Moffitt Pearls – 11.14.17 – Complete Heart Block and Cardiac Sarcoid

Thanks you, Arvind, for presenting a case of an older man with exercise-induced bradycardia found to have complete heart block 2/2 to cardiac sarcoidosis.


  1. In the consideration of bradycardia, one must first rule out MI. 15% of patients with an MI will present with complete heart block.
  2. Bradycardia in an inferior or posterior MI is driven by 1) ischemia AND 2) the Bezold-Jarisch Reflex. This is a cardiovascular decompressor reflex involving a marked increase in vagal (parasympathetic) efferent discharge to the heart, elicited by stimulation of chemoreceptors, primarily in the left ventricle.
  3. Complete AV dissociation with Ps faster than SLOW QRSs suggests complete heart block.

Etiology of Bradycardia


  • Healthy children/adults during sleep (HRs in 30s, pauses up to 2 seconds may occur)
  • Well-conditioned athletes
  • Some elderly patients


An easy way to break down bradycardia is into extrinsic vs intrinsic causes.

  • Intrinsic
    1. Idiopathic degenerative d/o
    2. Ischemia (ACS or chronic)
    3. Lyme disease
    4. Viral myocarditis
  • Extrinsic
    1. Drugs – antiarrhythmics, b-blocker, calcium channel blocker
    2. Hypothyroid
    3. Hypothermia
    4. Hypoxia
    5. Vagal tone


Evaluation of Patient with Complete Heart Block

  1. Rule out Ischemia – ~15% of patient with an acute MI will have complete heart block (usually RCA)
  2. Check for systemic, reversible causes of heart block:
  • Meds: Digoxin, beta-blockers, calcium channel blockers, or anti-arrhythmics
  • Hypothermia
  • Electrolyte abnormalities – hypokalemia
  • Hypothyroid

3. Look for the primary cardiac causes in 3 broad categories:

  • Infiltrative: Amyloidosis, hemochromatosis, sarcoidosis
  • Inflammatory: SLE, scleroderma
  • Infectious: Rheumatic fever, Chagas, endocarditis, viral myocarditis,i syphilis, Lyme disease

Diagnostic Criteria for Cardiac Sarcoid

cardiac sarcoid

Here is a great JACC review on cardiac Sarcoidosis –


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