Hi welcome to HCM I have gone thru your query regarding heart palpitations . Palpitation is a perceived abnormality of the heartbeat characterized by awareness of heart muscle contractions in the chest: hard beats, fast beats, irregular beats, and/or pauses As you have described you have had palpitations off and on for about 20 years . Otherwise your tests are normal and have good health . That s a good sign . Still you have palpitation , which is of and on , so your doctor is right to advise you not to worry . For your info , extra-cardiac stimulation of nervous system, particularly the vagus nerve as a captain , plays a role in controlling the speed of the ship-of your heart , can cause anxiety and stress due to acute or chronic elevations , distress such as bloating or indigestion, along with muscular imbalances and poor posture, can also irritate the vagus nerve causing palpitations . If I were your doctor I would have suggested you that there are some reasons for every happening and you should observe your life style and food habits and removing the cause will help you to be normal . To avoid anxiety and stress due to acute chronic elevation gastrointestinal distress such as bloating or indigestion , include balanced diet -fiber vitamins, minerals in natural form and antioxidants as turmeric powder , Aloe vera juice ,Amla, ginger, garlic to balance your air factor in your body & having essential nutrients and regular physical activity- for proper blood circulation , pranayam -deep breathing ,Yoga, Meditation , proper rest , sound sleep , sufficient hydration will help you remove your worry . One thing I suspect side effects of your Atenolol may be one of the causes I would like to suggest you to consult your doctor and take his advice . Hope this helps solve your query .Take care .All the best