Experiencing Arrhythmic Tachycardia, Had An Episode Of Low Heart Rate With Severe Cramps In Legs. Cause?

Greetings: For many years I have experienced arrhythmic tachycardia . I can easily reduce my heart rate by quick pressure on my solar plexus. (I assume this sends impulses via the vagus?) I am a 71 year old male and very physically fit; canadian and international badminton player. The anomaly was last week when I was snowshoeing and this occurred. I could not correct it so that my heart rate slowed. What was also different was that my leg strength was also affected and I got 2 severe cramps in both legs which I would call my vastus medialis muscles; a circulation symptom?. To make a long story short, I went out by snowmobile and checked into a hospital. By this time my condition was normal ie EKG , BP , pulse. So now I am curious about the possible cause of this extended tachycardia? On this weekend, I played 29 badminton games in a tournament, and no problems. I would appreciate your thoughts. Regards, David