Premature Atrial Contractions (PACs)

What happens in a PAC

Normally, each heartbeat starts in the sinoatrial (SA) node, the heart's natural pacemaker. In a PAC, another spot in the atria fires early. The early beat travels through the heart, and then there is usually a short pause as the heart's electrical system resets. The next normal beat after the pause is often stronger, which is the "thump" many people feel.

How common they are

PACs are among the most common rhythm findings. Most adults have some on a 24-hour monitor, and they become more frequent with age. Having occasional PACs is normal.

Causes and triggers

• caffeine (coffee, energy drinks, some teas and sodas)
• alcohol, including binge drinking
• nicotine and vaping
• stress, anxiety and adrenaline surges
• lack of sleep and fatigue
• dehydration and low potassium or magnesium
• stimulant medicines and drugs: decongestants (pseudoephedrine), some asthma inhalers, ADHD medicines, cocaine, amphetamines
• hyperthyroidism
• sleep apnea
• heart and lung conditions: high blood pressure, heart valve disease, heart failure, cardiomyopathy, COPD
• pregnancy

Symptoms

Many people have no symptoms. When noticed, PACs feel like:

• a skipped or missed beat
• a flip-flop or flutter in the chest
• a strong or pounding beat after a pause
• a brief cough or tight feeling in the throat
• palpitations that are worse at rest, lying on the left side, or when falling asleep

PACs vs PVCs and other rhythms

PACs and PVCs feel very similar, and an ECG is needed to tell them apart.

When PACs matter

PACs deserve closer attention when:

• they are very frequent, for example more than several hundred per day on a monitor
• they come in runs (atrial tachycardia)
• they trigger episodes of atrial fibrillation or supraventricular tachycardia
• there is underlying heart disease
• they cause dizziness, fainting or reduced exercise ability

Studies have linked frequent PACs to a higher future risk of atrial fibrillation and stroke, so these people may be monitored more closely.

Diagnosis

• ECG: may capture PACs if they are frequent
• Holter monitor: records every beat for 24 to 48 hours, or longer with patch monitors
• Event monitor or smartwatch recordings for occasional symptoms
• Blood tests: thyroid function, electrolytes, blood count
• Echocardiogram to check heart structure if PACs are frequent or there are other concerns
• Sleep study if sleep apnea is suspected

Treatment

Most PACs need no treatment. Helpful steps:

• reduce or avoid caffeine, alcohol and nicotine
• avoid decongestants and stimulants where possible
• prioritize sleep
• manage stress with exercise, relaxation or therapy
• stay hydrated
• treat underlying conditions such as thyroid disease, high blood pressure and sleep apnea

If symptoms are bothersome:

• beta-blockers or calcium channel blockers can reduce PACs and symptoms
• antiarrhythmic medicines are rarely needed
• catheter ablation can be used for very frequent PACs from a single spot, or when they trigger atrial fibrillation

Frequently asked questions

Are premature atrial contractions dangerous?

Usually not. Occasional PACs are very common in healthy people and are generally harmless. Very frequent PACs, runs of PACs, or PACs with underlying heart disease may need evaluation because they can be linked to atrial fibrillation.

What causes PACs?

Common triggers include caffeine, alcohol, nicotine, stress, poor sleep, dehydration, stimulant medicines and decongestants. Thyroid problems, sleep apnea, high blood pressure and heart or lung disease can also cause them.

Can anxiety cause PACs?

Yes. Stress and anxiety increase adrenaline, which can trigger PACs. Noticing skipped beats can then increase anxiety, creating a cycle. Reassurance from a normal heart evaluation and stress management often help.

How do I stop PACs?

Cut back on caffeine, alcohol and nicotine, get enough sleep, stay hydrated, manage stress and avoid decongestants. If PACs are frequent and bothersome, a doctor may prescribe a beta-blocker. Ablation is an option in rare cases.

What is the difference between PACs and PVCs?

PACs start in the heart's upper chambers, PVCs in the lower chambers. Both feel like skipped or extra beats, and both are usually harmless. An ECG or heart monitor is needed to tell them apart.