Exercise induced paroxystic tachycardia

I am a 39 years old male, BMI 23. I exercise regularly 3-4 times, running 25 miles per week. I have been experiencing lately palpitations in my neck while exercising, of sudden onset and end, few seconds in duration, without accompanying chest pain or dyspnea. I can keep my 8 minutes per mile pace while having the tachycardia (as a fact, if I stop, the tachycardia usually lasts longer than if I just keep running). When I check my heart rate monitor while having these palpitations, my heart rate goes up from about 150 bpm to 210 bpm all of the sudden; and then, after a few seconds, back to the base rate, again abruptly. I have never experienced palpitations or tachycardia at rest, nor faints, chest pain or shortness of breath, and I feel otherwise fine.
I have had a treadmill test (actually two), which were negative for ischemia and arrhythmias (I did not experience any palpitations while having them); and an echocardiogram, which showed a mild to moderate aortic regurgitation, with no dilatation of aortic root and no left ventricular dilatation or hypertrophy, with preserved ejection fraction.
Although I think they are probably paroxysmal supraventricular tachycardias, should I be concerned about other possibilities? I have been told to mantain a target HR of less than 80% of my predicted maximal value while exercising. Should I have any more tests, like a Holter and alike?. Thank you very much.

[CCFCardio MD2]

I'm sorry to hear that you're having some difficulty when you exercise.  The symtoms (symptoms) you describe do in fact sound like they may be due to a paroxysmal supraventricular tachycardia (SVT).  A heart rate of 210 is higher than a typical exercise-induced heart rate in a normal individual, which usually doesn't go above about 180 beats per minute.  The fact that it abruptly jumps from 150 to 210 then back to 150 is consistent with SVT.  SVTs are not that uncommon but should be treated.  The fact that you are not having other symptoms such as lightheadedness, chest pain, or shortness of breath is reassuring.  The rapid onset of a high heart rate can be seen with more sinister heart rhythms such as ventricular tachycardia (VT), and you should work with your doctor to make sure a diagnosis is made so treatment can be initiated.  It sounds as if you might benefit from a Holter monitor or Event monitor.  These are monitors that you wear home and will record your heart rhythm during the events.  Your doctor can then look at the recordings to correlate any heart rhythm changes to your symptoms.  Please discuss this diagnostic workup with your doctor.  

Thank you for your question.  Best of luck to you.

[is_something_wrong]

Hi,

While you wait for the doctor to reply, I just have some comments (I'm a long time PAC sufferer).

An important point is: Do you feel the pulsations in your neck for each heart beat? If you do, you can be almost certain this is PSVT (AV nodal reentrant tachycardia). I strongly believe it is, if you had a ventricular tachycardia at rate 210, you would be really affected and you would probably not be able to run. Atrial tachycardias will rarely cause this pulsation. Ventricular tachycardia can cause some pulsations, but not synchronized with the heart rate.

A doctor must answer if it's safe to keep running, but it's not strange that you can break the arrhythmia easier while running, because your sinus node may "overdrive pace" the tachycardia, terminating it. There are easier ways to terminate AVNRT (if that's your diagnosis, again, a doctor can tell you for sure) such as vagal maneuvers and other methods that a doctor can teach you. If all fails, you could go to the ER and convert it with a shot of adenosine. Maybe you should, just to capture the event on EKG and get a certain diagnosis.

Best wishes to you. I think things will be clearer when you get an answer from the experienced Cleveland Clinic cardiologists. If you can, try to answer my questions, I believe it will be easier for them to answer your question then.

[antoniopablo]

I don't think I feel each pulsation in my neck. I just feel "palpitations", like a pounding. They last a few seconds (so no time to go to ER or have them captured on ECG). I know about vagal manoeuvres, but again, the tachycardia usually goes more quickly if I just keep running than if I stop and massage my carotid or do Valsalva. I can exercise few days in a row without having them, and then, they will bother me for another few days, for no apparent reason. As far as I know, caffeine, sleep (or lack of) and other factors do not seem to influence them (as a fact, the day I had the highest number of episodes, 4 to be precise, I had slept like a baby the night before and did not have a drop of coffee!).

[is_something_wrong]

One last question: Is the heart rate regular or irregular?

[antoniopablo]

I can't really figure out whether it's regular or irregular, I just feel some "pulsations" on my neck.