What about thyroid function testing, as it is involved in metabolism and if you have hyperthyroidism, one of the symptoms of it is palpitations?
I would wonder what your blood sugar level was like during that time.
What about orthostatic blood pressures laying for about 10 minutes and taking your BP and pulse using a home machine (omron is said to be a good brand for instance). Then you would take it again after standing for at least two minutes.
Or, if you do it after a meal, try it sitting and then standing. If your pulse increases with the change in position by more than 30 beats per minute, you should ask your cardiologist to order a tilt table test to see if you have postural orthostatic tachycardia syndrome (POTS). I have this condition and one of the times it can get worse is after eating a large meal. For awhile, I would try to sit for about two hours (same number as what you have the problem!) to try to avoid the headache I could get from rising after a main meal of the day from my pounding heart.
People often try to pass off the problem of orthostatic intolerance as anxiety but it is a real condition and you can find other people with this and other forms of dysautonomia (dysfunction of the autonomic nervous system) on the dysautonomia forum here on medhelp. I also have been diagnosed with inappropriate sinus tachycardia or IST (prior to the POTS diagnosis). They don't know what causes IST. It can happen regardless of your position. Once, after eating my heart was racing so fast while SITTING (which bothered me) that a nurse told me to go the ER. They ran a few basic blood tests, gave me a potion for heartburn, etc. and sent me home. My heart rate slowed down quite a bit on its own while there except it sped back up when I would stand.
I believe I have the hyperadrenergic form of POTS, because my catecholamine levels, epinephrine, norepinephrine and their inactive metabolites, metanephrine and normetanephrine have all been high at one time or another in testing. When I stand, my heart rate goes into overdrive and my blood pressure can spike as well. The catecholamines play important roles with pulse and maintaining blood pressure. If you are getting episodes of very high blood pressure with your rapid pulse, you will want to get a plasma free metanephrines fasting blood test, the best test they say online for detecting pheochromocytoma, a rare tumor of the adrenal glands that can affect output of catecholamines.
Lastly, because it has aggravated my own tachycardia condition, I recommend asking your doctor to check your iron and ferritin (iron stores) level checks on your blood. Low iron can cause rapid heart rate. It can come from blood loss, a malabsorption problem or even lack of adequate intake in your diet.
the hyperadrenergic POTS definitely sounds interesting, I will follow up on that. I should mention that they did 24 hour urine catecholamines & metanephrines as well as the full thyroid panel and they were all painfully normal as well. I should mention that I am a 27 year old male and in good health other than for these horrible symptoms that are seemingly unsolvable to medical science so far. Work out regularly, eat better than avg. etc...
Hi - I know it's been 11 years, did you ever discover an answer? This happens to me also and I've thought I had POTS as well. I do fit the criteria at times but was cleared by Mayo and many other tests. The only thing I've discovered is the possibility of postprandial hyperemia, which is an increase in blood flow that occurs in response to a meal. So at about 30-60 minutes after eating, the blood has rushed to the stomach to aid in digestion and this can increase the heart rate.