I had an ICD with a pacemaker implanted in Aug 2013. In my case it was for an arrhythmia (Ventricular Tachycardia) not bradycardia. I went in for an ablation to correct the V Tach but they were unable to totally fix it so I was told that it would be unwise to go home without the ICD (Implanted Cardiac Defibrillator) implanted since that type of arrhythmia can result in death. To put it mildly I wasn't happy about it but the alternative well you see what I mean. In any event I was told it was like having an EMT with with me 24-7. I was cleared to resume cycling but to moderate it.
About a year later I was taking medication for an unrelated condition but the meds exacerbated the arrhythmia and the ICD fired more than once. Always happened when I was riding so I limited my riding to thee trainer until the treatment for the other condition was finished.
Just about a year ago I had a second ablation that was successful. I haven't had an issue since then. Being able to continue cycling was very important to me and I stressed that point with my cardiologist. He really worked with me and respected my priorities. Now I'm riding over 9000 miles a year with a lot of intensity. You have to work with your Doc but it seems to me that you should be able to get back to it with a pacemaker it's actually safer than riding without one. At least in my case it was.
You might want to check out this link. Pacemaker Club - Support & Information For Pacemaker & Defibrillator Patients
Best of luck.