You post under the subject "arrhythmia" but you do not mention any PVC, PAC, AFib or Flutter in the heart study you underwent. That being the case, then it seems you do not have an arrhythmia, again except for what I already mentions. That is a sustained (unexplained) HR of in the area of 160 is tachycardia, and needs attention. At your age a HR of 160 when exercising is just in the aerobic-zone, no problem if you are exercising. No problem even if you're not exercising if it passes in a few minutes.
It seems reasonable to get a second-opinion (medical) - best if a cardiologist. Or, to discuss further with your current doctor and ask what are you being treated for. In the absence of any substantive reason you could ask that you stop taking the medication and will keep a close watch on and for any new symptoms. That is, you do not appear from what you have posted, have any serious symptoms to deal with.
I am 18 years old and the main concern about taking this drug is about the long life time taking drug. Drugs costs are completely not a concern for me. The main concern is that i am afraid that the diagnoses was wrong and i might start by mistake with this course of medication.
Every since i have known about this problem i have started being worried about my heart even i could not sleep. if you have any advice for me please i look forward to hear it.
Many thanks
The lack of response here is due at least in part to the fact that none of us are about to make recommendations contrary to those given by your doctor.
That said, the only thing you report in your post that raises a "flag" to me is the HR of 162 (you didn't give your age, but high regardless) which should not happen unless there is some stress, either physical or emotional, that causes the heart to increase. I suppose an average HR of 85 is a bit high unless you are very active, not sitting at a desk 8 hours a day or something like that would give you many hours of resting HR time. A full rest/sleep HR of 55 looks real good to me, you must not be having troubling dreams.
I am not sure what your concern about medications are. Cost? many are available in generic forms which are much lower cost...or perhaps you are very young and it is troubling to think of a long life-time taking a drug.
Many of us are on regular drugs for life. I take both a statin and an anticoagulant that I will most likely be on for the rest of my life, well I'm now also on a beta blocker.