41 Questions
In a hexaxial lead diagram, what indicates negative poles?
A dashed line
Which lead's positive pole is directed downward?
aVF
What does the arrow in Figure 21 represent?
The direction of the positive electrode
Which precordial leads have a better view of the anterior septal wall?
V2, V3, and V4
What is measured on the y-axis of an electrocardiogram?
Voltage
How much time is represented by each small box on an electrocardiogram?
0.04 seconds
What is the speed of the paper on an electrocardiogram?
25mm/sec
Which leads record voltages transmitted in the horizontal plane of the heart?
Precordial leads
What is measured in leads II, III, and aVF?
The electrical activity coming from the inferior wall of the heart
What is represented by an ECG as a static heart graph?
Activity of the heart written and printed on paper as a tracing
What is the duration of the small ticks on the horizontal axis in ECG?
40ms
What is the vertical axis of an ECG graph?
Magnitude (voltage) of the waves/deflections
What is the calibration requirement before taking an ECG?
The machine should be properly calibrated
What is the representation of 10mm on the ECG graph?
1mV
What is the advantage of ECG as a static heart graph?
It gives more time to look over the graph
What is the location of the electrical activity measured in leads V1 and V2?
Septum
What is the rate at which the atria fire in abnormal P wave?
250-350 bpm
What is the characteristic of the baseline in abnormal P wave?
Chaotic
What is the origin of tachycardias with normal QRS complexes and no discernable P waves?
Ventricles
What is the atrial-to-ventricular conduction ratio in fibrillatory waves?
2:1, 3:1, or 4:1
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
What is the range of the atrial rate in sawtooth/flutter waves?
250-350 bpm
What is the characteristic of P waves in tachycardia?
Buried in the T wave of the preceding beat
What is the location of the ventricles in relation to the AV node?
Below the AV node
What is the direction of the wave of depolarization in a positive deflection in ECG?
Towards the positive pole of the lead
What type of deflection is seen when the mean depolarization path is directed at right angles to the lead axis?
Biphasic deflection
What is the purpose of using standardized and augmented limb leads in ECG?
To get the frontal plane of the heart
What is the location of V1 in children?
Area of V3R and V4R
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
What type of deflection is seen when the wave of depolarization spreads towards the negative pole of the lead?
Negative deflection
What is the purpose of using precordial/chest leads in ECG?
To get the horizontal plane of the heart
What is the characteristic of a biphasic deflection?
Equal size of positive and negative deflection
What is the reference point for the ECG machine?
Negative pole
Which lead represents the voltage between the right arm and the left arm?
Lead I
What is the direction of view for Lead II?
Inferior left view
What type of leads are aVR, aVL, and aVF?
Unipolar leads
Which lead views the heart from the upper right side?
aVR
What is the direction of view for Lead III?
Inferior right view
What is the character of the chest leads?
Unipolar
What is the reference negative value for the chest leads?
The average of inputs from the 3 limb electrodes
What is the result of depolarization towards a lead?
Positive deflection
Understand the Hexaxial Lead Diagram and Reference System in Electrocardiography, including negative and positive poles, and their relevance in identifying action potentials.
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