Yes they can be slowed down or even stopped by medications such as beta blockers or other antiarrhythmics, but the problem is that these medications can cause further slowing of you slow heart rate and worsening of your apathy and general lack of energy, Hence you need both these medications to slow down the fast rates and the the pacemaker to prevent the slowing of the heart rate any further.
Having a Pacer inserted was the best decision I ever made. Since having a pacemaker inserted, I've had a huge surge of energy. Procede with confidence, it will change your life.