Sinus bradycardia means you aren't in arrhythmia, so that's good. It could also mean, technically, that your heart beats on average only 50 times per minute when at rest. Or, it could mean that when you are being tested on a treadmill that your heart is both slow to raise its rate and that it doesn't raise its effort to sustain you sufficiently, maybe only climbing to 65-75 beats a minute instead of the needed 115 beats per minute. So, without our understanding of what your bradycardia 'looks like', it's hard for us to offer much to you. In fact, technically any resting HR lower than 60 BPM is officially in bradycardia territory (some cardiologists have begun to question the wisdom of this too-high number and think that bradcyardia is really only at 50 and below).

A pacemaker is designed to speed your heart rate into 'normal' territory. They don't normally slow a heart rate unless the heart is solely reliant on the pacemaker and the AV node has been destroyed via an ablation. In that case, the pacemaker is all that keeps the heart beating and the pacemaker must adjust per the effort required by the host.