Heart arrhythmias are problems with the rate or rhythm of your heartbeat. Your heart might beat too fast, too slow, or in an irregular pattern. Some arrhythmias are harmless and barely noticeable, while others can be life-threatening. A normal resting heart rate falls between 60 and 100 beats per minute, and arrhythmias are generally defined by how they deviate from that range or disrupt the heart’s normal electrical sequence.
How Your Heart’s Electrical System Works
Your heart runs on a built-in electrical system that coordinates every beat. A small cluster of cells in the upper right chamber acts as your heart’s natural pacemaker, firing an electrical signal that tells both upper chambers (the atria) to contract and push blood downward. That signal then pauses briefly at a relay point between the upper and lower chambers, giving the atria time to fully empty. From there, specialized nerve fibers carry the signal rapidly into the lower chambers (the ventricles), causing them to contract and pump blood out to your lungs and the rest of your body.
An arrhythmia happens when something disrupts this sequence. The signal might fire too quickly, too slowly, or from the wrong location. It might get stuck in a loop, or it might scatter chaotically so the heart quivers instead of pumping. Where and how the disruption occurs determines which type of arrhythmia you have, and how dangerous it is.
Types of Arrhythmias
Fast Heart Rhythms (Tachycardia)
Tachycardia means your heart is beating faster than 100 times per minute at rest. Several distinct conditions fall under this umbrella. Supraventricular tachycardias originate in the upper chambers and are usually not immediately dangerous, though they can cause uncomfortable symptoms. Atrial fibrillation, the most common sustained arrhythmia, is one of these. During atrial fibrillation, the upper chambers contract chaotically rather than in a coordinated rhythm. An estimated 12.1 million people in the United States are projected to have atrial fibrillation by 2050.
The biggest concern with atrial fibrillation is stroke. Because the upper chambers aren’t moving blood efficiently, blood can pool and clot in the grooves of the heart. If a clot breaks free and travels to the brain, it causes a stroke. People with atrial fibrillation have three to five times the stroke risk of people without it.
Ventricular tachycardia originates in the lower chambers and is more serious. The ventricles beat much faster than normal, though the electrical process still follows its usual order. This can deteriorate into ventricular fibrillation, where the lower chambers twitch and quiver erratically instead of contracting. Blood essentially stops being pumped. Ventricular fibrillation is the most common deadly arrhythmia and can cause a person to collapse within seconds, losing their pulse and stopping breathing. Both ventricular tachycardia and ventricular fibrillation can lead to sudden cardiac arrest.
Slow Heart Rhythms (Bradycardia)
Bradycardia means your heart rate drops below 60 beats per minute. This isn’t always a problem. Well-trained athletes often have resting heart rates in the 40s or 50s because their hearts pump blood so efficiently. Bradycardia becomes a concern when the heart is beating too slowly to deliver enough blood to the body, causing symptoms like dizziness, fatigue, or fainting. It can result from the heart’s natural pacemaker slowing down with age or from problems with the electrical pathways that carry signals through the heart.
What Arrhythmias Feel Like
Many arrhythmias produce no symptoms at all and are discovered incidentally during a routine exam or unrelated test. When symptoms do appear, the most common sensation is palpitations: a fluttering, pounding, or racing feeling in your chest. You might feel like your heart skipped a beat or added an extra one.
Other symptoms include lightheadedness, dizziness, fatigue that seems out of proportion to your activity level, shortness of breath, chest pain, sweating, and anxiety. Some people faint or nearly faint. Ventricular fibrillation is dramatic: blood pressure drops so sharply that the person collapses, and within seconds their breathing and pulse stop. This requires immediate emergency treatment.
The tricky part is that many of these symptoms overlap with other conditions, from panic attacks to dehydration. What distinguishes arrhythmia symptoms is that they tend to start and stop abruptly, sometimes lasting seconds and sometimes hours, and they correlate with a heartbeat you can feel is genuinely off.
Common Risk Factors
Heart arrhythmias can affect anyone, but certain conditions raise the likelihood significantly. High blood pressure is the most common risk factor because it forces the heart to work harder over time, which can change the structure and electrical properties of the heart muscle. Heart failure and heart valve diseases also increase risk by altering how blood flows through the chambers.
Beyond the heart itself, several other conditions play a role. An overactive thyroid gland speeds up the body’s metabolism and can push the heart into abnormal rhythms. Sleep apnea repeatedly drops oxygen levels during the night, stressing the heart. Diabetes, chronic kidney disease, lung diseases like COPD, and obesity all contribute to arrhythmia risk through different mechanisms, from chronic inflammation to changes in blood chemistry.
Lifestyle factors matter too. Heavy alcohol use, high caffeine intake, and stimulant drugs can all trigger arrhythmias. Viral infections occasionally inflame the heart muscle and disrupt its electrical system. Even extreme emotional stress or intense exercise can provoke episodes in people who are susceptible.
How Arrhythmias Are Diagnosed
A standard electrocardiogram (ECG) is usually the first step. It records your heart’s electrical activity through sensors placed on your skin, but it only captures a snapshot of what’s happening at that moment. Since many arrhythmias come and go, a normal ECG doesn’t rule one out.
For arrhythmias that are intermittent, your doctor may use a Holter monitor, a small wearable device that continuously records your heart rhythm for one to two days during your normal activities. If episodes are less frequent than that, an event recorder works over several weeks and typically requires you to press a button when you feel symptoms, triggering it to save the recording from that moment. For truly rare episodes, a tiny device can be implanted just under the skin of your chest and left in place for years, silently monitoring for abnormal rhythms.
Stress tests, which monitor your heart during exercise, can reveal arrhythmias that only appear when your heart is working hard. Imaging tests like echocardiograms help identify structural problems that might be causing the rhythm disturbance.
Treatment Options
Treatment depends entirely on the type of arrhythmia, how severe it is, and whether it’s causing symptoms or posing a danger. Many arrhythmias need no treatment at all. Occasional premature beats, where your heart fires an extra beat slightly early, are extremely common and almost always harmless.
Medications can slow a fast heart rate, control rhythm, or thin the blood to reduce clot risk in conditions like atrial fibrillation. These are often the first approach, though they work better for some arrhythmias than others.
Cardioversion uses a controlled electrical shock to reset the heart’s rhythm back to normal. It’s effective immediately, but the arrhythmia often returns. In studies of persistent atrial fibrillation, fewer than half of patients treated with cardioversion maintained a normal rhythm at 12 months.
Catheter ablation is a more targeted approach. A thin, flexible tube is guided through a blood vessel to the heart, where it uses heat or extreme cold to destroy the small patches of tissue that are sending faulty electrical signals. For persistent atrial fibrillation, ablation has shown significantly better durability, with about 72% of patients remaining free of the arrhythmia at one year in studies using cold-based ablation combined with medication. Recovery from the procedure typically takes a few days to a week, with some soreness at the catheter insertion site.
For slow heart rhythms that cause symptoms, a pacemaker can be implanted under the skin near the collarbone. It monitors the heart continuously and delivers small electrical pulses to keep the rate from dropping too low. For people at risk of life-threatening ventricular arrhythmias, a similar but more powerful device can detect dangerous rhythms and deliver a shock to restore a normal heartbeat. Both devices are about the size of a small matchbox and last for years before their batteries need replacing.