An arrhythmia is any heartbeat that doesn’t follow the normal rhythm, whether it’s too fast, too slow, or irregular. Some arrhythmias are completely harmless and happen to nearly everyone at some point. Others can be life-threatening. The difference depends on the type, where in the heart it originates, and how it affects blood flow.
How a Normal Heartbeat Works
Your heart has its own built-in pacemaker, a small cluster of cells called the sinoatrial (SA) node, located in the upper right chamber. This node fires an electrical signal that travels a precise path through the heart, coordinating each beat. The signal first tells the two upper chambers (atria) to contract and push blood downward. Then it pauses for a fraction of a second at a relay point near the center of the heart, giving the upper chambers time to empty completely. Finally, it travels down through specialized nerve fibers to the two lower chambers (ventricles), which contract and pump blood out to the lungs and body.
This entire sequence happens 60 to 100 times per minute in a healthy resting adult. Your nervous system adjusts the speed automatically: your “fight or flight” response speeds it up during exercise or stress, and your “rest and digest” system slows it down when you’re relaxed or sleeping. An arrhythmia occurs when something disrupts this electrical pathway, whether the SA node fires too fast, too slowly, or other parts of the heart generate rogue electrical signals of their own.
Types of Arrhythmia
Arrhythmias are broadly grouped by speed. A heart rate above 100 beats per minute at rest is called tachycardia (too fast). A rate below 60 beats per minute is bradycardia (too slow). Within those categories, the specific type depends on where in the heart the abnormal signal starts.
Atrial Fibrillation
Atrial fibrillation (AFib) is the most common serious arrhythmia, affecting roughly 59 million people worldwide as of 2023, with the majority of cases in adults over 65. In AFib, the upper chambers quiver chaotically instead of contracting in an organized way. Because blood isn’t being pumped out of those chambers efficiently, it can pool and form clots. If a clot travels to the brain, it causes a stroke. Non-valvular AFib increases stroke risk nearly fivefold, which is why people with this condition are often prescribed blood thinners.
Supraventricular Tachycardia
Supraventricular tachycardia (SVT) refers to abnormally fast rhythms that originate above the ventricles. Episodes often start and stop suddenly, causing a racing or pounding sensation. SVT is usually not life-threatening, though it can be frightening and uncomfortable.
Ventricular Fibrillation
Ventricular fibrillation is the most dangerous type. The lower chambers, responsible for pumping blood to the body, twitch uselessly instead of contracting. Blood pressure drops immediately. A person can collapse within seconds, lose their pulse, and stop breathing. This is a cardiac arrest and requires emergency defibrillation.
Premature Heartbeats
These are extra beats that feel like a flutter, a skipped beat, or a brief thud in the chest. They’re extremely common and generally not a concern. Occasionally they happen in patterns that alternate with your regular rhythm. In most people, they’re benign, though in someone with existing heart disease, frequent premature beats originating in the ventricles can sometimes weaken the heart over time.
What Causes Arrhythmias
Many arrhythmias stem from structural changes in the heart, including damage from a heart attack, heart valve problems, or heart failure. But plenty of arrhythmias happen in people with otherwise healthy hearts. Common triggers include:
- Electrolyte imbalances. Your heart’s electrical signals depend on minerals like potassium, magnesium, and calcium. When levels of these minerals are too high or too low, the electrical system misfires. Low potassium combined with low magnesium is a particularly high-risk combination for severe rhythm disturbances.
- Alcohol. Binge drinking can trigger what’s sometimes called “holiday heart syndrome,” a short-term arrhythmia (usually AFib) that typically resolves within 24 hours. Drinking five or more alcoholic beverages is the classic trigger, though individual thresholds vary.
- Stimulants. Caffeine, nicotine, and certain medications or recreational drugs can provoke fast or irregular rhythms.
- Sleep apnea. Repeated drops in oxygen during sleep put stress on the heart and are strongly linked to AFib.
- Thyroid disorders. An overactive thyroid can cause tachycardia, while an underactive thyroid may contribute to bradycardia.
- High blood pressure. Over time, elevated blood pressure thickens the heart walls, which can alter the electrical pathways.
What Arrhythmias Feel Like
Some arrhythmias cause no symptoms at all and are only discovered during a routine exam or an unrelated medical test. When symptoms do occur, the most common sensation is palpitations: a feeling that your heart is racing, fluttering, pounding, or skipping beats. You might also feel lightheaded, unusually tired, short of breath, or notice that you can’t exercise as hard as you used to.
Chest pain, fainting, and severe shortness of breath are red flags that require emergency care. Fainting during an arrhythmia episode suggests your brain isn’t getting enough blood, which can indicate a dangerous rhythm. Ventricular fibrillation in particular causes sudden collapse, loss of pulse, and cessation of breathing within seconds.
How Arrhythmias Are Diagnosed
A standard electrocardiogram (ECG) records your heart’s electrical activity, but it only captures a snapshot of about 10 seconds. Since many arrhythmias come and go, catching one in the act often requires longer monitoring.
A Holter monitor is a small, portable device you wear for one to two days, or up to two weeks, that continuously records your heart rhythm while you go about your life. If your symptoms are less frequent, an event monitor worn for up to 30 days may be more useful, as it can be activated when you feel something off. For the most elusive arrhythmias, a tiny monitor can be implanted just under the skin of the chest. These devices have batteries lasting three to seven years and silently record every abnormal rhythm during that time.
Treatment Options
Treatment depends entirely on the type of arrhythmia, its severity, and the risk it poses. Many arrhythmias need no treatment at all. Occasional premature beats in an otherwise healthy heart, for example, are typically left alone. For arrhythmias that do require intervention, the main approaches fall into a few categories.
Catheter Ablation
This is a minimally invasive procedure in which a thin, flexible tube is threaded through a blood vessel to the heart. The tip delivers heat or cold energy to destroy the small patch of tissue generating the abnormal electrical signals. For SVT, success rates are 90% to 95%. For AFib, atrial tachycardia, and ventricular tachycardia, the success rate drops to 60% to 80%. Some people need a second procedure, and it can take several weeks after ablation before symptoms fully improve.
Implanted Devices
A pacemaker is a small device placed under the skin near the collarbone that sends steady electrical pulses to keep the heart beating at an appropriate rate. It’s primarily used for bradycardia or hearts that pause too long between beats. An implantable cardioverter-defibrillator (ICD) serves a different purpose: it continuously monitors your rhythm and delivers a shock if it detects a life-threatening arrhythmia like ventricular fibrillation. Most modern ICDs can also function as pacemakers.
Medications
Several types of medication can slow a fast heart rate, stabilize erratic rhythms, or prevent blood clots. For AFib in particular, blood-thinning medication to reduce stroke risk is often the most important part of the treatment plan, regardless of whether the rhythm itself is controlled.
Lifestyle Factors That Matter
For many people with arrhythmias, especially AFib, lifestyle changes make a measurable difference. Reducing or eliminating alcohol is one of the clearest interventions: even moderate drinking raises AFib risk, and heavy episodes can trigger holiday heart syndrome directly. Maintaining a healthy weight, treating sleep apnea, managing blood pressure, and staying physically active all help reduce the frequency and severity of episodes. Keeping electrolytes balanced through a varied diet rich in fruits, vegetables, and whole grains supports the heart’s electrical stability, particularly potassium and magnesium levels.