What Causes Tingling Sensation In Breast While Sleeping?

Dear Dr Rynne, Last night I was almost asleep until suddenly, I felt tingling sensation, as if a pin pricked my breastbone area and that woke me up. It happened twice consecutively. At that time, I was thinking it was possibly caused by my clogged nose which prevented me to breath through both my nostrils and had effect on my lungs. On the second thought, however, was this a symptom of an impending heart attack? My background: I had an elective heart bypass surgery four years ago. Since then, I see my cardiologist every three months who prescribed the following maintenance medicine: Atenolol(after breakfast), Aspirin(after lunch) , Atorvastatin(after dinner) and ISDN(one hour before going to bed.The latter medicine was added by my cardiologist only eight months or so ago when I started to feel the symptoms from time-to-time of what I came to know as angina pectoris after my cardiologist saw the result of a stress test she asked me to undergo. The past few days being a Christmas season, I tended to be careless in my diet, meaning, I ate some fatty foods here and there. Now I regret it. Going back to the pricking sensation, as I experienced it while I was lying on my back, I tried to sleep sideways and fortunately, I was able to sleep. When I woke up in the morning, I felt normal. However, I m still bothered though I have nt experienced it again since then. I just don t know when I lie down to sleep again tonight. Thank you.