Is cardiac neurosis or cardiac anxiety curable and whats the treatment and are they life threatening im 23 my ecg says i only have si us tachycardia and my echo is perfect my blood test is normal im smoker but i quit and i stopped caffeine completely?

It is not feasible to provide an opinion without additional history, physical examination may be some tests. It would be prudent to see your doctor to see if you may be depressed. Depression is treatable. Counter-intuitive as it may seem, exercise may help. Start with low intensity exercise such as walking and gradually increase the intensity as tolerated. Drink more water. Wish you good health!

I assume you don't have an overactive thyroid. Cardiac anxiety in the absence of cardiac pathology is best treated by reassurance and stress management therapy administered by a qualified mental health professional. Avoid alcohol which can also cause sinus tachycardia.