No doubt HR monitors take on additional importance in older adults My first "known"Afib event was discovered after jogging on a warmer than usual Spring day.
I experienced the classic triple P-Wave which accounted for producing a 130bpm HR reading while at rest. Like many of you i still have terrifically low resting HR of 40-42 ......
For what it's worth - I would suggest using a HR monitor an mobile app that record HR over a period of time - but do it once in a while as you lay perfectly still.
In most cases - you should record a really flat HR for minutes at time that does not very by more than two or three BPM . If you have a result showing a resting HR jumping up and down by five or more BPM - you probably are in arrhythmia and highly likely to experience AFIB in the future. Dick Cranium is not a doctor but he does play one on the forums.....