Talk to Ent Specialist on Synus Tachycardia

Iam diagnosed with sinus tachycardia now I have improved my diet so that I am feeling a positive change in my health but still IAM facing symptoms like headache,lightheadness,tiredness, uncomfatablness in lower region of head,neck and shoulders, pain and uncomfatablness in my legs also IAM 19 years I take beta blockers?is beta blocker safe for my age group?is metoprolol save to use ? is there any test required for identification of cause like echo or any other test?