Temporary Cardiac Pacing

Bradyarrhythmias

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  Bradyarrhythmias can be classified into five groups:

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    Sinus bradycardia

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    Sinus pause

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    Junctional rhythm

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    Sinoatrial (SA) exit block

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    Idioventricular rhythm ( Table 21.1 ).

    Table 21.1

    Different Types of Bradyarrhythmias

    Bradyarrhythmias	Definition	ECG Changes
    Sinus bradycardia	Rate: < 60 beats/min Rhythm: regular P waves: normal in morphology and duration PR interval: between 0.12 and 0.20 sec
    Sinus pause	Sinus node fails to generate an impulse No P wave or its associated QRS and T wave Lasting from 2.0 sec to several minutes
    Junctional rhythm	AV node becomes the principal pacemaker Rate: 40–60 beats/min
    Idioventricular rhythm	Ventricle becomes the principal pacemaker Wide QRS complexes (> 120 msec) Rate: lower, between 20 to 40 beats/min
    Sinoatrial Exit Block a
    Second-degree type 1 SA block	Shortening of the PP interval until a P-QRS-T complex is dropped Takes progressively longer for each SA node impulse to exit the node until an impulse fails to exit the node
    Second-degree type 2 SA block	Impulse generated in the SA node occasionally fails to propagate into the atria, which appears as a dropped P-QRS-T complex PP interval surrounding the dropped complexes is two times (or a multiple) the baseline PP interval
    Third-degree SA exit block	None of the generated impulses exits the SA node Pause or junctional rhythm

    AV , Atrioventricular; ECG , electrocardiogram; SA , sinoatrial.

    a First-degree SA block, which is a delay between generation of impulse in SA node and its exit from the node, is not detectable on surface ECG.

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  Atrioventricular (AV) conduction blocks may also result in bradycardia and require pacemaker implantation.

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    AV blocks are defined in three groups ( Table 21.2 ).

    Table 21.2

    Indications and Contraindications for Permanent and Temporary Cardiac Pacing Based on Causes

    	Indications	Contraindications
    Permanent cardiac pacing	Any symptomatic bradycardia Sinus node dysfunction Acquired Mobitz II or third-degree atrioventricular block in adults Hypersensitive carotid sinus syndrome and severe neurocardiogenic syncope After cardiac transplantation Pacing to prevent ventricular tachycardia Patients with congenital heart disease	Local infection at implantation site Active systemic infection with bacteremia Severe bleeding tendencies (relative contraindication) Active anticoagulation therapy (relative contraindication)
    Temporary cardiac pacing	Reversible injury to the sinus node or other parts of the conduction system after cardiac surgery (e.g., injuries, postcoronary bypass) Chest and cardiac trauma associated with temporary sinus node or AV node dysfunction Metabolic and/or electrolyte imbalance (e.g., hyperkalemia) Drug-induced bradyarrhythmia (e.g., digitalis toxicity) Infectious diseases (e.g., Lyme disease or bacterial endocarditis)	Asymptomatic patient with stable rhythm (e.g., a first-degree AV block or a Mobitz 1 or stable escape rhythm)

    AV , Atrioventricular.