Magnesium plays a key role in cardiovascular health. Along with Vit E, I knew a man who reversed CHF with this combination. He used UltraMag from Source Naturals and the best vitamin E you can buy, A.C. Grace. It is important to read the dosing instructions on their site (AC Grace).
Calcium channel blockers are needed b/c calcium becomes too high relative to magnesium. If you raise magnesium then calcium drops. High calcium is known to cause trouble because of its magnesium suppressing properties. There are many studies posted on NIH Medline concerning this .
Magnesium also plays a pivotal role in potassium balance. It also plays a role in sodium. Sodium is intracellular while potassium is extracellular meaning potassium has a relaxing effect on the cells while sodium constricts. The same holds true for cal/mag balance.
It is best to check mineral status through a lab such as Trace Elements which can be done cost effective. This will give you some readings on the mineral balances. Serum testing of minerals is problematic and generally not a good measure of minerals stores in the body.
HeartCare from Himalaya is a good product you might want to speak to your doctor about. It contains many boosting herbs including arjuna which has been used by Ayurvedic medicine for a long time.
And as the other poster stated, Vitamin C is perhaps a miracle.