What Causes Skipped Heart Beat?

I am a 49 year old female which has been diagnosed with svt and mild to moderate mvp with ejection fraction of 60%. I have been having a lot of skipped beats and extra beats and feels like pauses to me. I recently wore a holter monitor and it showed up 306 skipped beats and extra beats in groups of three at 231bmp and one pause for 2.1 seconds. I wrote in my diary exactly at the time it showed this, so it was what I was feeling. But when I visited the cardiologist he tried to tell me that it probably was an electrode that came loose or just a reading that wasnt correct due to the heart monitor. I take tenormin and have been on it for about 28 years. I have had the svt for a long time and have know about the mvp for several years, and was told at the emergency room one time that I had the atrial septal aneurysm and that it needed to be evaluated with a tee scope. The heart dr didn t even tell me about it whenever he did the echo test, and I found out like I said, whenever I visited er.