Nicorandil is a unique drug in that it has two effects on the heart. It is used in angina.
The first, and most important, is that it inhibits a specific channel called the KATP channel, in the heart. This is most marked in the coronary blood vessels and less so in the peripheral vasculature. In essence, it dilates coronary blood vessels, but there is also evidence that it acts in a more specific way. It appears that the opening of the KATP channel in the mitochondria, is cardio protective.
Like nitrates, it can cause a headache when you first use it. Interestingly, if you are on the diabetes tablet Glibenclamide, Nicorandil does not work.