Background: Geographical differences in patient characteristics, management and outcomes in heart failure (HF) trials are well recognized. The aim of this study was to assess the consistency of the treat- ment effect of coenzyme Q10 (CoQ10) in the European sub-population of Q-SYMBIO, a randomized double-blind multinational trial of treatment with CoQ10, in addition to standard therapy in chronic HF. 

Methods: Patients with moderate to severe HF were randomized to CoQ10 300 mg daily or placebo in addition to standard therapy. At 3 months the primary short-term endpoints were changes in New York Heart Association (NYHA) functional classification, 6-min walk test, and levels of N-terminal pro–B type natriuretic peptide. At 2 years the primary long-term endpoint was major adverse cardiovascular events (MACE).

Results: There were no significant changes in short-term endpoints. The primary long-term endpoint of MACE was reached by significantly fewer patients in the CoQ10 group (n = 10, 9%) compared to the placebo group (n = 33, 27%, p = 0.001). The following secondary endpoints were significantly improved in the CoQ10 group compared with the placebo group: all-cause and cardiovascular mortality, NYHA classification and left ventricular ejection fraction (LVEF). In the European sub-population, when compared to the whole group, there was greater adherence to guideline directed therapy and similar results for short- and long-term endpoints. A new finding revealed a significant improvement in LVEF.

Conclusions: The therapeutic efficacy of CoQ10 demonstrated in the Q-SYMBIO study was confirmed in the European sub-population in terms of safely reducing MACE, all-cause mortality, cardiovascular mortality, hospitalization and improvement of symptoms.