This document provides an overview of common cardiac rhythms seen on electrocardiograms (ECGs) including normal sinus rhythm, sinus tachycardia, sinus bradycardia, premature atrial contractions, atrial flutter, atrial fibrillation, paroxysmal atrial tachycardia, premature junctional contractions, junctional escape rhythm, junctional tachycardia, supraventricular tachycardia, premature ventricular complexes, and ventricular tachycardia. For each rhythm, the typical heart rate, rhythm, P wave characteristics, PR interval, QRS duration, and examples are described. Causes of each rhythm are also listed.

1. ECG review – ACLS Program Ohio State University Medical Center
Rhythm ECG Characteristics Example
Normal Sinus Rhythm Rate: 60-100 per minute
Rhythm: R- R =
(NSR)
P waves: Upright, similar
P-R: 0.12 -0 .20 second
& consistent
qRs: 0.04 – 0.10 second
P:qRs: 1P:1qRs
Sinus Tachycardia Rate: > 100
Causes: Rhythm: R- R =
Exercise P waves: Upright, similar
Hypovolemia P-R: 0.12 -0 .20 second
Medications & consistent
Fever qRs: 0.04 – 0.10 second
Hypoxia P:qRs: 1P:1qRs
Substances
Anxiety, Fear
Acute MI
Fight or Flight
Congestive Heart Failure
Sinus Bradycardia Rate: < 60
Causes: Rhythm: R- R =
intrinsic sinus node P waves: Upright; similar
disease P-R: 0.12 -0 .20 second
increased & consistent
parasympathetic tone qRs: 0.04 – 0.10 second
drug effect. P:qRs: 1P:1qRs
Published by: Department of Educational Development and Resources, OSU Medical Center 1
© December 2001 by The Ohio State Univeristy Medical Center All Rights Reserved

2. ECG review – ACLS Program Ohio State University Medical Center
Rhythm ECG Characteristics Example
Premature Atrial Rate: usually < 100,
Contractions (PAC) dependant
On underlying rhythm
♦ ♦ ♦
Causes:
Rhythm: irregular
normal
P waves: Early & upright,
excessive use of caffeine,
different from Sinus
tobacco, or alcohol
CHF
PR: 0.12 – 0.20 second;
different from Sinus
PAC = ♦
Myocardial ischemia or
qRs: 0.04 – 0.10 second
injury
P:qRs = 1:1
Hypokalemia, Dig
toxicity
COPD
Atrial Flutter Rate: Atrial rate 250-350
Causes: Vent 150 common
ischemic heart disease Rhythm: Atrial = Regular
Hypoxia Vent = Reg. or irreg
Acute MI P waves: Not identifiable
Dig Toxicity F waves: Uniform (sawtooth
Mitral or Tricuspid valve or picket fence )
disease PRI: not measurable
Pulmonary embolism qRs: 0.04 – 0.10 second
Atrial Fibrillation Rate: Atrial: 400-700
Ischemic heart disease Vent. 160-180/minute
Hypoxia Rhythm: Atrial: irregular;
Acute MI Vent.: irregular
Digitalis toxicity P waves: No identifiable Ps
Mitral or tricuspid f waves: may be seen.
disease PRI: unable to measure
(No identifiable P)
Published by: Department of Educational Development and Resources, OSU Medical Center 2
© December 2001 by The Ohio State Univeristy Medical Center All Rights Reserved

3. ECG review – ACLS Program Ohio State University Medical Center
Rhythm ECG Characteristics Example
qRs: usually normal
Paroxysmal Atrial Rate: usually 160-220
Rhythm: Regular
Tachycardia
P waves: differ in shape from
Causes:
Sinus Ps; usually difficult
Same as PACs
to identify (rate related)
PR Interval: Normal when the Ps
can be identified;
short if WPW present
qRs: usually normal
Other: Onset sudden, often
initiated by a PAC
Premature Junctional Rate: usually < 100,
dependant on the
Contraction (PJC)
underlying rhythm
Causes:
Rhythm: irregular
Same as PACs
P waves: Inverted before or after
qRs or not visible
PR interval: < 0.12 second when
inverted P is before
qRs
qRs: 0.04 – 0.10 second
P:qRs = 1:1 if Ps are visible
Junctional escape Rate: 40-60
61 – 100 (accelerated)
Rhythm
Rhythm: Regular
Causes:
P waves: Inverted before or after
healthy athlete at rest
qRs or not visible
related to medications-
PR interval: < 0.12 second when
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© December 2001 by The Ohio State Univeristy Medical Center All Rights Reserved

