SVT or sinus tach?

  My 35 year old sister has been diagnosed with esophageal reflux. Although I have also posted a question in the GI section, I have some specific questions pertaining to her cardiological evaluation. A year ago, she began having episodes of fast heart rate, which lasted several hours. She was seen at the emergency dept. for two of these episodes. The heart rate got as high as the 150's at which point she was dizzy and having some tightness in her chest so she was given medication to bring it down. The opinion of the doctors who saw her was that it was very fast sinus tachycardia and not SVT (because of the presence of normal P waves in her EKG). The second time this happened, also lasting several hours, the doctors observed her heart rate jump from 100 to 150's from one second to the next. Still, because of the P wave it was ruled a fast sinus tach. She was put on beta blockers but when she started experiencing shortness of breath on them she was referred to a thalium stress test. The thalium test was normal. She also wore an event monitor for 2 weeks and it registered some sinus tach but she did not have one of her "episodes" during that time. She hasn't had one in about 5 months but since then she has begun experiencing chest pain resembling angina, substernal, radiating to the inside of both arms and to her jaw. The pain is sometimes triggered by exertion but not consistenly and it is mostly triggered by stress. A 12 lead EKG after such an episode was normal and she was prescribed Prilosec, since her dr. is assuming she is having esophageal spasms, rather than angina (a GI cocktail relieves some of her jaw pain but not all). He thinks her heart is great, based on the normal thalium and doesn't think she is a candidate for cardiac cath. She is considered low risk because she is thin, pre menopausal, non smoker, non drinker, normal blood pressure and normal cholesterol, no significant family history. She was diagnosed, with an echo, years ago, as having MVP. My questions are:
  1) Is the diagnosis of esophageal reflux instead of angina a resonable one, under the circumstances?
  2) How accurate is the thalium stress test? In her case, are the chances of heart disease low enough not to warrant a cath?
  3) Is the diagnosis of sinus tach instead of SVT, based solely on the presence of a normal P wave, reasonable?
  Thank you,
  Octavio
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Dear Octavio:
I would feel better about the diagnosis of esophageal reflux if there were a test, such as an upper GI series, that supported the diagnosis.  I prefer having hard data, instead of assuming that she has reflux.
Based on what you have written, her chances of having coronary artery disease are very slim.  If the thallium you refer to was an exercise thallium, and if she got her heart rate up high enough on the treadmill, then it is even less likely she has heart disease, if in fact this test was normal.  Like any test, thallium scans can be wrong.  A cardiac catheterization would answer the question of whether she really has significant heart artery blockages.  I suspect that if she keeps coming in with different cardiac symptoms, one of her doctors will ultimately catheterize her.  Realize though that a catheterization does have risks associated with it.
Without looking at the EKGs, I could not say what heart rhythm she was in.  The mere presence of P waves does not exclude an SVT.  It is unusual for patients to have heart rates jump as you described, if it is only a sinus tachycardia.  Perhaps she has an inappropriate sinus tachycardia.  A consultation with an electrophysiologist, a cardiologist who specializes in heart rhythms, would be reasonable.
Information provided here is of a general nature.  Specific diagnoses and treatments can only be made by your doctor.  If you would like to be seen at the Cleveland Clinic, please call 1-800-CCF-CARE for an appointment with a cardiac electrophysiologist at Desk F15.