What Causes Arrhythmias and Heart Palpitations? Triggers, Underlying Conditions, and When to Worry

Short Answer

An arrhythmia is a problem with the heartbeat’s rate or rhythm: the heart may beat too fast, too slowly, or in an irregular pattern. A fast rhythm is called tachycardia; a slow rhythm is called bradycardia. Many people notice the same problem as palpitations — a racing, pounding, fluttering, flip-flopping, or “skipped beat” feeling in the chest, throat, or neck. (heart.org)

There is rarely one neat cause. In an otherwise healthy person, palpitations can be set off by everyday body stressors: caffeine, alcohol, nicotine or other stimulants, strong emotion, hard exercise, fever, dehydration, poor sleep, and some medications. The heart is an electrical muscle; anything that pushes adrenaline up, changes fluid balance, or makes the heart work harder can make extra beats or a faster rhythm easier to feel. (mayoclinic.org)

At the same time, arrhythmias can be a clue that something deeper is irritating the heart’s electrical system. Doctors look for causes such as coronary or structural heart disease, scarring after a heart attack or procedure, heart failure, thyroid disease, electrolyte changes such as potassium, sodium, calcium, or magnesium imbalance, obstructive sleep apnea, and — less commonly — inherited electrical conditions. (heart.org)

Rhythm problems can also come from the heart’s own remodeling: “The pathophysiology of atrial fibrillation involves electrical and structural remodeling of the atria, often referred to as atrial myopathy, that together increase the risk for arrhythmias”.

The practical takeaway is simple: occasional skipped beats can be harmless, especially when they are brief and tied to a clear trigger, but a new, persistent, fast, worsening, or symptomatic irregular heartbeat deserves medical evaluation. The reason is that the feeling alone cannot tell you whether it is benign or serious; an arrhythmia has to be checked by recording the heart’s electrical activity with an ECG or a clinician-reviewed monitor. (heart.org)

Arrhythmia causes at a glance

Arrhythmia causes usually fall into two broad buckets: things that temporarily push your heart’s electrical system harder and medical conditions that change the heart, blood chemistry, hormones, breathing, or nervous-system control. Everyday triggers can cause brief palpitations or extra beats in many people, but the same sensation can also be the first clue of atrial fibrillation, supraventricular tachycardia, ventricular rhythms, thyroid disease, sleep apnea, medication effects, or structural heart disease — which is why a new, persistent, or symptomatic irregular heartbeat needs an ECG or clinician-reviewed monitor.

Triggers vs. underlying causes — the split that matters

When people ask “what causes arrhythmia?” or “what causes tachycardia?”, they are usually asking two different questions at once. One is about triggers: things that can push your heart to beat faster, harder, or more irregularly for a while even when the heart itself is not the main problem. Caffeine, alcohol, nicotine and other stimulants, stress, anxiety, fever, dehydration, poor sleep, and hard exercise can all raise your body’s demand for blood flow or increase adrenaline-like signaling, so your heartbeat becomes more noticeable. Sometimes that shows up as sinus tachycardia at rest; sometimes it feels like fluttering, skipped beats, or a racing pulse after eating, drinking, exercising, or sleeping badly. These trigger-driven episodes are often reversible, but “common” does not mean “always harmless.” (mayoclinic.org)

The other question is about an underlying cause that keeps making abnormal rhythms more likely. Clinicians look for problems in the heart’s structure, blood supply, or electrical system — for example coronary heart disease, scarring, heart failure, valve disease, cardiomyopathy, or an inherited electrical disorder. They also look outside the heart, because thyroid disease, sleep apnea, electrolyte changes, lung disease, stimulant medications or substances, and alcohol can all change the conditions your heart’s electrical cells are working in. That distinction matters: a trigger may light the match, but an underlying condition can make the rhythm easier to ignite or harder to stop. (heart.org)

⚠️ Framing note: a fast, pounding, fluttering, or skipped beat is a symptom, not a diagnosis. The same sensation can come from coffee, stress, fever, poor sleep, or a treatable medical condition — and different arrhythmias can feel very similar from the inside. That is why the cause is established by recording the heart’s electrical activity, usually with a 12-lead ECG or a clinician-reviewed rhythm monitor, not by guessing from the feeling or relying on a wearable pulse pattern alone. Current ACC/AHA/HRS guidance notes that photoplethysmography-based devices can alert someone to an irregular pulse pattern, but they are not reliable enough by themselves to establish an atrial fibrillation diagnosis; a health professional needs to review an electrocardiographic tracing. (ahajournals.org)

