Your Heart Skips a Beat

TL;DR: That feeling where your heart seems to pause for a second and then thump is almost always an extra beat that came too early. The early beat is too small to feel. The pause after it gives your heart extra time to fill, and the next beat hits harder than usual. That hard beat is the one you feel. In a normal heart this is common and safe, but it is annoying, and we can usually find the cause. The common triggers are low magnesium, low potassium, thyroid trouble, low iron, caffeine, alcohol, nicotine, dehydration, and short sleep or sleep apnea. To catch the rhythm at home, a continuous patch measures your daily burden, while a 6-lead personal EKG (KardiaMobile 6L) records 6 views of your heart in 30 seconds without needing a monthly membership. Get checked right away if you faint or nearly faint, if beats worsen during exercise, or if a close relative died suddenly and young.

Why does a skipped beat feel like a pause and then a thump?

The sensation matches what your heart is physically doing, and seeing the mechanics takes most of the fear out of it.

Your heart normally beats on an electrical signal that starts in one spot and travels in order. Sometimes a separate patch of heart muscle fires early on its own. If that early signal starts in the lower chambers, it is a premature ventricular contraction (PVC). If it starts in the upper chambers, it is a premature atrial contraction (PAC).

The early beat fires before the heart has finished filling with blood. Because the chamber is only partly full, that beat pushes out very little blood and you rarely feel it. A brief pause follows while the electrical system resets. During that pause, the heart fills with more blood than usual. The next regular beat then squeezes out that larger volume with extra force. That strong beat is the thump in your chest.

What feels like a skipped beat is an early, quiet beat followed by a pause and a heavy beat. People notice it most when lying down at night, when the room is quiet and the chest rests against the mattress.

Are they dangerous?

In a structurally normal heart, occasional premature beats are safe and very common. Multi-day heart monitors on healthy people without symptoms pick them up all the time.

That reassurance is important, yet it is also where many patients feel brushed off. Hearing that a rhythm is benign often sounds like being told to ignore it, even while your chest keeps thumping every evening. A symptom can be safe and still worth fixing. Most premature beats have clear physical triggers underneath. Finding and fixing those triggers usually lowers both how often the beats happen and how strongly you feel them.

Two situations change how we approach them. The first is a structurally abnormal heart, including a past heart attack, heart muscle weakness (cardiomyopathy), valve disease, or heart failure. In those cases, premature beats carry more weight and belong with a cardiologist. The second is a high daily burden. When PVCs make up more than 10% to 15% of all heartbeats over 24 hours, that constant off-beat squeezing can tire out the heart muscle over months or years. Doctors call this PVC-induced cardiomyopathy, and it is reversible once the beats are controlled. That is why we measure how many beats happen over a full day instead of only confirming that you have them.

What drives them?

A short list accounts for most cases we see in clinic, so we check each one step by step.

Magnesium moves the needle most often. A standard blood magnesium test is a poor way to check your supply, because your body pulls magnesium out of bone and muscle to keep the blood number steady. An RBC magnesium test measures what is inside your cells, and we aim for the upper half of the range. We use magnesium glycinate because it absorbs well without upsetting your stomach the way magnesium oxide does. Taking it in the evening helps both heart rhythm and sleep.

Potassium steadies the same electrical channels in heart muscle. We check it at the same time, and we pay close attention if you take blood pressure medication.

Thyroid hormone. An overactive thyroid speeds up your heart and makes every extra beat feel louder. A TSH blood test belongs in every palpitation workup.

Iron. Low iron stores make the heart pump harder and make skipped beats much more noticeable. We always check ferritin (stored iron) alongside a complete blood count.

Stimulants and everyday triggers. Caffeine, alcohol, nicotine, vapes, cannabis, cold medicines like pseudoephedrine, and prescription stimulants all trigger extra beats. Alcohol surprises many people because the extra beats often show up the next day as the body clears it.

Sleep and nighttime breathing. Short sleep, high stress, and untreated sleep apnea all raise adrenaline and trigger premature beats. Sleep apnea is a common hidden driver, even in lean, active adults who do not snore loudly. If you wake up groggy after 7 or 8 hours in bed, moan in your sleep, or ever wake up gasping for air, a 1-night home sleep apnea test is an easy way to check.

Dehydration shifts electrolytes and raises heart rate after hockey, running, or a long workday.

What does the workup look like?

We match the testing to how often your symptoms happen.

An in-office 12-lead ECG captures the beats if they are happening during your visit and checks your baseline electrical pathways. A continuous patch monitor worn at home (such as a Zio patch) records every beat for 2 to 14 days. The continuous patch is the gold standard for counting your 24-hour PVC percentage and matching your symptom log to the rhythm strip.

What if you already had a cardiology workup, or your skipped beats come and go over months, and you want a way to check your rhythm at home whenever they flare?

Why we use a 6-lead personal EKG instead of a smartwatch

Many people try to track skipped beats with a smartwatch, a fitness strap, or a smart mattress sensor. While a watch is convenient, it only records a single electrical lead across your wrists, and a mattress sensor only estimates heart rate from movement. When patients bring a folder of smartwatch alerts into a hospital or cardiology clinic, the data often gets dismissed because a 1-lead tracing cannot show the shape and direction of a premature beat clearly.

When you want a tool you can keep at home and bring to your cardiologist with confidence, we recommend the KardiaMobile 6L ($129, HSA and FSA eligible). It is a pocket-sized pad with 2 metal sensors on top for your thumbs and 1 sensor underneath that rests against the skin of your left knee or left ankle. In 30 seconds, without wires, gels, or sticky patches, it records 6 limb leads (I, II, III, aVR, aVL, and aVF).

