What is one result of decreasing blood flow to the heart or brain?

Depends upon whats the level of restriction

If there is a little decrease in blood flow in the brain,it leads to  headaches ,dizziness , confusion  

If there is little decrease in blood flow in the heart it can cause chest pain or what we call angina

But if there is clogged vessel of the brain ,it can cause stroke because the part of the brain the vessel is supplying will become ischemic or deprived of the oxygen and nutrients

Similarly if the artery supplying the heart gets clogged ,it leads to heart attack ,the reason being the same that the tissue of the heart become ischemic .

ia. mver.y..sor .r..yinee..i am.ina.rush.pleas eforg.ive   meiknowiama. nas.s holei apalo.gize