Fitbit app is showing lower heart rate readings than my Blaze itself

[Clubgregory5]

My FitBit routinely shows a much higher heart rate than my app records on the graphs. My app is updated and device regularly synced. I have postural orthostatic tachycardia and my heart rate will rise and fall very quickly. For example, last night I had an episode and my heart rate was 136 while sitting. I immediately synced with the app, and I watched my heart rate on the device quickly rise and fall a few times before stabilizing at 80. My app showed a rise to 104. Getting out of the shower my heart rate was 156 and the app recorded 120. I wonder if my heart rate changes are so fast that some algorithm decides the data is junk and doesn’t record. It’s incredibly frustrating as I can’t seem to capture a record of the tachycardia. Instead I’m constantly taking photos of the device, and I’ve done so alongside the app. My two kids with the same condition are having the exact same issue. Any ideas of what is happening?

Moderator Edit: Clarified subject

[Rich_Laue]

This could happen because the watch shows a real time readout and the app shows an average over, I think 5 or 10 second periods.