1 The Morphology of the Electrocardiogram

The 12-lead electrocardiogram (ECG) is the single most commonly performed investigation. Almost every hospitalized patient will undergo electrocardiography, and patients with known cardiovascular disease will do so many times. In addition, innumerable ECGs recorded are made for life insurance, occupational fitness and routine purposes. Most ECG machines are now able to read the tracing; many of the reports are accurate but some are not. However, an accurate interpretation of the ECG requires not only the trace but also clinical details relating to the patient. Thus, every cardiologist and physician/cardiologist should be able to understand and interpret the 12-lead ECG. Nowadays, many other groups, for example accident and emergency physicians, anaesthetists, junior medical staff, coronary care, cardiac service and chest pain nurses, also need a Summary good grounding in this skill. In the last several decades a variety of new electrocardiographic techniques, such as short- and long-term ambulatory ECG monitoring using wearable or implantable devices, event ECG monitoring, single averaged ECGs in the time, frequency and spatial domains and a variety of stress recoding methods, have been devised. The cardiologist, at least, must understand the application and value of these important clinical investigations. This chapter deals comprehensively with 12-lead electrocardiography and the major pathophysiological conditions that can be revealed using this technique. Cardiac arrhythmias and other information from ambulatory and averaging techniques are explained only briefly but are more fully covered in other chapters, for example those devoted to specific cardiac arrhythmias