I Am A Month And A Half Out Of A

I am a month and a half out of a quintuple bypass. I am a retired police officer. The last twenty years of my career were spent as a bomb and arson investigator. When I retired in 2009 I transitioned into the private sector specializing in fire and explosion investigations. Very toxic scenes. I was at a fire the other day and the first time I got out of the truck my pulse dropped to 34 and stayed between 34 and 36 for 10 minutes. I knew something was wrong and had a monitor in the truck and watched it until it got back into the 70's. The next two times I got out of the truck I went into SVT's (two times) Highest rate was 180. I have had SVT's for years. They dont freak me out but I will say they generally occur in heat not cold. I am taking diltiazam for the SVT's. If this to be expected? Am I trying to work to soon? The ER doc at a small rural clinic said extreme temperatures will screw with the electrical signals to my heart after this kind of surgery. I have an appointment with my general tomorrow who I am sure will call my cardiologist. I'm just curious what may be causing this consisted pulse rate issue in extreme cold. The ER doc said I may need a pacemaker which is not uncommon. These are all things my doctors have not told me to this point.