Chapter 5 Assignment 2022

Running head: CHAPTER 5
CHAPTER 5
Name of the Student
Name of the University
Author Note

CHAPTER 51
1. How are leads I, II, and III determined; why is there an interaction; and how you
can determine if you have a good connection using the interaction of these leads?
The standard electrocardiogram (ECG) consists of twelve leads. Out of twelve leads six
leads are referred as limb leads. These leads are situated on the extremities (arms and
legs) of an individual. These six leads are lead I, II, III, aVl, aVR, aVF. Out of these six
limb leads the three limb leads (Lead I, II and III) are basically referred as bipolar limb
leads. These are referred as bipolar leads because one lead is positive whereas the other
lead is negative. These two electrodes are equidistantly placed from heart. These bipolar
limb leads record the flow of electricity in the direction from negative electrode to
positive electrode. According to Novel Laureate physiologist Willem Einthoven, these
three bipolar limb leads are connected by Einthoven’s triangle (Hampton, 2013). This
Einthoven’s triangle is the main key factor in order to develop an interaction among
bipolar limb leads. Considering the orientation of these bipolar leads I, II and III in an
individual, it has been observed that the summation of voltage present in lead I and III is
equal to lead II (Dunbar & Saul, 2009). The interaction between the three bipolar limb
leads exist as
Lead I: Right Atrium (-) to Left Atrium (+)
Lead II: Right Atrium (-) to Left Leg (+)
Lead III: Left Atrium (-) to Left Leg (+)
In order to confirm whether a good connection exists among these bipolar limb leads or
not, the Einthoven’s triangle summation formula has to be checked. If a positive deflection is
observed in ECG due to the movement of a depolarization wave towards the positive
electrode then lead I + lead III= lead II. This formula thus evaluates the proper connection
between these three bipolar limb leads (Hampton, 2013).

CHAPTER 52
2. Describe in detail where electrodes are placed during a resting ECG and how they
differ during a stress test. Explain why they differ.
12-lead ECG that signifies a spatiotemporal information regarding the electrical activity of
an individual’s heart, is placed during a resting ECG in different orientations.
Bipolar limb leads (horizontal plane) are placed as:
 Lead I: RA (-) to LA (+) (Right Left, or lateral)
 Lead II: RA (-) to LL (+) (Superior Inferior)
 Lead III: LA (-) to LL (+) (Superior Inferior)
Augmented unipolar limb leads (frontal plane) are placed as:
 Lead aVR: RA (+) to [LA & LL] (-) (Rightward)
 Lead aVL: LA (+) to [RA & LL] (-) (Leftward)
 Lead aVF: LL (+) to [RA & LA] (-) (Inferior)
Unipolar (+) chest leads (horizontal plane) are placed as:
 Leads V1, V2, V3: (Posterior Anterior)
 Leads V4, V5, V6:(Right Left, or lateral)
This type of ECG placement is applicable for resting supine ECGs. ECG is normally
recorded in the supine position. However, in some cases ECG can be performed in different
conditions. When ECG is recorded during a stress test, it has been observed that the limb
leads are placed in a different position. During stress test, the limb electrodes are placed onto
the trunk of the human body which is referred as torso whereas the chest electrodes are
placed in the same position. This type of lead placement can be referred as Mason-Likar Lead
placement (Dunbar & Saul, 2009).