Alternate theory: most deadly heart attacks are reported on a Monday, because that's when the admin assistant tasked with doing the paperwork gets around to clearing out the backlog. And since most reports don't include the actual time of death, Monday 08:02 it will be...
Well, I certainly changed my mind now! Sorry, that was sarcasm, I know this isn't Reddit... Anyway: so I tried to track down the actual paper being presented (since the linked article, of course, does not cite that). No luck. Lots of clickbait re-peats and re-re-peats. But I guess you have the link and will gladly provide it?
Here you go:
https://heart.bmj.com/content/109/Suppl_3/A78.abstract(I searched 'Laffan cardio monday' on Google Scholar, Laffan was quoted as lead author in OP.)
Your argument at least in its current form seems not to hold - there's higher incidence over the weekend too.
Thanks! This still seems to be just an abstract, though, and I was unable to find any details about the actual method of data collection. Been downvoted enough for today, though, so...