What possible hazards can be expected for my untreated bradycardia if I don't get pacemaker implantation?

Bradycardia. Bradycardia can cause dizziness, fatigue, near-fainting, fainting, shortness of breath, chest pain, and confusion. Some young healthy people have bradycardia but no problems related to it. For other people, the low heart rate can produce the symptoms mentioned and can require treatment, such as a pacemaker. You should discuss with your doctor.
It depends. It depends on how slow and what the rhythm is , but fatigue , dizziness, and fainting are possibilties.