World Heart Day: Sending Your Smartwatch ECG to a Doctor? Export the PDF, Don't Screenshot It

If you're sharing a smartwatch ECG with a doctor, send the PDF export from your health app, not a screenshot. The PDF contains the full recording, the date and time, and the app's classification, laid out on a proper grid a clinician can read. A screenshot usually has part of the trace and none of that context, and after a messaging app has compressed it, the waveform can become too blurred to interpret.

World Heart Day, run by the World Heart Federation, falls on Tuesday, September 29. It's a good time to do this one small practical thing: find the export button on your watch's health app before you're sitting in a waiting room trying to work it out.

This isn't medical advice. If you have chest pain, shortness of breath, fainting or other emergency symptoms, call emergency services. Don't take a watch reading first.

What a Smartwatch ECG Is, and Isn't

A watch ECG is a single-lead recording, usually 30 seconds long, taken by touching the crown or a sensor with your finger. The FDA has cleared features on Apple, Samsung, Google/Fitbit and other watches to check for signs of atrial fibrillation (AFib), an irregular rhythm that raises stroke risk and can come and go, which makes it hard to catch during a clinic visit.

That's exactly why clinicians sometimes ask to see these recordings. If you felt palpitations on a Tuesday night and recorded them, that trace may be the only record of the episode. But a single lead is not the 12-lead ECG done in a clinic, and it can't detect a heart attack. It's a clue for your doctor to interpret, not a diagnosis.

Why Screenshots Fail

The information that makes an ECG readable is fine detail: thin waveform lines, a background grid of small squares, and the timing between beats. A screenshot runs into three problems:

1. It's partial. Most apps show a scrolling or compressed view. A screenshot captures a few seconds of a 30-second trace, and not necessarily the seconds that matter.
2. It drops context. The date, time, heart rate, the app's classification ("Sinus Rhythm", "Atrial Fibrillation", "Inconclusive") and any symptoms you logged may be on a different part of the screen or missing.
3. It gets compressed. Send a screenshot through WhatsApp, Messenger or SMS and it gets recompressed, often as a JPEG. JPEG handles photos well and thin lines on a grid badly. The waveform picks up blocky halos and the small grid squares blur together.

How to Export the PDF

Apple Watch (Health app on iPhone): Browse, then Heart, then Electrocardiograms (ECG). Tap the recording you want, then Export a PDF for Your Doctor. Use the share sheet to send it to your patient portal app, save it to Files, or print it.

Samsung Galaxy Watch (Samsung Health Monitor app): Open the ECG history, select the recording, and use the share option to create a PDF.

Google Pixel Watch and Fitbit: The ECG results in the Fitbit app include an option to download or share a report of the reading. The exact menu path varies by app version.

The same applies to blood pressure. Most connected cuffs and their apps can export a log as a PDF or CSV. One tidy table covering two weeks of morning and evening readings is far more useful to a clinician than 28 separate screenshots.

If You Have to Send an Image

Sometimes an image is all a portal or a form will accept. In that case:

• Use PNG, not JPEG. PNG is lossless and keeps thin lines and grids sharp. If you need to make a JPEG screenshot smaller, convert it to PNG rather than compressing it harder.
• Don't crop the grid or labels. The grid squares are the scale that makes the waveform measurable. Leave them in, along with the date and the result text.
• Rotate the phone so the trace fills a landscape screenshot, and take several overlapping screenshots if the full trace doesn't fit. Number them in order.
• Check file size before uploading. If the portal has an upload limit, resize PNGs to about 2000px wide instead of converting to JPEG. At that width the lines stay sharp and the file usually drops well under 1 MB.

Send It Through the Right Channel

Heart recordings are health information. The safest route is your clinic's patient portal or another method your care team recommends, not a group chat, a social media DM or a personal email thread you don't control. Portals attach the file to your record, where the next clinician will find it, instead of leaving it in someone's inbox.

And before you share any image, check that it contains only what you intend to share. A screenshot can capture notification banners, other health data on the same screen, or your full name and date of birth when you only meant to send the trace. If an image carries device details or location you don't need to send, remove the metadata first. The PDF export avoids most of this, because it contains only what the app puts into the report.

One Thing to Do This Week

On World Heart Day, open your health app and find the export option, even if you have no recordings worth sending. The day you actually need it, after an episode of palpitations or before an appointment, isn't the time to be working out menus. Knowing where the PDF button is takes two minutes and could make the recording that matters readable when it counts.

Related reading:

• Telehealth HIPAA Image Compliance 2026: how clinics handle images patients send
• Flu Season 2026: Pharmacy Vaccine Record Photo Guide: keeping another health record readable
• PNG vs WebP for UI Design Assets: why lossless formats keep thin lines sharp