Keep an eye on your QT interval — right from your Apple Watch ECGs
SSRI QT Tracker automatically analyzes the ECGs in Apple Health and computes your QT and rate-corrected QTc — ideal when you're starting an SSRI or another QT-prolonging medication and want to follow your heart's repolarization over time.
Everything you need to follow your QTc over time
Record an ECG on your watch as usual — QT Tracker takes care of the rest, entirely on your iPhone.
Automatic ECG import
Reads every ECG from Apple Health on-device — no manual export, no cables, no cloud.
Precise QT measurement
Averages your heartbeats into one clean, low-noise beat and finds the T-wave end with the clinically established tangent method.
Four QTc formulas
Fridericia, Bazett, Framingham and Hodges — compare them side by side and pick your reference.
Trends with thresholds
Trend chart with normal-range thresholds and comparison against your personal baseline.
Heart rate & HRV
Resting heart rate and HRV (SDNN) trends from Apple Health round out the picture.
Medication log
Store your medications and therapy start dates, so every QTc value has its context.
Measurement reminders
Gentle reminders help you record ECGs regularly — trends need data points.
PDF doctor report
Export a report with curves, table and measurement points — made to hand to your physician.
A look inside the app
QT measurement on an averaged beat, your QTc trend over time, the full measurement list and on-device settings.
From wrist to trend chart in three steps
Record an ECG
Take a normal 30-second ECG with your Apple Watch (Series 4 or later) — just like you always do.
Automatic analysis
QT Tracker imports the recording from Apple Health, averages the beats into a clean signal, and detects QRS onset and T-wave end using the tangent method.
Follow your QTc
QT and rate-corrected QTc land on your personal trend chart — with normal-range thresholds, baseline comparison and PDF export for your doctor.
Why watch the QT interval on SSRIs?
The QT interval is the time your heart's ventricles need to electrically discharge and recharge (depolarization and repolarization). Because it naturally shortens as the heart beats faster, it is normalized to a heart rate of 60 bpm — the result is the corrected QT, or QTc.
Some SSRIs — most notably citalopram and escitalopram — can prolong the QT interval in a dose-dependent way. A markedly prolonged QTc (commonly flagged from about 450–470 ms, with 500 ms considered a critical threshold) raises the risk of a rare but serious arrhythmia called torsades de pointes. That is why prescribing information recommends caution, dose limits, and — for at-risk patients — ECG monitoring. Regular self-recorded ECGs make it easier to spot a personal trend early and bring concrete data to your doctor.
QTc = QT / RR1/3Default — robust across a wide heart-rate range.QTc = QT / RR1/2The classic formula, most widely used clinically.QTc = QT + 0.154·(1−RR)Linear correction from the Framingham Heart Study.QTc = QT + 1.75·(HR−60)Heart-rate-based linear correction.Your heart data stays on your iPhone. Period.
100% offline
All analysis runs on-device. The app makes no network requests at all.
No accounts
No sign-up, no login, no e-mail address. Install and go.
No data collection
No analytics, no ads, no tracking SDKs. Apple's App Privacy label: data not collected.
Frequently asked questions
What does SSRI QT Tracker do?
It reads ECG recordings from Apple Health (e.g., from an Apple Watch), averages the heartbeats into a clean low-noise signal, measures the QT interval with the tangent method, and computes the rate-corrected QTc using the Fridericia, Bazett, Framingham and Hodges formulas. All values are plotted over time against normal-range thresholds.
Why should I watch my QT interval when taking an SSRI?
Some SSRIs — most notably citalopram and escitalopram — can prolong the QT interval in a dose-dependent way. A markedly prolonged QTc increases the risk of a rare but dangerous arrhythmia (torsades de pointes). Regular ECG self-checks make it easier to spot a trend early and discuss it with your doctor.
Which devices does it work with?
Any single-lead ECG stored in Apple Health works — for example recordings from an Apple Watch Series 4 or later. The app runs on iPhone with iOS 15.1 or newer and is available in 30 languages.
How accurate is the automatic measurement?
QT Tracker averages many beats of a recording into one low-noise beat and applies the tangent method — the same approach used in clinical QT studies. Still, automatic measurements on a single-lead wearable ECG can differ from a 12-lead ECG read by a physician. Treat the values as personal trend data, not as diagnostics.
Is my health data uploaded anywhere?
No. The app works 100% offline and entirely on-device. No cloud, no accounts, no analytics, no data collection. Your ECGs never leave your iPhone.
Can the app replace my doctor?
No. SSRI QT Tracker is not a medical device and does not replace a physician's ECG interpretation or diagnosis. If you have symptoms or a QTc of 500 ms or more, seek medical advice — and never stop an SSRI on your own.
How much does it cost?
A small one-time purchase on the App Store (US price $0.99). No subscription, no ads, no in-app purchases.