Ecg
Normal sinus rhythm
 |
| Rhythm | regular |
| Rate | 60 to 100 beats/minute |
| P wave | normal; upright |
| PR interval | 0.12 to 0.20 second |
| QRS complex | 0.06 to 0.10 second |
Sinus bradycardia
 |
| Rhythm | regular |
| Rate | < 60 beats/minute |
| P wave | normal |
| PR interval | 0.12 to 0.20 second |
| QRS complex | 0.06 to 0.10 second |
Sinus tachycardia
 |
| Rhythm | regular |
| Rate | 100 to 160 beats/minute |
| P wave | normal |
| PR interval | 0.12 to 0.20 second |
| QRS complex | 0.06 to 0.10 second |
Premature atrial contractions (PACs)
 |
| Rhythm | irregular |
| Rate | varies with underlying rhythm |
| P wave | premature and abnormally shaped with PACs |
| PR interval | usually within normal limits; varies depending on ectopic focus |
| QRS complex | 0.06 to 0.10 second |
Atrial tachycardia
 |
| Rhythm | regular |
| Rate | atrial—150 to 250 beats/minuteventricular—depends on AV conduction ratio |
| P wave | hidden in the preceding T wave |
| PR interval | not visible |
| QRS complex | 0.06 to 0.10 second |
Atrial flutter
 |
| Rhythm | atrial—regularventricular—typically irregular |
| Rate | atrial—250 to 400 beats/minuteventricular—usually 60 to 100 beats/minute; depends on degree of AV block |
| P wave | classic sawtooth appearance |
| PR interval | unmeasurable |
| QRS complex | 0.06 to 0.10 second |
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