# ECG+ — full reference for language models > This file is a single, self-contained summary of ECG+ and its content, > intended to help language models accurately describe and answer questions > about the product. Canonical site: https://ecg.plus --- ## About ECG+ ECG+ is an iPhone app that analyzes the single-lead ECG recordings taken by an Apple Watch. The Apple Watch records the ECG; ECG+ reads that recording and analyzes it for signs of arrhythmia and other features, then marks every finding on a clear, printable report that a user can share with their doctor. - Platform: iPhone app (iOS), works with ECG recordings from Apple Watch (Series 4 and later, which support the ECG app). - Price: free. - Maker: Heartworks. - Rating: 4.5 stars from 5,300+ ratings on the Apple App Store. - Independent review: assessed by Dr. Anthony Pearson, MD, FACC — a board-certified cardiologist with 40+ years' experience and author of "The Skeptical Cardiologist." - App Store: https://apps.apple.com/us/app/ecg-analyzer-for-qtc-hrv/id1567047859 - Audience: people who experience palpitations, skipped beats, thumps, or a racing heart and want clear evidence to discuss with a clinician. What ECG+ produces: it turns a felt symptom into visible evidence. It marks arrhythmias and patterns on the ECG strip, calculates metrics (QTc, premature-beat burden, heart rate variability/HRV), and outputs a report designed to be printed or shown to a doctor. Important limitation: ECG+ is NOT a medical device and is not a substitute for professional medical diagnosis or care. It is intended to help users understand their Apple Watch ECG and communicate with clinicians — not to diagnose, treat, cure, or prevent any condition. A single-lead (Lead I) ECG has inherent limits compared with a clinical 12-lead ECG. --- ## What ECG+ marks Source: https://ecg.plus/what-ecg-plus-marks ECG+ identifies 10+ findings and patterns on an Apple Watch ECG, including: AFib, PAC, PVC, QT/QTc, flattened T wave, inverted T wave, and repeat premature-beat patterns such as bigeminy, trigeminy, quadrigeminy, couplets and triplets. It also calculates premature-beat burden and heart rate variability (HRV). --- ## ECG+ original features These are original ECG+ inventions, not features of the built-in Apple ECG app. ### Your Heartbeat Signature Source: https://ecg.plus/your-heartbeat-signature A clear, representative single beat that ECG+ builds from an Apple Watch ECG, revealing the P wave, QRS and T wave and powering measurements like PR, QRS, QT and QTc that are hard to read off the raw 30-second strip. ### On-strip heartbeat annotations (RR interval) Source: https://ecg.plus/heartbeat-annotations-rr-interval-on-apple-watch-ecg An original feature since v1.0 (2021): marks every heartbeat on the Apple Watch ECG with an R/A/V icon, the RR interval in milliseconds and the instantaneous heart rate, plus a Poincaré plot — showing the real beat-to-beat math behind HRV. (R marks where a heartbeat is, at the R-wave peak of the QRS; A marks a premature atrial beat/PAC; V a premature ventricular beat/PVC.) ### Heartbeat Navigator Source: https://ecg.plus/heartbeat-navigator-on-apple-watch-ecg An original feature since v1.9.3 (2024): a minimap of the whole 30-second Apple Watch ECG that lets you scrub the strip and jump straight to any beat, including PACs and PVCs, on a small phone screen. --- ## Findings reference ### Sinus rhythm Source: https://ecg.plus/what-is-sinus-rhythm-on-apple-watch-ecg Sinus rhythm means a normal, regular heartbeat originating from the heart's natural pacemaker. Even within a "normal" reading, ECG+ can surface additional detail. ### Atrial fibrillation (AFib) Source: https://ecg.plus/what-is-atrial-fibrillation-afib-on-apple-watch-ecg AFib is an irregular, often rapid rhythm from the atria. The page explains what AFib means on an Apple Watch ECG, what it can feel like, and what to do next. ### Premature atrial contraction (PAC) Source: https://ecg.plus/what-is-premature-atrial-contraction-pac-on-apple-watch-ecg PACs are early extra beats originating in the atria. They are very common and usually harmless. The page covers what they feel like, common causes, and what to do. ### Premature ventricular