People have pacemakers put in for many different reasons and a discussion of all of these diseases is beyond the scope of this web site. However, you should be able to recognize a paced EKG. The key to correctly identifying a paced rhythm is finding a pacer spike. These are short (almost instantaneous) bursts of electrical current that initiate a waveform on the EKG. Some are very small in amplitude because they use very little energy. This is advantageous to the pacemaker to conserve its battery life so the patient will not need a procedure to open the pacemaker up and install a new battery. Unfortunately, this makes some pacemaker spikes very difficult to identify. Pacing spikes can be found in front of the P wave if they come from an atrial pacer or in front of the QRS complexes if they are ventricular. There are even biventricular pacers that can generate very strange QRS complex morphology. However, the common factor between all pacemaker driven rhythms is they generate a small, straight line on the EKG at the beginning of the complex they initiate. Do not confuse a pacemaker spike with the hash mark that separates lead tracings. It is important to point out that the rhythm strip will never have hash marks because the rhythm strip prints one single lead tracing all the way across the EKG page. The best leads to identify pacer spikes are typically leads V3-5.
See examples of paced rhythms