Cardiac Dysrhythmias Advanced Question and Answers
100% Accuracy, 2024
What is the pacemaker of the heart normally?
SA Node.
Where does the SA node originate?
Upper right atrium.
What is the pathway of conduction in the heart?
SA node -> atria -> AV node -> bundle of his -> bundle branches -> purkinje fibers ->
ventricles.
What does stimulation of the vagus nerve cause?
Decreased firing of the SA node and slowed impulse conduction of the AV node.
What does stimulation of the sympathetic nerves cause?
Increased firing of the SA node and increased impulse through the AV node, and
cardiac contractility.
What does the P wave represent?
Time for the passage of the electrical impulse through the atrium causing atrial
depolarization (contraction).
What is the normal P wave duration?
0.06 - 0.12.
What is a possible variation cause of a P wave?
Disturbance in conduction within the atria.
What does the PR interval represent?
The measure from the beginning of the P wave to the beginning of the QRS complex,
represents time taken for impulse to spread through the atria, AV node, and bundle of
his, the bundle branches and purkinje fibers, to a point of immediately preceding
ventricular contraction.
What is the normal PR interval?
0.12 - 0.20.
What is a possible variation cause with PR interval?
, Disturbance in conduction usually in the AV node, bundle of his, or bundle branches but
can be atria as well.
What does the QRS interval represent?
Measure from beginning to end of QRS complex, represent time taken for
depolarization (contraction) of both ventricles (systole).
What is the normal QRS interval?
<0.12.
What is a possible variation cause with the QRS interval?
Disturbance in conduction in the bundle branches or in the ventricles.
What does the ST Segment represent?
Measure from the S wave of the QRS complex to the beginning of the T wave;
represents time between ventricular depolarization and repolarization (Diastole); should
be isoelectric (flat).
What is the normal ST segment?
0.12.
What is a possible variation cause with the ST segment?
Disturbance usually caused by ischemia, injury or infarction.
What does the T wave represent?
Represents time for ventricular repolarization, should be upright.
What is the normal T wave?
0.16.
What is a possible variation cause for a T wave?
Disturbance usually caused by electrolyte disturbances; ischemia or infarction.
What does the QT interval represent?
Measured from beginning of the QRS to end of the T wave, represents time taken for
entire electrical depolarization and repolarization of the ventricles.
What is the normal QT interval?
0.34 - 0.43.
What is the possible variation cause for a QT interval?
Disturbance usually affected repolarization more than depolarization and cause by
drugs, electrolyte imbalances, and change in hr.
100% Accuracy, 2024
What is the pacemaker of the heart normally?
SA Node.
Where does the SA node originate?
Upper right atrium.
What is the pathway of conduction in the heart?
SA node -> atria -> AV node -> bundle of his -> bundle branches -> purkinje fibers ->
ventricles.
What does stimulation of the vagus nerve cause?
Decreased firing of the SA node and slowed impulse conduction of the AV node.
What does stimulation of the sympathetic nerves cause?
Increased firing of the SA node and increased impulse through the AV node, and
cardiac contractility.
What does the P wave represent?
Time for the passage of the electrical impulse through the atrium causing atrial
depolarization (contraction).
What is the normal P wave duration?
0.06 - 0.12.
What is a possible variation cause of a P wave?
Disturbance in conduction within the atria.
What does the PR interval represent?
The measure from the beginning of the P wave to the beginning of the QRS complex,
represents time taken for impulse to spread through the atria, AV node, and bundle of
his, the bundle branches and purkinje fibers, to a point of immediately preceding
ventricular contraction.
What is the normal PR interval?
0.12 - 0.20.
What is a possible variation cause with PR interval?
, Disturbance in conduction usually in the AV node, bundle of his, or bundle branches but
can be atria as well.
What does the QRS interval represent?
Measure from beginning to end of QRS complex, represent time taken for
depolarization (contraction) of both ventricles (systole).
What is the normal QRS interval?
<0.12.
What is a possible variation cause with the QRS interval?
Disturbance in conduction in the bundle branches or in the ventricles.
What does the ST Segment represent?
Measure from the S wave of the QRS complex to the beginning of the T wave;
represents time between ventricular depolarization and repolarization (Diastole); should
be isoelectric (flat).
What is the normal ST segment?
0.12.
What is a possible variation cause with the ST segment?
Disturbance usually caused by ischemia, injury or infarction.
What does the T wave represent?
Represents time for ventricular repolarization, should be upright.
What is the normal T wave?
0.16.
What is a possible variation cause for a T wave?
Disturbance usually caused by electrolyte disturbances; ischemia or infarction.
What does the QT interval represent?
Measured from beginning of the QRS to end of the T wave, represents time taken for
entire electrical depolarization and repolarization of the ventricles.
What is the normal QT interval?
0.34 - 0.43.
What is the possible variation cause for a QT interval?
Disturbance usually affected repolarization more than depolarization and cause by
drugs, electrolyte imbalances, and change in hr.