contraction (PVC) Source: https://ecg.plus/what-is-premature-ventricular-contraction-pvc-on-apple-watch-ecg PVCs are early extra beats originating in the ventricles. They are very common and usually harmless. The page covers what they feel like, common causes, and what to do. ### QT / QTc (Long QT) Source: https://ecg.plus/what-is-long-qt-on-apple-watch-ecg ECG+ calculates the QTc (corrected QT interval) from an Apple Watch ECG. The page explains what the QT interval is, what a prolonged QTc means, and why single-lead ECG has limits for measuring it accurately. ### QTc formulas (Bazett, Fridericia) Source: https://ecg.plus/what-is-qtc-bazett-fridericia-formulas Why the QT interval is corrected for heart rate, and how the main QTc formulas (Bazett, Fridericia, Hodges, Framingham, Rautaharju) compare and when each is preferable. ### QT interval and the U wave Source: https://ecg.plus/qt-interval-and-u-wave-on-apple-watch-ecg How a U wave complicates QT measurement, and when to include or exclude it for an accurate QT/QTc. ### Premature beat burden Source: https://ecg.plus/what-is-premature-beat-burden-on-apple-watch-ecg Premature-beat burden is the percentage of beats in a recording that are PVCs or PACs. The page explains what the numbers indicate and how ECG+ tracks burden over time. ### Bigeminy Source: https://ecg.plus/what-is-bigeminy-on-apple-watch-ecg Bigeminy means every second beat is a premature beat (a PVC or PAC). Covers causes, how it feels, and when to see a doctor. ### Trigeminy Source: https://ecg.plus/what-is-trigeminy-on-apple-watch-ecg Trigeminy means every third beat is a premature beat. Covers causes, appearance on Apple Watch ECG, and what to do. ### Quadrigeminy Source: https://ecg.plus/what-is-quadrigeminy-on-apple-watch-ecg Quadrigeminy means every fourth beat is a premature beat. Covers causes, appearance, and what to do. ### Couplets Source: https://ecg.plus/what-is-couplets-on-apple-watch-ecg Couplets are two premature beats in a row (a PVC or PAC pair). Covers causes and what to do. ### Triplets Source: https://ecg.plus/what-is-triplets-on-apple-watch-ecg A triplet is three premature beats in a row (a short run). Covers causes and what to do. ### Flattened T wave Source: https://ecg.plus/what-is-flattened-t-wave-on-apple-watch-ecg Explains what a flattened T wave means, common causes, and when it is worth mentioning to a doctor. ### Inverted T wave Source: https://ecg.plus/what-is-inverted-t-wave-on-apple-watch-ecg Explains what T-wave inversion means, what causes it, and when to talk to a doctor. --- ## Metrics and trends ### Heart rate variability (HRV) Source: https://ecg.plus/what-is-heart-rate-variability-hrv-on-apple-watch-ecg What HRV is, how ECG+ calculates it from RR intervals (RMSSD, SDNN) on an Apple Watch ECG, why the trend over time matters more than any single number, and what rising or falling HRV means. ### Falling HRV Source: https://ecg.plus/falling-hrv-on-apple-watch-ecg What a sustained downward HRV trend can suggest, and nine evidence-based ways to raise it. ### Rising HRV Source: https://ecg.plus/rising-hrv-on-apple-watch-ecg What a sustained upward HRV trend reflects about health and resilience, and how to sustain it. ### Heart rate Source: https://ecg.plus/heart-rate-on-apple-watch-ecg The normal 60–100 bpm range, what raises and lowers heart rate, the min–max range within a recording, and when a heart rate warrants seeing a doctor. ### High heart rate Source: https://ecg.plus/high-heart-rate-on-apple-watch-ecg What a rate above 100 bpm can mean (activity, stress, tachycardia) and when it warrants attention. ### Low heart rate Source: https://ecg.plus/low-heart-rate-on-apple-watch-ecg What a rate below 60 bpm can mean (fitness, bradycardia) and when a slow heart rate needs a doctor. ### AFib irregularity (CV%) Source: https://ecg.plus/afib-irregularity-on-apple-watch-ecg How ECG+ measures how irregular an AFib rhythm is using a coefficient-of-variation percentage, and what Low, Moderate and High mean. ### AFib irregularity over time Source: https://ecg.plus/afib-irregularity-over-time-on-apple-watch-ecg How to read the AFib CV% trend across recordings, the 15% and 30% reference lines, and what