If you are using the Apple Watch to record an ECG, you can upload the reading to the Pattern app by sharing the PDF file generated by Apple.
Open the Apple Health app and select Electrocardiograms (ECG) card on the Summary screen.
Then, select ECG you would like to share from the list of previous ECGs collected.
Once the PDF is generated, you will need to click the share button in the top right corner to initiate sharing the PDF with the app. Then, select the Pattern app from the list of sharing options.
Note: that you may have to scroll to right in order to find the Pattern app.
If you do not see Pattern listed as one of your options, you may need to add it to this list (you should only have to do this once).
To do this, click on the More option and ensure that the Pattern toggle is green. Then tap Done.
Once you ECG has been shared, your ECG task will complete in the Pattern app and you will see the PDF in your History and completed tasks.