This rhythm strip shows complete heart block. The characteristic features demonstrated here include P waves that occur at regular intervals and QRS complexes that also occur at regular but usually slower intervals. The PR interval is not constant. There is no relationship between the Ps and the QRSs. In this case, the QRS complexes are narrow and originate from the junctional area. In some cases, the QRS complexes may be wide and slower due to an intrinsic ventricular focus.