Thanks for your question on Healthcare Magic. I can understand your concern. Pulled sternal muscle can not cause chest Heaviness and heart beating louder. In my opinion, we should first rule out heart diseases for your symptoms. So get done ecg, 2d echo and stress test (trade mill test). If all these are normal then no need to worry for heart diseases. Sometimes, stress and anxiety can also cause similar symptoms. So avoid stress and tension, be relax and calm. Apply warm water pad on sternum. Take simple painkiller and muscle relaxant drugs. Avoid heavyweight lifting and strenuous exercise. Don t worry, you will be alright with all these. Hope I have solved your query. I will be happy to help you further. Wish you good health. Thanks.