Well, this is the focal point at which you must take a stand. Realize that there's nothing physically wrong with your heart. The palpitations are occuring outside the heart by simple stimulation by the vagus nerve in response to something called the fight or flight mechanism.

It is the terror itself that has induced this physiological response and it does not constitute anything dangerous. This much you must come to understand and take control where unwarranted fears are concerned.

Realize that in more than 40 years as a physician, I've never even once heard of a single individual ever experiencing any type of cardiac event or other imminent risk as a consequence of the type of palpitations you and others on this site are experiencing. Your symptoms aren't special, unique, different or otherwise anything apart from others on the forum. In fact, none of these people have actually ever experienced any type of physical consequence from the palpitations as well.

This type of stimulation by the vagus nerve has no ability to interfere with the heart's natural pacemaker and although they can make you experience odd sensations, it does not constitute anything dangerous.

The fear represents the absolute most difficult hurdle to overcome because most persons become rigid in their own beliefs that something physical is wrong and they must continue to search until it's found. This never comes to pass for these persons and they end up sacrificing many years of their lives based upon an entirely misconceived notion that the palpitations represent something harmful. Understand that the more you become fearful, the more the likelihood the palpitations will increase in frequency and variation because you are elevating the fight or flight response to an ever-higher degree.

What persons with palpitations of this type fear most is the loss of control that looms so ominously over them, stripping them of every ounce of self-confidence. It's critical to understand that nothing waits in hiding to suddenly leave you incapacitated in any way and the only thing that can ever occur with these palpitations is the symptoms you are now experiencing. Nothing more.

You must also come to terms with your fear of the medical environment and physicians, which erroneously represents the portal through which some discovery of an irreversible condition will be made and you will find yourself facing the premise of too little, too late. This is a misconception in its entirety. The fact that your fears can so dramatically affect your heart rate and other physiological reactions is clear evidence that you have a health anxiety disorder.  

There is nothing about your condition that can actually harm you and a visit to the doctor will not under any circumstances reveal some hidden horror that will forever dampen your outlook. You must realize that all the tests are negative because nothing physical is wrong. It is the body reacting to stress and fear and you are mistaking the physiological responses as symptoms of some type of disease because you do not understand how the body responds under such conditions.

Spend some time reading the various postings and we'll talk more.

You're going to be just fine.

Best regards and Good Health