How To Treat Rapid Raise In Heart Rate And Chest Pain During Exercise?

Over the past several years, during exercise, I have suddenly had a rapid shallow heart rate and slight pain in the middle of my chest. This has occurred 4 times over many years and I routinely play soccer and ride my bike. Today after completing a strenuous 45 minute spin class and after a short warm down this occurred as I was getting off of the spin bike and it took me nearly 30 minutes to recover. past episodes I recovered in a matter of a few minutes and resumed exercise with no problems. I am now 51 years old, do not smoke, and am in good health. What are the possible reasons and what diagnostic steps should I consider.