Doctors said that CoQ10 (coenzyme Q10) and selenium are essential for cells, and low levels can weaken the heart muscle, but there are few studies testing this.In one trial, 443 men and women, aged 70 to 88, took 200 mg of CoQ10 with 200 mcg of selenium yeast per day or a placebo for four years. After five years of follow-up, the CoQ10 with selenium group experienced a lower rate of heart disease mortality (5.9%) compared to the placebo group (12.6%). 

Reference: International Journal of Cardiology, 2012, May 23, Electronic Publication.