This is an electrocardiogram taken of from a patient after implantation of pacemaker. This electrocardiogram is interesting as it comes from a patient who previously had had a ventricular lead pacing his left ventricle. In this recording one clearly sees a QRS which now shows a left a bundle branch like configuration, suggesting that the New lead is in the right ventricle. One can also see that the patient has what is called trifasicular block, as we can see a first-degree block, a left axis deviation, and a right to bundle branch block. It is clear, that the pacemaker is not sensing the atrium or the ventricle. In this case, this is because a magnet was place over the pacemaker. This was required to demonstrate the QRS morphology from the paced beats as the patient's own heart rate was faster than the rate of the pacemaker.