1. Updated March 2006: D. Tucker, RPh, BCPS
ECG Dysrhythmias
Updated March 2006: D. Tucker, RPh, BCPS

2. Overview ECG waveforms Normal sinus rhythm Asystole Bradycardia
Ventricular fibrillation
Ventricular tachycardia

3. ECG Rhythm Strip
Electrocardiogram or ECG is used to measure the activity of the heart
ECG is used to represent the conduction of electrical impulses from the atria to the ventricles
ECG is used to characterize rhythms and conduction abnormalities of the heart

4. ECG Waveforms P Wave PR Segment QRS Complex ST Segment T Wave U Wave
Electrical activation (depolarization) of the right then left atrium due to discharge from the sinoatrial (SA) node
PR Segment
Passage of the impulse through the atrioventricular (AV) node and bundle of HIS
QRS Complex
Electrical depolarization of the ventricles
ST Segment
Plateau phase
T Wave
Repolarization of the ventricle
U Wave
Repolarization of the HIS-Purkinje system

5. ECG Waveforms
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6. Normal Sinus Rhythm Normal impulse conduction through the heart
Normal sinus rhythm (NSR) is the standard against which all other rhythms are compared
NRS contains no ectopic or aberrant beats

7. ECG Rhythms
Normal sinus rhythm
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8. ECG Rhythms Asystole Bradycardia Ventricular fibrillation
Ventricular tachycardia
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9. Asystole Asystole is a cardiac standstill, i.e., flatline
Asystole is the absence of electrical activity in the venticles
Asystole usually results from a prolonged period of cardiac arrest without resuscitation
Asystole usually means the patient’s life has ended

10. ECG Rhythms
Ventricular asystole
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11. Bradycardia
Bradycardia is when the heart is < 60 beats/minute or when the heart rate is slower than expected
Sinus bradycardia usually occurs as a response to a reduced demand for blood flow
Signs and symptoms might include:
Chest pain, shortness of breath
Hypotension, pulmonary edema, congestive heart failure

12. ECG Rhythms
Sinus bradycardia
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13. Ventricular Fibrillation
Ventricular fibrillation (VF) occurs as a result of electrical impulses coming from multiple ectopic pacemaker in the ventricles
VF results in no cardiac output as a result of producing no effective ventricular contractions
With VF the ventricular muscle quivers instead of contracting

14. ECG Rhythms
Ventricular fibrillation
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15. Ventricular Tachycardia
Ventricular tachycardia (VT) is a result of 3 or more ventricular contractions occur earlier than expected resulting in a ventricular rate of >10 beats/minute
VT usually preceeds VF
Causes of VT include myocardial ischemia, heart failure, drug toxicity from procainamide, quinidine, or cocaine
Pulseless VT refers to the fact that the heart has electrical activity but is not pumping blood to the extremities

16. ECG Rhythms
Ventricular tachycardia
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17. Name These ECG Rhythms C A D E B healthcentral.org
A: Ventricular Fibrillation
B: Asystole
C: Sinus Bradycardia
D: Normal Sinus Rhythm
E: Ventricular Tachycardia E B
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