46 Questions
What is the primary purpose of an electrocardiogram (ECG)?
To quantify heart rate and detect changes in heart activity
Which term is used to describe the measurement of electrical activity from the heart?
Electrocardiogram (ECG)
What produces the trace seen on the screen of a heart monitor during an ECG recording?
Electrical activity from the heart
How many deflections above baseline are generally present in a 'standard trace' produced by an ECG recording?
Three
What important component of the trace produced by an ECG recording tells us about heart function?
Segments between deflections
Besides quantifying heart rate, what can an ECG help detect?
Changes in heart activity under different conditions
What is the most severe type of heart block?
Third degree heart block
What does it mean when P-waves are not followed by QRS complexes?
The heart is in a serious problem
What are escape QRS complexes indicative of?
Pacemaker rhythm being generated in the ventricles
Where does the heart become unstable if escape QRS complexes originate below?
Below the bundle of His
What is the angle of lead II in electrocardiography (ECG)?
+60 degrees
Which segment of the ECG represents the time of ventricular systole?
Q-T distance
What does a normal sinus rhythm in ECG refer to?
Upright and uniform P-waves, 1:1 P wave:QRS complex ratio
What does sinus arrhythmia show up as on an ECG trace?
Irregularly-spaced QRS complexes
What indicates a wandering atrial pacemaker on an ECG trace?
Variable P-wave morphology and changing P-R distances
What does the presence of wide QRS complexes on an ECG trace indicate?
Heart block
Which type of heart block is characterized by slightly prolonged P-R distances?
First degree heart block
What happens to the space in between beats in a trace showing bradycardia?
It becomes larger
What does the angle of lead aVR in ECG indicate?
-120 to -150 degrees
Which segment of the ECG can be used to calculate heart rate?
R-R distance
What do wide QRS complexes on an ECG trace indicate?
Heart block
What does sinus arrhythmia show up as on an ECG trace?
Unevenly-spaced QRS complexes
What is the primary reason for the P-wave being significantly smaller than the QRS complex in an ECG?
Depolarisation of the atria produces much smaller deflections than does the depolarisation of the ventricles.
What does the QRS complex on an ECG primarily reflect?
Depolarisation of the ventricles and atrial repolarisation
What does the T-wave on an ECG represent?
Depolarisation of the ventricles
What causes a slight delay between the P-wave and the QRS complex on an ECG?
Conduction through the AV node
How do augmented unipolar limb leads differ from standard bipolar limb leads in an ECG?
They have a different orientation for electrode placement.
What is the primary effect of any disease state that leads to growth of muscle mass in the ventricles on an ECG?
It results in a larger QRS complex.
What is reflected as the first phase of the P-wave on an ECG?
Pacemaker potential in the SA node
Which component of an ECG trace reflects both similar and quite different traces compared to bipolar limb leads?
Augmented unipolar limb leads (aVR, aVL, and aVF)
On an ECG trace, what does the flat segment between the P-wave and QRS complex reflect?
Time for electrical activity to conduct through AV node
What is represented by a small downward deflection called the Q-wave on an ECG?
Ventricular depolarization
What reflects the final deflection on an ECG trace after the QRS complex, and represents ventricular repolarization?
T-wave
On an ECG, what causes a significant difference between augmented unipolar limb leads and standard bipolar limb leads?
Orientation for electrode placement
What does an ECG measure?
Electrical activity on the body surface originating in the heart
What is the mean axis through the middle of the heart in which electrical activity flows?
60 degrees
Which term refers to a slow heart beat?
Bradycardia
Where are the electrodes placed for simple bipolar ECG limb leads?
Left arm and right arm
What does Einthoven's Law state?
The potential in any wave in lead II is equal to the sum of the potentials in leads I and III
What is associated with the first, small deflection called the P-wave?
Depolarization of the atria
What does a wave of depolarization traveling toward the left leg appear as?
Positive deflections in leads II and III
What change does an ECG reveal if the heart has undergone hypertrophy?
Increased muscle mass
What does lead I cross through over the heart?
Center horizontally
What disrupts a normal rhythm of the heart?
Ventricular arrhythmias
What can cause changes in the ECG according to the text?
Electrolyte imbalances in extracellular fluid and blood
What does a negative deflection appear as if a wave of depolarisation travels away from the left arm?
Lead I
Test your knowledge of the stages of the P-wave and the components of ECG waves with this quiz. Identify the various phases and deflections of the cardiac conduction system.
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