This rhythm strip shows sinus rhythm with aberrantly conducted premature atrial complexes. The underlying sinus rhythm is reflected by normal P waves preceding each sinus QRS at a rate of sixty beats per minute. The earlier premature P waves differ in shape from the sinus P waves and are followed by early and wide QRS complexes. The first premature P wave is superimposed on the preceding T wave. Note that this is a V1 lead, and the aberrantly conducted beats have a right bundle branch block configuration. This is typical, as the right bundle has a longer refractory period than the left. Isolated atrial premature beats are usually benign.