In a 12-lead Electrocardiogram (ECG), what changes indicate right side involvement?

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From the Guidelines

Right side involvement in a 12-lead ECG is primarily indicated by ST-segment elevation in leads II, III, and aVF with ST elevation in lead III greater than lead II, along with ST elevation in right-sided leads V3R and V4R. These changes are typically seen in the context of inferior wall myocardial infarction, particularly when the right coronary artery is occluded, and are suggestive of right ventricular infarction 1. The key findings that indicate right side involvement include:

  • ST-segment elevation in leads II, III, and aVF, with lead III having greater elevation than lead II
  • ST-segment elevation in right-sided leads V3R and V4R
  • ST-segment depression in leads I and aVL
  • Possible right bundle branch block patterns It is crucial to recognize these patterns as they suggest right ventricular infarction, which requires specific management considerations, including adequate fluid administration and avoidance of certain medications 1. Obtaining right-sided chest leads (V3R-V6R) is recommended for confirmation when these patterns are observed, as standard left-sided leads may miss right ventricular pathology 1. The physiological basis for these changes relates to injury currents flowing away from the affected right ventricular myocardium. Recognizing right ventricular involvement is vital because these patients require careful monitoring for complications like bradyarrhythmias and high-degree heart blocks.

From the Research

Right Side Involvement in 12-Lead ECG

The following changes in a 12-lead Electrocardiogram (ECG) indicate right side involvement:

  • ST-segment elevation in lead III > lead II 2
  • ST-segment depression in lead I > lead aVL 2
  • ST-segment elevation in lead V1 with no ST-segment elevation in lead V2 [(2,3)]
  • ST-segment elevation in right precordial leads (V3R, V4R) [(4,5)]
  • Q wave in lead III > lead II 2
  • Width of Q wave in lead III > lead II 2

Specific ECG Patterns

Certain ECG patterns are indicative of right ventricular infarction, including:

  • Simultaneous ST-segment elevation in lead V1 and ST-segment depression in lead V2 3
  • ST-segment elevation in lead V4R being higher than that in leads V1 to V3 5

Lead-Specific Changes

Changes in specific leads can indicate right side involvement:

  • Lead V1: ST-segment elevation [(2,3)]
  • Lead V2: ST-segment depression 3
  • Lead V3R: ST-segment elevation [(4,5)]
  • Lead V4R: ST-segment elevation [(4,5)]

References

1
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

2
Research

The diagnostic value of 12-lead electrocardiogram in predicting infarct-related artery and right ventricular involvement in acute inferior myocardial infarction.

Annals of noninvasive electrocardiology : the official journal of the International Society for Holter and Noninvasive Electrocardiology, Inc, 2001

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This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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