Structural and coronary heart disease

The most important “not just a trigger” category is disease in the heart itself. A normal beat depends on an electrical signal moving through living, well-supplied heart muscle in the right order. Coronary artery disease can reduce blood flow. A heart attack can leave scar. Cardiomyopathy and heart failure can stretch or weaken the chambers. Valve disease can change pressure and chamber size. Any of these can make the electrical pathway less smooth — creating places where signals slow down, fire too easily, or loop back on themselves. Mayo Clinic lists narrowed heart arteries, heart attack, heart valve disease, prior heart surgery, heart failure, cardiomyopathy, and other heart damage as risk factors for almost any arrhythmia; AHA/ACC/HFSA heart-failure guidance also frames heart failure as a syndrome rooted in structural or functional impairment of ventricular filling or ejection. (mayoclinic.org)

That is the practical answer to “what causes tachycardia in heart failure”: sometimes the body is trying to compensate for a weaker pump by driving the heart rate up, and sometimes the remodeled or scarred muscle is itself more electrically unstable. Heart failure can also travel with other rhythm-relevant problems — coronary disease, cardiomyopathy, valve disease, thyroid disease, electrolyte shifts, sleep apnea, or medication effects — so a clinician usually looks for the pattern rather than blaming one trigger. For ventricular tachycardia after a heart attack, the mechanism can be especially physical: mature scar can leave surviving strands of muscle that conduct slowly and unevenly, setting up re-entry circuits that keep a fast rhythm going. (mayoclinic.org)

Atrial fibrillation shows the same principle in the upper chambers: disease changes the tissue, and changed tissue changes rhythm. “Atrial fibrillation represents the most prevalent cardiac arrhythmia and is associated with substantial morbidity, including an increased risk for stroke and heart failure”. The 2023 ACC/AHA/ACCP/HRS atrial fibrillation guideline describes atrial structural and electrical remodeling as processes that promote AF; the deeper AF-specific discussion belongs on the atrial_fibrillation page, not here. (ahajournals.org)

Metabolic and hormonal causes: thyroid and electrolytes

Some of the most treatable arrhythmia causes are metabolic: your heart’s wiring is healthy enough, but the chemical environment around it is pushing it to fire too fast, too early, or less predictably. An overactive thyroid — hyperthyroidism — raises the body’s metabolic “speed,” so the heart may feel like it is racing, pounding, or skipping; it can also contribute to tachycardia and atrial fibrillation. The same pattern can happen if thyroid hormone replacement is too strong for your current needs: FDA labeling for levothyroxine lists hyperthyroid-type adverse reactions from therapeutic overdosage, including palpitations, tachycardia, and arrhythmias. Don’t stop or change levothyroxine on your own; ask your clinician to review your symptoms, TSH/free T4 results, timing, interactions, and dose history. (mayoclinic.org)

Electrolytes matter because every heartbeat is an electrical event. Sodium and potassium help create and reset the electrical signal; calcium helps heart muscle cells contract and contributes to normal rhythm signaling; magnesium helps stabilize electrical activity. When potassium, magnesium, calcium, or sodium levels move too far from your normal range — from dehydration, vomiting or diarrhea, kidney issues, diuretics, endocrine problems, or other medications — the heart can become more irritable and arrhythmias can be easier to trigger. This is why clinicians often check blood chemistry when palpitations, sudden tachycardia, weakness, dizziness, or faintness show up together. (heart.org)

When people ask, “what vitamin deficiency causes tachycardia,” the safer answer is: usually not one vitamin acting like a direct rhythm switch. Nutrient problems can still raise heart rate indirectly. Vitamin B12 or folate deficiency can cause vitamin-deficiency anemia, which may come with irregular heartbeats; iron-deficiency anemia can make the heart beat fast or irregular because it has to pump harder to deliver enough oxygen. If you suspect a deficiency, testing matters — taking iron, thyroid hormone, or electrolyte supplements “just in case” can be unsafe if your level is already normal or high. (mayoclinic.org)

