LONDON, UNITED KINGDOM. Atrial fibrillation (AF) is a common adverse effect following cardiac surgery. It is estimated that between 30 and 60% of patients are affected and that 10-year mortality is up to 48% higher among patients developing post-operative AF (POAF) compared to those who do not experience this complication. There is growing evidence that POAF is caused by oxidative stress and inflammation resulting from the trauma associated with cardiac surgery. The release of free radicals (superoxide, peroxynitrite, hydroxyl and hydrogen peroxide) during and after surgery depletes the body's endogenous antioxidants such as glutathione and thus increases oxidative stress. Several clinical trials have been performed to determine if vitamin C and E would arrest the progression of free radical damage and oxidative stress.
Vitamins C and E are chain-breaking antioxidants which scavenge free radicals and terminate the propagation of free radical reactions. Vitamin E is pivotal to maintenance of membrane stability, acting to prevent lipid peroxidation, whereas vitamin C independently scavenges water-soluble free radicals, acts synergistically with vitamin E and helps regenerate vitamin E.
Researchers at Imperial College now report that pre- and post-surgery supplementation with vitamins C and E does indeed reduce the incidence of POAF. Their meta-analysis included three randomized, controlled clinical trials involving 183 patients given vitamin C and E and 182 controls. The incidence of post-operative AF and flutter was 28% in the antioxidant group and 44% in the control group.
The overall incidence of cardiac arrhythmia was 24% in the antioxidant group and 36% in the control group in a meta-analysis of five randomized, controlled clinical trials involving 284 patients on antioxidants and 283 controls. The most common supplement protocol was 2000 mg of vitamin C prior to surgery followed by 500 to 1000 mg twice daily for up to 5 days following surgery. Vitamin E (400 to 600 IU) was given for 2 days prior to surgery and for 2 days following surgery or until discharge.
The researchers noted a significant decrease in the duration of time needed in the intensive care unit and in the overall hospital stay in patients who had received antioxidant therapy. They conclude that prophylactic use of antioxidant vitamins C and E significantly reduces the incidence of POAF and all-cause arrhythmia following cardiac surgery.
Harling, L, et al. Do antioxidant vitamins have an anti-arrhythmic effect following cardiac surgery? Heart, Vol. 97, 2011, pp. 1636-42
Editor's comment: Researchers at the Cleveland Clinic and Ohio State University have found that AF patients show signs of extensive oxidative injury to their myofibrillar creatine kinase (MM-CK). MM-CK is involved in the control of the contraction of individual heart cells (myocytes). The researchers also determined that the oxidative damage was caused by peroxynitrite, a highly potent free radical. They concluded that peroxynitrite-induced oxidative stress can damage individual heart cells to such an extent that their normal function is disrupted and AF results. Although not proven, it would seem plausible that supplementation with vitamins C and E would be beneficial for afibbers, especially pre- and post-ablation and maze surgery.