If it's a PVC event (Premature Ventricular Contraction) it is quite common. I have it and yes, it's very scary but my Cardio guy said nothing to worry about. Any EKG will pick it up if you have one done.
Do you notice them when your maybe tired or upset about something? I seriously doubt your heart will "explode" but it sure feels that way huh?
Keep an eye on it and see if it happening any certain time of the day or night or after certain foods are eaten. Naturally if it keeps up, get an appt, with a Cardio person even if just for reassurance.