Hello -- While a TMT is helpful, it's not the gold standard for ruling out heart disease. However, in this case it was the most appropriate test, along with the others, and I think it reasonably ruled out coronary artery disease. Since you suffer from IBS and have some GI complaints, it is highly likely this is at least partly responsible for the increased rate, the palpitations, etc., as anything that can upset the stomach will automatically affect the vagus nerve. Digestion -- and indigestion -- as well as bloating, gas, diarrhea, etc., all can stimulate the vagus nerve, which not only runs the peristaltic process in the GI tract but also serves to slow the heart rate (and if the rate is unnecessarily increased it tries to slow it anyway, causing PVCs, which you might compare to backfire from an internal combustion engine when downshifting to slow the machine). This is likely what's going on, and at your age you've had sufficient testing to at least rule out coronary artery disease. You may, however, have either an anxiety issue (always a consideration, but we must be careful not to assume this is the root cause without ruling out physical issues and addressing them).
Treating IBS will be important and may well help reduce these symptoms. The Holter monitor wouldn't do any harm, and might even serve as as a good reassurance for you, so you might ask for this as a rather conclusive rule-out. Otherwise, you might have to look at anxiety as a potential partial cause of all the problems (including IBS) once all physical problems have been accounted for or ruled out.
I hope this is helpful. Please do follow up with us here as needed. Good luck to you.
John Kenyon, EMT, CCT
Non-invasive cardiology tech, Emergency and Critical Care technician, Critical Incident Stress Mgmt. specialist