83 year old woman with very long history of palpatations

Presenting in the evening with shortness of breath the patient explains she used to get palpatations every few months "for a very long time" but now she just gets paroxysmal SOB.
At presentation, she was symptom free. This was her ECG.

She is normotensive, has clean pathology, clear chest and no cardiac murmur. Echo showed mild mitral regurge, trivial TR, AR and LVH. As the lady had no one to go home to, she was admitted. During the night she called in the nurse with her usual symptoms. Her ECG is as follows:

Now what do we have here?