1 Case 7 Bradycardia © 2001 American Heart Association

2 Case Scenario An 87-year-old woman reports feeling weak and short of breath for 2 hours while walking short distances. She feels exhausted moving from the car to the ED stretcher. On physical exam she is pale and sweaty; HR = 35 bpm; BP = 90/60 mm Hg; RR = 18 rpm. Rhythm: see next slide.

3 87-Year-Old Woman: Symptomatic Bradycardia t Identify A, B, and C t Which one is most likely to be her rhythm? A B C

4 Learning Objectives 1.By the end of Case 7 be able to discuss Asymptomatic vs symptomatic bradycardia Signs and symptoms of symptomatic bradycardia Intervention agents and sequences to use Recognition criteria for heart blocks: 1 st, 2 nd (types I and II), and 3 rd degree Pathology of conduction system in heart blocks

5 Learning Objectives 2.By the end of Case 7 be able to discuss Significance of bradycardia in AMI patients Significance of RV infarction plus bradycardia Atropine pharmacology: why atropine helps some heart blocks and not others Set up, start, troubleshoot transcutaneous pacing

6 Rhythms to Learn t Sinus bradycardia t Heart blocks 1 st degree 2 nd degree type I 2 nd degree type II 3 rd degree

7 Drugs to Learn t The actions, indications, administration, and precautions for these drugs and therapies: Atropine Dopamine Epinephrine Transcutaneous pacing Isoproterenol (rarely used)

8 Cardiac Conduction System 1 Bachmann’s bundle Left bundle branch Posterior division Anterior division Purkinje fibers Right bundle branch Bundle of His AV node Internodal pathways Sinus node

9 Cardiac Conduction System 2 Relationship of ECG to anatomy

10

11 Determining the Rate

12 Analyzing Rhythm Strips t Key questions Are QRS complexes present? Are P waves present? How is the P wave related to the QRS complex?

13 Relationship of P Waves and QRS Complexes t Every P wave is followed by a QRS complex with a normal P–R interval t Every P wave is followed by a QRS complex but the P–R interval is prolonged t Some P waves are not followed by a QRS complex; more P waves than QRS complexes

14 What Is This Rhythm?

15 AV Block First-degree AV block

16 Diagnosis?

17 Diagnosis?

18 AV Block Second-degree type I AV block

19 Diagnosis?

20 AV Block Second-degree type II AV block

21 Differentiation of Second- and Third-Degree AV Blocks More P’s than QRSs PR fixed? no QRSs that look alike regular? no yes 2 nd -degree AV block Fixed Mobitz II 3 rd -degree AV block 2 nd -degree AV block Variable Mobitz I Wenckebach

22 Bradycardia Algorithm (1 of 2) Bradycardia Slow (absolute bradycardia = rate <60 bpm) or Relatively slow (rate less than expected relative to underlying condition or cause) Assess ABCs Secure airway noninvasively Ensure monitor/defibrillator is available Primary ABCD Survey Secondary ABCD Survey Assess secondary ABCs (invasive airway management needed?) Oxygen–IV access–monitor–fluids Vital signs, pulse oximeter, monitor BP Obtain and review 12-lead ECG Obtain and review portable chest x-ray Problem-focused history Problem-focused physical examination Consider causes (differential diagnoses)

23 Bradycardia Algorithm (2 of 2) Intervention sequence Atropine 0.5 to 1.0 mg Transcutaneous pacing if available Dopamine 5 to 20 µg/kg per minute Epinephrine 2 to 10 µg/min Isoproterenol 2 to 10 µg/min Serious signs or symptoms? Due to bradycardia? Type II second-degree AV block or Third-degree AV block? Observe Prepare for transvenous pacer If symptoms develop, use transcutaneous pacemaker until transvenous pacer placed NoYes No

24 What Is This Rhythm?

25 AV Block Third-degree AV block

26 What Is This Rhythm?

27 Treatment?

28 What Is This Rhythm?

29 Treatment?

30 Indications for Transcutaneous Pacing t Hemodynamically unstable bradycardias t In the setting of AMI: sinus node dysfunction, type II 2 nd -degree block, 3 rd -degree heart block t Bradycardia with symptomatic ventricular escape beats

31 Transcutaneous Pacing

32 Transcutaneous Pacing: “Capture” vs “No Capture” Pacing below threshold: no capture Pacing above threshold: with capture Pacing Spike Capture: Spike + broad QRS QRS: opposite polarity 25 Feb 88 Lead I Size 1.0 HR=41 25 Feb 88 Lead I Size 1.0 HR=43 35 mA 25 Feb 88 Lead I Size 1.0 HR=71 60 mA Bradycardia: No Pacing Pacing Below Threshold (35 mA): No Capture Pacing Above Threshold (60 mA): With Capture (Pacing-PulseMarker ) Bradycardia: no pacing

33 Rates of Intrinsic Cardiac Pacemakers t Primary pacemaker Sinus node ( bpm) t Escape pacemakers AV junction (40-60 bpm) Ventricular (<40 bpm)

34 Pulse Generators for Transvenous Pacing Characteristics t Variable output in milliamps t Fixed versus demand mode t Variable rate setting t Firing and sensing indicators t Familiarize yourself with the equipment!

35 Arrhythmias Determining the pattern Regular Premature Speeding/slowing Pause Group beats Irregularly Irregular

36 Escape Patterns

37 Action Potential of Pacemaker Cell

38 Second-Degree AV Block Type I