It depends. Some people use salt substitutes to help cut down on their sodium intake. Less salt (and less sodium) is good for high blood pressure
. Most of these salt substitutes contain potassium.
However, many blood pressure medications will naturally increase your potassium levels. Which may be where you may get the idea that it is a good thing. But potassium levels that are too high can be very dangerous - leading to fatal heart arrhythmias.
Bottom line - salt substitutes are a good choice. But if you are on any medications for your heart, be sure to talk to your pharmacist FIRST.
Hope this helps!