PAC's causing episodic Bradycardia?

I am a RN 54,female post-menopausal, h/o HTN x30 yrs,multinodular goiter(labs wnl),mod active but no formal exercise.. H/O anxiety & panic atacks but not in recent yrs. IBS, and GERD.Meds Tenormin 50mg for BP and IST, Aciphex, occ K+ 20Meq (used for documented K+ loss when IBS bad
In 2003, w sudden position change- had irreg HR w chest tightness,SOB. No CP,No dizziness.  To ER=Dx 2nd degree AV Block,RBBB HR 38-45, in hosp x 5 days, tenormin DC'd. Cardio thought might need pacer. On 3rd day of no tenormin HR shot up to 180's.Narrow QRS complex SVT.  Had EP done-High grade AV Block, RBBB, IST. Could not reproduce rhythms. Back on tenormin and home. (said I should never need pacer, non life-threatening, come back if it continues freq)
had 5-6 episodes since 03-same sx  brought on suddenly w pos chge, heavy meal,etc. 4 trips to ER told K+ low 2.7 on these occ, multiple PAC's (causing the bradycardia?)
Well it happened again. Same symptoms, except this time lasted longer K+ ok, rate fluctuated between normal 70-80, to 45-55 brought on by minimal movement i.e. twisting, standing, had same uncomfortable symptoms.  The 1st EKG showed theAV & RBBB , low rate,etc, 3 hrs later the EKG was "perfect" per the ER Doc.  I went home w orders to see Cardio.  The symptoms have persisted off and on x1 wk-stairs are a nitemare rate drops, chest tight, sob, then flips back to normal rate and sx disappear.
Echo done 6/2007 was normal. 30 day event monitor 4 yrs ago showed occ runs a-tach, occ  pvcs/pacs, 1 short run svt.  My new cardio said we caught it red-handed this time on a rhythm strip-I had 2 things going on the 2nd degree AVblock PLUS the PAC's and resulting Bradycardia??. I have EP study tomorrow, don't really know this Dr (now in Fl) worried he might want to ablate something and cause worse sx. 1) your thoughts please-can you "flip" in and out of symptomatic block? 2) Can high vagal tone last this long? 3)any other thoughts?  Thanks

[Michael J. McWilliams, M.D.]

1) your thoughts please-can you "flip" in and out of symptomatic block?

Yes you can have transient periods of block.  It is also possible to PACs that cause block in the AV node that results in bradycardia.

2) Can high vagal tone last this long?

If you second degree AV block type I and RBBB, I don't think it is caused by high vagal tone.  There must be some conduction system disease.  The real answer is in the rhythm strips and possible EP study.  High grade AV block usually requires a pacemaker but your EP told you he didn't think you would ever need one -- that one confuses me a bit.

I am not sure what you would ablate considering what you discussed.  Ablations are occasionally done for inappropriate sinus tach but this is always the last resort.

3)any other thoughts?

It is hard to say without seeing the EKG and rhythm strips what is going on.  There a lot of information but I would need to see the heart rhythm that is causing your symptoms to truly comment on options.

I hope this helps.  Good luck.