bradycardia & heart block

Bradycardia & Heart Block23 August 2011

BradycardiaBradycardia& &

Heart BlockHeart Block


Cardiac rhythm:

• Impulse formation - SA node

• Impulse conduction


Diagnosis of Heart Blocks

• Sinoatrial block

• Atrioventricular block- First degree- Second degree

Mobitz I (Wenckebach)Mobitz II

- Third degree


Bradyarrhythmia Diagnosis

Sinus Bradycardia


Sick sinus syndrome


First degree Constant PR intervalPR Interval > 0.20 s

Second degreeMobitz I (Wenckebach) Progressive increase PR

Dropped QRS complexGrouping of beatsFirst PR after drop QRS is shorter

Mobitz II Constant PR intervalQRS usually widenedSuddenly blocked P wave

Third degree AV dissociationQRS narrow or wide

AV Blocks


Relationship between P and QRS

1:1 Intermittent block Dissociated

First degree AV Block

Complete Heart Block

Second degree Mobitz I(Wenckebach)Second degree Mobitz II2:1 AV block


AV Block Diagnosis

First-Degree AV Block


AV Block Diagnosis

Second-Degree Type I AV Block


AV Block Diagnosis

Second-Degree Type II AV Block


Second degree AV block, type IIRate : Atrial rate > ventricular rateRhythm : Atrial regular (P’s plot through); Ventricular IRREGULARP waves : Normal in size and configuration

Some P waves are not followed by a QRS (more P’s than QRS)

PRI : May be within normal limits or prolonged but is CONSTANT FOR EACH CONDUCTED QRS

QRS : >.10 but is dropped periodically


AV Block Diagnosis

2:1 AV Block With Wide QRS


AV Block Diagnosis

Third-Degree AV Block With Narrow Complexes


AV Block Diagnosis

Third-Degree AV Block With Wide Complexes


Bradycardia Algorithm

Primary ABCD Survey Primary ABCD Survey

Serious signs or symptoms?Due to the bradycardia?


Secondary ABCD SurveySecondary ABCD Survey

Assess rhythmAssess rhythm

Bradycardia• Slow (absolute bradycardia = rate<60 bpm

or• Relatively slow (rate less than expected relative to underlying condition or cause)

Bradycardia• Slow (absolute bradycardia = rate<60 bpm

or• Relatively slow (rate less than expected relative to underlying condition or cause)


Bradycardia Algorithm



Type II second-degree AV blockor

Third-degree AV block?

Type II second-degree AV blockor

Third-degree AV block?

ObserveObserve

Intervention sequence• Atropine 0.6 to 1.2 mg a

• Transcutaneous pacing if availableb

• Dopamine 2 to 20 mcg/kg per minute• Adrenaline 2 to 10 mcg/min Infusion

Intervention sequence• Atropine 0.6 to 1.2 mg a• Transcutaneous pacing if availableb

• Dopamine 2 to 20 mcg/kg per minute• Adrenaline 2 to 10 mcg/min Infusion

No Yes

• Prepare for transvenous pacer• If symptoms develop, use

transcutaneous pacemaker until transvenous pacer placed

• Prepare for transvenous pacer• If symptoms develop, use

transcutaneous pacemaker until transvenous pacer placed

YesNo

Note a. Atropine is given in a dose of 0.6 mg intravenously & may be repeated every 3-5 min up to a maximum dose of 2.4 mg

Note b. If the patient is symptomatic, do not delay transcutaneous pacing while awaiting IV access & IV atropine to take effect


• If the patient has serious signs or symptoms, make sure they are related to the slow rate

• Look for symptoms and signs related to the slow heart rate


Symptoms: Chest painShortness of breathDecreased level of consciousnessDizziness/syncopeWeak/tiredness

Signs : HypotensionHeart failure (bibasal crepitations)Cool, clammy peripheriesVentricular ectopics


Denervated transplanted hearts will not respond to atropine, go at once

to pacing, catecholamine infusion or both


Never treat third-degree heart block plus ventricular escape beats with lignocaine(or any agent that suppresses ventricular

escape rhythms)


Transcutaneous pacemakers

Basic features :

• Either fixed-rate or demand mode• Rate selection from 30 to 180 beats per minute• Current output from 0 to 200 mA• Pacing electrodes can be used as defibrillation

electrodes


Technique of Transcutaneous pacing

• Attach pacing electrodes. Set at rate of 80 beats per minute

•In symptomatic bradycardia, increase current slowly until capture (may require sedation)

• Assess electrical and mechanical capture

• Continue pacing at a slightly higher output (10%)

Presenter

Presentation Notes

It is ok to set the rate at 80 bpm as during resuscitation we often need a faster heart rate.


Transcutaneous pacing


Pitfalls and Complications of Transcutaneous Pacing

• Failure to recognize underlying VF

• Failure to recognize failure of capture

• Pain

• Induction of VF (rare)

• Skin burns (rare)

bradycardia & heart block

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