KardiaMobile is a pocket-sized EKG device that records your heart’s electrical activity through two metal sensor pads you touch with your fingertips. A reading takes 30 seconds, and the result is sent to an app on your phone where an algorithm instantly classifies your heart rhythm as normal or potentially abnormal. It’s FDA-cleared to detect the three most common heart arrhythmias: atrial fibrillation (AFib), bradycardia (heart rate too slow), and tachycardia (heart rate too fast).
How the Sensors Capture Your Heart’s Signals
Your heart generates a small electrical impulse every time it beats. That electrical signal travels through your body and can be picked up at the surface of your skin. KardiaMobile uses two metal electrodes built into a slim device roughly the size of a stick of gum. You place one finger from each hand on each electrode, creating a circuit that runs across your chest, through your heart.
The device samples your heart’s electrical signal 300 times per second. That’s enough resolution to produce a medical-grade waveform showing the characteristic peaks and valleys of each heartbeat. The raw data transmits wirelessly to the Kardia app on your smartphone using ultrasonic sound waves (on older models) or Bluetooth, where it’s rendered as a scrolling EKG tracing you can see in real time.
The entire recording takes 30 seconds. You don’t need to remove clothing, attach sticky patches, or use any gel. You simply hold the device while sitting still, and the app tells you when it’s finished.
What the App Does With Your Recording
Once the 30-second recording is complete, KardiaMobile’s built-in algorithm analyzes the waveform and assigns one of several classifications. The most common results are “Normal” (meaning your rhythm and rate fall within expected ranges), “Possible AFib” (an irregular rhythm consistent with atrial fibrillation), “Bradycardia” (heart rate below 50 beats per minute), or “Tachycardia” (heart rate above 100 beats per minute). If the algorithm can’t confidently classify the result, it returns “Unclassified,” which means a doctor should review the tracing.
The app stores every recording with a timestamp, your heart rate, and the full EKG tracing. You can email a PDF of any recording directly to your doctor, or share your history during an appointment. This is one of the device’s main practical advantages: arrhythmias often come and go unpredictably, and by the time you reach a clinic, your heart may be beating normally again. Having a recording captured during symptoms gives your doctor something concrete to evaluate.
How Accurate Is It?
Clinical studies reviewed by the UK’s National Institute for Health and Care Excellence (NICE) found that KardiaMobile’s algorithm detects atrial fibrillation with a sensitivity between 92% and 99% per recording, and a specificity between 92% and 98%. In practical terms, sensitivity measures how reliably it catches AFib when it’s actually happening, while specificity measures how often it correctly identifies a normal rhythm as normal. Both figures are high enough that physicians frequently use KardiaMobile recordings to guide clinical decisions.
There are important limits, though. The device records heart rate and rhythm only. It does not detect all types of heart waveform changes, particularly those related to reduced blood flow to the heart muscle (ischemic conditions like a heart attack). A normal KardiaMobile reading does not rule out all heart problems. It’s designed for rhythm monitoring, not comprehensive cardiac diagnosis.
Single-Lead vs. Six-Lead Models
KardiaMobile comes in two versions. The standard KardiaMobile records a single-lead EKG, meaning it captures your heart’s electrical activity from one angle. This is enough to reliably detect common rhythm abnormalities and is the version most people start with.
KardiaMobile 6L adds a third electrode on the bottom of the device that you press against your leg or knee. This lets it record six different electrical views of your heart simultaneously, providing substantially more detail about how electrical signals are moving through different parts of the heart. A standard hospital EKG uses 12 leads, so the 6L captures half that level of detail from a device you can carry in your pocket. The 6L model is FDA-cleared and is typically more useful for people who already have a diagnosed heart condition and need richer data for their cardiologist to review.
What You Need to Use It
KardiaMobile requires a compatible smartphone or tablet with the free Kardia app installed. The device itself has no screen, no buttons, and no charging port. It runs on a built-in battery that lasts up to two years with normal use and cannot be replaced, meaning the device has a finite lifespan. Some features within the app, such as unlimited recording storage and more detailed analysis, require a paid subscription.
To get the clearest reading, you should sit down, rest your arms on a flat surface, and stay still during the 30-second recording. Movement, tremors, or dry skin can introduce noise into the tracing and lead to an “Unclassified” result. Moistening your fingertips slightly before placing them on the electrodes can improve contact if your skin tends to be dry.
How Doctors Use Your Recordings
The recordings KardiaMobile produces are genuine single-lead (or six-lead) EKG tracings, not simplified estimates. Doctors can read them the same way they’d read a hospital EKG strip, examining the shape and timing of each wave to assess rhythm regularity, heart rate, and certain conduction patterns. The PDF reports the app generates include the raw waveform, average heart rate, and the algorithm’s classification.
For many people, the most valuable use case is capturing intermittent symptoms. If you feel palpitations, dizziness, or a fluttering sensation that comes and goes, you can take a recording during the episode and bring that data to your next appointment. Traditional monitoring options, like a Holter monitor worn for 24 to 48 hours, sometimes miss events that happen outside the monitoring window. KardiaMobile lets you record on demand, as many times as you want, for as long as you have the device.