An arrhythmia is an abnormal or irregular heartbeat. It can mean your heart beats too fast, too slow, or with an uneven rhythm. Some arrhythmias are completely harmless and never need treatment, while others are medical emergencies. The difference depends largely on where in the heart the irregular signal originates and how much it disrupts blood flow.
How Your Heart Keeps Rhythm
Your heart has a built-in electrical system that coordinates every beat. A cluster of specialized cells called the SA node fires a signal that causes the upper chambers (atria) to contract first, pushing blood down into the lower chambers (ventricles). The signal then travels through a relay point called the AV node and branches out through the walls of the ventricles, causing them to contract and pump blood to the lungs and the rest of your body. A normal resting heart rate for adults falls between 60 and 100 beats per minute.
An arrhythmia happens when something disrupts this electrical sequence. The signal might fire too quickly, too slowly, or from the wrong location. It might also take a detour through the heart muscle instead of following its normal path, which changes the timing and strength of contractions.
Types of Arrhythmias
Arrhythmias are grouped by where they start and how they affect heart rate.
Supraventricular arrhythmias originate in the upper chambers. These are generally less dangerous. The most common is atrial fibrillation (often called AFib), where the atria quiver chaotically instead of contracting in a coordinated way. AFib doesn’t immediately threaten your life the way some other arrhythmias do, but it allows blood to pool in the upper chambers, which can form clots. If a clot travels to the brain, it causes a stroke. The stroke risk varies widely by age and other health factors. For people under 65 with no additional risk factors, the annual stroke rate is around 1%. For those over 75 with conditions like high blood pressure or diabetes, it climbs to roughly 8%.
Ventricular arrhythmias originate in the lower chambers and tend to be more serious because the ventricles are responsible for pumping blood to your organs. Ventricular fibrillation is the most dangerous arrhythmia. The ventricles quiver uselessly, almost no blood reaches the brain, and the person can collapse within seconds. About 220,000 deaths from heart attacks each year are attributed to ventricular fibrillation.
Bradycardia means the heart beats fewer than 60 times per minute. This is normal for well-conditioned athletes but can cause problems in others if the heart isn’t pumping enough blood. Tachycardia means a resting heart rate above 100 beats per minute.
What It Feels Like
Many arrhythmias produce no symptoms at all. People sometimes learn about an irregular rhythm during a routine checkup for something else entirely.
When symptoms do appear, they often include a fluttering, pounding, or racing sensation in the chest (commonly called palpitations), along with a feeling that your heart “skipped a beat.” Other common signs are lightheadedness, dizziness, shortness of breath, unusual fatigue, anxiety, and sweating. Some people faint or feel like they’re about to.
Premature heartbeats, the kind that feel like a skip or an extra thump, are extremely common and rarely signal a serious problem. Nearly everyone experiences them occasionally. Chest pain, sudden shortness of breath, or fainting are more concerning and warrant emergency care. If someone collapses and has no pulse, that points to a potentially fatal arrhythmia like ventricular fibrillation, which requires immediate help.
Common Triggers and Causes
Arrhythmias can stem from structural heart problems, other medical conditions, or external triggers. High blood pressure, coronary artery disease, heart failure, obesity, diabetes, an overactive thyroid, and sleep apnea all raise the risk. Some people are born with extra electrical pathways in the heart that create shortcuts for signals.
Alcohol is a well-established trigger. Studies show that alcohol in the bloodstream makes the heart more prone to AFib, and experts recommend no more than three alcoholic drinks per week for people with a history of it. Caffeine, on the other hand, has a more nuanced reputation. Research, including randomized trials, has found that typical amounts of coffee don’t increase the risk of an AFib episode. That said, individual sensitivity varies, and high-dose caffeine from energy drinks is worth avoiding.
Electrolyte imbalances (particularly low potassium or magnesium), stimulant medications, tobacco use, and extreme physical or emotional stress can also provoke episodes. Staying physically active, aiming for about 150 minutes of brisk walking per week, and avoiding tobacco both offer protection against recurrent episodes.
How Arrhythmias Are Diagnosed
The primary tool is an electrocardiogram, commonly called an EKG or ECG. Sticky patches with sensors are placed on your chest (and sometimes your arms or legs), and the test records your heart’s electrical activity. It takes just a few minutes and can reveal whether the heart is beating too fast, too slow, or irregularly.
The catch is that many arrhythmias come and go. If your heart happens to be in normal rhythm during the test, the EKG will look fine. That’s where a Holter monitor comes in. It’s a portable EKG device you wear for a day or more while going about your normal routine. It continuously records your heart’s activity, catching irregular rhythms that a brief office EKG might miss.
Treatment Options
Treatment depends on the type and severity of the arrhythmia. Many don’t need treatment at all, especially premature beats and mild supraventricular arrhythmias that cause minimal symptoms.
When treatment is necessary, one common approach is catheter ablation. A thin tube is guided to the heart, and targeted energy destroys the tiny area of tissue responsible for the abnormal electrical signals. For supraventricular tachycardia (a type of fast heartbeat from the upper chambers), ablation has a success rate of 90% to 95%. For AFib and ventricular tachycardia, the success rate is lower, typically 60% to 80%, and some people need more than one procedure.
For slow heart rhythms, a pacemaker can be implanted. It’s a small device placed under the skin near the collarbone that sends electrical pulses to prompt the heart to beat at a normal rate. It can speed up a slow rhythm and coordinate the chambers of the heart.
For people at risk of dangerous ventricular arrhythmias, an implantable cardioverter-defibrillator (ICD) serves a different purpose. It continuously monitors heart rhythms and delivers a shock if it detects a life-threatening pattern. Think of it as a personal defibrillator that works automatically. For people with AFib, blood-thinning medications are often prescribed specifically to reduce stroke risk by preventing clot formation.