That doesn't sound very good. If you think your symptom is related to your heart, you really should call your doctor and/or visit an urgent care clinic.
Another thing to consider is that sometimes breakthrough acid occurs despite the PPIs. I've taken a double dose of aciphex for years now, but I usually have to supplement with Zantac OTC because the PPIs aren't perfect (gosh, they're good, though, aren't they?).
I hope you figure out what it is soon, and you start feeling better.
Current dx: Rheumatoid Arthritis
Suspected dx: Early Lupus/MCTD
Current Meds: Enbrel, Plaquenil, Aciphex, Ultracet, Zyrtec, Allavert-D, Zantac, Tylenol PM
Past Meds: Relafen, Vioxx, Mobic, Voltaren, Sulfasalazine, Entocort, Prednisone, Humira, Reglan