Hello...
Rarely, Erythromycin has been associated with the production of ventricular arrhythmias, including ventricular tachycardia and torsades de pointes, in individuals with prolonged QT intervals.
I stress that this is a very rare event. If you do not have LQTS, and there is no family history of sudden cardiac death than I would not pay attention to what you may have heard. If this is your 6th time on it this year, then I think it is safe to assume that it will not affect your rhythm in any adverse ways.
It is not wise to discontinue medication without the approval of your Dr. I hope that I helped relive some of your fears surrounding this:)
http://en.wikipedia.org/wiki/Erythromycin
It says things like that are rare and under Interactions it talks more about that.