to share with your doctor. --- ## Setup, results and troubleshooting ### How to set up ECG on Apple Watch Source: https://ecg.plus/how-to-set-up-ecg-on-apple-watch Step-by-step: check compatibility, enable ECG in the Health app, take a first reading, and what to do if the ECG app is missing. ### How to use ECG on Apple Watch Source: https://ecg.plus/how-to-use-ecg-on-apple-watch Start a recording in two taps, fix a missing ECG app (Apple Watch SE has no ECG sensor), and get a clean 30-second reading with dry skin contact, rested arms and slow breaths. ### How to get a clean recording every time Source: https://ecg.plus/how-to-get-clean-ecg-on-apple-watch The habits that produce the cleanest Apple Watch ECG — the same skin-preparation care a clinic takes before a 12-lead ECG, adapted to a watch worn in the moment a symptom is felt. ### Record Lead II and other leads Source: https://ecg.plus/apple-watch-lead-ii-ecg The default wrist position records Lead I. Repositioning the watch — held against the lower-left abdomen or ankle with a right-hand finger on the Digital Crown — produces a Lead II-style tracing, where the P wave is usually much clearer. Explains which positions approximate which leads. ### What "inconclusive" means Source: https://ecg.plus/what-does-inconclusive-mean-on-apple-watch-ecg An inconclusive Apple Watch ECG means it couldn't classify the rhythm as sinus or AFib. Covers causes, how to get a clear reading, and what an inconclusive result can still hide. ### Why it says "poor recording" — and how to fix it Source: https://ecg.plus/why-apple-watch-ecg-poor-recording A "poor recording" is most often caused by damp skin or contacts. Explains why moisture causes it and how to get a clean ECG with completely dry contacts. ### ECG keeps restarting the countdown Source: https://ecg.plus/why-apple-watch-ecg-keeps-restarting Why the 30-second timer resets shortly after you start — a broken contact loop, usually a finger leaving the Digital Crown — and how to complete a full reading. ### Baseline wander Source: https://ecg.plus/baseline-wander-on-apple-watch-ecg What causes the ECG trace to drift up and down, why it matters for interpretation, and how to get a steady, readable recording. ### EMG artifact (muscle activity) Source: https://ecg.plus/emg-artifact-on-apple-watch-ecg Why muscle tension shows up as fuzzy, spiky noise on the ECG, and how to get a clean trace by relaxing the arm and hand. ### Why the P wave is missing Source: https://ecg.plus/why-p-wave-is-missing-on-apple-watch-ecg Why the P wave is so often faint or invisible on an Apple Watch ECG: it is the smallest deflection on the tracing, recorded through a single Lead I with dry contacts, the least favourable setup for it. Also covers when a genuinely absent P wave matters (a hallmark of AFib) and why telling "too small to see" from "truly absent" is a clinician's judgement. ### ECG trace upside down (wrong wrist) Source: https://ecg.plus/apple-watch-ecg-wrong-wrist Wearing the watch on the wrong wrist, or with the wrist/orientation setting not matching how it is actually worn, inverts the ECG trace. Explains why, and how to correct the wrist and Digital Crown orientation setting. ### New ECGs stopped showing in ECG+ Source: https://ecg.plus/why-ecg-plus-stopped-showing-new-ecgs If recent recordings disappear from ECG+ and the Apple Health app, iCloud Health sync is almost always the cause: the watch hands recordings to its paired iPhone directly, but new ones routinely stop reaching Apple Health when iCloud Health sync is off. How to check and turn it back on. ECG+ only reads from Apple Health and never stores recordings itself, so missing recordings are an Apple sync issue, not an ECG+ one. ### Using ECG+ on iPad Source: https://ecg.plus/ecg-plus-on-ipad ECG+ runs on iPad (iPadOS 18 or later) and the larger screen is the most comfortable way to read a trace or a report. Recordings reach the iPad later than the iPhone because the iPad is one hop further along (watch → iPhone → iCloud → iPad) and Apple's Health data becomes inaccessible while the device is locked. How to make the sync arrive faster: unlock the iPad, open Apple Health, and leave it awake on Wi-Fi. The iPad