Which coronary artery supports each lead of an electrocardiogram (EKG)?

From the Guidelines

Each lead of an EKG is supported by specific coronary arteries, with leads II, III, and aVF corresponding to the inferior wall, primarily supplied by the right coronary artery (RCA) in right-dominant hearts or the left circumflex artery (LCx) in left-dominant hearts, as stated in the 2009 AHA/ACCF/HRS recommendations 1.

EKG Leads and Corresponding Coronary Arteries

The relationship between EKG leads and coronary arteries is crucial for diagnosing and managing cardiac conditions. Key correlations include:

• Lead I, aVL, and V5-V6: lateral wall, supplied by the left circumflex artery (LCx) and diagonal branches of the left anterior descending artery (LAD)
• Leads II, III, and aVF: inferior wall, primarily supplied by the RCA in right-dominant hearts or the LCx in left-dominant hearts
• Leads V1-V4: anterior wall, supplied by the LAD
• Lead aVR: view of the right atrium and base of the heart
• V1 and V2: also show the right ventricle, supplied by the RCA Understanding these correlations is essential for identifying which coronary artery might be affected during ischemic events, as noted in the 2009 AHA/ACCF/HRS recommendations 1.

Clinical Implications

Recognizing the relationship between EKG leads and coronary arteries enables clinicians to:

• Rapidly diagnose cardiac conditions, such as inferior wall myocardial infarction, which typically involves the RCA
• Make informed treatment decisions in cardiac emergencies
• Use right-sided chest leads, like VR and V4R, to diagnose right ventricular involvement in inferior wall infarction and distinguish between RCA and LCx occlusion, as recommended by the joint task force of the AHA and the American College of Cardiology 1.

From the Research

EKG Leads and Coronary Artery Support

• Every lead of an EKG is supported by a specific coronary artery, as shown in studies 2, 3.
• The 12-lead ECG can be used to localize the site of coronary artery narrowings, with certain leads corresponding to specific coronary arteries 2.
• For example:
  • Leads I, aVL, and V1-V4 are associated with left anterior descending coronary artery disease 2.
  • Leads II, III, and aVF are associated with right coronary artery (RCA) or circumflex coronary artery (LCx) narrowings 2.

Specific EKG Findings and Coronary Artery Disease

• Certain EKG findings, such as Q waves, ST-segment elevation, and T-wave inversion, can be used to predict the site of coronary artery narrowing 2.
• The accuracy of these findings varies, with Q waves being the most accurate (98%) and ST depression being the least accurate (60%) 2.
• The 12-lead ECG can also be used to identify areas of myocardial ischemia, injury, and death, as discussed in 3.

Limitations of EKG in Localizing Coronary Artery Disease

• No electrocardiographic criteria can distinguish between RCA and LCx disease, even in patients with a right-dominant circulation 2.
• The EKG should be interpreted in conjunction with other clinical information and diagnostic tests to accurately diagnose and manage coronary artery disease.