Morning Report 73107

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Morning Report7/31/07

• 3rd Degree AV block
• Jason Haag

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Heart Block

• 1st Degree AV Block
• one-to-one relationship exists between P waves
  and QRS complexes, but the PR interval is longer
  than 200 ms

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Heart Block

• 2nd Degree Mobitz Type I AV Block (Wenckebach)
• PR interval is prolonging with each P wave to the
  point when the P wave is no longer conducted

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Heart Block

• 2nd Degree Mobitz Type II AV Block
• PR interval is constant, but occasionally P waves
  are not followed by the QRS complexes

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Heart Block

• 3rd Degree Heart Block
• More P waves than the QRS complexes exist and no
  relationship exists between them

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3rd Degree Heart Block

• Block can be in AV node or infranodal conduction
  system
• AV node
• 2/3 escape rhythms have narrow QRS (junctional)
• Fascicular or bundle branches
• Wide QRS (subjunctional)
• Rate typically in low 40s

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Frequency

• In the US 0.02
• Internationally 0.04.
• Age Bimodal peak, at infancy given congenital
  complete AV block and at advance d age due to
  progressive fibrosis and ischemia

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History

• Syncope, near-syncope, and lightheadedness
• Fatigue, dyspnea, and angina
• Asymptomatic
• Sudden cardiac death

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Physical

• Vital Signs (stable vs. unstable, always check HR
  manually)
• Signs of heart failure JVD, a waves, Pulmonary
  edema
• New murmurs or gallops
• Target lesions (Lyme)
• Splinter hemm, Osler nodes, etc (endocarditis)
• Neuromuscular changes (mytonic/muscular
  dystrophy)

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Etiologies

• Idiopathic Progressive Cardiac Conduction Disease
• ½ of cases of AV block
• Lenegres disease
• Progressive, fibrotic, sclerodegeneration of the
  conduction system
• Younger individuals, may be hereditary
• Levs disease
• Calcification extending from fibrous structures
  (aortic/mitral rings) into the conduction system
• Older individuals, ? ESRD
• Fibrosis NOS
• Typically mitral and aortic rings
• Mitral ? narrow QRS
• Aortic ? wide QRS

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Etiologies (cont.)

• Ischemic heart disease
• 40 of cases
• Either from chronic ischemia or acute MI
• Acute MI AV blocks (20 of patients)
• 1st degree (8)
• 2nd degree (5)
• 3rd degree (6)
• LBBB/RBBB (10-20)
• AV nodal block (narrow QRS) associated with
  inferior wall MI
• Bundle blocks (wide QRS) associated with anterior
  wall MI
• Drugs
• Calcium channel blockers, beta blockers, digoxin,
  amiodarone, adenosine, quinidine, procainamide

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Etiologies (cont.)

• Infection
• Lyme disease, endocarditis, Rheumatic fever,
  Chagas disease, myocarditis
• Rheumatic disease
• Ankylosing spondylitis, Reiter syndrome,
  relapsing polychondritis, rheumatoid arthritis,
  scleroderma
• Infiltrative disease
• Amyloidosis, sarcoidosis, multiple myeloma,
  hemachromatosis, Wilsons disease

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Etiologies

• Hyperthyroidism
• Metabolic
• Hypoxia, hyperkalemia
• Neuromuscular disease
• Muscular dystrophy, dermatomyositis

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Treatment

• Correct underlying problem if you can
• Correct K, stop AV blocking medications, etc.
• If unstable
• Transcutaneous pacing
• If stable
• Plan for permanent pacemaker placement

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Permanent Pacemaker

• Class I - Conditions for which evidence and/or
  general agreement exists that a given procedure
  or treatment is beneficial, useful, and effective
• Third-degree AV block and advanced second-degree
  AV block at any anatomic level associated with
  any one of the following conditions
• Bradycardia with symptoms, heart failure,
  arrhythmias, pauses greater than 3 seconds,
  escape rate

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Permanent Pacemaker

• Class IIa - Weight of evidence or opinion is in
  favor of usefulness or efficacy
• Asymptomatic third-degree AV block at any
  anatomic site with average awake ventricular
  rates of 40 bpm or faster, especially if
  cardiomegaly or left ventricular (LV) dysfunction
  is present

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References

• Gregoratos G, Abrams J, Epstein AE, et al
  ACC/AHA/NASPE 2002 guideline update for
  implantation of cardiac pacemakers and
  antiarrhythmia devices summary article a report
  of the American College of Cardiology/American
  Heart Association Task Force on Practice
  Guidelines. Circulation 2002 Oct 15 106(16)
  2145-61.
• Kojic EM, Hardarson T, Sigfusson N, Sigvaldason
  H The prevalence and prognosis of third-degree
  atrioventricular conduction block the Reykjavik
  study. J Intern Med 1999 Jul 246(1) 81-6.
• McEnvoy GK, ed AHFS Drug Information 2000.
  Bethesda, Md American Society of Health-System
  Pharmacists 2000 1187-95.
• Ostaner LD, Brandt RL, Kjelsberg MI, et al
  Electrocardiographic findings among the adult
  population of a total natural community. 1965
  31 888-98.
• Rardon DA, Miles WM, Mitrani RD, et al
  Electrocardiographic Recognition
  Atrioventricular Block and Dissociation. In
  Zipes DP, Jalife J, eds. Cardiac
  Electrophysiology From Cell to Bedside, 2nd ed.
  Philadelphia, Pa WB Saunders 1995.