ConditionHeart & circulation
Cardiac Arrhythmias (Irregular Heart Rhythms)
Cardiac arrhythmias are problems with the heart's electrical system that make it beat too fast (tachycardia), too slow (bradycardia) or irregularly. Many, such as occasional extra beats, are harmless. Others, such as atrial fibrillation, raise the risk of stroke, and some ventricular arrhythmias can cause cardiac arrest. Symptoms include palpitations, dizziness, breathlessness and fainting. An ECG identifies the rhythm, and treatments include medicines, catheter ablation, pacemakers and defibrillators.
Also called: Heart arrhythmia, arrhythmia, dysrhythmia, irregular heartbeat, abnormal heart rhythm
At a glance
- What it is
- An abnormal heart rhythm: too fast, too slow or irregular.
- Most common types
- Extra beats, atrial fibrillation, SVT, heart block.
- Causes
- Heart disease, high blood pressure, aging, thyroid disease, electrolyte problems, stimulants, inherited conditions.
- Symptoms
- Palpitations, dizziness, breathlessness, chest discomfort, fainting; sometimes none.
- Treatment
- Treat triggers, rate or rhythm medicines, blood thinners, ablation, pacemakers, ICDs.
When to get help
Call 911 or go to the ER
- Collapse with no pulse or no normal breathing: call 911, start CPR and use an AED if available
- Fainting during exercise or without warning
- Palpitations with chest pain, severe breathlessness, confusion or near-fainting
- A very fast heartbeat (over about 150 beats a minute at rest) that does not settle
- Sudden weakness of the face, arm or leg or speech problems (stroke) in someone with an irregular heartbeat
See a doctor within a day or two
- A new irregular pulse, especially over age 65
- A very slow pulse (under about 40 beats a minute) with dizziness or fatigue
- Palpitations in pregnancy, or with a family history of sudden death under 50
- Palpitations after starting a new medicine
Book a routine appointment
- Occasional skipped or extra beats that are bothersome
- Episodes of fast heartbeat that start and stop suddenly and settle on their own
- Fatigue or reduced exercise tolerance with a known rhythm problem
Usually safe to manage at home
- Occasional fluttering or skipped beats after caffeine, alcohol or poor sleep in an otherwise healthy person
How the heart's rhythm works
Each heartbeat starts in the sinus node, a natural pacemaker in the right upper chamber (atrium). The signal spreads through both atria, passes through the AV node (a gateway that briefly delays it), then travels down specialized pathways to the lower chambers (ventricles), which pump blood. A normal resting rate is 60 to 100 beats a minute, slower in fit people and during sleep. Arrhythmias arise when signals start in the wrong place, circle in a loop, or are blocked.
Types of arrhythmia
| Type | What happens | Seriousness |
|---|---|---|
| Premature beats (PACs, PVCs) | Early beats felt as skips or thumps | Usually harmless |
| Atrial fibrillation | Chaotic atrial activity; irregular, often fast pulse | Common; raises stroke risk about fivefold |
| Atrial flutter | Rapid, regular atrial circuit | Similar stroke risk to AFib |
| Supraventricular tachycardia (SVT) | Sudden-onset fast regular rhythm, often 150 to 250 beats a minute | Usually not dangerous; often curable |
| Wolff-Parkinson-White syndrome | An extra electrical pathway causing SVT | Rarely dangerous with AFib |
| Ventricular tachycardia | Fast rhythm from the ventricles | Can be life-threatening |
| Ventricular fibrillation | Chaotic quivering of ventricles; no pumping | Cardiac arrest; fatal without CPR and defibrillation |
| Sinus bradycardia, sick sinus syndrome | Slow or pausing sinus node | May need a pacemaker if symptomatic |
| Heart block | Delayed or blocked signals from atria to ventricles | Complete block usually needs a pacemaker |
| Inherited channelopathies (long QT, Brugada) | Electrical faults in heart cells | Risk of sudden cardiac death in young people |
Symptoms
- palpitations: fluttering, racing, pounding or skipped beats
- lightheadedness or dizziness
- shortness of breath
- chest discomfort
- tiredness or reduced exercise ability
- fainting or near-fainting
- sometimes no symptoms, found on a routine exam or smartwatch alert
Causes and risk factors
- coronary artery disease and previous heart attack
- high blood pressure
- heart failure, cardiomyopathy and heart valve disease
- older age
- overactive or underactive thyroid
- electrolyte imbalances: low or high potassium, low magnesium
- sleep apnea, obesity, diabetes
- alcohol (including "holiday heart" after binge drinking), caffeine, nicotine, cocaine and amphetamines
- medicines: some antibiotics, antidepressants, antipsychotics, decongestants and others that prolong the QT interval
- congenital heart disease and inherited rhythm conditions
- heart surgery
Diagnosis
- ECG (electrocardiogram): records the rhythm; diagnostic if taken during symptoms.
