Bradycardia & Heart Block

Transcription

1 Bradycardia & Heart Block

2 Cardiac rhythm: Impulse formation - SA node Impulse conduction

3 Diagnosis of Heart Blocks Sinoatrial block Atrioventricular block - First degree - Second degree Mobitz I (Wenckebach) Mobitz II - Third degree

4 Bradyarrhythmia Diagnosis Sinus Bradycardia

5 Sick sinus syndrome

6 AV Blocks First degree Second degree Mobitz I (Wenckebach) Mobitz II Third degree Constant PR interval PR Interval > 0.20 s Progressive increase PR Dropped QRS complex Grouping of beats First PR after drop QRS is shorter Constant PR interval QRS usually widened Suddenly blocked P wave AV dissociation QRS narrow or wide

7 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 II 2:1 AV block

8 AV Block Diagnosis First-Degree AV Block

9 AV Block Diagnosis Second-Degree Type I AV Block

10 AV Block Diagnosis Second-Degree Type II AV Block

11 Second degree AV block, type II Rate : Rhythm : P waves : PRI : QRS : Atrial rate > ventricular rate Atrial regular (P s plot through); Ventricular IRREGULAR Normal in size and configuration Some P waves are not followed by a QRS (more P s than QRS) May be within normal limits or prolonged but is CONSTANT FOR EACH CONDUCTED QRS >.10 but is dropped periodically

12 AV Block Diagnosis 2:1 AV Block With Wide QRS

13 AV Block Diagnosis Third-Degree AV Block With Narrow Complexes

14 AV Block Diagnosis Third-Degree AV Block With Wide Complexes

15 Bradycardia Algorithm Primary Primary ABCD ABCD Survey Survey Assess Assess rhythm rhythm Bradycardia Bradycardia Slow Slow (absolute (absolute bradycardia bradycardia = = rate<60 rate<60 bpm bpm or or Relatively Relatively slow slow (rate (rate less less than than expected expected relative relative to to underlying underlying condition condition or or cause) cause) Secondary Secondary ABCD ABCD Survey Survey Serious Serious signs signs or or symptoms? symptoms? Due Due to to the the bradycardia? bradycardia?

16 Bradycardia Algorithm Serious Serious signs signs or or symptoms? symptoms? Due Due to to the the bradycardia? bradycardia? No Yes Type Type II II second-degree second-degree AV AV block block or or Third-degree Third-degree AV AV block? block? No Yes Intervention Intervention sequence sequence Atropine Atropine to to mg mg a a Transcutaneous Transcutaneous pacing pacing if if available available b b Dopamine Dopamine 2 2 to to mcg/kg mcg/kg per per minute minute Adrenaline Adrenaline 2 2 to to mcg/min mcg/min Infusion Infusion Observe Observe 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 Prepare Prepare for for transvenous transvenous pacer pacer If If symptoms symptoms develop, develop, use use transcutaneous transcutaneous pacemaker pacemaker until until transvenous transvenous pacer pacer placed placed Note b. If the patient is symptomatic, do not delay transcutaneous pacing while awaiting IV access & IV atropine to take effect

17 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

18 Symptoms: Signs : Chest pain Shortness of breath Decreased level of consciousness Dizziness/syncope Weak/tiredness Hypotension Heart failure (bibasal crepitations) Cool, clammy peripheries Ventricular ectopics

19 Denervated transplanted hearts will not respond to atropine, go at once to pacing, catecholamine infusion or both

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

21 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

22 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%)

23 Transcutaneous pacing

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28 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)