An Unusual Case Of Recurrent Atrial Fibrillation

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An Unusual Case Of Recurrent Atrial Fibrillation

• Mark Linzer MD
• Section of GIM Scholars
• GIM Conference 4-16-08

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Financial Disclosure

• No support for this talk

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Learning Objectives

• To learn an uncommon cause of recurrent atrial
  fibrillation
• More objectives after the case report

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Case Report

• Robust 73 yo man with mild HBP, lipid d/o
• Develops episodic afib 2003, ETT neg. Echo
  dilated LA, EF 60 TSH 2
• Started on amiodarone and coumadin
• Chest pain in 2005 LAD stent
• Did well until 2007 usual HR 50-60

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2007 Abnormal Liver Function Tests

• 7/07 ALT 160, AST 80 amio discontinued.
• 10/07 frequent afib, SOB, anxiety.
• PMH CAD, BPH, GERD, lipids, OA
• Meds ASA, lipitor, doxazosin, lisinopril,
  metoprolol, PPI, warfarin
• PE BP 130/70, pulse 60-80, o/w neg

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Next steps? (Dont turn page)
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Objectives

• Know two types of amiodarone-induced
  thyrotoxocosis (AIT)
• Know how to attempt to distinguish them
• Know the treatments

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Work Up

• TSH 0, FT4 high LFTs near nl amio zero
• Paged Endocrine, bumped beta blockers
• Scan arranged for Txgiving wkend
• Uptake 1 (very low)
• Dx amiodarone induced thyroiditis (likely)
• Rx high doses steroids, beta blockers

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Amio-induced thyrotoxicosis (AIT)

• Prevalence 3 (2-3 yrs after Rx onset)
• Type 1 exacerbation of latent Graves
• Type 2 drug-induced thyroiditis (majority)
• Some patients have mixed picture
• Amio half life 100 days
• Note amio and hyperthyroidism can increase
  sensitivity to warfarin
• Kurnik et al. Medicine. 200483107-113.

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Amio and iodine

• Very high iodine content (20x usual)
• Can cause hypo or hyperthyroidism
• Has beta blocking properties and decreases T4 to
  T3 conversion
• can mask hyperthyroidism
• stopping amio may make sx worse.
• UpToDate, Ross DS. Amio and thyroid dysfunction.
  2008.

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Type 1 vs. Type 2 AIT

• Type 1 Exacerbation latent Graves usually with
  MNG due to excess Iodine. Can (but may not) have
  high scan uptake
• Type 2 Destructive thyroiditis, amio toxicity
  follicular cells, excess release T4. Scan uptake
  low.
• Remember patients must not be pregnant if scanned

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Ways to distinguish

• Thyroid scan low uptake Type 2 (thyroiditis)
  can be low Type 1 (amio competes with tracer)
• Other methods
• Color flow doppler 80 sensitive Type 1 due to
  increased vascularity
• Goiter (type 1)
• IL-6 elevated in Type 2
• Amio duration longer (gt2 yrs) in Type 2
• Response to prednisone implies Type 2
• Basaria S, Cooper DC. Amiodarone and the
  thyroid. Am J Med. 2005118706-14

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Basaria S, Cooper DC. Amiodarone and the
thyroid. Am J Med. 2005118706-14.
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Treatment

• AIT complex Dx and Rx challenge.
• Type 1 antithyroid meds, beta blockers
• Type 2 prednisone 40 mg x 1-3 months, slow taper
  
• Mixed or uncertain antithyroid meds and steroids
• Other Rx surgery, plasmapharesis
• Rajeswaran. Swiss Med Wkly 2003133579-85

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Clinical course for my patient

• Prednisone 40 mg daily x 2 wks tapered
• Free T4 fell, TSH 0 (can lag).
• Relapsed, with free T4 rising. Refer Endo.
• Re-Rx with prednisone, longer taper.
• After 4 weeks, TSH 1, Free T4 normal. BMD
  osteopenia
• Next time Color flow doppler IL-6, longer
  prednisone Rx, early Endo.