Heart rhythm problems (arrhythmias) occur when the electrical impulses in your heart that coordinate your heartbeats don’t function properly, causing your heart to beat too fast, too slow or irregularly.
Most people have experienced occasional, brief, usually harmless arrhythmias, such as the feeling of a skipped, fluttering or racing heartbeat. However, more than 4 million, mainly older Americans experience heart arrhythmias that may cause bothersome — sometimes even dangerous — signs or symptoms. These may include shortness of breath, fainting or even sudden cardiac death — an unexpected loss of heart function, breathing and consciousness that leads to death within minutes without emergency medical treatment.
Advances in medical technology have added new treatment methods to the array of procedures that doctors may use to try to control or eliminate arrhythmias. In addition, because troublesome arrhythmias are often made worse — or even caused — by a heart weakened or damaged by coronary artery disease (CAD), you may be able to reduce your arrhythmia risk by adopting a heart-healthy lifestyle.
Arrhythmias may not produce any symptoms. In fact, your doctor might detect them before you do during a routine examination. But often, abnormal heart rhythms cause noticeable signs and symptoms, which may include:
Your heart is divided into four hollow chambers. Divided top to bottom, the chambers on either half of your heart form two adjoining pumps with an upper chamber (atrium) and a lower chamber (ventricle). During a single heartbeat, the pumps operate in a two-phase cycle. First, the smaller, less muscular atria contract and fill the relaxed ventricles with blood. A split second later, the powerful ventricles contract and discharge blood as the atria relax and fill. Efficient blood circulation requires rhythmic coordination of this priming and pumping system. In addition, it requires proper heart rate control, which, in a normal heart, is 60 to 100 beats a minute when the body is at rest. Orchestration of these two factors is performed by the heart’s electrical system. Ideally, this system operates in the following three-step sequence:
In a healthy person with a normal, healthy heart, it’s unlikely for a sustained arrhythmia to develop without some outside trigger such as an electrical shock or the use of illicit drugs. That’s primarily because his or her heart is free from any abnormal elements such as a spot of scarred tissue. Scarring can result from numerous forms of disease — most commonly, from a previous heart attack — and may disrupt the initiation or conduction of electrical impulses. In addition, the inability of heart cells to conduct electrical impulses during the refractory period acts as a buffer, preventing the occasional offbeat electrical impulse from developing into an arrhythmia.
However, in a heart with some form of disease or deformity, the initiation or conduction of the heart’s electrical impulses may be destabilized, which makes arrhythmias more likely to develop.
Any pre-existing structural heart condition can lead to arrhythmia development due to:
These pre-existing heart conditions may include:
Types of arrhythmias
Heart arrhythmias may occur when any phase in the heart’s electrical system malfunctions. Doctors classify arrhythmias by where they originate (atria or ventricles) and by the speed of heart rate they cause. Tachycardia (tak-ih-KAHR-de-uh) refers to a fast heartbeat — a heart rate greater than 100 beats a minute. Bradycardia (brad-e-KAHR-de-uh) refers to a slow heartbeat — a resting heart rate less than 60 beats a minute. Not all tachycardias or bradycardias indicate disease. For example, during exercise, it’s normal to develop sinus tachycardia as the heart speeds up to provide your tissues with more oxygen-rich blood. Athletes at rest often have a heartbeat less than 60 beats a minute because their hearts are so efficient.
Tachycardias originating in the atria include:
Although it often feels like a skipped heartbeat, a premature heartbeat is actually an extra beat between two normal heartbeats. Premature heartbeats occurring in the ventricles come before the ventricles have had time to fill with blood following a regular heartbeat.
Thus, the beat feels weak if it’s felt at all. This premature beat is usually followed by a pause, during which time the ventricles fill with more than the usual amount of blood. The ejection of more blood from the ventricle causes the next regular heartbeat to feel stronger than normal.
Although you may feel an occasional premature beat, they seldom indicate a more serious problem. Still, a premature beat can trigger a longer-lasting arrhythmia — especially in people with heart disease.
Certain factors may increase your risk of developing an arrythmia. These include:
To diagnose a heart arrhythmia, your doctor may ask about — or test for — conditions that may trigger your arrhythmia, such as heart disease or a problem with your thyroid gland. Your doctor may also perform heart monitoring tests specific to arrhythmias. These tests either passively monitor your heart or try to actively induce an arrhythmia while closely monitoring your heart.
Passive heart monitoring tests may include:
Heart monitoring tests that your doctor may use to induce an arrhythmia include:
If you’ve received a diagnosis of arrhythmia, treatment may or may not be necessary. Usually, it’s required only if the arrhythmia is causing significant symptoms or if it’s putting you at risk of a more serious arrhythmia or arrhythmia complication.
If symptom-producing bradycardias don’t have a cause that can be corrected — such as hypothyroidism or a drug side effect — doctors often treat them with a pacemaker. A pacemaker is a small, battery-powered device that’s usually implanted near your collarbone. One or more electrode-tipped wires run from the pacemaker through your blood vessels to your inner heart. If your heart rate is too slow or if it stops, the pacemaker sends out electrical impulses that simulate your heart to beat at a steady, proper rate. The newest pacemakers can monitor and pace your atria or ventricles — or both — in proper sequence to maximize the output of blood from your heart. In addition, your doctor can program your pacemaker to meet your pacing needs.
For tachycardias originating in the atria or ventricles, treatments may include one or more of the following:
Except for digitalis, antiarrhythmic drugs are often classified by the effect they have on your heart’s electrical conduction.
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