Six leads give me and your cardiologist 6 simultaneous camera angles of your heart's electrical wave. That makes it much easier to see whether a funny feeling in your chest is a harmless PVC, a run of atrial fibrillation (AFib), or normal sinus rhythm.

Two practical tips when ordering the KardiaMobile 6L:

1. Choose the standard KardiaMobile 6L ($129) without the paid KardiaCare subscription. Kardia sells an optional annual membership (KardiaCare, bundled with the pricier 6L Max) that adds automated software tags for beats like PVCs or wide QRS complexes. You do not need to pay for that subscription when you have a doctor reading your strips. With the standard device, you can record unlimited 30-second 6-lead EKGs, export the PDF rhythm strip for free, and upload it to your Fishtown Medicine portal so I (or your cardiologist) can read the waveform directly.
2. Keep the device in the house for years. A prescribed patch goes back in the mail after 2 weeks, while this stays in your drawer whenever you need it. Anyone in your household can use it for a 30-second check when a heartbeat feels irregular. It is not recommended for people with a pacemaker or implantable defibrillator (ICD) and never replaces emergency care for chest pain or fainting.

Bloodwork rounds out the check with RBC magnesium, potassium, TSH, ferritin with iron studies, a complete blood count, and a metabolic panel. An echocardiogram (heart ultrasound) is added when the daily PVC burden is high or when we want to verify that the heart muscle and valves look normal.

What helps?

Fixing the physical triggers comes first, because that solves the problem for most people without needing a daily prescription.

Replete magnesium with evening magnesium glycinate, rebuild iron stores if ferritin is low, and balance the thyroid if it is off. Pause or cut back on caffeine and alcohol for a clear 2-week trial to see how much quieter your chest feels. Protect your sleep schedule, and run a 1-night home sleep study if morning grogginess or high hemoglobin points toward overnight oxygen drops.

When skipped beats stay frequent and disruptive after the triggers are addressed, a low-dose beta blocker is the usual next option. A beta blocker calms adrenaline receptors and softens the heavy beat that follows the pause, which is the thump you feel. Which form of metoprolol you take matters depending on whether you want steady 24-hour coverage or an as-needed dose. In patients who also have a history of paroxysmal atrial fibrillation managed with a "pill-in-the-pocket" antiarrhythmic such as flecainide, having a 6-lead EKG at home helps confirm whether an episode is true AFib or simply frequent PVCs before taking an as-needed rhythm medication.

For the small group of patients with a persistently high PVC burden that does not respond to lifestyle steps or medication, catheter ablation maps and quiets the specific spot of heart muscle firing early, and we coordinate that with an electrophysiologist.

When should I be seen sooner?

Certain symptoms mean we should evaluate you right away instead of waiting for a routine checkup:

• Fainting or feeling like you are about to black out during palpitations.
• Skipped beats or racing rhythms that multiply during exercise instead of calming down as your heart rate rises.
• Chest pain, pressure, or shortness of breath alongside the rhythm change.
• A family history of sudden cardiac death or an inherited heart muscle or rhythm condition.
• Known structural heart disease, such as a past heart attack or valve condition.
• A fast rhythm that takes off suddenly and stays fast for minutes or hours.

Chest pain with a racing heart, or fainting, requires calling 911 or going to an emergency department right away. Do not wait to record a home EKG or wait on a portal reply.

Guidance from the Clinic

"Being told a symptom is benign and being told it does not matter are 2 very different messages, and patients almost always hear the second one. Skipped beats in a healthy heart will not hurt you, yet they can still ruin your evening, and when they happen often enough they start to feel like your new normal. Whether we check your intracellular magnesium and sleep quality or put a 6-lead Kardia EKG in your pocket so your cardiologist can see clear 6-view strips instead of dismissing a smartwatch alert, the goal is giving you clear data and a quiet chest."

Related at Fishtown Medicine

• Getting Answers from a Heart Monitor (Zio Patch) - how continuous patch monitoring measures 24-hour burden
• Metoprolol: Tartrate vs Succinate - short-acting vs extended-release beta blockers
• Magnesium Glycinate Clinical Guide - intracellular RBC targets and dosing
• Racing Heart When Standing (POTS) - when heart rate climbs with posture changes
• Home Sleep Apnea Testing - checking for nighttime oxygen drops that drive extra beats
• Understanding High Blood Pressure at Home - home cuff technique and targets
• Chest Wall Pain - chest tenderness that reproduces when pressed
• Heart Disease in Women - how cardiac symptoms present differently across sexes

Scientific References

1. Ng GA. "Treating patients with ventricular ectopic beats." Heart. 2006;92(11):1707-1712. PubMed
2. Baman TS, Lange DC, Ilg KJ, et al. "Relationship between burden of premature ventricular complexes and left ventricular function." Heart Rhythm. 2010;7(7):865-869. PubMed
3. Marcus GM. "Evaluation and Management of Premature Ventricular Complexes." Circulation. 2020;141(17):1404-1418. PubMed
4. Workinger JL, Doyle RP, Bortz J. "Challenges in the Diagnosis of Magnesium Status." Nutrients. 2018;10(9):1202. PubMed
5. Kleiman R, Darpo B, Brown R, et al. "Comparison of 6-lead smartphone ECG to 12-lead ECG for rhythm and interval analysis." Heart Rhythm. 2021;18(8):S340.