ECG Hexaxial System Quiz and Flashcards: Master Lead Diagrams

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Questions and Answers

In a hexaxial lead diagram, what indicates negative poles?

A solid line

A dashed line (correct)

A bold font

An arrow pointing upwards

Which lead's positive pole is directed downward?

aVF (correct)

Lead 1

What does the arrow in Figure 21 represent?

The direction of the heart's electrical activity

The direction of the negative electrode

The direction of the action potential

The direction of the positive electrode (correct)

Which precordial leads have a better view of the anterior septal wall?

V2, V3, and V4 Signup and view all the answers

What is measured on the y-axis of an electrocardiogram?

Voltage Signup and view all the answers

How much time is represented by each small box on an electrocardiogram?

0.04 seconds Signup and view all the answers

What is the speed of the paper on an electrocardiogram?

25mm/sec Signup and view all the answers

Which leads record voltages transmitted in the horizontal plane of the heart?

Precordial leads Signup and view all the answers

What is measured in leads II, III, and aVF?

The electrical activity coming from the inferior wall of the heart Signup and view all the answers

What is represented by an ECG as a static heart graph?

Activity of the heart written and printed on paper as a tracing Signup and view all the answers

What is the duration of the small ticks on the horizontal axis in ECG?

40ms Signup and view all the answers

What is the vertical axis of an ECG graph?

Magnitude (voltage) of the waves/deflections Signup and view all the answers

What is the calibration requirement before taking an ECG?

The machine should be properly calibrated Signup and view all the answers

What is the representation of 10mm on the ECG graph?

1mV Signup and view all the answers

What is the advantage of ECG as a static heart graph?

It gives more time to look over the graph Signup and view all the answers

What is the location of the electrical activity measured in leads V1 and V2?

Septum Signup and view all the answers

What is the rate at which the atria fire in abnormal P wave?

250-350 bpm Signup and view all the answers

What is the characteristic of the baseline in abnormal P wave?

Chaotic Signup and view all the answers

What is the origin of tachycardias with normal QRS complexes and no discernable P waves?

Ventricles Signup and view all the answers

What is the atrial-to-ventricular conduction ratio in fibrillatory waves?

2:1, 3:1, or 4:1 Signup and view all the answers

What is the reason why the ventricles cannot respond to each atrial impulse?

The ventricles are unable to respond to each of the atrial impulses Signup and view all the answers

What is the range of the atrial rate in sawtooth/flutter waves?

250-350 bpm Signup and view all the answers

What is the characteristic of P waves in tachycardia?

Buried in the T wave of the preceding beat Signup and view all the answers

What is the location of the ventricles in relation to the AV node?

Below the AV node Signup and view all the answers

What is the direction of the wave of depolarization in a positive deflection in ECG?

Towards the positive pole of the lead Signup and view all the answers

What type of deflection is seen when the mean depolarization path is directed at right angles to the lead axis?

Biphasic deflection Signup and view all the answers

What is the purpose of using standardized and augmented limb leads in ECG?

To get the frontal plane of the heart Signup and view all the answers

What is the location of V1 in children?

Area of V3R and V4R Signup and view all the answers

What is the purpose of using V3R and V4R leads in children?

To determine what is going on in the right side of the heart Signup and view all the answers

What type of deflection is seen when the wave of depolarization spreads towards the negative pole of the lead?

Negative deflection Signup and view all the answers

What is the purpose of using precordial/chest leads in ECG?

To get the horizontal plane of the heart Signup and view all the answers

What is the characteristic of a biphasic deflection?

Equal size of positive and negative deflection Signup and view all the answers

What is the reference point for the ECG machine?

Negative pole Signup and view all the answers

Which lead represents the voltage between the right arm and the left arm?

Lead I Signup and view all the answers

What is the direction of view for Lead II?

Inferior left view Signup and view all the answers

What type of leads are aVR, aVL, and aVF?

Unipolar leads Signup and view all the answers

Which lead views the heart from the upper right side?

aVR Signup and view all the answers

What is the direction of view for Lead III?

Inferior right view Signup and view all the answers

What is the character of the chest leads?

Unipolar Signup and view all the answers

What is the reference negative value for the chest leads?

The average of inputs from the 3 limb electrodes Signup and view all the answers

What is the result of depolarization towards a lead?

Positive deflection Signup and view all the answers

Study Notes

ECG Machine and Leads

The ECG machine uses the negative pole as zero reference, with the positive pole as the point of view and the line connecting the two poles as the line of sight.

Limb Leads

Leads I, II, and III are bipolar, measuring electrical potential between two of the three limb electrodes.
Lead I: Represents voltage between the right arm (negative) and the left arm (positive), viewing the heart from the left.
Lead II: Sees signal movements between the right arm (negative) and the left leg (positive), forming the inferior left view.
Lead III: Measures electrical potential between the left arm (negative) and the left leg (positive), looking at the heart from an inferior right angle.
Leads aVR, aVL, and aVF are unipolar, using one limb electrode as the positive pole and taking the average of inputs from the other two as the zero reference.
aVR: Looks at the upper right side of the heart.
aVL: Looks at the upper left side of the heart.
aVF: Looks at the inferior wall of the heart.

Chest Leads

The chest leads (precordial leads) view the heart in a horizontal plane.
The corresponding chest electrodes serve as the positive poles.
The reference negative value is calculated as the average of inputs from the three limb electrodes.
Depolarization toward a lead produces a positive deflection.

Hexaxial Lead Diagram

The Hexaxial Reference System shows the positive poles of each axis labeled with the name of the lead.
Arrows pointed to where there is a positive electrode indicate the direction of action potentials.

Precordial Leads

Precordial leads measure electrical activities in different areas of the heart:
- V1 & V2: Posterior wall.
- V2, V3, V4: Anterior septal wall.
- V5 & V6: Lateral wall.

Electrocardiogram Basics

The amplitude of the waves or deflections is measured in mm on the y-axis.
Each small box on the graph paper equals 0.04sec (40ms), while each large box equals 0.2sec (200ms).

Abnormal P Waves

Absent P wave: Sawtooth/Flutter waves, indicating atrial firing at 250-350 bpm.
P waves buried in the T wave of the preceding beat: Can arise from atria, rapid depolarization overriding the SA node.
Fibrillatory waves: Atrial-to ventricular conduction ratio of 2:1, 3:1, or 4:1.

Basic Laws of ECG

Positive (upward) deflection: Wave of depolarization spreads towards the positive pole of the lead.
Negative (downward) deflection: Wave of depolarization spreads towards the negative pole of the lead.
Biphasic deflection: Equal size of positive and negative deflections, seen when the mean depolarization path is directed at right angles to any lead axis.

ECG Measurements

ECG as a static heart graph: Represents heart activity written and printed on paper as a tracing.
ECG as a dynamic heart graph: Real-time graph of the heartbeat, usually seen in ICUs in cardiac monitors.
Calibration of the ECG machine is necessary before taking readings.

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Description

Understand the Hexaxial Lead Diagram and Reference System in Electrocardiography, including negative and positive poles, and their relevance in identifying action potentials.

ECG: Hexaxial Lead Diagram and Reference System

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