Basic Dysrhythmias & EKG Interpretation Comprehensive Exam
Questions and Correct Answers | Updated 2026/2027 Graded A+.
1. Normal Sinus Rhythm: NSR
Rate: 60-100 bpm
Regularity: RegularP
Waves: Normal
PR Interval: 0.12-0.20 s
QRS Duration: 0.04-0.12 s
QT Duration: 0.36-0.44 s
2. Sinus Node: Sinus Node Problems:
The SA node can:
--Fire too slow (Sinus Bradycardia [SB])
--Fire too fast (Sinus Tachycardia [ST])
3. Sinus Bradycardia (SB): Rate <60 bpm
Etiology--SA node is depolarizing slower than normal, impulse is conducted normal-ly
--Normal PR interval and QRS interval
--Once SA node fires, everything else happens normalCan be
normal for super athletes
4. Atrial cells: Atrial Arrhythmias
Atrial cells can:
--Fire occasionally from a focus (Premature Atrial Contractions [PACS])
--Fire continuously due to a looping re-entrant circuit (Atrial Flutter)
--Fire continuously from multiple foci OR fire continously due to multiple microre-
entrant "wavelets" (Atrial Fibrillation)
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, 5. Premature Atrial Contractions (PACs): These ectopic cells origionate in the atria
(but not the SA node), therefore the contour of the P wave, the PR interval, and the timing
are DIFFERENT than normally generated pulse from the SA node Etiology--Excitation of
an atrial cell forms an impulse that is then conducted normallythrough the AV node and the
ventricles
--One cell randomly firing (anywhere in atria)
6. Atrial Flutter (A Flutter): No P waves. Instead, flutter waves ("sawtooth pattern")are
formed at a rate of 250-300 bpm
Only some impulses conduct through the AV node (usually every other impulse)
Etiology--every 2nd, 3rd, or 4th impulse generating a QRS
--Others are blocked in the AV node as the node repolarizes
7. Sinus Tachycardia (ST): May be appropriate response to stressRate
>100 bpm
Etiology--SA node is depolarizing faster than normal, impulse is conducted normally
Remember: it is a response to physical or psychological stress, not primary arrhyth-mia
8. Atrial Fibrillation (AF): No organized atrial depolarization, so no normal P waves
(impulses are not originating from sinus node)
Etiology--Impulses are formed in a totally unpredictable fashion. The AV node allowssome
of the impulses to pass through at variable intervals (so rhythm is irregularlyirregular)
--Just quivers
--Very common in elderly
--HR>100, AF with RVR (rapid ventricular response)
9. AV Junction: AV Node Arrhythmias
The AV Junction can:
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Questions and Correct Answers | Updated 2026/2027 Graded A+.
1. Normal Sinus Rhythm: NSR
Rate: 60-100 bpm
Regularity: RegularP
Waves: Normal
PR Interval: 0.12-0.20 s
QRS Duration: 0.04-0.12 s
QT Duration: 0.36-0.44 s
2. Sinus Node: Sinus Node Problems:
The SA node can:
--Fire too slow (Sinus Bradycardia [SB])
--Fire too fast (Sinus Tachycardia [ST])
3. Sinus Bradycardia (SB): Rate <60 bpm
Etiology--SA node is depolarizing slower than normal, impulse is conducted normal-ly
--Normal PR interval and QRS interval
--Once SA node fires, everything else happens normalCan be
normal for super athletes
4. Atrial cells: Atrial Arrhythmias
Atrial cells can:
--Fire occasionally from a focus (Premature Atrial Contractions [PACS])
--Fire continuously due to a looping re-entrant circuit (Atrial Flutter)
--Fire continuously from multiple foci OR fire continously due to multiple microre-
entrant "wavelets" (Atrial Fibrillation)
1/4
, 5. Premature Atrial Contractions (PACs): These ectopic cells origionate in the atria
(but not the SA node), therefore the contour of the P wave, the PR interval, and the timing
are DIFFERENT than normally generated pulse from the SA node Etiology--Excitation of
an atrial cell forms an impulse that is then conducted normallythrough the AV node and the
ventricles
--One cell randomly firing (anywhere in atria)
6. Atrial Flutter (A Flutter): No P waves. Instead, flutter waves ("sawtooth pattern")are
formed at a rate of 250-300 bpm
Only some impulses conduct through the AV node (usually every other impulse)
Etiology--every 2nd, 3rd, or 4th impulse generating a QRS
--Others are blocked in the AV node as the node repolarizes
7. Sinus Tachycardia (ST): May be appropriate response to stressRate
>100 bpm
Etiology--SA node is depolarizing faster than normal, impulse is conducted normally
Remember: it is a response to physical or psychological stress, not primary arrhyth-mia
8. Atrial Fibrillation (AF): No organized atrial depolarization, so no normal P waves
(impulses are not originating from sinus node)
Etiology--Impulses are formed in a totally unpredictable fashion. The AV node allowssome
of the impulses to pass through at variable intervals (so rhythm is irregularlyirregular)
--Just quivers
--Very common in elderly
--HR>100, AF with RVR (rapid ventricular response)
9. AV Junction: AV Node Arrhythmias
The AV Junction can:
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