Sinoatrial Node Arrhythmias: Identifying Features
| Name | Rate | Rhythm | P Waves | PR Interval | QRS |
|---|---|---|---|---|---|
| Normal sinus rhythm | Normal (60–100 beats per minute [bpm]) | Regular | Normal (upright and uniform) | Normal (0.12–0.20 seconds [sec]) | Normal (0.06–0.10 sec) |
| Sinus bradycardia | Slow (less than 60 bpm) | Regular | Normal (upright and uniform) | Normal (0.12–0.20 sec) | Normal (0.06–0.10 sec) |
| Sinus tachycardia | Fast (greater than 100 bpm) | Regular | Normal (upright and uniform) | Normal (0.12–0.20 sec) | Normal (0.06–0.10 sec) |
| Sinus arrhythmia | Usually normal (60–100 bpm); frequently increases with inspiration and decreases with expiration; may be less than 60 bpm | Irregular; varies with respiration; difference between shortest R-R and longest R-R intervals is equal to or greater than 0.12 sec | Normal (upright and uniform) | Normal (0.12–0.20 sec) | Normal (0.06–0.10 sec) |
| Sinus pause (sinus arrest) | Normal to slow; determined by duration and frequency of sinus pause (arrest) | Irregular whenever a pause (arrest) occurs. The pause (arrest) time interval is not a multiple of the normal R-R interval. | Normal (upright and uniform) except in areas of pause (arrest) | Normal (0.12–0.20 sec) | Normal (0.06–0.10 sec) |
| Sinoatrial (SA) block | Normal to slow; determined by duration and frequency of SA block | Irregular whenever an SA block occurs. The SA block occurs in some multiple of the R-R interval. | Normal (upright and uniform) except in areas of dropped beats | Normal (0.12–0.20 sec) | Normal (0.06–0.10 sec) |
Atrial Arrhythmias Identifying Features
| Name | Rate | Rhythm | P Waves | PR Interval | QRS |
|---|---|---|---|---|---|
| Wandering atrial pacemaker | Normal (60–100 bpm) | Irregular | At least three different forms, determined by focus in atria | Variable; determined by focus | Normal (0.06–0.10 sec) |
| Multifocal atrial tachycardia | Fast (greater than 100 bpm) | Irregular | At least three different forms, determined by focus in atria | Variable; determined by focus | Normal (0.06–0.10 sec) |
| Premature atrial contraction (PAC) | Depends on rate of underlying rhythm | Irregular whenever a PAC occurs | Present; in the PAC, may have a different shape | Varies in the PAC; otherwise normal (0.12–0.20 sec) | Normal (0.06–0.10 sec) |
| Atrial tachycardia | 150–250 bpm | Regular | Normal (upright and uniform) but differ in shape from sinus P waves | May be short (less than 0.12 sec) in rapid rates | Normal (0.06–0.10 sec) but can be aberrant at times |
| Supraventricular tachycardia | 150–250 bpm | Regular | Frequently buried in preceding T waves and difficult to see | Usually not possible to measure | Normal (0.06–0.10 sec) but may be wide if abnormally conducted through ventricles |
| Paroxysmal supraventricular tachycardia | 150–250 bpm | Irregular | Frequently buried in preceding T waves and difficult to see | Usually not possible to measure | Normal (0.06–0.10 sec) but may be wide if abnormally conducted through ventricles |
| Atrial flutter | Atrial: 250–350 bpm; ventricular: variable | Atrial: regular; ventricular: variable | Flutter waves have a saw-toothed appearance; some may not be visible, being buried in QRS | None, not measurable | Usually normal (0.06–0.10 sec), but may appear widened if flutter waves are buried in the QRS |
| Atrial fibrillation | Atrial: equal to or greater than 350 bpm; ventricular: variable | Irregular | No true P waves; chaotic atrial activity | None | Normal (0.06–0.10 sec) |
| Wolff-Parkinson-White syndrome | Depends on rate of underlying rhythm | Regular unless associated with atrial fibrillation | Normal (upright and uniform) unless atrial fibrillation is present | Short (less than 0.12 sec) | Wide (greater than 0.10 sec); delta wave present |
Junctional Arrhythmias: Identifying Features
| Name | Rate | Rhythm | P Waves | PR Interval | QRS |
|---|---|---|---|---|---|
| Junctional rhythm | 40–60 bpm | Regular | Absent, inverted, buried, or retrograde | None, short, or retrograde | Normal (0.06–0.10 sec) |
| Accelerated junctional rhythm | 61–100 bpm | Regular | Absent, inverted, buried, or retrograde | None, short, or retrograde | Normal (0.06–0.10 sec) |
| Junctional tachycardia | 101–180 bpm | Regular | Absent, inverted, buried, or retrograde | None, short, or retrograde | Normal (0.06–0.10 sec) |
| Junctional escape beat | Depends on rate of underlying rhythm | Irregular whenever an escape beat occurs | None, inverted, buried, or retrograde in the escape beat | None, short, or retrograde | Normal (0.06–0.10 sec) |
| Premature junctional contraction (PJC) | Depends on rate of underlying rhythm | Irregular whenever a PJC occurs | Absent, inverted, buried, or retrograde in the PJC | None, short, or retrograde | Normal (0.06– 0.10 sec) |
Ventricular Arrhythmias Identifying Features
| Name | Rate | Rhythm | P Waves | PR Interval | QRS |
|---|---|---|---|---|---|
| Idioventricular rhythm | 20–40 bpm | Regular | None | None | Wide (greater than 0.10 sec), bizarre appearance |
