My Husband Had A Pacemaker Inserted About Three Years Ago...in

My husband had a pacemaker inserted about three years ago...in the last thre months he has started having a burning sensation around his pacemaker in his shoulder. The maker of the pacemaker is St. Jude...if he drinks coffee it seems to subside, his pacemaker is working 85 percent of the time.. wondering if this could be a problem with the pacemaker itself or a problem with the heart. He counted 22 times of extreme burning in one day..we have contacted his doctor but the appointment is still more than a week away. the burning sensation is scaring both of us and we are concerned as to wheat her the pacemaker will stop working before we actually see the doctor. do we need to be so concerned??