1. Pharmacological Management of Amiodarone-Induced Thyrotoxicosis Type I in Mitral Valve Replacement
Joanne Lau, BScPhm; Rita Dhami, BScPhm
Amiodarone-induced thyrotoxicosis (AIT) delays urgent cardiac surgeries
Patients are at risk of thyroid storm if exposed to anesthesia and surgery while hyperthyroid
Options for converting AIT patients to euthyroidism:
Thyroidectomy: rapidly achieves euthyroidism (demonstrated in multiple case reports)
Medical management: may require months of treatment
In this case thyroidectomy was not possible. Only one other case report describes an AIT Type II patient undergoing urgent surgery without conversion to euthyroidism. ID
53 year old female
Past Medical History
Atrial fibrillation (x3 years)
Mitral valve stenosis/regurgitation
Lupus
Hypertension
Hyperlipidemia
History of ovarian cancer (hysterectomy 2 years ago)
Medications
Amiodarone mg x 3.5 years
Carbamazepine mg AM and 200 mg PM
Hydroxychloroquine mg BID
Lansoprazole mg daily
Atorvastatin mg daily
Candesartan mg daily
Calcium mg (elemental) daily
Alendronate mg QMonday
Warfarin mg daily
Rationale
Patient presented to hospital with signs and symptoms of hyperthyroidism and was diagnosed with AIT Type I:
TSH<0.01 mU/L [0.4-5 mU/L]
T3=16.7 pmol/L [3-6.5 pmol/L]
T4=84 pmol/L [11-22 pmol/L]
Shortness of breath, tachypnea, fine tremor, and weight loss (10 lbs over 2 weeks)
She required mitral valve replacement (MVR) for severe mitral valve stenosis and regurgitation
Case Description
Discussion
Treatment for AIT:
For our case:
Resolution of hyperthyroid symptoms occurred with initiation of propylthiouracil therapy
Treatment success of propylthiouracil over methimazole may be due to its mechanism of inhibiting T4 and conversion to active T3
Evaluation of Literature:
One case report of necessary surgery (excluding thyroidectomies to treat AIT) in unresolved AIT Type II:
Propylthiouracil, prednisone, and propranolol achieved symptom control, but patient remained hyperthyroid
Despite this, percutaneous tracheotomy was performed  recurrent thyrotoxicosis unresponsive to treatment and patient died 7 days later
The authors recommend thyroidectomy be performed with percutaenous tracheotomy in this setting.
Conclusions
Patients with AIT can be rapidly converted to euthyroidism by thyroidectomy.
Where urgent surgery is required and thyroidectomy is not possible, this case demonstrates the plausibility of pharmacological resolution of hyperthyroid symptoms and suppression of thyroid storm peri- and post-operatively.
AIT Type I
AIT Type II
Thyroid hormone overproduction
Thyroid hormone release via destructive thyroiditis
Propylthiouracil mg TID Or
Methimazole mg BID
Prednisone mg daily
References
Amiodarone was discontinued
(sotalol 20 mg BID started for rhythm control)
If mechanism is unclear, use a combination of thionamide and steroid therapy
Noble K. Thyroid Storm. Patho Corner. Journal of PeriAnesthesia Nursing April;21(2):
Conen D, Melly L, Kaufmann C, Bilz S, Ammann P, Schaer B, Sticherling C, Muller B, Osswald S. Amiodarone-Induced Thyrotoxicosis: Clinical Predictors and Outcomes. J Am Coll Cardiol Jun 19;49(24):
Papaioannou V, Terzi I, Dragoumanis C, Konstantonis D, Theodorou V, Pneumatikos I. A fatal case of recurrent amiodarone-induced thyrotoxicosis after percutaneous tracheotomy: a case report. Journal of Medical Case Reports Nov 13;1:134.
Tsang W, Houlden RL. Amiodarone-induced thyrotoxicosis: A review. Can J Cardiol 2009;25(7):
Methimazole was started
No clinical effect seen after 4 weeks
Subsequently discontinued
If poor response consider thyroidectomy
Patient Information
Propylthiouracil 100 mg TID started
Symptomatic control within 1 week
MVR urgently needed
(Rapid conversion to euthyroidism by thyroidectomy not possible as
anticoagulation will be necessary for MVR)
Pre-surgery medical management (3 weeks):
Propylthiouracil 200 mg TID
Dexamethasone 2 mg BID
Propranolol 80 mg TID
(patient unable to tolerate sotalol)
Pace maker rate controlled
Symptom free but still hyperthyroid:
TSH <0.01 mU/L [0.4-5 mU/L]
T3=10.1 pmol/L [3-6.5 pmol/L]
T4=47 pmol/L [11-22 pmol/L]
Post-MVR:
signs and symptoms of thyroid storm absent
Patient successfully discharged