Vitamin C for Postoperative Atrial Fibrillation Risk
September 1, 2018
Clinical Assistant Professor, Department of Family Medicine, University of Wisconsin; Clinical Assistant Professor of Medicine, Arizona Center for Integrative Medicine, University of Arizona, Tucson
Dr. Kiefer reports no financial relationships relevant to this field of study.
SUMMARY POINT
- The authors of a systematic review of 13 studies found convincing evidence that vitamin C supplementation, beginning before cardiac surgery and continuing for a few days postoperatively, can decrease the risk of atrial fibrillation.
SYNOPSIS: Vitamin C supplementation decreases the risk of developing postoperative atrial fibrillation.
SOURCE: Shi R, Li ZH, Chen D, et al. Sole and combined vitamin C supplementation can prevent postoperative atrial fibrillation after cardiac surgery: A systematic review and meta-analysis of randomized controlled trials. Clin Cardiol 2018;41:871-878.
Vitamin C, the water soluble ubiquitous nutrient, has many purported uses, to which the overwhelming number of articles on PubMed can attest. One interesting use, as per the recent systematic review detailed here, is for postoperative atrial fibrillation. It is a compelling problem to address; the authors mentioned an incidence ranging from 17-33%, with resulting complications, even though 80% of such patients return to sinus rhythm spontaneously. With a possible mechanism of oxidative stress, it would follow that an antioxidant, such as vitamin C, might have a role in preventing atrial fibrillation postoperatively.
Shi et al identified randomized, controlled (placebo or other control) trials in adults undergoing cardiac surgery, with vitamin C either as solo therapy or as adjunctive therapy. They reviewed 13 studies involving 1,956 patients. The primary outcome was the occurrence of postoperative atrial fibrillation; the pooled analysis revealed that vitamin C supplementation reduced the incidence of atrial fibrillation (relative risk, 0.68; 95% confidence interval, 0.54-0.87; P = 0.002), even more so when vitamin C was added to other therapies. (See Table 1.)
Table 1: Incidence (Relative Risk) of Postoperative Atrial Fibrillation When Vitamin C Supplementation Was Used Alone or in Combination With Pharmaceuticals |
||
Vitamin C supplementation |
Relative risk (95% confidence interval) |
P value |
|
All groups |
0.68 (0.54-0.87) |
0.002 |
|
Alone |
0.75 (0.63-0.90) |
0.002 |
|
With beta-blockers |
0.29 (0.16-0.53) |
< 0.001 |
|
With statins |
0.40 (0.17-0.96) |
0.040 |
|
With medications, combined |
0.32 (0.20-0.53) |
< 0.001 |
Furthermore, secondary analyses revealed that vitamin C supplementation led to shorter stays in the intensive care unit, less overall time in the hospital, and a reduced risk of adverse effects (not further specified other than advice that “high-dose intake of vitamin C should be avoided”).
The authors noted that there was a “moderate” amount of heterogeneity among the studies regarding methodology and a “moderate likelihood” of publication biases as per their statistical analyses, although the power of these tests was low because of the small number of studies involved. This systematic review nudges clinicians toward using vitamin C, either alone or in combination with typical cardiac medications, after cardiac surgery. These recommendations are qualified slightly by the heterogeneity and risk of publication bias, not unheard of for systematic reviews, and possibly not a “real” issue given the small number of studies included and the effect that has on the power of the statistical methodology. Furthermore, an article of this type does not tell us how to use vitamin C, that is, in what dose or for how long. To answer those practical questions, it is necessary to look to the individual studies, where there were a variety of approaches, including a range (1,000 to 2,000 mg) of oral or intravenous doses beginning one to two days before surgery and continuing for four to five days postoperatively.