From the Guidelines
Leads 2,3, and aVF are placed on the right arm, left leg, and left leg, respectively, with specific electrode configurations to record the heart's electrical activity. According to the American Heart Association electrocardiography and arrhythmias committee 1, lead II is defined as the potential difference between the left leg and the right arm (LL-RA), and lead III is defined as the potential difference between the left leg and the left arm (LL-LA). Some key points about the placement of these leads include:
- Lead 2 records the potential difference between the right arm (negative electrode) and left leg (positive electrode)
- Lead 3 measures the potential difference between the left leg and the left arm (LL-LA)
- aVF is an augmented unipolar limb lead that records electrical activity from the positive electrode on the left leg These leads are essential for monitoring the inferior wall of the heart and detecting conditions such as inferior wall myocardial infarctions, as stated in the recommendations for the standardization and interpretation of the electrocardiogram by the American Heart Association 1. The proper placement of these leads is crucial for accurate ECG interpretation, and incorrect positioning can lead to misdiagnosis of cardiac conditions. The relationship between these leads is also defined by Einthoven’s law, which states that lead II = lead I + lead III at any instant in the cardiac cycle, according to Kirchhoff’s law 1.
From the Research
Lead Placement
The placement of leads 2,3, and aVF in an electrocardiogram (ECG) is crucial for accurate diagnosis and monitoring of cardiac conditions.
- Lead 2 is placed on the right leg,
- Lead 3 is placed on the left leg,
- Lead aVF is placed on the chest or abdomen, but the exact placement can vary depending on the specific ECG technique being used 2.
ECG Techniques
ECG techniques and technologies have evolved over the years, with advancements in signal processing and the use of additional leads allowing for more accurate and detailed information to be extracted from cardiac electrical activity 3.
Clinical Applications
ECG is a critical component of the evaluation of patients with signs and symptoms of emergency cardiac conditions, and its use has been a standard in clinical practice for over half a century 3, 4, 5.
- The placement of leads 2,3, and aVF is important for creating waveforms for leads I, II, III, aVR, aVL, aVF, and V1-V6 2.
- ECG methods and variables derived from the analysis of the ECG signal are powerful predictors of major cardiac events in several clinical conditions 4.
- Cardiac conduction disorders are common in a primary care population, especially among older individuals with cardiovascular risk factors, and ECG is an important tool for diagnosing and monitoring these conditions 5.