I'm also curious as to why a pacemaker hasn't worked. A HR of 25 can cause anything from being unconscious to dizziness, altered mental status, shortness of breath, and so on. I have seen somebody have a HR in the 20's due to a 3rd degree block and they were in their early 80's and symptom free but they only had to sustain that rate for a couple of hours before receiving pacing. I've also seen the other end of the spectrum where the individual was unresponsive. I would also wonder if the slow HR would put them at an increased risk of stroke due to blood having more time to sit around in the heart and possibly start clotting. Do you know why his HR is so slow? How old is he and does he have any other medical problems? Is the HR at that rate an issue for him now?
There's a lot to consider in order to give you an answer. How well is his heart pumping blood? what is his ejection fraction? What's his age? Why isn't the pacemaker working?
Are you sure you mean his pulse rate or are you talking about his ejection fraction?
As an example, hyper-trained athletes in their 20s can have resting pulse rates in the high 20s, the record is 27. That's great for them. But if someone is 70, even if they were very athletic with a wonderful heart, I can't imagine them having a resting pulse this low and still be conscious.