4. ECG review – ACLS Program Ohio State University Medical Center
Rhythm ECG Characteristics Example
Beta Blockers, Calcium inverted P is before
Channel Blockers, Dig qRs
Toxicity qRs: 0.04 – 0.10 second
or increased P:qRs 1:1 if Ps are visible
parasympathetic tone
Acute Inferior Wall MI
Rheumatic Heart Disease
Post-Cardiac Surgery
Valvular Disease
SA Node Disease
Hypoxia
Junctional Tachycardia Rate: 101-200
Causes:
Same as Paroxysmal Same as Junctional Escape
Atrial Tachycardia (PAT) Rhythms.
Supraventricular Rhythm: Absolutely regular
Rate: > 150 per minute
Tachycardia (SVT)
P Waves: Not visible
An umrella term used (PRI not measurable)
when unable to qRs: normal 0.04 – 0.10 sec
distinguish which
rhythm is present.
Causes:
Same as Sinus, Atrial, and
Junctional Tachycardia, and
Atrial Flutter
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© December 2001 by The Ohio State Univeristy Medical Center All Rights Reserved
PVC PVC

5. ECG review – ACLS Program Ohio State University Medical Center
Rhythm ECG Characteristics Example
Premature Ventricular Rate: Dependent upon
Complex (PVC) underlying rhythm
Causes: Rhythm: R – R ≠
Gastric overload P waves: Usually absent, if
Stress present, not associated
Caffeine, Alcohol, with PVC
Nicotine qRs: 0.12 second or greater;
Heart Disease bizarre and notched
Acid-Base Imbalance ST & T: Often opposite in
Electrolyte Imbalance direction to the qRs.
Cyclic Antidepressants
Hypoxia Timing
Acidosis One on a strip = Rare
Acute MI One in a row = Isolated
Two in a row = Pair, couplet
Three in a row = V Tachycardia
Pattern
Every other = Bigeminy
Every third = Trigeminy
Morphology
Similar shape = Uniformed
Different shape = Multiformed
Location
R – on – T = PVC falls on the T
wave of the complex before the
PVC
Ventricular Rate: > 100 per minute and
usually not > 220
Tachycardia
Rhythm: Usually regular
Causes:
P Waves: ∅ P waves or if
Same as PVCs
present, not
R on T Phenomenon
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© December 2001 by The Ohio State Univeristy Medical Center All Rights Reserved

6. ECG review – ACLS Program Ohio State University Medical Center
Rhythm ECG Characteristics Example
associated with qRs
qRs: Wide (≥ 0.12 sec),
bizarre
ST/T wave: Opposite direction
of qRs
A group of three PVCs in a row or
more at a rate greater than 100/
minute or more constitutes
Ventricular Tachycardia.
Ventricular Fibrillation Rate: ∅
Causes: Rhythm: ∅ regularity,
Acute Myocardial chaotic undulating
Infarction waves
Untreated Ventricular P Waves: ∅
Tachycardia qRs: ∅
Hypothermia ST/T Wave: ∅
R-on-T PVCs Organized activity: ∅
Electrolyte imbalance
Electrical shock No Cardiac Output or Pulse
Idioventricular Rate: 20-40 per minute
Rhythm: R – R =
Rhythm
P waves: No P waves associated
Causes:
to qRs
Myocardial Infarction
qRs: > 0.12 sec, notched,
Digitalis toxicity
bizarre appearance
Metabolic imbalances
ST/T : Opposite direction of qRs
Post resuscitation rhythm
Rate > 40 to 100 = Accelerated
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© December 2001 by The Ohio State Univeristy Medical Center All Rights Reserved

7. ECG review – ACLS Program Ohio State University Medical Center
Rhythm ECG Characteristics Example
Asystole Rate: Ventricular rate = 0
Causes: Rhythm: ∅ unless Ps are present,
Extensive myocardial then regular or irregular
damage P waves: may be present
Acute respiratory failure qRs: ∅
Ischemia or Infarction P:qRs ∅
Traumatic cardiac arrest
Ventricular aneurysm
Countershock
Hypoxia, Hypothermia
Hyperkalemia,
Hypokalemia
Preexisting acidosis
Drug overdose
1st degree AV Block υ 1P : 1 qRs
υ Prolonged PRI
(> 0.20 sec not > 0.40 sec)
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© December 2001 by The Ohio State Univeristy Medical Center All Rights Reserved

8. ECG review – ACLS Program Ohio State University Medical Center
Rhythm ECG Characteristics Example
2nd degree AV Block, υ More P waves than qRs
Type I υ PRI progressively increases
in a cycle until P appears
w/o qRs.
υ Cyclic pattern reoccurs
υR–R≠ = non-conducted P wave
2nd degree AV Block, More P waves than qRs
υ PRI consistent
Type II
υ qRs normal or wide (bundle
branch block)
υ R - R≠ or R – R =
= non-conducted P wave
3rd degree AV Block υ More P waves than qRs
υ P not r/t qRs
(P too close, P too far)
υ PRI varies greatly
υ qRs normal or wide
υR–R=
= non-conducted P wave
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© December 2001 by The Ohio State Univeristy Medical Center All Rights Reserved

9. ECG review – ACLS Program Ohio State University Medical Center
Published by: Department of Educational Development and Resources, OSU Medical Center 9
© December 2001 by The Ohio State Univeristy Medical Center All Rights Reserved