A 67 year-old lady with a history of MI with one stent 5 years prior presents for evaluation of a brief episode of chest tightness with diaphoresis that resovled spontaneoulsy. Her initial ECG is unremarkable and her symptoms have resolved. During her workup, she developed another brief episode of similar symptoms, which resolved spontaneously. Review of the cardiac monitor during the event revealed the rhythm above. What is it?