Several small clinical studies of coenzyme Q10 that have not been randomized indicate an improvement in physical activity. A nonrandomized, nonblinded, four-week study of 1715 patients reported improvement in symptoms and quality of life. A longer study using 100 mg daily for over 6 years reported improvement in ejection fraction. A small study suggested degeneration in symptoms and hemo-dynamic features on discontinuation of the enzyme. A randomized study without placebo control in 806 patients showed improvement in functional class and heart failure symptoms over a 6-month follow up.
The results of a few small double-blind, randomized placebo-controlled trials are given in Table 1. In most of the studies involving less than 50 patients no reasonable conclusion can be drawn. In 1993 the largest double-blind, randomized study involving 591 patients followed for one year showed hospitalizations were decreased with the enzyme; 40% versus 20% for placebo ( p < 0.001). The enzyme group had fewer patients with pulmonary edema, 20 versus 51, and cardiac asthma, 97 versus 198 ( p < 0.001). There was no difference in survival between the two groups. More recently studies with less than 55 patients receiving optimal heart failure therapy showed no differences.