To continue the series donated by Jenda Enis Štros, ECG 2 shows spontaneous resolution of the ST elevation, coinciding with relief of the patient's chest pain.  Spontaneous reperfusion can occur when the artery diameter is increased, the offending clot shifts position to allow blood flow, or other reasons.  This does not mean, however, that the lesion has disappeared.

Here are the links to all six of the ECGs in this series:

http://www.ecgguru.com/ecg/teaching-series-1113-ecg-1-6-acute-anterior-wall-mi

http://www.ecgguru.com/ecg/teaching-series-1113-ecg-2-6-acute-anterior-wall-mi

http://www.ecgguru.com/ecg/teaching-series-1113-ecg-3-6-acute-anterior-wall-mi

http://www.ecgguru.com/ecg/teaching-series-1113-ecg-4-6-acute-anterior-wall-mi

http://www.ecgguru.com/ecg/teaching-series-1113-ecg-5-6-acute-anterior-wall-mi

http://www.ecgguru.com/ecg/teaching-series-1113-ecg-6-6-acute-anterior-wall-mi