Heart Rate Fluctuations

[59withAfibEvent]

My resting heart rate us 42.

During a typical workday (Very Physical job) my heart rate fluctuates from 42 up to 120's.

One time it went to 155 and wouldn't come down. Had to go to Dr who sent me to Emergency to recieve a electric shock to reset my heart Rythum.

Since then never had another episode, but I'm concerned it may reoccur.

Is this Tachycardia a common occurrence?