Hi. I am a 15 year old female. Throughout the course of my life, I have had short episode in which I feel my heart somewhat stop, and compress, and I struggle to breathe for the next minute. These episodes last about 3 to 5 seconds, and I feel just fine after that. This has happened maybe about 20 times in my life (for what I can remember, maybe starting since I was 8) , and I walk around just fine. I also tend to get dizzy when I get up, maybe about once a month or so. What is this? Is it an early part of heart disease, or could this be an early symptom of heart failure? Please help!