<prompt> Comment on the diagnosis of the ECG tracing shown below.First degree AV block, intranodalSecond degree AV block type1, intranodalSecond degree AV block type 2, infranodalThird degree AV block  <response>: Symmetry in PR interval before and after the missed beat -- Indicating Second degree AV block type 2: infranodal. In Second degree AV block type 1 -- Serial lengthening of PR interval before and after the missed beat. In Third degree AV block -- complete dissociation bw atria and ventricles. 