A 12-lead electrocardiogram (ECG) graphically displays the heart's electrical activity. It is the most common clinical tool for detection and diagnosis of heart disease, and is especially useful for detecting conditions related to abnormalities of cardiac rhythm. ECG should be considered in patients who have known cardiovascular disease or an increased risk for it. The responsibility for correctly interpreting an ECG lies with the physician, who should be able to recognize patient-dependent errors, operator-dependent errors, and artifact. Current ECG tracings should always be compared with previous tracings. Following a specific routine and methodical analysis of the data will ensure an accurate interpretation result. In the worst-case scenario, they can always be faxed or transmitted for inter-consultation with a more experienced reader.