Heart rate graph is not accurate

[DecHannigan]

I wake in the early hours, with heart palpitations,  my watch face reading is often 80s or 90s heartbeat, 

When I check the cardiac graph later it has normal readings of 50s and 60 heartbeats..​The two readings don't correspond at all.. 

Moderator Edit: Clarified subject

[LZeeW]

@DecHannigan   The heart rate that is shown in the heart rate tile is averaged over five minutes.  It's possible that these palpitations don't last long enough to be reflected in that graph.

[DecHannigan]

Possibly, but I have sometimes noticed if I stand up fast from a sitting position, the heart rate often registers a steep rise and fall, all within  a few seconds .. Also the graph often doesn't appear at all in the early a, hours after midnight.