ECG Basics Quiz

Questions and Answers

What is the result of sympathetic stimulation on the heart?

Increase in P-R interval and increase in conduction velocity

Increase in P-R interval and decrease in conduction velocity

No effect on P-R interval and conduction velocity

Decrease in P-R interval and increase in conduction velocity (correct)

What does the QRS complex represent in an ECG?

Atrial repolarization

Ventricular depolarization (correct)

Ventricular repolarization

Atrial depolarization

What is the primary function of the R-R interval in ECG interpretation?

To evaluate the heart rate

To evaluate the Q-T interval

To evaluate the P-R interval

To evaluate the heart rhythm (correct)

What is the significance of the S-T segment in an ECG?

It correlates with the plateau of the ventricular AP Signup and view all the answers

What does the P wave in an ECG represent?

Depolarization of the atrial muscle Signup and view all the answers

What is the result of parasympathetic stimulation on the heart?

Increase in P-R interval and decrease in conduction velocity Signup and view all the answers

What is the significance of the Q-T interval in an ECG?

It represents ventricular systole and ventricular refractory period Signup and view all the answers

What is the heart rate in beats per minute (BPM) if the interval between beats is 0.36 seconds?

166 BPM Signup and view all the answers

What is the main function of the atrial muscle?

To depolarize and contract Signup and view all the answers

What is the significance of the T wave in an ECG?

It represents ventricular repolarization Signup and view all the answers

What is the P-R interval in an ECG?

The time between the P wave and the QRS complex Signup and view all the answers

Why is there no deflection for SA node discharge in an ECG?

Because the SA node consists of a small number of cells Signup and view all the answers

What is associated with an increased P-R interval in an ECG?

A-V blocks Signup and view all the answers

Why should the interval between the P wave and the QRS complex be named P-Q instead of P-R?

Because the interval includes the P wave and the QRS complex Signup and view all the answers

What is the term for the time length between two specific points on an ECG that are supposed to be at the baseline amplitude?

Segment Signup and view all the answers

What is the normal cardiac rhythm where depolarization begins at the SA node?

Sinus Rhythm Signup and view all the answers

What is the direction of the electrical current when cardiac impulses pass through the heart?

Into the heart tissue and also to the surface of the body Signup and view all the answers

What is the term for the abnormal heart rhythm?

Arrhythmia Signup and view all the answers

What is the term for a positive and a negative charge separated by a small distance?

Dipole Signup and view all the answers

What is the ultimate result of the sum of all the currents originated from the electrical activity of the heart?

A vector Signup and view all the answers

What is the location where electrodes are usually placed to record the electrical activity of the heart?

On the limbs Signup and view all the answers

What is the purpose of augmented unipolar leads?

To provide additional frontal plane views Signup and view all the answers

What is the purpose of unipolar precordial chest leads?

To provide transverse plane views Signup and view all the answers

What does the horizontal axis on ECG paper represent?

Time in milliseconds Signup and view all the answers

What happens to the complexes on ECG paper if slower variations of electrical potentials occur?

They become wider Signup and view all the answers

What is the standard calibration paper speed for ECG recording in small animals?

50 mm/sec Signup and view all the answers

Why do more muscle cells depolarizing result in higher waves on ECG paper?

Because more tissue is depolarizing Signup and view all the answers

What is the purpose of aVL lead?

Compares LA with the sum of the 2 other limbs Signup and view all the answers

How is heart rate calculated on ECG paper?

By measuring the time between complexes Signup and view all the answers

What is the standard calibration paper speed for ECG recording in humans?

25 mm/sec Signup and view all the answers

Study Notes

ECG Basics

Heart rate (HR) calculation: HR = 60/0.36 = 166 BPM
A single heartbeat consists of the P wave, P-R interval, QRS complex, Q-T interval, and T wave

P Wave

Represents depolarization of atrial muscle
Occurs due to discharge of the SA node
No deflection for SA node discharge, as it involves a small number of cells
No deflection for atrial repolarization

P-R Interval

Represents the time it takes for the electrical impulse to conduct through the atria, AV node, and Bundle of His
Mostly delayed through the AV node
Increased P-R interval is associated with A-V blocks
Starts from the beginning of the P wave to the first deflection of the QRS
Sympathetic stimulation decreases P-R interval, increasing conduction velocity
Parasympathetic stimulation increases P-R interval, decreasing conduction velocity

QRS Complex

Generated as the impulse activates the HIS-Purkinje system and ventricular muscle
Represents ventricular depolarization
Faster conduction velocity compared to the P wave
Each wave represents a specific place of the ventricle being depolarized

Q-T Interval

Reflects the approximate duration of ventricular systole and ventricular refractory period
Measured from the beginning of the Q wave to the end of the T wave
The S-T segment correlates with the plateau of the ventricular AP

T Wave

Represents ventricular repolarization
Has a longer duration than the QRS complex due to non-synchronized propagation
High degree of variability in dogs and cats
Can be positive, negative, biphasic, or very low amplitude

R-R Interval

Represents the time between one R wave and the next
Used to evaluate the regularity of the heartbeats (rhythm)
Used to calculate HR when the rhythm is regular

ECG Interpretation

Heart rate: number of heartbeats per minute
Segment: time length between two specific points on an ECG at the baseline amplitude
Interval: time length between two specific ECG events
Sinus rhythm: normal cardiac rhythm where depolarization begins at the SA node
Arrhythmia: abnormal heart rhythm
Tachycardia: increased heart rate
Bradycardia: decreased heart rate

How ECG Works

A positive and a negative charge separated by a small distance is a dipole, which generates local current flow and a small electrical field
Cardiac muscle cells act like a dipole when depolarizing or repolarizing
The electrical field generated by a single dipole is too small to be measured, but the sum of multiple dipoles can be detected
When cardiac impulses pass through the heart, the electrical current also spreads into adjacent tissues
A small portion of the current spreads to the surface of the body, which can be recorded by electrodes

ECG Paper

Allows the determination of duration and amplitude of waveforms and intervals/segments
Standard calibration paper speed is 25 mm/sec in humans and 50 mm/sec in small animals
The horizontal axis represents time in milliseconds
The vertical axis represents amplitude in millivolts

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Description

Test your knowledge of Electrocardiography basics, including heart rate calculation, P wave, and P-R interval. Learn about the electrical activity of the heart and its representations on an ECG graph.