An Unusual Case Of Recurrent Atrial Fibrillation Mark Linzer MD Section of GIM Scholars GIM Conference

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

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

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

Next steps? (Don’t turn page)

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

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

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. 2004;83:

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

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

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 (>2 yrs) in Type 2 Response to prednisone implies Type 2 *Basaria S, Cooper DC. Amiodarone and the thyroid. Am J Med. 2005;118:706-14

Basaria S, Cooper DC. Amiodarone and the thyroid. Am J Med. 2005;118:

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 2003;133:579-85

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.