 4 stages. The acute stage, is just hours after onset and the myocardium is not dead yet. Rapid intervention may reduce or even stop necrosis. The later pattern stage is when the infarct is already days old and the myocardium starts to exhibit necrosis. The late pattern stage is when the infarct is already weeks old and the zone of injury has now evolved into an MI. The old infarct stage is after months or years from onset, assuming that the MI was treated. The area of infarct has recovered and returned to almost normal. Diagnosis of an MI may include the following: Electrocardiogram (ECG) – single or repeated over several hours and Echocardiography.
Electrocardiography provides a graphic recording of the heart’s electrical activity. The electrocardiogram (ECG) is very useful for diagnosing and locating areas of infarction. Electrodes placed on the skin transmit the electrical impulses to a graphic recorder. Contraction of cardiac smooth muscle produces electrical activity, resulting in a series of waves on the ECG. With the wave forms recorded, the ECG can then be examined to detect dysrhythmias and alterations in conduction indicative of myocardial damage, enlargement of the heart, or drug effects. An ECG monitors the regularity and path of the electrical impulse through the conduction system. The normal sequence on the ECG is called normal sinus rhythm (NSR). NSR implies that the impulse originates at the SA node and follows the normal sequence through the conduction system.

ACCURACY OF ECG PLACEMENTS
To record the ECG, various standard leads can be used. Contact with the body surface is made with disposable electrodes consisting of a metal disc covered with a thin film of conducting paste. Before application of the electrode, the skin where it is to be applied is cleared with alcohol and abraded with fine sandpaper to remove the skin’s shed layer.
The ECG electrodes are connected to ECG amplifiers where small voltages at the body surface are intensified so that they can activate (a) recorders which write the ECG on a moving strip of paper or (b) oscilloscope monitors placed beside the patient’s bed to give continuous recording of ECG. Different placements and combinations of leads provide different views of the heart, usually 12 leads. ECGs at rest are performed as a routine to give information about the cardiac rhythm and the size and workload of the cardiac chambers.


CARDIAC ARRYTHMIAS AND THEIR ELECTROCARDIOGRAPHIC INTERPRETATION
The cardiac arrhythmias consist of a number of acute and chronic disorders of heart rate and rhythm (2001). Categories include disorders that cause ventricular heart rates fewer than 60 beats per minute (bradycardia) and ventricular heart rates faster than 100 beats per minute (tachycardia). In tachycardia, the ECG is normal except that the heartbeat, as determined from the time intervals between QRS complexes, is about 150 per minute instead of the normal 72 per minute (2000).
Ventricular fibrillation is the most serious of all cardiac arrhythmias, which if not stopped within 2 to 3 minutes, is almost invariably fatal. Because no pumping of the blood occurs during VF, this state is lethal unless stopped by some heroic therapy, such as immediate electroshock through the heart. In ventricular fibrillation (VF), the ECG is bizarre, and ordinarily shows no tendency towards a regular rhythm of any type (2000). The normal pattern of the ECG is lost, and the heart stops acting as a functioning pump.
Acute coronary syndromes are severe and sudden heart conditions that require immediate treatment. Acute coronary syndromes include the following: unstable angina and NSTEMI (non ST-segment elevation MI) – this condition is also called non Q-wave MI and is diagnosed when blood tests and ECGs suggest a developing MI. This is less severe than MI but may develop into attacks if not treated. In acute coronary syndrome, common ECG abnormalities include T-wave tenting or inversion, ST-segment elevation or depression (including J-point elevation in multiple leads), and pathologic Q waves.

ECG PATTERN IN AN MI PATIENT
The ECG may be normal early in myocardial infarction. While only about one percent of patients with a completely normal ECG will have infarction, one-quarter of patients with myocardial infarction will present with a normal ECG. The ECG alone cannot diagnose infarction. A combination of compatible history, ECG, and enzyme changes is required. New Q waves or ST segment elevation is about 75 percent accurate at predicting MI.

In an acute MI, the initial symptoms are similar to chest pain but are more severe and persistent. Sweating, nausea, and vomiting are also common. The predominant symptoms may be the sudden onset of dyspnea (shortness of breath), confusion, worsening of heart failure, and syncope, as opposed to crushing chest pain (2001). Some common risk factors include smoking, high-fat diet, family history of MI, diabetes, high blood pressure, obesity and a sedentary lifestyle. Occasionally, sudden overwhelming stress can trigger an MI.
Cardiopulmonary resuscitation (CPR) is a combination of oral resuscitation (mouth-to-mouth breathing), which supplies oxygen to the lungs, and external cardiac massage (chest compression), which is intended to reestablish cardiac function and blood circulation. It is vital that all nurses be trained to perform CPR so resuscitation measures can be initiated immediately when a cardiac or respiratory arrest occurs ( 2004).
enzymes should be monitored continuously. The intensity, radiation, character and location of chest pain should be assessed and the physician notified if chest pain is unrelieved. Heart sounds and breath sounds should be frequently monitored. If any significant changes in breathing, heart sounds or ECG patterns occur, the physician should be immediately notified.
Typical ECG changes include ST segment elevation in two or more contiguous leads of over 1 mm in limb leads or 2 mm in chest leads. Thrombolytics can be started in the emergency room, in the field by paramedics, or even in the doctor’s office. To wait for coronary care unit (CCU) admission decreases myocardial salvage.
Beta blockers block the sympathetic beta receptors, which prevents sympathetic enhancement of heart rate and cardiac metabolism during emotional episodes (2000). They are often given to decrease myocardial oxygen consumption, and to reduce the incidence and severity of arrhythmia in reperfusion therapy. They are part of most thrombolytic treatment protocols. Blood pressure and pulse should be monitored frequently during dosage adjustment and periodically throughout therapy with beta blockers.

Nurses managing recovering cardiac patients should do routine screening and should offer patients with generic stress management and relaxation, in addition to health education and exercise rehabilitation in order to bring back the patient’s health – mentally and physically. A healthy recovery after a cardiac event has become a priority in nursing care as more and more lives are saved.

CONCLUSION
During the past decade there has been a widespread movement in the field of medicine, particularly on the part of nurses, towards a more accurate and efficient treatment of myocardial infarction. Diagnosis, medication and treatment of myocardial infarction errors results in thousands of adverse events and preventable reactions and deaths per year. Nurses, along with other healthcare professionals, share in the responsibility of determining how these errors occur and designing strategies on how to reduce them, and in the process saving other people’s lives.
Knowledge of the ECG patterns and its changes and interpretations can help a lot in effective nursing management of myocardial infarction.http://www.oppapers.com/essays/Electrocardiogram/442287

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