The sensation of your heart “skipping a beat” is almost always caused by an extra heartbeat, not a missed one. These extra beats, called premature contractions, originate from an abnormal electrical signal that fires before your heart’s normal pacemaker does. The early beat is weaker than usual, followed by a longer-than-normal pause before the next regular beat. That pause, and the forceful contraction that follows it, is what you actually feel as a skip, flutter, or thud in your chest.
Most people experience these extra beats occasionally, and in the majority of cases they’re harmless. But understanding what triggers them, and what separates a benign skip from something worth investigating, can help you make sense of what your body is doing.
How an Extra Beat Happens
Your heart has a built-in electrical system. Normally, each beat starts from a single spot in the upper right chamber that acts as your natural pacemaker. The signal travels in an orderly path through the upper chambers, then down into the lower chambers, producing a coordinated squeeze.
An extra beat occurs when a different spot in the heart fires an electrical impulse on its own, jumping ahead of the normal signal. If that rogue impulse comes from one of the upper chambers, it’s called a premature atrial contraction (PAC). If it comes from one of the lower chambers, it’s a premature ventricular contraction (PVC). About two-thirds of PVCs originate from the outflow tracts, the areas where blood exits the lower chambers into the major arteries. But they can also arise from the heart’s walls, valves, or the tissue separating the two sides.
Three electrical quirks make these early firings possible. Sometimes calcium buildup inside a heart cell triggers it to fire before it should. Other times, a small cluster of cells develops its own spontaneous rhythm, acting like a competing pacemaker. In a third scenario, an electrical signal gets caught in a loop, circling through scar tissue or abnormal pathways and producing an extra beat each time it completes the circuit.
PACs vs. PVCs
Both types of extra beats can feel identical from the inside: a flutter, a pause, or the sensation that your heart momentarily stopped. The difference is where they originate and what they mean over the long term.
PACs start in the upper chambers and are extremely common. Even in healthy hearts, they occur frequently and are rarely a cause for concern on their own. A high number of PACs is loosely associated with episodes of abnormal fast rhythms originating in the upper chambers, but PACs do not appear to weaken the heart muscle itself.
PVCs start in the lower chambers and are also common in otherwise healthy people. The distinction is that a very high PVC burden, meaning PVCs make up a significant percentage of all heartbeats over a 24-hour period, has been linked to gradual weakening of the heart’s pumping ability. One community-based study found that every 0.1% increase in daily PVC frequency was associated with more than double the risk of developing heart failure over time. For most people who notice an occasional skip, this threshold is nowhere close. But it’s why doctors sometimes investigate when PVCs are very frequent or persistent.
Everyday Triggers
A long list of ordinary substances and situations can provoke extra beats. You don’t need a heart problem for these to happen.
- Caffeine increases calcium release inside heart cells, which can trigger early electrical firing. It also blocks certain receptors that normally help keep your heart rate steady, and it stimulates the release of adrenaline-like chemicals that heighten cardiac excitability.
- Alcohol is a well-established trigger, particularly in larger amounts. Even moderate drinking can temporarily increase the likelihood of irregular rhythms.
- Nicotine raises adrenaline levels and directly stimulates the heart, making extra beats more likely.
- Sleep deprivation and stress both push your nervous system into a heightened state that increases the chance of ectopic firing.
- Dehydration and electrolyte shifts can destabilize the electrical balance in heart cells. Potassium and magnesium are particularly important for maintaining a stable rhythm, and even mild deficiencies can increase extra beats.
Many people notice that skipped beats come in clusters during certain periods of their life and then disappear entirely. This pattern often tracks with stress, poor sleep, or changes in caffeine or alcohol intake rather than any structural heart problem.
Medications That Can Cause Palpitations
Several common medications list palpitations or extra beats as a side effect. Rescue inhalers used for asthma, which work by relaxing airway muscles, also stimulate the heart and can produce a racing or fluttering sensation. Nasal decongestants containing pseudoephedrine or phenylephrine narrow blood vessels to reduce congestion, but that same mechanism raises heart rate and blood pressure, occasionally triggering extra beats.
Some antidepressants, stimulant medications for ADHD, and even certain herbal supplements (particularly those containing ephedra or high-dose caffeine) can have similar effects. If you notice palpitations starting or worsening after beginning a new medication, that connection is worth exploring.
Medical Conditions Behind Skipped Beats
When extra beats are frequent, persistent, or accompanied by other symptoms, an underlying condition may be contributing.
An overactive thyroid gland is one of the more common medical culprits. Excess thyroid hormone directly affects heart cells in several ways: it increases the activity of the heart’s natural pacemaker, shifts the balance of the nervous system toward a more stimulated state, and alters how heart cells handle calcium and electrical signals. These changes shorten the recovery time between heartbeats in ways that make abnormal rhythms more likely to start and sustain themselves. People with hyperthyroidism often notice a resting heart rate that feels faster than usual, along with skipped beats or fluttering.
Anemia, where your blood carries less oxygen than normal, forces the heart to beat faster and harder to compensate. That increased workload can provoke extra beats. Heart valve problems, prior heart attacks that left scar tissue, and structural abnormalities can also create the conditions for ectopic beats by disrupting normal electrical pathways.
The Role of Your Nervous System
Your heart doesn’t operate independently. It’s constantly receiving input from your autonomic nervous system, the branch that controls involuntary functions like digestion, breathing, and heart rate. The vagus nerve, which runs from your brainstem down to your abdomen, plays a central role in slowing the heart. Shifts in vagal tone, sometimes triggered by bloating, a full stomach, or even straining during a bowel movement, can temporarily alter your heart rhythm and produce the sensation of skipped beats.
This is why some people notice palpitations after large meals or when lying on their left side. The proximity of the stomach and diaphragm to the heart means that pressure changes in the abdomen can influence cardiac rhythm through vagal reflexes.
When Skipped Beats Need Investigation
Occasional extra beats in an otherwise healthy person are nearly always benign. The features that raise concern are skipped beats paired with dizziness, near-fainting, or actual fainting. These combinations suggest the extra beats may be triggering a faster, more dangerous rhythm. Palpitations that consistently occur during physical exertion also warrant evaluation, as exercise-induced arrhythmias can indicate coronary artery disease or other structural problems.
A family history of sudden cardiac death, fainting episodes, or known arrhythmia conditions raises the baseline risk and lowers the threshold for testing. People with known heart disease or prior heart abnormalities are also considered higher risk when they develop new palpitations.
How Skipped Beats Are Diagnosed
The challenge with diagnosing extra beats is that they need to happen while you’re being monitored. A standard electrocardiogram captures only about 10 seconds of your heart’s activity, so it often misses intermittent events.
A 24-hour Holter monitor is the next step up, but its usefulness depends on how often your symptoms occur. In one clinical study, Holter monitoring achieved a diagnostic yield of only about 16.5% for palpitations, largely because many people don’t have symptoms every day. If your skipped beats happen daily, a Holter is a reasonable choice. If they occur every few weeks, an external loop recorder worn for two to three weeks is far more effective. One comparison found that a diagnostic protocol using external loop recorders reached a diagnostic yield of 86%, compared to 21% for the standard Holter approach.
For truly infrequent symptoms, lasting weeks or months between episodes, implantable loop recorders can monitor continuously for up to three to four years. Exercise stress testing is used when palpitations are tied to physical activity or when coronary artery disease is suspected.
Blood work typically checks thyroid function, electrolyte levels, and red blood cell counts to rule out the common metabolic contributors. In most cases, the combination of a thorough history, targeted monitoring, and basic lab work is enough to determine whether skipped beats are harmless or need treatment.