Supposing you have a renal stenosis, what kind of affect does that have on the heart.

Question

What I do know:
- decreased flow to the kidneys
- kidneys assumes that overall blood volume have decreased
- RNN system is activated
- = increase in blood pressure (hypertension)

I'm having a hard time explaining how this all affects the heart. I know the kidneys are trying to increase blood volume so they start retaining salt but the volume of the blood is norma already. So you have an increased blood volume = increased blood pressure which I guess means the heart is under a lot more pressure because more blood is being pumped into the right atria? Could someone explain this to me. Thanks!