Basic Dysrhythmias & EKG
Interpretation Exam Questions
and Answers
Normal Sinus Rhythm - Correct Answers: NSR
Rate: 60-100 bpm
Regularity: Regular
P Waves: Normal
PR Interval: 0.12-0.20 s
QRS Duration: 0.04-0.12 s
QT Duration: 0.36-0.44 s
Sinus Node - Correct Answers: Sinus Node Problems:
The SA node can:
--Fire too slow (Sinus Bradycardia [SB])
--Fire too fast (Sinus Tachycardia [ST])
Sinus Bradycardia (SB) - Correct Answers: Rate <60 bpm
Etiology--SA node is depolarizing slower than normal, impulse is conducted normally
--Normal PR interval and QRS interval
--Once SA node fires, everything else happens normal
Can be normal for super athletes
Sinus Tachycardia (ST) - Correct Answers: May be appropriate response to stress
Rate >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 arrhythmia
, Atrial cells - Correct Answers: 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 micro re-entrant "wavelets"
(Atrial Fibrillation)
Premature Atrial Contractions (PACs) - Correct Answers: 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 normally through the AV
node and the ventricles
--One cell randomly firing (anywhere in atria)
Atrial Flutter (A Flutter) - Correct Answers: 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
Atrial Fibrillation (AF) - Correct Answers: 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 allows some of the
impulses to pass through at variable intervals (so rhythm is irregularly irregular)
--Just quivers
--Very common in elderly
--HR>100, AF with RVR (rapid ventricular response)
AV Junction - Correct Answers: AV Node Arrhythmias
The AV Junction can:
--Fire continuously due to a looping re-entrant circuit (Paroxysmal Supraventricular Tachycardia [PSVT or
SVT])
Interpretation Exam Questions
and Answers
Normal Sinus Rhythm - Correct Answers: NSR
Rate: 60-100 bpm
Regularity: Regular
P Waves: Normal
PR Interval: 0.12-0.20 s
QRS Duration: 0.04-0.12 s
QT Duration: 0.36-0.44 s
Sinus Node - Correct Answers: Sinus Node Problems:
The SA node can:
--Fire too slow (Sinus Bradycardia [SB])
--Fire too fast (Sinus Tachycardia [ST])
Sinus Bradycardia (SB) - Correct Answers: Rate <60 bpm
Etiology--SA node is depolarizing slower than normal, impulse is conducted normally
--Normal PR interval and QRS interval
--Once SA node fires, everything else happens normal
Can be normal for super athletes
Sinus Tachycardia (ST) - Correct Answers: May be appropriate response to stress
Rate >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 arrhythmia
, Atrial cells - Correct Answers: 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 micro re-entrant "wavelets"
(Atrial Fibrillation)
Premature Atrial Contractions (PACs) - Correct Answers: 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 normally through the AV
node and the ventricles
--One cell randomly firing (anywhere in atria)
Atrial Flutter (A Flutter) - Correct Answers: 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
Atrial Fibrillation (AF) - Correct Answers: 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 allows some of the
impulses to pass through at variable intervals (so rhythm is irregularly irregular)
--Just quivers
--Very common in elderly
--HR>100, AF with RVR (rapid ventricular response)
AV Junction - Correct Answers: AV Node Arrhythmias
The AV Junction can:
--Fire continuously due to a looping re-entrant circuit (Paroxysmal Supraventricular Tachycardia [PSVT or
SVT])