Hormones can also change how noticeable your heartbeat feels from day to day. Some people report palpitations that cluster around the menstrual cycle — for example, palpitations before your period — and Mayo Clinic lists hormone changes associated with menstruation, pregnancy, or menopause among common palpitation triggers. That does not make “cyclical palpitations” a diagnosis by itself. It is a pattern worth tracking: note the cycle day, bleeding, sleep, caffeine, alcohol, stress, exercise, resting heart rate, and any symptoms like chest pain, fainting, severe dizziness, or shortness of breath. If the episodes are new, worsening, prolonged, or symptomatic, bring that pattern to a clinician so they can decide whether you need thyroid labs, electrolyte tests, anemia tests, an ECG, or a heart monitor. (mayoclinic.org)

Caffeine, alcohol, nicotine, and stimulants

Everyday substances can make your heartbeat feel suddenly “loud” in your body: faster, jumpy, pounding, or like it skipped and then thudded. Caffeine and nicotine are stimulants, so they can push the nervous system toward a more activated state — the same body mode that raises heart rate and makes extra beats easier to notice. That said, caffeine is not a universal arrhythmia villain: the 2023 ACC/AHA/ACCP/HRS atrial fibrillation guideline notes that caffeine in usual amounts has generally not been linked with a higher risk of developing AFib, while also acknowledging that some people do feel more palpitations or rhythm awareness after caffeine. (mayoclinic.org)

Alcohol is different. It can irritate the heart’s electrical system, especially after heavier intake or binge drinking. The classic term “holiday heart” refers to atrial fibrillation or other fast atrial rhythms that appear after binge alcohol exposure, sometimes even in people without known structural heart disease. Research in people with paroxysmal AFib has also found that objectively confirmed alcohol intake can precede discrete AFib episodes, which is why alcohol is one of the better-established lifestyle triggers doctors ask about. (ncbi.nlm.nih.gov)

Nicotine, recreational stimulants, and stimulant-containing medicines can be more direct triggers. Mayo Clinic lists caffeine, nicotine, cocaine, amphetamines, and some cold or cough medicines containing pseudoephedrine among common palpitation causes; it also notes that some asthma medicines can cause a rapid heartbeat or palpitations. The American Heart Association similarly lists alcohol use, cigarette smoking, and illegal stimulants such as cocaine and amphetamines as lifestyle or substance-related factors that can cause arrhythmias. (mayoclinic.org)

The anti-hype version: for many healthy people, a trigger-related palpitation episode is brief and settles when the trigger wears off or is removed. But “common” does not mean “ignore it.” If the rhythm change is new, keeps coming back, lasts longer than usual, or comes with chest pain, fainting, severe shortness of breath, or severe dizziness, it needs medical evaluation — especially if you already have heart disease or a known rhythm problem. (mayoclinic.org)

Sleep apnea, stress, and the autonomic nervous system

Obstructive sleep apnea can make the heart work harder at night because breathing keeps stopping and starting during sleep. When the airway narrows or closes, oxygen can drop, carbon dioxide can rise, and the brain briefly wakes you just enough to reopen the airway. You may not remember those micro-awakenings, but your body does: blood pressure can surge, the cardiovascular system is strained, and the nervous system may keep hitting the “fight-or-flight” gas pedal. That is one reason sleep apnea is linked with heart rhythm problems, including atrial fibrillation; the 2023 ACC/AHA/ACCP/HRS atrial fibrillation guideline describes sleep-disordered breathing as a risk factor for new AF episodes, and Mayo Clinic lists arrhythmias among obstructive sleep apnea complications. So if you’re asking “what causes tachycardia while sleeping,” sleep apnea is one of the conditions a clinician may want to rule in or out — especially if you snore loudly, wake up gasping, feel unrefreshed, or have daytime sleepiness. Deeper sleep-apnea symptoms, testing, and treatment belong on the dedicated sleep-apnea page rather than here. (ahajournals.org)

