Husband Has H/R Of 57/min. Has SOB When Climbing Stairs,

husband has H/R of 57/min. Has SOB when climbing stairs, can not function outside doing normal yard work. Is having dizzy spells & chest pain just walking without exertion. Has had open heart, 3 stents for blockage. all are patent. No MI has been established. High BP is not an issue. Cardiologist wants to keep his HR low. I am concerned it is too LOW causing his fatigue, chest pain & inability to function. Should we considered a 2nd opinion? I'm worried his slow HR may be causing his symptoms. Current drugs are as follows: Losartan, Toprol , Plavix, baby aspirin, Isosorb, calcitriol, Glipozide.Please advise .