This recording shows sinus rhythm with premature atrial complexes. The p' wave can be seen deforming the T wave in the lead II rhythm strip. Note also that the atrial premature complexes reset the sinus node and hence there is no compensatory pause before the next sinus p wave. The QRS is deformed with a rsR' in V1 and a broad S in I with a duration of > 120 ms. diagnostic of aberrance with a right bundle branch morphology. The S1 Q3 and the right ward axis of the aberrant complexes suggest an additional left posterior fasicular block.