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Bradycardia

DEFINITION

Bradycardia is the medical term for a slower than normal heartbeat. A normal heart rate is between 60 and 100 beats per minute. If your heart beats less than 60 times per minute, you are considered to have a slow heartbeat or bradycardia. The organs of the body, especially the brain, are dependent on receiving oxygen-rich blood from the heart. If the heart pumps too slowly, the oxygen supply to the head may not be enough and a person may feel dizzy or lightheaded and pass out. Similarly, a person who has a slow heartbeat may experience chest pain or shortness of breath from not enough oxygen-rich blood reaching the heart or lungs. The heart’s normal pumping motion is coordinated by electrical activity that moves in an organized fashion from the top of the heart (the sinus node) through the middle of the heart (the atrioventricular node) and to the bottom of the heart (through the bundle of His and Purkinje fibers). First the electrical impulse reaches the atria at the top which causes them to contract, filling the ventricles with blood. Then, the electrical impulse travels to the bottom of the heart, causing the ventricles to contract, which forces blood out of the heart and through the lungs and body. Bradycardia is caused by breakdown at any of a variety of locations in this system. Bradycardia can be caused by sinus node dysfunction (where the node itself fires too slowly) or different types of heart block (where parts of the electrical system in the heart do not transmit the signal correctly). Bradycardia can be caused by a number of irregularities including tissue damage from heart attack, high blood pressure, aging, congenital heart conditions present at birth, infection of the heart tissue with a virus (myocarditis), heart surgery, poor thyroid function (hypothyroidism), electrolyte imbalance (especially low potassium), obstructive sleep apnea (a sleep disorder causing decreased breathing during sleep), diseases that cause inflammation like lupus or rheumatic fever), a genetic condition causing iron buildup called hemochromatosis, and some medications. Risk factor for having bradycardia include smoking, older age, recreational drugs, alcohol, high blood pressure, high cholesterol and a high level of stress. If left untreated, bradycardia can lead to fainting, heart failure (when the heart becomes unable to provide the body with enough blood), or even death.

SYMPTOMS
Dizziness, fainting, lightheadedness, chest pain, shortness of breath, abnormal heart beat, slow heart beat, difficulty sleeping, fatigue (especially during exercise), confusion

DIAGNOSIS
Your doctor will begin by talking to you about your symptoms and doing a physical exam, paying special attention to the heart. Your doctor will probably want to check the levels of the electrolytes in your blood. Your doctor will want to do an electrocardiogram (EKG or ECG) which involves placing small stickers on the skin of the chest which are then hooked up to a machine with wires or leads. The printout from this machine shows your doctor or cardiologist an electrical picture of the function of your heart. This test can help a doctor know why your pulse is slow. If your slow heart rate happens off and on, your doctor may have you wear a monitor called a holter monitor that records the electrical activity of your heart over a few days. An alternative type of recorder called an event monitor is worn for thirty days and requires the person wearing the monitor pushes a button when he or she feels an abnormal heartbeat or has symptoms of lightheadedness and records only at those times. Your doctor may also want to do other testing to measure how affected you are by your slow heartbeat. One of these tests is called the tilt table test where you lay on a table that is tilted from the lying to standing position. Your heart should begin beating faster. If it does not, your slow heart rate may be contributing to fainting episodes. Another test your doctor may want to do is called an exercise test where you run or engage in other physical activity to see if your heart rate picks up appropriately.

TREATMENT
Treatment for bradycardia depends on the cause. If you have an underlying cause like hypothyroidism, treatment of the underlying problem can often restore a normal heartbeat. If you are on a medication that can cause slow heart rate, your doctor will likely stop that medication. If you have a primary conduction problem (a problem with the electrical system of the heart), you may need a pacemaker placed. A pacemaker is a small electrical box with a battery placed into the chest during a small surgical procedure. The device has wires that go to the heart tissue and monitor the heart. If the heart is not going fast enough, the device delivers electrical impulse to stimulate a heartbeat and keep the heart beating fast enough so you do not get dizzy, pass out or have other problems. Pacemakers need to be monitored every six months or so by a cardiologist to make sure that they keep working correctly.

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