An irregular heartbeat, called an arrhythmia, is any change in the normal rhythm of your heart. It can mean your heart beats too fast, too slow, or with an uneven pattern. Most adults have a resting heart rate between 60 and 100 beats per minute, and arrhythmias occur when the electrical signals that coordinate each beat are disrupted. Some irregular heartbeats are harmless and fleeting, while others raise the risk of stroke or heart failure.
How Your Heart Keeps Rhythm
Your heart has a built-in pacemaker called the sinus node, a small cluster of cells in the upper right chamber. These cells generate electrical impulses that spread through the heart in a precise sequence, telling each chamber when to contract. The upper chambers (atria) squeeze first, pushing blood into the lower chambers (ventricles), which then pump blood to the lungs and the rest of the body.
An arrhythmia develops when something goes wrong at any point along this electrical pathway. The sinus node itself can malfunction, firing too slowly or too quickly. The signal can get blocked or delayed as it travels between chambers. Or rogue electrical impulses can fire from other parts of the heart, overriding the normal rhythm. When the sinus node fails, backup pacemaker cells elsewhere in the heart try to take over, but they typically produce a slower, less coordinated rhythm.
Common Types of Irregular Heartbeat
Arrhythmias fall into a few broad categories based on speed and location:
- Bradycardia: a resting heart rate below 60 beats per minute. This is sometimes normal in athletes but can cause dizziness and fatigue when it results from a faulty electrical signal.
- Tachycardia: a resting heart rate above 100 beats per minute. The heart races even when you’re sitting still.
- Atrial fibrillation (AFib): the most common arrhythmia, affecting an estimated 52.5 million people worldwide. The upper chambers quiver chaotically at rates exceeding 400 beats per minute instead of contracting in a coordinated way. That number is expected to keep climbing, with projections of over 8 million cases in the U.S. alone by 2050.
- Atrial flutter: similar to AFib but more organized, with the upper chambers beating 250 to 350 times per minute in a regular pattern.
- Premature heartbeats: the most common type you’ll actually feel. The signal to beat arrives too early, creating a brief pause followed by a stronger-than-usual beat. Many people describe this as a “skipped beat” or a flip-flop sensation in the chest.
- Ventricular tachycardia: a fast, regular rhythm originating in the lower chambers. It may last only seconds or persist long enough to become dangerous.
- Ventricular fibrillation: the ventricles quiver instead of pumping. This is a medical emergency that can cause cardiac arrest within minutes.
What Triggers an Irregular Heartbeat
The most commonly reported triggers in people with AFib are alcohol, caffeine, exercise, and lack of sleep. Caffeine stimulates the release of calcium inside heart muscle cells, which can disrupt the timing of electrical signals and cause extra beats. Heavy alcohol use has a similar effect, and the two together raise arrhythmia risk further. Smoking compounds the problem as well.
Underlying health conditions play a larger role than lifestyle in many cases. High blood pressure that thickens the heart muscle, heart failure, prior heart attacks, and congenital heart defects all create structural changes that interfere with electrical conduction. Thyroid disorders, electrolyte imbalances (particularly low potassium or magnesium), and lung disease can also set off irregular rhythms. Emotional stress and stimulant medications are common culprits for premature beats in otherwise healthy people.
What It Feels Like
Many arrhythmias produce no symptoms at all, especially in the early stages. When symptoms do appear, the most common include a fluttering or pounding sensation in the chest, a feeling that your heart “skipped” a beat, and awareness of your heartbeat in a way that feels unusual. Faster arrhythmias often cause lightheadedness, shortness of breath, or a sense of anxiety. Slower arrhythmias tend to cause fatigue, weakness, or dizziness.
Some warning signs demand immediate attention. Chest pain or pressure could indicate a heart attack. Sudden loss of balance, arm weakness on one side, or slurred speech are signs of stroke. The American Heart Association uses the acronym B.E. F.A.S.T. to help people recognize stroke symptoms: Balance loss, Eyes (vision changes), Face drooping, Arm weakness, Speech difficulty, Time to call 911.
Why Untreated Arrhythmias Are Risky
AFib carries a particularly serious complication: blood clots. When the upper chambers quiver instead of contracting properly, blood pools inside them. Pooled blood clots. If one of those clots gets pumped out of the heart, it can travel to the brain and cause a stroke, or lodge in the lungs, kidneys, or intestines.
Over time, a heart that beats too fast or too irregularly has to work harder than normal. The muscle weakens, and eventually it can’t pump enough blood to meet the body’s needs. This is heart failure. Recent research has also linked AFib to cognitive decline and dementia, likely because the irregular rhythm reduces the amount of oxygen reaching the brain over months and years.
How Arrhythmias Are Diagnosed
A standard EKG (electrocardiogram) gives your doctor a brief snapshot of your heart’s electrical activity, but it only captures what’s happening during those few seconds. Since many arrhythmias come and go, a normal EKG doesn’t rule them out.
For intermittent symptoms, a Holter monitor is the next step. It’s essentially a portable EKG you wear for 24 hours or more, recording every heartbeat continuously. Think of an EKG as a photograph and a Holter monitor as a movie. If your arrhythmia is even less frequent, a cardiac event recorder can be worn for a month or two, capturing data through small patches or clips that you can transmit to your doctor for analysis.
Wearable Devices and Home Monitoring
Consumer smartwatches and smartphone apps have become surprisingly capable at detecting irregular heart rhythms. A systematic review of wearable devices found that smartphones detect AFib with about 94% sensitivity and 96% specificity, while smartwatches show similar accuracy at 93% sensitivity and 94% specificity. The Apple Watch has demonstrated 87% sensitivity and 97% specificity in identifying silent AFib, the kind you don’t feel.
These devices are useful screening tools, but they have limitations. One study found that while a wrist-worn AFib sensor caught 97.5% of AFib episodes lasting an hour or more, its positive predictive value was only about 40%, meaning many of its alerts were false alarms. A wearable can prompt you to seek proper testing, but it can’t replace a medical-grade recording for a definitive diagnosis.
Treatment Options
Treatment depends on the type and severity of your arrhythmia. Premature heartbeats in an otherwise healthy heart often need no treatment at all, just reassurance and attention to triggers like caffeine and sleep.
For fast heart rhythms, medications that slow the heart rate (beta-blockers are the most widely used) are typically the first approach. These work by dampening the heart’s response to adrenaline, making it beat more slowly and with less force.
When medications aren’t enough, catheter ablation is a procedure where a thin tube is threaded through a blood vessel to the heart. Energy (radiofrequency heat, extreme cold, or laser) is delivered through the catheter tip to create a small scar on the tissue responsible for the abnormal signals. That scar blocks the faulty electrical pathway permanently. Electrical cardioversion is a faster option: controlled electric shocks delivered through pads on your chest reset the heart’s rhythm, similar to rebooting a computer. It’s often used to stop an ongoing episode of AFib or flutter.
For people at high risk of stroke from AFib, blood-thinning medications reduce the chance of clot formation in the heart’s upper chambers. For dangerously slow heart rhythms, an implanted pacemaker delivers small electrical pulses to keep the heart beating at an adequate rate.