Enable Alt Key Macros in LaTeX-Suite

In the vim latex-suite, there are some alt key macros should be available by latex-suite reference. However, I tried several times but it only output ¬, ∫, ç and ˆ for some reason.

Today I found that just adding set macmeta in .vimrc will work. It enables the mapping of meta key (alt/option) in macvim.