The ECG is a tool of remarkable clinical power; it can be mastered with ease and can provide helpful and even vital information in a wide range of situations. One glance at an ECG can diagnose an evolving myocardial infarction, identify a potentially life-threatening arrhythmia, pinpoint the chronic effects of sustained hypertension or the acute effects of a massive pulmonary embolus, or determine the likelihood of underlying coronary artery disease in a patient with chest pain. One must remember that the ECG is only a tool and, like all tools, is only as capable as its user. The purpose of this course is to understand the characteristics of junctional rhythms as well as the approach taken toward narrow complex tachycardia.