An arrhythmia is an abnormal heart rhythm, meaning your heart beats too fast, too slow, or in an irregular pattern. A normal resting heart rate falls between 60 and 100 beats per minute, set by a tiny cluster of cells in the upper right chamber of your heart that acts as a natural pacemaker. When something disrupts that electrical timing, the result is an arrhythmia. Some arrhythmias are harmless and barely noticeable; others can be life-threatening.
How Your Heart Keeps Rhythm
Your heartbeat starts with an electrical signal in the sinus node, a small patch of specialized tissue in the right upper chamber. This node fires 60 to 100 times per minute under normal conditions, sending an impulse that causes the upper chambers (atria) to contract and push blood downward. The signal then reaches a relay station called the AV node, which pauses it for a fraction of a second so the upper chambers finish contracting before the lower chambers begin. From there, the impulse travels through a network of fibers that splits into left and right branches, triggering the lower chambers (ventricles) to pump blood out to the lungs and body.
An arrhythmia happens when any part of this relay system misfires: the sinus node generates signals too quickly or too slowly, the AV node fails to delay properly, or rogue electrical signals pop up somewhere they shouldn’t. The location and nature of the disruption determine the type of arrhythmia and how serious it is.
Types of Arrhythmias
Arrhythmias fall into two broad speed categories. Bradycardia means the heart beats slower than 60 beats per minute at rest. Tachycardia means it beats faster than 100 beats per minute at rest. Within those categories, the key distinction is where the problem originates.
Supraventricular Arrhythmias
These start in the upper chambers or in the electrical gateway between the upper and lower chambers. The most common is atrial fibrillation (often called AFib), where the upper chambers quiver chaotically instead of contracting in an organized way. AFib increases stroke risk fivefold because blood can pool in the fluttering chambers and form clots. Among people over 80, more than 40% of all strokes are linked to AFib. Another common type, supraventricular tachycardia (SVT), causes sudden episodes of rapid heartbeat that may bring on dizziness and a pounding pulse but are rarely dangerous on their own.
Ventricular Arrhythmias
These start in the lower chambers and tend to be far more serious. Ventricular tachycardia produces a dangerously fast heart rate that can cause loss of consciousness and, when combined with underlying heart disease, cardiac arrest. Ventricular fibrillation is a medical emergency where the lower chambers quiver uselessly, pumping no blood at all. Without immediate treatment, it is fatal within minutes.
Common Causes and Triggers
Some arrhythmias are caused by structural problems in the heart, like damage from a heart attack, valve disease, or heart failure. Others stem from electrical wiring issues people are born with. But many arrhythmias have triggers that are surprisingly ordinary.
Electrolyte imbalances are a major culprit. Minerals like potassium, magnesium, sodium, and calcium help generate and transmit the electrical signals in your heart. When levels swing too high or too low (from dehydration, intense exercise, certain medications, or kidney problems), those signals can misfire. High blood pressure, thyroid disorders, sleep apnea, and diabetes also raise arrhythmia risk over time by putting chronic stress on the heart’s structure and electrical system.
External triggers include heavy alcohol use, stimulant drugs, excessive caffeine in some people, and high levels of emotional or physical stress. For many people who experience occasional palpitations, no specific cause is ever found, and the episodes are harmless.
What Arrhythmias Feel Like
The sensation varies widely. You might feel a fluttering in your chest, a skipped beat, a sudden pounding, or a racing pulse. Some arrhythmias produce no noticeable symptoms at all, particularly AFib, which can cause chest pain, palpitations, and shortness of breath in some people but go completely undetected in others. SVT often shows up as a sudden fast heartbeat with dizziness that starts and stops abruptly.
Palpitations alone are often just the normal sensation of your heart beating. They become more concerning when paired with lightheadedness, fainting, chest pain, or significant shortness of breath. Fainting during physical activity, or palpitations that last several minutes with a very fast rate, warrant prompt evaluation.
How Arrhythmias Are Diagnosed
The first step is usually an electrocardiogram (EKG), a quick, painless test that records your heart’s electrical activity through sensors on your skin. The catch is that an EKG only captures a snapshot. If your arrhythmia comes and goes, the EKG may look perfectly normal.
For intermittent symptoms, a Holter monitor is the next tool. This small wearable device continuously records your heart rhythm for one to two days while you go about your normal life, including sleep. You keep it on the entire time. If that window still doesn’t catch anything, an event monitor extends the recording period to several weeks, only storing data when you press a button during symptoms or when the device detects something unusual. For very infrequent episodes, a tiny monitor can be implanted just under the skin and left in place for years.
Treatment Options
Treatment depends entirely on the type, severity, and underlying cause. Many arrhythmias need no treatment at all, just reassurance and occasional monitoring. Others require intervention to prevent stroke, heart failure, or sudden cardiac arrest.
Medications
Several categories of heart rhythm drugs exist, each working on a different part of the electrical system. Some slow the heart rate by reducing how quickly the sinus node fires. Others alter how electrical signals move through heart tissue, making it harder for rogue impulses to sustain an abnormal rhythm. Beta-blockers, one of the most commonly prescribed types, work by dampening the effect of adrenaline on the heart, slowing the rate and calming erratic signals. For people with AFib, blood thinners are often prescribed separately to reduce stroke risk rather than to fix the rhythm itself.
Catheter Ablation
Ablation is a procedure where a thin, flexible tube is threaded through a blood vessel to the heart, and targeted energy (heat or cold) destroys the tiny area of tissue causing the abnormal signals. For SVT, success rates are 90% to 95%. For AFib, atrial tachycardia, and ventricular tachycardia, the success rate ranges from 60% to 80%.
The procedure itself takes two to four hours, sometimes longer. You typically go home the same day after six to eight hours of monitoring. Most people feel ready to return to non-physical work within five to seven days. One important detail: arrhythmias can continue for up to three months after ablation while the heart tissue heals. The full effect takes several weeks to settle in, so early recurrences don’t necessarily mean the procedure failed.
Implantable Devices
A pacemaker is used when the heart beats too slowly. It monitors the rhythm and delivers small electrical pulses to keep the rate from dropping too low. It is recommended when a slow heart rate causes dizziness, fainting, or signs of heart failure that medications cannot adequately control.
An implantable cardioverter-defibrillator (ICD) is used for dangerous ventricular arrhythmias. It continuously monitors the rhythm and delivers a stronger shock if it detects ventricular tachycardia or ventricular fibrillation. ICDs are recommended for people who have survived cardiac arrest from a ventricular arrhythmia, those with ventricular tachycardia that affects blood flow, and people with significantly weakened heart muscle who are at high risk for sudden cardiac death.
Long-Term Risks of Untreated Arrhythmias
Left untreated, certain arrhythmias cause cumulative damage. A heart that beats too fast for too long can weaken over time, a condition called tachycardia-induced cardiomyopathy. The sustained abnormal rhythm leads to changes at the cellular level that reduce the heart’s pumping efficiency, eventually progressing to heart failure. This applies to both AFib and certain ventricular arrhythmias. The encouraging part is that this type of heart failure can often be partially or fully reversed once the rhythm is controlled.
Chronic AFib carries the additional long-term risk of stroke. In untreated AFib patients, the overall stroke rate is roughly 2 events per 100 patient-years, a risk that climbs substantially with age and other factors like high blood pressure and diabetes. Blood-thinning medication dramatically reduces this risk, which is why rhythm control and stroke prevention are both central goals of AFib management.