What Causes Low Heart Rate Along With Dizziness?

My husband has been having a low heart rate along with very light headed feelings. At the same time his blood pressure was a little high even on the blood pressure meds. . He has a 70% blockage in one of his main arteries, (left Coronary) and has an unusual heart rhythm for a long time but has done pretty well with his PVC s. Our concern is the very light headed feeling with the low heart rate and yet high blood pressure.