1. 1 Case 7 Bradycardia © 2001 American Heart Association

2. 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. 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. 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. 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. 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. 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. 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. 9 Cardiac Conduction System 2 Relationship of ECG to anatomy

10. 10

11. 11 Determining the Rate

12. 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. 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. 14 What Is This Rhythm?

15. 15 AV Block First-degree AV block

16. 16 Diagnosis?

17. 17 Diagnosis?

18. 18 AV Block Second-degree type I AV block

19. 19 Diagnosis?

20. 20 AV Block Second-degree type II AV block

21. 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. 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. 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. 24 What Is This Rhythm?

25. 25 AV Block Third-degree AV block

26. 26 What Is This Rhythm?

27. 27 Treatment?

28. 28 What Is This Rhythm?

29. 29 Treatment?

30. 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. 31 Transcutaneous Pacing

32. 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. 33 Rates of Intrinsic Cardiac Pacemakers t Primary pacemaker Sinus node (60-100 bpm) t Escape pacemakers AV junction (40-60 bpm) Ventricular (<40 bpm)

34. 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. 35 Arrhythmias Determining the pattern Regular Premature Speeding/slowing Pause Group beats Irregularly Irregular

36. 36 Escape Patterns

37. 37 Action Potential of Pacemaker Cell

38. 38 Second-Degree AV Block Type I