Bradycardias

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  • Other definitions, failure to attain 85%, 75%
  • HR 46/min Put her on a treadmill reached HR of 137/min
  • 3.4 and 4.8 second pauses Patient had acute coronary syndrome with lesion in proximal RCA involving the branch to the SA node, placed a dual chamber pacemaker
  • ACC/AHA guidelines
  • Prolongation of of the PR interval > 200ms, 1:1 conduction, P before every QRS complex, both P and QRS are normal
  • Progressive prolongation of the PR interval terminated in a non conducted P wave
  • Bradycardias

    1. 1. BradycardiasSalah Abusin, MBBS, MRCP (UK), ABIM Cardiology Fellow Chicago, IL,USA
    2. 2. Bradycardias• SA node dysfunction or • AV Blocks Sick Sinus Syndrome – First Degree – Inappropriate sinus – Second Degree bradycardia • Mobitz I – Sinoatrial exit Block • Mobitz II – Sinus Pause/Arrest • 2:1 Block – Tachycarda/Bradycardia – Third Degree syndrome – High Grade AV Block – Persistent Atrial Standstill
    3. 3. Sinoatrial Node dysfunction• Inappropriate sinus bradycardia• Sinoatrial exit Block• Sinus Pause/Arrest• Tachycarda/Bradycardia syndrome
    4. 4. Causes - Intrinsic• Idiopathic degenerative disease• Coronary Artery Disease• Cardiomyopathy• Hypertension• Infiltrative Disorders (amyloidosis etc..)• Collagen Vascular Disorders (scleroderma etc.)• Inflammatory Processes (myocarditis)• Surgical Trauma• Musculoskeletal disorders (myotonic dystrophy)• Congenital heart disease (postoperative or absence of correction)
    5. 5. Causes – Extrinsic - 1• Medication – BBs, CCBs, digoxin – Clonidine, alpha methyldopa, reserpine – Antiarrhythmics Type • IA (quinidine, procainamide) • IC (flecainide) • III (amiodarone) – Lithium
    6. 6. Causes – Extrinsic - 2• Autonomic influences – High vagal tone – Carotid sinus syndrome – Vasovagal syncope• Electrolyte abnormalities – Hyperkalemia, hypercarbia, hypothyroidism• Increase intracranial pressure• Hypothermia• Sepsis
    7. 7. Sinoatrial Node dysfunction• Inappropriate sinus bradycardia• Sinus Pause/Arrest• Sinoatrial exit Block• Tachycarda/Bradycardia syndrome
    8. 8. Inappropriate Sinus Bradycardia Chronotropic Incompetence• HR<60 that doesn’t increase appropriately with exercise• Usually defined as failure to attain 80% of maximal age predicted HR (MAHR) on exercise testing• MAHR = 220 – Age• e.g. failure to reach a HR of 120 in a 70 year old patient
    9. 9. Sinus bradycardia
    10. 10. Sinoatrial Node dysfunction• Inappropriate sinus bradycardia• Sinus Pause/Arrest• Sinoatrial exit Block• Tachycarda/Bradycardia syndrome
    11. 11. Sinus Pause/Arrest• Defined as absence of a sinus beat for >=3 seconds while AWAKE• SA node fails to discharge so no atrial activity occurs
    12. 12. Sinus Pause/Arrest
    13. 13. Sinoatrial Node dysfunction• Inappropriate sinus bradycardia• Sinus Pause/Arrest• Sinoatrial exit Block• Tachycarda/Bradycardia syndrome
    14. 14. Sinoatrial Exit Block• SA node discharges an impulse that does NOT result in atrial activity
    15. 15. Sinoatrial Exit Block
    16. 16. Sinoatrial Node dysfunction• Inappropriate sinus bradycardia• Sinus Pause/Arrest• Sinoatrial exit Block• Tachycarda/Bradycardia syndrome
    17. 17. Tachycardia-Bradycardia Syndrome• Bradycardia/sinus pauses interspersed with atrial arrhythmias (AFL, A fib, A tach)• Sinus arrest manifests after termination of atrial arrhythmia (spontaneously or after DCCV)• Sinus Node Recovery Time (SNRT) uses the above observation to assess SA node function in EP studies
    18. 18. Tachycardia-Bradycardia Syndrome Hurst the Heart 12th Edition
    19. 19. Indications for pacing in SND• Class I (recommended) – SND with documented symptoms – SND due to irreversible factors or due to essential drug therapy – Chronotropic incompetence• Class III (NOT recommended) – Asymptomatic
    20. 20. Bradycardias• SA node dysfunction or • AV Blocks Sick Sinus Syndrome – First Degree – Inappropriate sinus – Second Degree bradycardia • Mobitz I – Sinoatrial exit Block • Mobitz II – Sinus Pause/Arrest • 2:1 Block – Tachycarda/Bradycardia – Third Degree syndrome – High Grade AV Block – Persistent Atrial Standstill
