Dang, phone crashed.. After i typed an entire response.. Sigh here goes again.
Its highly unlikely at your age that the problem is sick sinus syndrome.
I dont think its atrial tachycardia at over 200 (sa node reentry). I think you have 2 primary problems, avnrt and the pvc/bigeminy.
Avnrt is activated by a premature impulse, pvc or pac. Its self limiting meaning it resolves on its own, occuring in episodes of a few seconds or rarely minutes. Avnrt commonly has a rate over 200. P waves in avnrt are 'absent', abnormal and may occur before or after the qrs.
This is because in avnrt the atria and ventricles may depolarize at the same time, or one after the other on account of the av node being in the middle of the chambers.
As for your pauses i think they are more likely due to a abnormally long recovery period, which is distinct from a pause and doesnt necessarily have to accompany any significant conduction system disease. Its completely beningn so long as it doesn't accompany symptoms (such as syncope, or fainting)
As for the bigeminy it could be:
1. A reentrant mechanism (most likely)
2. An accelerated pvc with entry block
3. A single, or perhaps several exceptionally irritable idiopathic foci that give the appearence if bigeminy.
Regardless of mechanism the treatment is the same.
Basically a pac hits that fast pathway refractory period and puts you into avnrt, with a rate of 200+ and the abnormal p waves you described. After a few seconds the rhythm terminates and is followed by an exceptionally long refractory period. This causes ventricular escape/pvcs, possibly with bigeminy to follow on resumption of sinus rhythm.
As stated the treatment is the same, ep study, avnrt ablation and probable pvc ablation while theyre in there. I think once the mechanism of the ventricular phenomenon is better understood with the study its likely that some sort of connection between the 2 arrhythmias may surface.
Upper end of snrt after 200 BPM tachycardia is about 2000 ms (up to a 2 second pause).
So while its probably true your pause is a bit long i see nothing to support it being "concerningly" long.