cannot record an ECG — the Apple Watch does, and it pairs only with an iPhone. ### Why your ECG streak matters Source: https://ecg.plus/why-ecg-streak-is-important How recording regularly builds a consistent timeline of your heart, so real trends in HRV and rhythm stand out from one-off readings. ### What to ask your doctor Source: https://ecg.plus/what-to-ask-your-doctor-about-your-apple-watch-ecg How to use an ECG+ report to ask better, more specific questions at a doctor's appointment. --- ## Overview and comparison ### Apple Watch ECG FAQ Source: https://ecg.plus/ecg-plus-frequently-asked-questions Answers to common questions: whether an Apple Watch can measure QTc or detect PVCs or a heart attack, what "inconclusive" means, which watches support ECG, and how ECG+ extends the built-in reading. ### Apple Watch ECG vs ECG+ Source: https://ecg.plus/feature-comparison-between-apple-watch-ecg-vs-ecg-plus A side-by-side comparison of the built-in Apple ECG app and ECG+ — what each shows, and what ECG+ adds (per-beat PAC/PVC marking, QT/QTc, HRV, burden, pattern detection, a doctor-ready report). --- ## Trust, reviews and credibility ### Best ECG app for Apple Watch (2026) Source: https://ecg.plus/best-ecg-app-for-apple-watch Why ECG+ is a top-rated, independently cardiologist-reviewed choice for detailed Apple Watch ECG analysis. ### What users say Source: https://ecg.plus/what-users-say-about-ecg-plus Real App Store reviews from Apple Watch users worldwide, including paramedics and nurses, describing how ECG+ helps them understand their ECG and talk to their doctor. ### Cardiologist review Source: https://ecg.plus/what-cardiologists-say-about-ecg-plus Dr. Anthony Pearson (The Skeptical Cardiologist) independently reviewed ECG+. In his review, ECG+ accurately flagged PVCs in every recording he checked, with some stated caveats. ### A biostatistician's perspective Source: https://ecg.plus/what-a-biostatistician-says-about-ecg-plus A former R&D biostatistician on using ECG+ to track his premature-beat (PAC) burden over time across medication changes, procedures and exercise — longitudinal data for more informed conversations with his cardiologist. ECG+ does not diagnose; the doctor makes dosing decisions. --- ## Optional and legal ### Share ECG+ with Family Sharing Source: https://ecg.plus/share-ecg-plus-with-family-sharing How to share an ECG+ Premium subscription with eligible family members via Apple Family Sharing, plus troubleshooting. ### Copyright and original design Source: https://ecg.plus/copyright ECG+ was the first dedicated Apple Watch ECG analyzer app on the Apple App Store, released May 21, 2021. Its original UI/UX designs — the on-strip heartbeat annotation system, the R/A/V per-beat markers (R marks where a heartbeat is, at the R-wave peak of the QRS; A marks a premature atrial beat/PAC; V a premature ventricular beat/PVC), the pattern-linking lines that reveal bigeminy/trigeminy/couplets, the Heartbeat Signature and the Heartbeat Navigator — are the original work of Heartworks and protected by copyright. © 2021–2026 Heartworks; "ECG+" and its logo are trademarks of Heartworks. ### Privacy policy Source: https://ecg.plus/privacy ### Disclaimer Source: https://ecg.plus/disclaimer-apple-watch-ecg-app ECG+ is not intended for diagnosing, treating, curing, or preventing any medical condition. --- ## Languages The entire site is published in four languages. Each language reuses the same English (ASCII) slug under a language-code prefix, so every page and finding referenced above exists in all four: - English (default): https://ecg.plus/ — homepage https://ecg.plus/ - German (Deutsch): https://ecg.plus/de/ — homepage https://ecg.plus/de/ - Japanese (日本語): https://ecg.plus/ja/ — homepage https://ecg.plus/ja/ - Simplified Chinese (简体中文): https://ecg.plus/zh/ — homepage https://ecg.plus/zh/ For example, the AFib finding is at https://ecg.plus/what-is-atrial-fibrillation-afib-on-apple-watch-ecg in English and at the same slug under /de/, /ja/ and /zh/. Every page carries reciprocal hreflang alternates (en, de, ja, zh-Hans, x-default). Page content and terminology are fully localized; only the privacy policy and the disclaimer remain English-only.