My 73 yo father's heart rate is 105 but his blood pressure is normal. should we be worried?

Elevated heart rate: Heart rates - assumed at rest - of 105 BPM in a 73 yo person are usually abnormal. I would recommend seeing his primary care physician for an ecg. If intermittent, he may need to wear a monitor. This could be an abnormal heart rhythm that needs treatment or elevated normal rhythm because of some other underlying medical problem.