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Which of the following is (are) unipolar leads?
aVL
Lead II
V6
Lead III
aVR
3 only
1 and 5 only
2 and 4 only
1,3, and 5 only
Introduction:
The electrocardiogram (ECG) is the representation of the electrical activity of the heart in the form of a graph, which is of clinical significance. ECG uses unipolar and bipolar leads, of which the unipolar leads are the single conductor leads with an electrode at one tip while the bipolar leads have two separate and isolated conductors. Unipolar leads monitor the activities of the heart between the positive electrodes and the zero electrical reference point, at the center of the heart but the heart also functions as the negative electrode and the bipolar leads monitor its function.
Answer to Problem 1RQ
Correct answer:
aVL, V6 and aVR only.
Explanation of Solution
Justification/ Explanation for the correct answer:
Option (d) is 1, 3, and 5. These are aVL, aVR, and V6. The aVR lead is the unipolar lead that faces the right superior surface. The aVR lead is generally ignored because it does not contribute significant information to the 12-ECG interpretation. The AV here stands for augmented vector and ‘R’ refers to the right arm and ‘L’ refers to the left arm. The aVL is the lead of the left arm and its contribution is higher, in the ECG. The V6 is the precordial lead, which monitors the horizontal activities of the heart. It views the left ventricle and is also known as a lateral lead. Hence, option (d) is correct.
The explanation for the incorrect answers:
Option (a) is 3 only. The V6 is a unipolar chest leads but the aVL and aVR are also unipolar leads. The V6 is a lateral lead. So, it is an incorrect option.
Option (b) is 1 and 5 only. The V6 is also a unipolar lead, which is placed in the chest region to monitor the horizontal activities of heart in an electrocardiogram. So, it is an incorrect option.
Option (c) is 2 and 4 only. The lead II and lead III are the bipolar leads. This means they are derived from electrodes attached to arms and legs. These use a negative and a positive electrode to monitor the heart activities. So, it is an incorrect option.
Hence, options (a), (b), and (c) are incorrect.
The aVL, aVR, and V6 are unipolar leads. The V6 is placed in the chest region and it monitors the horizontal activities of the heart. It is a precordial lead.
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