Magnesium seems like a better guess and seems to not have been studied for aortic stenosis though it does help with vascular calcification.
https://www.ahajournals.org/doi/10.1161/ATVBAHA.117.309182
Especially since heart murmur is a symptom of aortic stenosis and magnesium is critical to regulation of the heartbeat.
https://www.mayoclinic.org/diseases-conditions/aortic-stenos...
https://health.clevelandclinic.org/magnesium-for-heart-palpi...