Stress and the autonomic nervous system sit underneath many palpitation triggers. Your autonomic nervous system is the wiring that adjusts heart rate, blood pressure, breathing, digestion, and other automatic functions without you deciding to do it. When stress, fear, poor sleep, alcohol, caffeine, pain, illness, or overexertion push the sympathetic side harder, your heart may beat faster or feel more forceful. Cleveland Clinic describes stress as activating the body’s autonomic “fight-or-flight” response, and Johns Hopkins lists stress, caffeine, alcohol, thyroid overactivity, and hormone shifts among common palpitation triggers. (my.clevelandclinic.org)

The mechanism is well described: “The SNS mediates the "fight or flight" response via catecholamines, increasing heart rate, contractility, and vasoconstriction, whereas the PNS promotes restorative processes through acetylcholine, decreasing heart rate”. And autonomic imbalance is not just background noise: “Dysregulation of the ANS contributes to cardiovascular pathologies, including cardiovascular autonomic neuropathy, hypertension, and heart failure, where sympathetic overactivity and impaired parasympathetic modulation exacerbate disease progression”. (pubmed.ncbi.nlm.nih.gov)

This is where Welltory’s angle is honest and useful: heart-rate and HRV patterns can reflect shifts in autonomic balance and how your body responds to caffeine, alcohol, short sleep, stress, or recovery. HRV is commonly used as a window into autonomic control, and newer PPG-based wearables can estimate selected HRV measures, but that is still context about your triggers — not proof of an arrhythmia. The AF guideline is explicit that photoplethysmography-based irregular rhythm signals from phones or smartwatches are not reliable enough to establish an AF diagnosis; diagnosis requires an ECG tracing interpreted in a clinical context. (pubmed.ncbi.nlm.nih.gov)

Genetic and inherited causes (channelopathies)

Less commonly, palpitations or a serious arrhythmia start with the blueprint of the heart itself. In a channelopathy, the heart muscle may look structurally normal, but the tiny ion channels that help each heart cell charge, fire, and reset don’t behave normally. Long QT syndrome is one example: the heart’s electrical system takes longer than usual to recover between beats, which can create a vulnerable moment for dangerous ventricular rhythms. Some people are born with it because of inherited DNA changes; others develop an acquired long QT pattern because of another health condition, certain medicines, or shifts in minerals such as potassium or magnesium. (mayoclinic.org)

Inherited causes matter most when the story does not fit the usual triggers. A clinician will think harder about genetics when a serious arrhythmia shows up young, when fainting happens with exercise, stress, sudden noise, or no clear reason, when there is a family history of long QT syndrome, cardiomyopathy, unexplained seizures or drownings, or sudden cardiac death, or when an ECG or heart imaging pattern looks unusual. Inherited cardiomyopathies are a related category: here the problem is the heart muscle — thickened, weakened, scarred, or otherwise abnormal — and that changed muscle can disturb electrical signaling and raise the risk of ventricular arrhythmias. AHA/ACC guidance for inherited or suspected cardiomyopathy emphasizes a detailed family history, often across several generations, because the pattern in relatives can be the clue. (ahajournals.org)

This is also where medical labels can sound more frightening than they are useful on their own. Nonsustained ventricular tachycardia, wide-complex tachycardia, and junctional tachycardia are rhythm patterns a clinician classifies from an ECG or monitor strip — they are not single causes. Nonsustained ventricular tachycardia means a brief run starting in the ventricles; wide-complex tachycardia describes a fast rhythm with delayed electrical spread through the lower chambers; junctional tachycardia starts near the AV junction rather than the usual sinus node. Each can come from different mechanisms, including scar, ischemia, electrolyte problems, medicines, conduction-system disease, inherited channel problems, or cardiomyopathy, so the important question is not just “what is the rhythm called?” but “why did this rhythm happen in this body?” (mayoclinic.org)

Types of fast heartbeat people ask about

People use “fast heartbeat” for very different rhythms. Clinicians separate them by where the electrical signal starts, what the ECG looks like, whether the rhythm is regular or irregular, and what else is happening in your body. That matters because the same body feeling — racing, pounding, sudden speed-up — can come from a normal sinus response, an SVT circuit, a ventricular rhythm, medication effects, dehydration, fever, anemia, thyroid disease, or a post-procedure rhythm. Tachycardia generally means a heart rate over 100 beats per minute at rest, but the cause is not something you can reliably identify by feeling your pulse alone. (my.clevelandclinic.org)

