Thanks @Khaled Sleik, right on! Young patient.

In addition to the(#1) respiratory variation in heart-rate described by Dr. Sleik (due to stronger autonomic influence on sinus node in younger patients), there is a relatively subtle, but noticeable (#2) minimal, concave ST elevation with distinct J point in several leads suggestive of early repolarization pattern (e.g., Leads V4-V6, II-III-AVF), which is a somehow prevalent in young African Amercian cohort, and finally (#3), a rightward QRS depolarization axis (between 80-90 degrees, with lead I is almost equal R and S) which is again more common in younger people compared to older people (as the axis shifts leftward as we get older).

This EKG was done on a 22 year-old African American patient in the ED with URTI.