    21. 21. AV Blocks• First Degree• Second Degree – Mobitz I – 2:1 Block – Mobitz II• Third Degree• High Grade AV Block
    22. 22. First Degree AV Block• PR interval > 200msec• If QRS is normal, block is usually at the level of the AV node• If QRS shows bundle branch block, block maybe in His-Purkinje System
    23. 23. First degree AV block
    24. 24. Management• Usually no specific therapy is required
    25. 25. Second Degree Heart Block Mobitz I or Wenchebach• Progressive Prolongation of the PR interval and shortening of the RR interval until a P wave is blocked• RR interval containing the non conducted P wave is less than two PP intervals• PR interval longer after the non conducted P wave• Grouped beating
    26. 26. Second Degree – Mobitz IP P P P P P
    27. 27. Causes Features• Normal • Usually asymptomatic• Athletes • Usually narrow QRS complex• Medications  block at AV node• Myocardial Infarction • The presence of bundle branch block suggests the possibility (inferior wall) of block below the AV node in• Acute rheumatic fever His Purkinje system• Myocarditis
    28. 28. Management• Usually do not require permanent pacing
    29. 29. Second Degree – Mobitz II• Constant PR interval with intermittent nonconducted P wave and no evidence for PACs• RR interval between non conducted P waves is equal to two PP intervals• Each QRS is preceded by multiple P waves• 3:1, 4:1 also called high grade AV block• Other variations include 3:2• 2:1 block maybe Mobitz I or Mobitz II
    30. 30. 3:2 AV Block• Add ECG example here
    31. 31. High Grade AV Block
    32. 32. Second Degree Heart Block 2:1 BlockP P P P
    33. 33. Management• Usually require permanent pacing especially if symptomatic due to high likelihood of progression to high grade AV block and third degree AV block
    34. 34. Differentiating mechanism of 2:1 blockFeature Mobitz I Mobitz IIQRS duration Narrow WideResponse to increasing Improves WorsensHR & AV conduction i.e.exercise, atropineResponse to decreasing Worsens ImprovesHR & AV conduction i.e.carotid sinus massageAcute MI Inferior Anterior
    35. 35. Third Degree AV block• Atrial impulses consistently fail to reach the ventricles, resulting in atrial and ventricular rhythms that are independent of each other• PR interval varies• PP and RR intervals are constant• Ventriculophasic sinus arrhythmia – PP interval containing QRS is shorter than PP interval without a QRS complex
    36. 36. Third Degree AV blockP P P P P P P P P P P
    37. 37. Escape Rhythms• Junctional – Usually narrow (may be wide if underlying BBB) – 40-60/min• Ventricular Escape Rhythm – Wide complex – 30-40/min (range 20-50)
    38. 38. Causes• Myocardial Infarction – Inferior wall, usually transient, associated with a stable junctional escape rhythm – Anterior wall, usually permanent• Degenerative Disease• Infiltrative Disease (amyloid, sarcoid)• Endocarditis (Aortic Root abscess)• Hyperkalemia• Medication• Post Cardiac Surgery
    39. 39. Management• Usually require permanent pacing
    40. 40. Acclerated Idioventricular rhythm
    41. 41. Acclerated Idioventricular rhythm• Regular Wide complex rhythm• 60-110/min• AV dissociation• Benign phenomenon• Causes – Normal – Coronary reperfusion – Digoxin toxicity
    42. 42. Problems
    43. 43. 3rd degree AV block, junctional escape
    44. 44. Second Degree Mobitz I
    45. 45. P P P P P P P P P P P 3rd degree AV block, junctional escape
    46. 46. P P P P P P P P P P3rd degree AV block, junctional escape or high grade AV block
    47. 47. Problem• 50 year old female with no PMH presents with acute onset of shortness of breath on exertion of 4 days duration• HR 50/min, BP 140/80• Initial ECG sinus bradycardia• TropI 1.2
    48. 48. Sinus arrest with ventricular escape
    49. 49. Sinus arrhythmia
    50. 50. Problem• 65 year old male presented with 4 day history of shortness of breath on exertion, orthopnea and PND• HR 50/min, regular, BP 150/70
    51. 51. Atrial Fibrillation with 3rd degree AV block & junctional escape
    52. 52. Thank You

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