if you ran 6:06 for 10mi 2 years ago then i assume you are no older than, say, 50. the fact that you’re out there getting a calcium score means you’re probably 50 or not far from one on one side or the other. so, i don’t want to get over my skis here. but since you brought up the question of heart health, and on the assumption this might bug you until you get to the bottom of it…
this could be a good time for you (again, simply based my experience and some men i know in my cohort) to think about a relationship with a cardiology group. this very forum, maybe 15 years ago, was one of the first places (maybe the first) to end-user-crowdsource the high incidence of arrhythmias among hard charging endurance athletes who’ve had the gas pedal to the floor for decades, such arrhythmias often beginning to express themselves roughly around age-50 plus/minus.
i have no idea why you’re struggling to run a 7min mile. maybe you’re anemic. maybe you forgot to tell us you’re 25lb heavier. that said, i don’t know that your garmin watch is the best device (tho maybe there’s functionality there nowadays with which i’m not familiar). in my own experience a kardia device ($79) will give you a medical grade EKG trace as often as you want. when you feel like poop sit yourself down for 2 or 3 30sec traces. maybe it’s afib. maybe it’s sinus rhythm with a bunch of premature ventricular contractions thrown in. maybe it’s some other kind of arrhythmia. just, when you click and message that trace off to your cardiologist now that doctor has some data other than a whiny patient who’s misdiagnosing indigestion. also an apple watch will give you some useful 24/7 data according to cardiologists to whom i’ve spoken.
you might have a blockage. notwithstanding your low calcium score. ask tom hampton about that. again, having a relationship with a cardiologist could help you forestall a problem. i have a friend who’s going through this. my age. is with kaiser in california. they were treating him in the most cavalier way. gave him an appointment to cardiovert him out of afib in 2 months. why worry about afib? how much heart function do you need to sit and watch judge judy all day? which is what you do when you’re 68 years old, right? (so, we got that straightened out.)
if it turns out that your slow runs are the effect of age welcome to the club. or because you had a thyroid condition. it’s still not going to hurt you to establish a relationship with a cardiology group and best to do your homework and pick the right group before it becomes an emergency. for me, it was an emergency, and i started by picking the right electrophysiologists and that determined the medical group i would be with, since my problem was electrical rather than plumbing. i’m coming up on my 2yr anniversary of my ablation for afib.
if your cardiologist thinks you warrant a holter to check your heart’s function over a period of time i’ve had 2 brands: Zio by iRhythm, and ePatch by Philips. what you want is the one from Philips. both are a patch which you place on your chest yourself (they’ll mail you the kit). you shave that part of your chest and stick this thing on and its got to stay on for a week. the Zio came off during the first zwift ride. the ePatch stayed on for runs, rides, including indoor rides, for a week, no problem. but your cardiologist won’t know this because they have no real data on which is the better holter for folks who do what you do, so be an active participant on the process and ask here if you have any questions.
good luck. report back.