While Drifting Off To Sleep I Felt A Distinct Zigzag

While drifting off to sleep I felt a distinct zigzag pattern on my breastbone, then a few minutes later my heart inflated like a balloon!! Then a few minutes later it inflated like a balloon again, then after a few minutes as I was drifting off to sleep it inflated like a balloon again!! Although it was not painful it was a distinct inflation of my heart muscle. The first time I ever felt my heart in such a way!! It happened on the night of the day I had taken a breathing test at the hospital. What was this??