- Holter monitor: a 24-hour to 14-day recording.
- Event recorder or patch monitor: worn for weeks.
- Implantable loop recorder: placed under the skin for up to several years for rare episodes.
- Smartwatch ECGs: can detect atrial fibrillation; confirm with a medical ECG.
- Echocardiogram: checks heart structure and pumping.
- Exercise test: for rhythms triggered by exertion.
- Blood tests: thyroid, electrolytes, kidney function.
- Electrophysiology study: catheters inside the heart map the electrical system, often combined with ablation.
Treatment
Lifestyle and triggers
Reduce alcohol and caffeine if they trigger symptoms, stop smoking and stimulant use, treat sleep apnea, lose excess weight, manage blood pressure, and correct thyroid or electrolyte problems.
Vagal maneuvers
For SVT, bearing down as if straining (Valsalva) or splashing cold water on the face can stop an episode. A modified Valsalva, with legs raised immediately after straining, works better.
Medicines
- Rate control: beta-blockers, calcium channel blockers or digoxin slow the heart in AFib.
- Rhythm control: antiarrhythmics such as flecainide, amiodarone or sotalol.
- Blood thinners (anticoagulants): apixaban, rivaroxaban, dabigatran or warfarin to prevent stroke in AFib and flutter, based on a stroke risk score (CHA₂DS₂-VASc).
Procedures
- Cardioversion: a controlled electric shock or medicine to restore normal rhythm.
- Catheter ablation: heats or freezes the tissue causing the arrhythmia; curative for most SVT and flutter, and effective for many with AFib.
- Pacemaker: for slow rhythms and heart block.
- Implantable cardioverter-defibrillator (ICD): detects and shocks dangerous ventricular rhythms in people at high risk.
- Left atrial appendage closure: for people with AFib who cannot take blood thinners.
Complications
- stroke and blood clots (mainly AFib and flutter)
- heart failure from prolonged fast rates
- fainting and injuries
- sudden cardiac arrest
Frequently asked questions
What are the main types of cardiac arrhythmia?
The main types are premature (extra) beats, atrial fibrillation and flutter, supraventricular tachycardia, ventricular tachycardia and fibrillation, and slow rhythms such as sinus node disease and heart block. They differ greatly in how serious they are.
Are heart arrhythmias dangerous?
Many are not. Occasional extra beats are common and harmless. Atrial fibrillation increases stroke risk and needs treatment. Ventricular tachycardia and fibrillation can cause cardiac arrest. An ECG and assessment by a doctor determine the type and risk.
What does an arrhythmia feel like?
People describe fluttering, racing, pounding or skipped beats in the chest, sometimes with dizziness, breathlessness or chest discomfort. Some arrhythmias, especially atrial fibrillation in older adults, cause no symptoms and are found by chance.
What triggers heart arrhythmias?
Common triggers include caffeine, alcohol, nicotine, stress, lack of sleep, dehydration, stimulant drugs, some medicines, thyroid problems and low potassium or magnesium. Underlying heart disease and high blood pressure make arrhythmias more likely.
Can arrhythmias be cured?
Some can. Catheter ablation cures most supraventricular tachycardias and atrial flutter, and reduces or eliminates atrial fibrillation in many people. Others are controlled long term with medicines, pacemakers or defibrillators. Treating triggers also helps.
Sources
This guide was written from current patient and clinical guidance, including:
- American Heart Association: About arrhythmia
- ACC/AHA/ACCP/HRS: Guideline for the diagnosis and management of atrial fibrillation
- National Heart, Lung, and Blood Institute: Arrhythmias
- Heart Rhythm Society: Arrhythmias
- MedlinePlus: Arrhythmia