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Cardiac Arrhythmias by Claire Perry 4 | CPR St. Louis

By at December 24, 2012 | 8:03 am | Print

Certain factors may increase the risk of developing an arrhythmia, including Coronary Artery Disease, previous heart surgeries, high blood pressure, thyroid problems, obesity, etc.  Narrowed arteries, heart attack, abnormal valves, and other physical heart damage are risk factors for almost every kind of cardiac arrhythmia. High blood pressure increases the risk of developing coronary artery disease and may also cause the walls of the heart to become thick and stiff.

When the thyroid gland secretes an abnormal level of thyroid hormone to control metabolism, this can cause fast or irregular heartbeats and has been linked to atrial fibrillation (MayoClinic, 7).  When metabolism is slowed down, the thyroid does not produce enough thyroid hormone leading to bradycardia or slow heart rate.  Obesity is perhaps a preventable risk factor for heart arrhythmias.  Along with being a risk factor for coronary artery disease, obesity increases the risk for arrhythmias.

Diabetes increases the risk for high blood pressure and coronary artery disease which in turn are risk factors for cardiac arrhythmias.  Obstructive sleep apnea is a disorder in which breathing is disturbed during sleep, and can cause bursts of bradycardia and atrial fibrillation.  A study done at St. Michael’s Hospital in Toronto, Canada suggests that people with arrhythmias have more severe sleep apnea and nocturnal hypoxemia (decreased oxygen levels during sleep) than patients without heart arrhythmias.  They concluded from their study that “Patients with sleep apnea as a group have higher prevalence of cardiac arrhythmias than non-apneic patients and that snoring alone, without sleep apnea, is not associated with increased frequency of cardiac arrhythmias” (Hoffstein, 2003).

Drinking too much alcohol can affect the electrical impulses of the heart and increase the chance of developing atrial fibrillation.  Chronic alcohol abuse can cause the heart to beat less effectively and can lead to cardiomyopathy.  Caffeine, nicotine, and other stimulants cause the heart to beat faster and may contribute to the development of more serious arrhythmias.  Illegal drugs, such as cocaine and amphetamines, may overwhelmingly affect the heart and lead to sudden death due to ventricular fibrillation.  While there are a vast number of risk factors for heart arrhythmias, certain arrhythmias may increase the risk for other serious conditions such as stroke and heart failure.

To diagnose a heart arrhythmia, heart-monitoring tests are used to detect which arrhythmia is present.  Some of these tests include Electrocardiogram (ECG), Holter monitor, Event monitor, Echocardiogram, Cardiac computerized tomography (CT) and Magnetic Resonance Imaging (MRI).  During an ECG, electrode patches are placed on the chest and limbs to detect the electrical activity of the heart.  A Holter monitor is simply a portable ECG device that can be worn for a day or more to record the heart’s activity during a normal day’s routine. An event monitor is used only when symptoms of an arrhythmia are occurring.  This device measures the heart rhythm at the time of the symptoms have arose.

A CT scan is used to collect images of the heart and chest.  In an MRI, the magnetic field aligns particles within the cells of the body, and in this case the heart, so the doctor can determine the cause of the arrhythmia.  If the doctor does not find an arrhythmia during the above procedures, an arrhythmia may be triggered by a stress test, Tilt table testing, or electrophysiological testing.  Some arrhythmias are brought on by physical activity.  In a stress test, the heart is “stressed” to determine if an arrhythmia is present.  By exercising, the heart beats faster and harder therefor increasing the amount of work the heart is required to perform.  If an arrhythmia is present, it will likely show up during this peak in activity.  A tilt table test is often recommended when a patient has had fainting spells.  Blood pressure and heart rate are measure when the patient is lying flat and then again when the table is raised to mimic the patient standing.  The doctor is looking for a serious drop in blood pressure or increase in heart rate as the patient’s position is changed.

Electrophysiological testing is a catheterization test in which electrode catheters are inserted into the heart in order to study the heart’s electrical system.  A patient is flat on an examination table and given local and possible general anesthesia.  The electrode catheters are then inserted into one or more blood vessels usually in the wrist or groin.  Using an x-ray machine, the catheters are then advanced up through the blood vessels and into the heart.  Once they are positioned, the catheters are used to do two main tasks: record the electrical signals generated by the heart and to pace the heart.  By recording these impulses, most types of cardiac arrhythmias can be diagnosed.  The EP studies can help diagnose both bradycardias and tachycardias.

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