ECG Dysrhythmias

Updated March 2006: D. Tucker, RPh, BCPS

Overview

ECG waveforms Normal sinus rhythm Asystole Bradycardia Ventricular fibrillation Ventricular tachycardia

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

ECG Waveforms

P WaveElectrical activation (depolarization) of the right then left atrium due to discharge from the sinoatrial (SA) node

PR SegmentPassage 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

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ECG Waveforms

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

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ECG Rhythms

Normal sinus rhythm

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ECG Rhythms

Asystole

Bradycardia

Ventricular fibrillation

Ventricular tachycardia

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

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ECG Rhythms

Ventricular asystole

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

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ECG Rhythms

Sinus bradycardia

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

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ECG Rhythms

Ventricular fibrillation

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

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ECG Rhythms

Ventricular tachycardia

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Name TheseECG Rhythms

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