Electrocardiogram (ECG/EKG): An electrocardiogram (ECG/EKG) uses a special recording machine attached to the legs, arms, and chest via 10 electrodes to produce a graphical representation of the electric signals that create heart rhythms. The data obtained from an ECG can be analyzed by doctors to identify an abnormal heart rhythm. Alterations in ECG readings may also represent damaged heart muscle, which may occur after myocardial infarction.
Echocardiogram: An echocardiogram uses a special imaging machine with a microphone-like attachment in order to create a videotaped image of the heart, such as the heart's four chambers, valves, and its movements. In contrast to ECGs (which graphically represent electrical impulses), echocardiograms are created using sound waves, much like an ultrasound. Thus, echocardiograms may also be referred to as cardiac ultrasounds. Both ECGs and echocardiograms are widely used to diagnose a variety of cardiovascular conditions, including myocardial infarction and arrhythmia. Echocardiograms may also be used to identify physical abnormalities that contribute to arrhythmias.
Holter monitoring: Holter monitoring detects irregular heart rhythms. Patients wear a walkman-sized recording box attached to their chest by five adhesive electrode patches for 24-48 hours. Doctors analyze the results to determine if arrhythmia is present.
Exercise stress test: The exercise stress (treadmill) test enables doctors to record the heart's electrical activity that may not occur at rest. The heart will need to pump more and more blood and oxygen to the body as the individual exercises. The test can show if the blood supply is reduced in the arteries that supply the heart. It also helps doctors know the kind and level of exercise appropriate for a patient. The stress test is performed in an exercise laboratory (in a hospital or clinic) where the heart rate and blood pressure are recorded at rest. Sticky electrodes are attached to the chest, shoulders, and hips and connected to the electrocardiogram (ECG or EKG) portion of the stress test machine. The treadmill is then started at a relatively slow warm-up speed, then the slope and speed are increased to simulate exercise stress. The doctor monitors the heart rate, blood pressure, changes in the ECG pattern, irregular heart rhythm, and the individual's appearance and symptoms. The treadmill is stopped when the patient achieves a target heart rate (85% of the maximal heart rate predicted for the patient's age). However, if the patient is doing extremely well at peak exercise, the treadmill test may be continued further. The test may be stopped prior to achievement of the target heart rate if the patient develops significant chest discomfort, shortness of breath, dizziness, or unsteady gait, or if the EKG shows alarming changes or serious irregular heart beats. It may also be stopped if the blood pressure (BP) rises or falls beyond acceptable limits. Please note that the systolic BP (upper number) may normally rise to 200 at peak exercise. At the same time, the diastolic BP (lower number) remains unchanged or falls to a slight degree. In contrast, the BP of patients with hypertension or high BP will show a rise of both systolic and diastolic readings. The latter may rise above 90-100. In preparing for an exercise stress test, healthcare professionals recommend not to eat or drink for three hours prior to the procedure. This reduces the likelihood of nausea that may accompany strenuous exercise after a heavy meal. Diabetics, particularly those who use insulin, will need special instructions from the doctor's office. Also, it is recommended to wear comfortable clothing and shoes that are suitable for exercise. An explanation of the test is provided and the patient is asked to sign a consent form. The risk of the stress portion of the test is very small and similar to what you would expect from any strenuous form of exercise (jogging or running up a flight of stairs). As noted earlier, experienced healthcare professionals are in attendance to manage any rare complications such as sustained irregular heart beats, unrelieved chest pain, or even a heart attack.
Event recorder: An event recorder (loop recorder) is a small portable monitor that may be worn for several weeks. This type of recorder is good for individuals who do not experience symptoms of arrhythmias very often. The monitor "loops" a two-minute recording into its memory, which is continually overwritten. When symptoms are experienced, the individual presses a "record" button on the monitor in order to store a correlating strip of EKG material. The recordings are monitored electronically 24 hours a day from a monitoring station or medical office.
Tilt table test: Tilt table testing is used to diagnose fainting or black-out spells by trying to reproduce the black-out episodes. The individual will be tilted upright to about 60 degrees on a special table for a period of time with continuous recording of ECG and blood pressure.
Electrophysiology (EP) study: The electrophysiology (EP) study allows doctors to acquire more accurate, detailed information and, in many cases, provide treatment during the same session. During an EP study, a specially trained cardiac specialist may provoke arrhythmia events and collect data about the flow of electricity during actual events. As a result, EP studies can help locate the specific areas of heart tissue that give rise to the abnormal electrical impulses or arrhythmias.
signs and symptoms
Tachycardia refers to a fast heart rate (beat), greater than 100 beats a minute. When the heart beats too quickly, the ventricles do not have enough time to fill with blood and cannot effectively pump blood to the rest of the body. The lack of oxygen can cause symptoms including the heart skipping a beat or palpitations, shortness of breath, dizziness, blackouts or fainting, temporary blind spots, chest pain, and even death.