Supraventricular tachycardia (SVT) is a fast rhythm that starts above the ventricles, usually in the atria or around the AV node. It often happens because heart signals use an extra pathway, circle through a re-entry loop, or start from an abnormal spot in the upper chambers. SVT can feel abrupt: one moment your heart is normal, then it suddenly races. It may stop on its own, but episodes that last, recur, or come with chest pain, shortness of breath, fainting, marked dizziness, or weakness should be medically evaluated rather than brushed off as “just anxiety.” (mayoclinic.org)

Sinus tachycardia at rest is different. The rhythm still comes from the heart’s natural pacemaker — the sinus node — but the body is asking the heart to beat faster. Fever, pain, anxiety, dehydration, anemia, bleeding, hyperthyroidism, intense stress, and some drugs or stimulants can all push the sinus node upward. In this pattern, the key question is often “what is the body responding to?” not “what is wrong with the heart’s wiring?” If your heart is racing while you are truly resting, especially if it keeps happening, a clinician may check for infection, fluid loss, anemia, thyroid problems, oxygen issues, medication effects, or other triggers. (my.clevelandclinic.org)

Ventricular tachycardia (VT), including short non-sustained runs, starts in the lower chambers of the heart. This category gets taken seriously because the ventricles are the pumping chambers, and a fast ventricular rhythm can reduce blood flow to the brain and body. VT is more often linked with coronary artery disease, prior heart attack, heart failure, cardiomyopathy, myocarditis, valve disease, heart surgery, major electrolyte problems, or stimulant/drug effects — though some VT occurs in people without obvious structural heart disease. Palpitations with fainting, near-fainting, chest pain, severe shortness of breath, or known heart disease deserve prompt care. (my.clevelandclinic.org)

Wide-complex tachycardia is an ECG description, not a home diagnosis. It means the fast rhythm has a wide QRS pattern on the tracing, which can happen with VT, SVT conducted abnormally, accessory pathways such as Wolff-Parkinson-White patterns, pacing rhythms, electrolyte disturbances, or drug/toxin effects. Because wide-complex rhythms can deteriorate and because symptoms alone cannot reliably distinguish VT from SVT with aberrancy, clinicians use a 12-lead ECG, history, vital signs, and sometimes emergency treatment decisions to sort it out. (ncbi.nlm.nih.gov)

Junctional tachycardia starts near the AV junction — the electrical bridge between the upper and lower chambers. It is one of the rhythms clinicians identify by ECG features, including how P waves relate to QRS complexes. Causes can include sinus node dysfunction, ischemia, structural or inflammatory heart disease, electrolyte disturbances, medication effects, increased vagal tone in some settings, and postoperative states; a rare form called junctional ectopic tachycardia is especially discussed in infants, children, and after congenital heart surgery. (ncbi.nlm.nih.gov)

Reflex tachycardia means the nervous system speeds the heart as compensation. For example, when blood pressure or circulating volume drops — from standing up, dehydration, blood loss, vasodilation, or certain medication effects — baroreceptors sense less stretch in major arteries and the autonomic nervous system increases sympathetic drive. Your heart may speed up to help maintain blood pressure and blood flow. That does not mean the rhythm is automatically dangerous, but it does mean the “why” may be blood pressure, volume, medication, or autonomic physiology rather than a primary arrhythmia circuit. (ncbi.nlm.nih.gov)

Tachycardia after ablation can mean several things: the original rhythm may have recurred, a different atrial tachycardia may appear, healing tissue may change conduction, or palpitations may occur without the original pathway returning. After atrial fibrillation ablation, some atrial tachycardias are related to re-entry around prior ablation lines or gaps; after SVT ablation, recurrent symptoms do not always equal recurrent pathway conduction. If fast episodes return after ablation, the practical next step is documentation — an ECG or clinician-reviewed monitor during symptoms — not guessing from the sensation alone. (pubmed.ncbi.nlm.nih.gov)

