Thanks for your question on Health Care Magic. I can understand your concern. Colon pathology is unlikely to cause throbbing pain in left sided chest. So no need to worry for colon related problems. Your cardiac work up is also normal, so possibility of anxiety related symptoms are more. Anxiety and stress causes tachycardia and this can give you symptoms of throbbing pulsation in left chest area. So better to consult psychiatrist and get done counseling sessions. Try to identify stressor in your life and start working on its solution. You may need anxiolytic drugs too. So avoid stress and tension. Be relax and calm. Don t worry, you will be alright. Hope I have solved your query. Wish you good health. Thanks.