| Accelerated idioventricular rhythm | 41–100 bpm | Regular | None | None | Wide (greater than 0.10 sec), bizarre appearance |
| Premature ventricular contraction (PVC) | Depends on rate of underlying rhythm | Irregular whenever a PVC occurs | None associated with the PVC | None associated with the PVC | Wide (greater than 0.10 sec), bizarre appearance |
| Premature ventricular contraction: Uniform | Depends on rate of underlying rhythm | Irregular whenever a PVC occurs | None associated with the PVC | None associated with the PVC | Wide (greater than 0.10 sec), bizarre appearance; PVCs look the same |
| Premature ventricular contraction: Multiform | Depends on rate of underlying rhythm | Irregular whenever a PVC occurs | None associated with the PVC | None associated with the PVC | Wide (greater than 0.10 sec), bizarre appearance; PVCs vary in appearance |
| Premature ventricular contraction: Ventricular bigeminy | Depends on rate of underlying rhythm | Irregular whenever a PVC occurs | None associated with the PVC | None associated with the PVC | Wide (greater than 0.10 sec), bizarre appearance; PVCs occur with every other beat |
| Premature ventricular contraction: Ventricular trigeminy | Depends on rate of underlying rhythm | Irregular whenever a PVC occurs | None associated with the PVC | None associated with the PVC | Wide (greater than 0.10 sec), bizarre appearance; PVCs occur with every third beat |
| Premature ventricular contraction: Ventricular quadrigeminy | Depends on rate of underlying rhythm | Irregular whenever a PVC occurs | None associated with the PVC | None associated with the PVC | Wide (greater than 0.10 sec), bizarre appearance; PVCs occur with every fourth beat |
| Premature ventricular contraction: Couplets | Depends on rate of underlying rhythm | Irregular whenever a PVC occurs | None associated with the PVC | None associated with the PVC | Wide (greater than 0.10 sec), bizarre appearance; PVCs occur in pairs |
| Premature ventricular contraction: R-on-T phenomenon | Depends on rate of underlying rhythm | Irregular whenever a PVC occurs | None associated with the PVC | None associated with the PVC | Wide (greater than 0.10 sec), bizarre appearance; PVCs fall on the T wave of the preceding beat |
| Premature ventricular contraction: Interpolated | Depends on rate of underlying rhythm | Irregular whenever a PVC occurs | None associated with the PVC | None associated with the PVC | Wide (greater than 0.10 sec), bizarre appearance; PVC occurs between two regular beats with no compensatory pause |
| Ventricular tachycardia: Monomorphic | 100–250 bpm | Regular | None or not associated with the QRS | None | Wide (greater than 0.10 sec), bizarre appearance; QRS complexes are the same in shape and amplitude |
| Ventricular tachycardia: Polymorphic | 100–250 bpm | Regular or irregular | None or not associated with the QRS | None | Wide (greater than 0.10 sec), bizarre appearance; QRS complexes vary in shape and amplitude |
| Torsade de pointes | 200–250 bpm | Irregular | None | None | Wide (greater than 0.10 sec), bizarre appearance; QRS complexes show a spindle effect |
| Ventricular fibrillation | Indeterminate | Irregular (chaotic) | None | None | None |
| Pulseless electrical activity | No pulse; only electrical activity | Reflects underlying rhythm | Reflects underlying rhythm | Reflects underlying rhythm | Reflects underlying rhythm |
| Asystole | None | None | None | None | None |
Atrioventricular and Bundle Branch Blocks Identifying Features
| Name | Rate | Rhythm | P Waves | PR Interval | QRS |
|---|---|---|---|---|---|
| First-degree atrioventricular block | Depends on rate of underlying rhythm | Regular | Normal (upright and uniform) | Prolonged (greater than 0.20 sec) | Normal (0.06–0.10 sec) |
| Second-degree atrioventricular block: Type I (Mobitz I or Wenckebach) | Depends on rate of underlying rhythm | Atrial: regular; ventricular: irregular | Normal (upright and uniform), more P waves than QRS | Progressively longer until one P wave is blocked and a QRS is dropped | Normal (0.06–0.10 sec) |
| Second-degree atrioventricular block: Type II (Mobitz II) | Atrial: usually 60–100 bpm; ventricular: slower than atrial rate | Atrial regular and ventricular may be regular or irregular | Normal (upright and uniform); more P waves than QRSs | Normal or prolonged but constant | May be normal, but usually wide (greater than 0.10 sec) if the bundle branches are involved |
| Third-degree atrioventricular block | Atrial: 60–100 bpm; ventricular: 40–60 bpm if escape focus is junctional, less than 40 bpm if escape focus is ventricular | Usually regular, but atria and ventricles act independently | Normal (upright and uniform); may be superimposed on QRS complexes or T waves | Varies greatly | Normal if ventricles are activated by junctional escape focus; wide if escape focus is ventricular |
| Bundle branch block | Depends on rate of underlying rhythm | Regular | Normal (upright and uniform) | Normal (0.12–0.20 sec) | Wide (greater than 0.10 sec) with or without a notched appearance |