Answer :
Well with blocked vessels, lets use plaque buildup as the reason for blocked vessels. It's Like trying to match together two puzzle pieces that don't fit. The piece if forced together, will be a tight fit much like how blood cells/platelets trying to fit through a small area. The pressure will be increase because the more pressure that is being put on will help to push blood through a clotted area.
The blood pressure will increase and low amounts of blood will reach the diff organs