12LeadEKG

The 12-lead electrocardiogram (12-lead ECG or EKG) is a noninvasive test that records the heart's electrical activity from 12 distinct views using a set of surface electrodes. It provides a concise snapshot of rhythm, rate, conduction, and the heart’s electrical axis.

Six limb leads (I, II, III, aVR, aVL, aVF) and six precordial leads (V1–V6) are placed on the arms, legs, and chest to generate the twelve tracings. Electrodes are positioned to capture signals from different angles, enabling a more complete assessment of cardiac activity than a single-lead recording.

The recording typically lasts about 10 seconds and is displayed as waveforms with measurable intervals, such as PR, QRS, and QT. Standard settings (e.g., speed and calibration) enable consistent interpretation across examinations and patients.

Clinically, a 12-lead ECG is used to detect myocardial ischemia or infarction, arrhythmias, conduction delays, electrolyte disturbances, and chamber enlargement. It also helps guide acute management and risk stratification in various settings, including emergency care and preoperative evaluation.

Interpretation involves assessing rate and rhythm, looking for axis deviation, and evaluating the morphology of waves across all leads. Key features include ST-segment changes, Q waves, T-wave abnormalities, and interval durations, all interpreted in the clinical context.

Limitations include susceptibility to artifacts and electrode misplacement, and the inability to detect certain conditions (e.g., posterior or some right ventricular infarctions) without additional leads or imaging. Serial ECGs and correlation with symptoms and biomarkers enhance diagnostic accuracy.

The 12-lead ECG is a safe, rapid, and standardized tool widely used in clinical practice to assess cardiac electrical activity.