Randomized trials have suggested that folic acid may not have any beneficial effects for preventing heart attacks especially a second episodes. However in a meta-analysis published Wednesday (2/2/11) Wald,et. al. suggest that previous studies have failed to account for the use of aspirin by study participants. The authors suggest folic acid could be a part of a preventative measure to reduce first attacks but not second due to the use of aspirin by those suffering from a previous attack.
The study was published online as part of the PLoS site, an open access peer reviewed site. You can download the study in its entirety here;
Wald DS, Morris JK, Wald NJ (2011) Reconciling the Evidence on Serum Homocysteine and Ischaemic Heart Disease: A Meta-Analysis. PLoS ONE 6(2): e16473. doi:10.1371/journal.pone.0016473