[Answer] A patient in the telemetry unit is receiving continuous cardiac monitoring. The patient has a history of myocardial infarction. The patient’s ECG rhythm strip is shown in the following figure. The provider interprets this strip as indicating which arrhythmia?

Answer: In third-degree AV block no electrical communication occurs between the atria and ventricles thus no relationship between P waves and QRS complexes exists. The RR interval is constant. The PP interval is constant or slightly irregular as with sinus arrhythmia. If pacemaker cells in the AV junction simulate ventricular contraction the QRS complexes will be narrow (less than 120 milliseconds in duration). Impulses that originate in the ventricles produce wide bizarre QRS complexes. This arrhythmia may result from damage caused by myocardial infarction.