An electrocardiogram, called an EKG or ECG, measures the electrical activity of the heart and collects data about heart's health. Typically, a doctor or technician places electrodes connected to a monitor on the skin to get algorithm and biometric information. Some of the insights an EKG can give include heart rate, stress level, heart age, mood, fatigue, breathing index, and heart rate variability. EEG, on the other hand, stands for electroencephalograms. This device detects electrical activity in the brain and has metal electrodes that attach to the scalp.

The Heart's Electrical Impulses

EKGs help illuminate how the heart functions from beat to beat. The sinoatrial node, also called the SA node, in the heart sends an electrical impulse across the heart muscle cells and makes the heart contract. This contraction is a heartbeat. When the SA node is sending these signals properly, the individual has a healthy heartbeat, even if there are some irregularities. EKGs measure electrical impulses from the SA node. Doctors sometimes match the data collected from an EKG with the same person's heart algorithms to learn more about his or her overall health. This information enables doctors to be more proactive about health issues.

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The Brain's Electric Impulses

The neurons in the brain communicate through rapid electrical impulses. This electrical activity allows your brain to control your behavior, body functions, sensations, emotions, and thinking patterns. Doctors measure this activity with EEGs and more recently with light-sensitive proteins embedded into neuron membranes. Once the protein is in the membrane, it gives off a fluorescent signal that can tell medical professionals the voltage of a particular cell. Studying the brain's electrical impulses is important for detecting brain tumors, brain damage from head injuries, brain inflammation, strokes, sleep disorders, and other brain dysfunction. EEGs also help confirm brain death in patients in persistent comas. If there is a medical need for doctors to induce a coma, EEGs help them find the right level of anesthesia.

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EKGs and Mental Health

Studies indicate heart rate variability readings from EKGs can indicate major depression or bipolar disorder. These two conditions are so similar that doctors sometimes misdiagnose bipolar disorder as depression. This is a significant error because each condition requires a different kind of treatment. If a patient has bipolar disorder, his or her moods swing between emotional highs, or mania, and severe depression. If a doctor sees a patient during the depression phase of bipolar disorder, a misdiagnosis could cause the doctor to prescribe antidepressants, mood stabilizers, or antipsychotics, which can trigger manic episodes.

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EEGs and Epilepsy

EEGs play a vital role in diagnosing brain disorders. Doctors analyze the electrical brain impulses, which show up as wavy lines on an EEG recording. These lines have a specific pattern that indicates epileptiform seizure activity in the brain. Doctors can see the brain activity change directly on the EEG reading. Sometimes, people who have epilepsy experience seizures that begin when they see flashing lights -- photosensitive epilepsy. During an EEG, a patient may be asked to look at a light that flashes at different speeds. The EEG reading and the patient's reaction determine the diagnosis for photosensitive epilepsy.

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EEGs Detecting Encephalitis

Encephalitis, or acute inflammation of the brain, is usually caused by a viral infection or a mistaken immune system attack on the brain tissue. Early symptoms include photophobia or extreme light sensitivity, fever, irritability, and headaches. Encephalitis is rarely life-threatening and is most common in children and older adults. It is also a risk for people with compromised immune systems, such as those with HIV. Doctors can use an EEG to identify the typical brain changes that suggest encephalitis.

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EEGs Detecting Strokes

Not only can an EEG help detect brain conditions that make patients vulnerable to strokes, but they are also used to analyze brain activity in patients who have already experienced a stroke. Doctors use this post-stroke information to design properly focused brain training to help people recover.

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EEGs Detecting Sleep Disorders

Because an EEG measures the electrical impulses in the brain, it is an effective test for detecting sleep disorders. During sleep, you are peacefully resting, but there is also an interplay of brain activity that moves you through various stages of sleep. Scientists discovered the different stages of sleep using an EEG in the 1950s by examining brain waves and measuring eye and limb movement.

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EKGs As Stress Detectors

The EKG stress test, also called the treadmill test, uses an EKG to record the heart's electrical activity. In the past, doctors performed stress tests as a part of routine check-ups for middle-aged and older patients, especially men. Doctors now use these tests to help diagnose heart disease -- the test can detect blood flow abnormalities and other problems. A doctor may recommend this test if a patient is experiencing chest pain or shortness of breath, but he or she must be able to exercise to take the test.

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Side Effects of EKGs and EEGs

The EKG itself does not often cause extreme side effects. Patients may find the adhesive on the electrodes irritate their skin. Following an EKG stress test, some patients may experience an irregular heart rhythm. In a few rare cases, patients have had a heart attack, though it was the exercise or medications that caused this reaction, not the EKG itself. EEGs are also fairly safe. People with epilepsy are at risk for seizures, which are triggered by flashing lights and other environmental factors during the procedure.

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What is Heart Rate Variability?

Heart rate variability or HRV is the variation in the time interval between heartbeats, within a specific time frame. Even healthy hearts have irregularities. A heart that is maintaining a rating of 60 beats per minute does not necessarily beat at one-second intervals. In other words, you can't keep time with a heartbeat like you can with a clock. Longer intervals happen when you exhale, and shorter ones occur when you inhale. When an EKG measures HRV, it indicates whether your heartbeats are constant. If they are, then your HRV is low. If the intervals vary, then your HRV is high. HRV readings give important information about the autonomic nervous system, which regulates heart and respiration rate as well as digestion. Your HRV reading tells your doctor if both the resting and activated branches of your autonomic nervous system are functioning properly.

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