ECG Rhythm Interpretation
atrial pacemaker
Rhythm: Regular if 1:1 pacing Rate: Varies with underlying rhythm P wave: Paced beats similar in size and shape, pacing artifact before P wave PR Interval: varies P:QRS Ratio: normal if normal AV conduction QRS duration: <0.12 seconds
ventricular pacemaker
Rhythm: Regular if 1:1 pacing Rate: Varies with underlying rhythm P wave: may be present PR Interval: varies P:QRS Ratio: varies with underlying rhythm QRS duration: Paced beats will be similar in size and shape, pacing artifact before QRS
Premature Ventricular Contraction (PVC)
Rhythm: Underlying rhythm, except for PVC Rate: Underlying rhythm P wave: Absent or disassociated from ectopic beat PR Interval: absent P:QRS Ratio: underlying rhythm QRS duration: widened or bizarre
Sinus Block and Sinus Arrest
Rhythm: Usually regular, irregular during pause Rate: 60-100 P wave: Normal, absent during pause PR Interval: 0.12-0.20 seconds P:QRS Ratio: 1:1 QRS duration: <0.12 seconds QT Interval: Normal, unmeasurable during pause
Asystole
Rhythm: absent Rate: 0 P wave: None PR Interval: None P:QRS Ratio: None QRS duration: None QT Interval: None
Ventricular Fibrillation
Rhythm: chaotic Rate: 0 P wave: None PR Interval: None P:QRS Ratio: None QRS duration: None OT Interval: None
Ventricular Tachycardia: Torsades de Pointes
Rhythm: irregular and chaotic Rate: Ventricular 250-350 P wave: obscured PR Interval: absent P:QRS Ratio: N/A QRS duration: >0.12
Junctional Tachycardia
Rhythm: regular Rate: 100-160 P wave: Inverted in Lead II or hidden, can be before or after the QRS PR Interval: short or not measurable P:QRS Ratio: 1:1, if P wave is visible QRS duration: <0.12 seconds
sinus tachycardia
Rhythm: regular Rate: 101-160 P wave: Normal PR Interval: 0.12 - 0.20 seconds P:QRS Ratio: 1:1 QRS duration: <0.12 seconds QT Interval: May be shortened
Junctional Rhythm
Rhythm: regular Rate: 40-60 P wave: Inverted in Lead II or hidden, can be before or after the QRS PR Interval: short or not measurable P:QRS Ratio: 1:1, if P wave is visible QRS duration: <0.12 seconds
Accelerated Junctional Rhythm
Rhythm: regular Rate: 60-100 P wave: Inverted in Lead II or hidden, can be before or after the QRS PR Interval: short or not measurable P:QRS Ratio: 1:1, if P wave is visible QRS duration: <0.12 seconds
normal sinus rhythm (NSR)
Rhythm: regular Rate: 60-100 P wave: PR Interval: 0.12-0.20 seconds P:QRS Ratio: 1:1 QRS duration: <0.12 seconds QT Interval: 0.32-0.44
Sinus Bradycardia
Rhythm: regular Rate: <60 P wave: normal PR Interval: 0.12-0.20 seconds P:QRS Ratio: 1:1 QRS duration: <0.12 seconds QT Interval: may be prolonged
ventricular tachycardia
Rhythm: regular Rate: >100 P wave: obscured PR Interval: absent P:QRS Ratio: N/A QRS duration: >0.12 seconds
Atrial Tachycardia/ Supraventricular Tachycardia (SVT)
Rhythm: regular Rate: >160 P wave: may be hidden PR Interval: unable to measure P:QRS Ratio: 1:1 QRS duration: <0.12 seconds
1st degree heart block
Rhythm: regular Rate: Underlying rhythm P wave: normal PR Interval: >0.20 seconds P:QRS Ratio: 1:1 QRS duration: <0.12 seconds
Atrial Flutter
Rhythm: regular or irregular Rate: Atrial 250-400 Ventricular varies P wave: flutter waves, sawtooth PR Interval: not measured P:QRS Ratio: Variable-3:1, 4:1 QRS duration: <0.12 seconds
Premature Atrial Contraction (PAC)
Rhythm: regular, except PAC Rate: depends on underlying rhythm P wave: Premature P wave different from other P waves, may be normal depending on location PR Interval: 0.12-0.20 seconds, PAC interval may be different P:QRS Ratio: 1:1 QRS duration: <0.12 seconds
2nd degree heart block (Type I) (Wenkebach)
Rhythm: Atrial Regular; Ventricular Irregular Rate: underlying rhythm P wave: normal PR Interval: progressively lengthens P:QRS Ratio: variable, more P's than QRS's QRS duration: <0.12 seconds
3rd degree heart block
Rhythm: Atrial regular; Ventricular regular Rate: Atrial 60-100; Ventricular 20-60 P wave: normal, may be hidden PR Interval: varies, no relationship between P's and QRS's P:QRS Ratio: varies QRS duration: normal or wide, depending on level of the block
2nd degree heart block (Type 2)
Rhythm: Atrial regular; Ventricular regular/ irregular Rate: underlying rhythm P wave: normal PR Interval: constant, may be normal or prolonged P:QRS Ratio: variable, more P's than QRS's QRS duration: normal if block is at bundle of His, wide if block is at bundle branches
Sinus Arrhythmia
Rhythm: Irregular Rate: 60-100 P wave: normal PR Interval: 0.12-0.20 seconds P:QRS Ratio: 1:1 QRS duration: <0.12 seconds QT Interval: may vary slightly
atrial fibrillation
Rhythm: Irregular Rate: Atrial >400 Ventricular Varies P wave: fibrillatory waves PR Interval: not measurable P:QRS Ratio: not measurable QRS duration: <0.12 seconds
AV sequential pacemaker
Rhythm: Regular if 1:1 pacing Rate: Varies with underlying rhythm P wave: P waves should follow atrial pacing spike PR Interval: varies P:QRS Ratio: Should be 1:1 for paced beats QRS duration: QRS complex should follow ventricular pacing spike