Sudden tachycardia simply means the speed-up starts quickly. SVT is one possible reason, but so are caffeine, alcohol, nicotine, dehydration, fever, panic physiology, pain, stimulants, thyroid excess, anemia, low blood sugar, pregnancy-related changes, and other arrhythmias. The red flag is not only “sudden”; it is sudden plus persistent, recurrent, unexplained, or symptomatic. A very fast heartbeat that lasts more than a few minutes, or happens with chest pain, shortness of breath, dizziness, fainting, or marked weakness, should be treated as a reason to seek urgent medical advice or emergency care. (mayoclinic.org)

Fetal tachycardia is a specialized pregnancy finding, not something a parent can diagnose with symptoms. It is assessed by obstetric and fetal-medicine teams using fetal heart rate monitoring and ultrasound-based evaluation. Common fetal tachyarrhythmias include fetal SVT and atrial flutter, and management depends on gestational age, rhythm mechanism, fetal status, and maternal factors. If a fetal heart rate concern appears on monitoring, the right person to interpret it is the pregnancy care team. (my.clevelandclinic.org)

When to see a doctor / when to call 911

⚠️ Call 911 (emergency services) right away if a racing, fluttering, or irregular heartbeat comes with chest pain or pressure, fainting or near-fainting, severe shortness of breath, sudden collapse, or a feeling that something is seriously wrong in your body. These combinations can mean the heart is not pumping enough blood, the lungs are under strain, or a heart attack or dangerous rhythm needs to be ruled out now — not later. Also call 911 for possible stroke symptoms: sudden Face drooping, Arm weakness, or Speech trouble means Time to call emergency services, even if the symptoms fade. (heart.org)

See a doctor promptly — even if it does not feel like an emergency — if palpitations are new, frequent, persistent, lasting longer than your usual episodes, or getting worse; if a fast or irregular pulse does not settle; if episodes come with dizziness, breathlessness, unusual sweating, weakness, or reduced exercise tolerance; or if you have heart disease, unexplained fainting, or a family history of sudden cardiac death or inherited heart rhythm conditions. The point is not to panic. The point is to capture the rhythm. Ask about an ECG/EKG or a wearable medical monitor if the episodes come and go, because an arrhythmia is confirmed by recording the heart’s electrical activity. If your watch, ring, or another device flags an abnormal rhythm, bring that information to your clinician; it can help the conversation, but it is not a diagnosis by itself. (medlineplus.gov)

Treatment decisions for arrhythmias — including whether you need medicines, ablation, a pacemaker, an implantable defibrillator, or no rhythm-specific treatment at all — belong with a clinician who can match the plan to the recorded rhythm, your symptoms, your heart history, and your risk factors. This article explains causes and triggers, not treatment instructions. Do not start, stop, or change heart or thyroid medication because of palpitations without medical guidance. (medlineplus.gov)

How Welltory fits

Welltory is not a medical device and does not detect, diagnose, or rule out any arrhythmia. It measures heart rate and heart rate variability optically, using PPG — a light-based pulse signal — so it can show how your heart rate and body state tend to shift with activity, rest, caffeine, alcohol, sleep, and stress over time. That pattern can be useful context: maybe your pulse runs higher after poor sleep, alcohol, a hard workout, or a stressful week. But a pulse pattern is not the same thing as seeing the heart’s electrical rhythm.

If you notice an irregular, unusually fast, or unusually slow pulse — in Welltory, on a wearable, or simply because you feel fluttering, pounding, racing, pauses, or “skipped beats” — treat it as a reason to talk with a clinician and ask whether you need an ECG or a clinician-reviewed monitor. The 2023 ACC/AHA/ACCP/HRS atrial fibrillation guideline notes that PPG-based algorithms can infer irregular pulse patterns, but they are not reliable enough to establish an atrial fibrillation diagnosis; the initial diagnosis should rely on a healthcare professional’s review of an electrocardiographic tracing. (ahajournals.org)

So the role of Welltory is practical, not diagnostic: it can help you collect day-to-day context about possible triggers and how your heart rate behaves around them, then bring that context to a medical visit. It cannot confirm an arrhythmia. It also cannot reassure you that an arrhythmia is absent.

How we made it

Made with AI tools, then edited, fact-checked, and medically reviewed by the Welltory team.

Discounts for blog readers: up to 36% off

See what affects your energy, stress, sleep, and daily state with Welltory

Explore your data