This rhythm strip shows sinus rhythm with premature atrial and ventricular complexes. The underlying sinus rhythm is reflected by normal P waves preceding each sinus QRS. The early or premature P waves differ in shape from the sinus P waves and are followed by early narrow QRS complexes that are the same shape as the sinus QRS. In addition, there are early or premature QRS complexes that are wide and different from the sinus QRS and not preceded by P waves.