An arrhythmia means your heart is beating too fast, too slow, or in an irregular pattern. For many people, this shows up as a fluttering or pounding sensation in the chest that comes and goes. For others, it causes dizziness, fatigue, or fainting. What happens next depends entirely on the type of arrhythmia you have: some are harmless and barely noticeable, while others can be life-threatening within minutes.
About 1 in 3 people worldwide will develop a potentially serious heart rhythm disorder in their lifetime. The most common type, atrial fibrillation, affects an estimated 59 million people globally, nearly double the number from a decade earlier.
What It Feels Like
The most recognizable symptom is palpitations: a fluttering, pounding, or racing feeling in your chest. Some people describe it as their heart “skipping a beat,” which is often a premature contraction where the heart fires an extra beat too early. You might also notice a heartbeat that feels unusually slow or fast without an obvious reason like exercise.
Beyond the chest sensations, arrhythmias can cause shortness of breath, chest pain, lightheadedness, dizziness, sweating, and anxiety. Some people feel unusually exhausted for no clear reason. In more serious cases, you may faint or come close to fainting. These symptoms happen because your heart isn’t pumping blood efficiently when its rhythm is off, so your brain and body aren’t getting the oxygen they need.
Not everyone with an arrhythmia feels symptoms. Some people discover they have one only during a routine physical or an unrelated medical test.
The Main Types and Why They Matter
Arrhythmias fall into a few broad categories based on where they start and how they affect your heart rate.
Atrial fibrillation (AFib) is the most common sustained arrhythmia. During AFib, the upper chambers of your heart quiver chaotically at rates exceeding 400 beats per minute instead of contracting in a coordinated way. The upper and lower chambers fall out of sync, so the lower chambers don’t fill with blood properly and can’t pump enough to your lungs and body. This is what makes AFib more than just an uncomfortable sensation.
Supraventricular tachycardia (SVT) causes sudden episodes of rapid heartbeat due to faulty electrical signals in the upper chambers. It tends to start and stop abruptly and can be triggered by vigorous physical activity. Many people with SVT feel alarmed during an episode but are otherwise healthy.
Ventricular fibrillation (v-fib) is the most dangerous type. The lower chambers, which are responsible for pumping blood to the rest of your body, quiver uselessly instead of contracting. Without effective pumping, cardiac arrest and death can occur within minutes. V-fib is a medical emergency that requires immediate defibrillation.
Premature ventricular contractions (PVCs) are extra heartbeats that originate in the lower chambers and cause that classic “skipped beat” feeling. They’re extremely common and, in most people without underlying heart disease, harmless.
Serious Risks of Untreated Arrhythmia
The long-term consequences depend on the type and severity, but AFib in particular carries significant risks when left unmanaged.
Blood Clots and Stroke
When the upper chambers of your heart quiver instead of contracting fully, blood can pool inside them. Pooled blood tends to clot. If one of those clots gets pumped out and travels to the brain, it causes a stroke. People with AFib have a significantly higher stroke risk than the general population, and AFib-related strokes tend to be more severe, with more complications and a higher chance of death.
Clots can also travel to the lungs, kidneys, intestines, or spleen, blocking blood flow to those organs. This is why many people with AFib take blood-thinning medications even if their symptoms feel mild.
Heart Failure
A heart that beats too fast or irregularly for extended periods has to work harder than it should. Over time, this extra workload weakens the heart muscle. The result is heart failure, a condition where the heart can no longer pump enough blood to meet the body’s demands. This doesn’t happen overnight, but chronic untreated arrhythmias can gradually push the heart toward failure.
Cognitive Decline
Recent research has also found an association between AFib and dementia, likely related to reduced blood flow to the brain over time or small, undetected clots.
How Arrhythmias Are Diagnosed
The first step is usually an electrocardiogram (ECG or EKG), a quick, painless test where sensors are taped to your chest to record your heart’s electrical activity. The catch is that an ECG only captures a snapshot of your heart rhythm during the few seconds it runs. If your arrhythmia comes and goes, it might not show up.
When a standard ECG doesn’t catch the problem, you may be asked to wear a Holter monitor, a small portable device that continuously records your heart rhythm for one to two days. You go about your normal activities while it collects data. If your episodes are even less frequent, an event monitor can be worn for several weeks, recording only when you press a button or when it automatically detects an irregularity.
Common Triggers
Certain substances and habits can set off arrhythmia episodes, particularly AFib. Alcohol has the strongest evidence behind it. Studies consistently show that alcohol in the blood makes the heart more susceptible to AFib, and clinical trials have found that people who stop drinking are less likely to have another episode than those who continue. The general recommendation for people with recurring AFib is no more than three alcoholic drinks per week.
Caffeine, surprisingly, gets a partial pass. Both observational studies and clinical trials have found that typical amounts of coffee don’t increase AFib risk. That said, individual sensitivity varies, and high-dose caffeine from energy drinks is a different story. Tobacco use clearly raises the risk of recurrent episodes. On the protective side, regular physical activity (around 150 minutes per week of brisk walking or similar exercise) helps prevent attacks.
Stress, sleep deprivation, and dehydration are other commonly reported triggers, though the evidence for these is more individual than population-wide.
How Arrhythmias Are Treated
Treatment ranges from simple breathing techniques to implanted devices, depending on the type and severity of the arrhythmia.
For certain fast heart rhythms, your doctor may first suggest vagal maneuvers: relaxation techniques that stimulate a nerve controlling heart rate. These include holding your breath and bearing down (called the Valsalva maneuver), coughing, or placing an ice-cold towel over your face. These can sometimes stop an SVT episode on the spot.
Medications are the next line of treatment. For fast heart rhythms, options include beta blockers (which slow the heart rate but can cause fatigue and sleep problems), calcium channel blockers, and other drugs that target the heart’s electrical signals. For slow heart rhythms, medications can be given in emergency settings to speed things up while a longer-term plan is made.
Cardioversion uses controlled electrical shocks delivered through pads on the chest to reset the heart back to a normal rhythm. It’s typically done in a hospital with sedation, and you’re usually home the same day.
Catheter ablation is a procedure where a thin tube is threaded through a blood vessel to the heart, then used to destroy the tiny areas of tissue responsible for sending abnormal electrical signals. It’s often effective for people whose arrhythmia doesn’t respond well to medication or keeps coming back.
For people at high risk of dangerous arrhythmias, an implantable cardioverter-defibrillator (ICD) can be surgically placed inside the body. It continuously monitors your heart rhythm and delivers a shock if it detects a life-threatening pattern like ventricular fibrillation. A pacemaker serves a different purpose: it sends small electrical pulses to keep a slow heart beating at a normal rate. Both devices are about the size of a matchbox and sit just under the skin near the collarbone.
When It’s an Emergency
A sudden collapse or loss of consciousness with a known or suspected arrhythmia requires immediate emergency care. The same goes for palpitations combined with dizziness and lightheadedness, or any episode that includes chest pain. These combinations can signal that the heart isn’t delivering enough blood to the brain or that the arrhythmia has shifted into a dangerous pattern. A racing heart that resolves on its own within a few seconds and leaves you feeling fine is less urgent, but still worth mentioning to your doctor, especially if it recurs.