Hmm - not sure about that sheila99.
The 2016 BMS/Women's Health Concern gives some info with lots of refs (I don't have time to look at them!) and discussion about stroke, cardio-vascular health and HRT and says this:
"Evidence from large observational studies has shown that transdermal administration of estradiol is unlikely to increase the risk of stroke above that in non-users and is associated with a lower risk of stroke compared with oral administration of estradiol."
https://journals.sagepub.com/doi/full/10.1177/2053369116680501As I expect you know observational studies are not the same as trials so you may well be right ie that there haven't been any specific research trials into this. Maybe someone who has time to delve into the literature can enlighten us but I woild have thought that if something has been published it wold be in that paper - unless something new in the last 3 years?
Hurdity x