Bradycardia refers to a slow heartbeat, or a resting heart rate less than 60 beats a minute. When the heart beats too slowly, not enough oxygen-rich blood flows through the body. Some bradycardias do not produce any symptoms; others do and warrant treatment. Symptoms of bradycardia include fatigue and weakness, dizziness, lightheadedness, fainting, and shortness of breath.
risk factors and causes
Age: With age, the heart muscle naturally weakens and loses some of its tone. This muscle weakening may affect how electrical impulses are conducted. Generally, the older the individual, the more the heart is weakened due to the number of years the heart has beat.
Alcohol consumption: Drinking excessive amounts of alcohol can alter the conduction of electrical impulses in the heart or increase the chance of developing atrial fibrillation. Chronic alcohol abuse may also depress the function of the heart and can lead to cardiomyopathy (heart muscle inflammation), leading to the development of arrhythmia.
Coronary artery disease: Heart diseases such as atherosclerosis (hardening of heart arteries), heart attack, abnormal valves, prior heart surgery, and cardiomyopathy (inflammation of the heart muscle) are risk factors for arrhythmias. When cardiac cells lack oxygen, they become weakened and may lead to arrhythmias. Hypertension, or high blood pressure, may also cause the walls of the left ventricle to thicken, possibly altering how the heart's electrical impulses are conducted. Scarring can result from numerous heart problems, most commonly from a previous heart attack. This scarring may disrupt the initiation or conduction of electrical impulses and cause arrhythmias.
Diabetes: The risk of developing coronary artery disease and hypertension greatly increases with uncontrolled diabetes. In addition, episodes of hypoglycemia (low blood sugar) may also cause an arrhythmia.
Electrolyte imbalance: Electrolytes, such as potassium, sodium, calcium, and magnesium, help trigger and conduct the electrical impulses in the heart. Electrolyte levels that are too high or too low can affect the heart's electrical impulses and contribute to arrhythmia development.
Genetics: Being born with a heart abnormality, such as holes in the heart, may affect the heart's electrical function.
Medications: Over-the-counter (OTC) cough and cold medicines containing pseudoephedrine and certain prescription drugs including amphetamines may contribute to arrhythmia development. The herbal supplement ephedra also increases the risk of arrhythmia, but in early 2004, the U.S. Food and Drug Administration banned ephedra from the marketplace because of such health concerns.
Obesity: Obesity, a known risk factor for developing coronary artery disease, may also increase the risk of developing an arrhythmia.
Obstructive sleep apnea: Obstructive sleep apnea is a sleep disorder that is characterized by periods of stopped breathing repeatedly during sleep, often for a minute or longer and as many as hundreds of times during a single night. This disorder can cause bradycardia and bursts of atrial fibrillation.
Stimulant use: Stimulants, such as caffeine, amphetamines, and nicotine, can cause premature heartbeats and may contribute to the development of more serious arrhythmias. Illicit drugs, such as methamphetamine ("crystal meth") and cocaine, may affect the heart nerve conductivity and lead to many types of arrhythmias or to sudden death due to ventricular fibrillation.
The body's metabolism speeds up when the thyroid gland releases excess thyroid hormones. This may cause fast or irregular heartbeats and is most commonly associated with atrial fibrillation. As metabolism slows, the thyroid gland hormone levels decrease, potentially causing bradycardia (slow heart beat).
Others: Tachyarrhythmias (fast arrhythmia) may be triggered by exercise, emotional stress, excessive alcohol consumption, smoking, or use of drugs that contain stimulants, such as cold and hay fever remedies. Bradyarrhythmias (slow arrhythmias) may be triggered by pain, hunger, fatigue, digestive disorders (such as diarrhea and vomiting), or swallowing, which can stimulate the vagus nerve excessively. The vagus nerve, the longest cranial nerve, can cause the heart to stop. In most of these circumstances, the arrhythmia tends to resolve on its own.
Sudden cardiac death: Sudden cardiac death is the sudden, abrupt loss of heart function in an individual who may or may not have diagnosed heart disease. Death occurs unexpectedly. Most cardiac arrests are due to ventricular tachycardia or ventricular fibrillation, while others are due to bradycardia. These events are called life-threatening arrhythmias and are responsible for sudden death. About half of all deaths from heart disease are sudden and unexpected, regardless of the underlying disease.
Congestive heart failure: Congestive heart failure (CHF) is a condition in which the heart cannot pump enough blood to supply the body tissues. CHF can result if the heart is pumping ineffectively for a prolonged period due to an arrhythmia. Sometimes, controlling the rate of an arrhythmia with medication or a pacemaker can lead to improved heart function. CHF can be caused by other factors such as hypertension (high blood pressure), atherosclerosis (hardening of the arteries), and certain medications.