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‘All in the I of the beholder’
Amy Joyce, Fiona Boyle, Sobana
Anandarajah, Aamir Iqbal, Philip
McGlone, Gareth Bowen-Perkins
Presenting Complaint
Free T4 > 100
TSH < 0.01
History of Presenting
Complaint
Diarrhoea 8-10 x /day
Tremor, increased sweating
SOB – could walk ~ 100m on a flat
surface
Dizzy, light-headed and weak
Hearing and visual disturbances
~ 3.5 stones wt. loss
Past Medical History
Dilated cardiomyopathy Dec 1999
ICD Sep 2000
Family History
Nil of note
Drug History
 Warfarin 6/7 mg – alternate doses
 Amiodarone 200 mg od
 Spironolactone 26 mg od
 Frusemide 40 mg od
 Ramipril 5 mg od
 Carvedilol 15 mg bd
 Zopiclone 3.75 mg od
 Carbimazole 20 mg bd
Allergies - amoxycillin
Social History
Occupation – Surveyor
Married with one seven month old son
Non-smoker
Alcohol – 6-8 units/week
Examination
Pt appeared comfortable at rest with an obvious
tremor, and sweating.
P 86 reg; BP 112/59; T 36.6; sats 96%; RR 14
CVS – normal HS, JVP, no murmur
Resp – lung fields clear
Abdo – soft, non-tender, bowel sounds present,
striae ++
Thyroid – not enlarged, no nodules, no goitre
What next?
Impression – Amoidarone induced
thyrotoxicosis
Plan:
Bloods: FBC, U+E, CRP, TFT, LFT, Thyroid AB’s
CXR, ECG, Echo, 24 hour tape
Iodine uptake scan
Stop amiodarone
Increase CBZ
INR
Dilated Cardiomyopathy
Characterized by ventricular dilatation +
depressed myocardial contractility
largest gp of myopathic disorders
responsible for systolic HF
prevalence: 0.2% in UK (inc in developing
countries)
Unknown aetiology
Associations:
Alcohol
Hypertension
Haemochromotosis
Viral infection
Autoimmune
Peri/post partum
Congenital (x-linked)
Thyrotoxicosis
Pathophysiology
 Relative degree of L + R ventricular impairment is
variable
 Compensatory  in sympathetic activity:
– maintains systolic function
–central redistribution of flow: ventricular filling
  inotropic responsiveness of failing heart
  CO + renal perfusion- 2º aldosteronism
 Na+ and H2O retention–progressive systemic + pulmonary congestion
– ventricular filling- progressive dilation/
hypertrophy
Clinical Features
Often asymptomatic in early stages
Symptoms/signs of CHF develop
Later, peripheral oedema and orthopnoea
develop
Tachycardia and signs of cardiac enlargement
are present
JVP: elevated often giant ‘v’ wave
Auscultation: 3rd heart sound
pansystolic mumurs of MR/TR
Complications
Cardiac arrhythmias are common (esp
AF, ventricular premature beats)
Sig incidence of sudden death due to
more complex ventricular arrhythmias
Systemic and pulmomary
thromboembolism from dilated R/L
cardiac chambers
Investigations
CXR: cardiomegaly, pulmonary oedema
ECG: tachycardia, non-specific T-wave
changes, poor R wave progression
Echo: globally dilated hypokinetic heart
with low ejection fraction
Also- look for MR, TR, LV mural thrombus
Management
 Treat any known aetiological cause
 As for heart failure
bed rest
ACE-inhibitor
diuretics
digoxin
 Amiodarone (if arrhythmias)
 Anticoagulation (if AF/ prev thromboembolic event)
 Consider transplant
AMIODARONE
Amiodarone in tx of dilative
cardiomyopathy:
Class III antiarrhythmic drug- prolongs a.p.
Less -vely inotropic than other drugs in its class
Effective in treating tachyarrythmias:
supraventricular (eg. AF)
ventricular (eg. VT, VF)
nb. High iodine content => propensity to cause
hypo/hyperthyroidism (hyperthyroidism being
associated with dilative cardiomyopathy)
AMIODARONE
Amiodarone
 Class 3 anti-arrhythmic drug
 Used in the treatment of SVT and ventricular
arrhythmia
 Long half-life, 13-103 days
 If toxicity occurs, it may persist long after drug
administration is discontinued
 15-30 days or more are required to load the body
stores with sufficient Amiodarone for full efficacy
 Loading doses are 0.8-1.2g daily for about 2 wks,
maintenance dose is 200-400mg daily
Side Effects
Cardiac effects:
symptomatic bradycardia
heart block
heart failure in
susceptible patients
Extra-cardiac effects:
pulmonary fibrosis
corneal/skin deposits
neurological effects
thyroid dysfunction
gastrointestinal tract
liver involvement
drug interactions
Amiodarone and The Thyroid
 Contains 30% by weight of iodine
 Causes thyrotoxicosis in 3% of patients who use it
 Inhibits type 1 5’ deiodinase enzyme activity
  peripheral conversion of T4 to T3
 Also clearance of T4 and rT3 and acts as a
competitive antagonist of T3
 Two types, types 1 and 2, based on pre-existing
thyroid disorder
Thyroid Hormone Metabolism
Find picture
Amiodarone induced
thyrotoxicosis
Type 1
Affects patients with latent/pre-existing thyroid
disorders
Due to excessive, uncontrolled synthesis of thyroid
hormone in response to the iodine
Type 2
Patients with previously N thyroid
Due to destructive inflammatory thyroiditis induced
by Amiodarone
Investigations
Specific
Serum TSH – Suppressed 
Serum T4 – Increased 
Serum T3 - Increased 
Technetium Scan – will show little or no
uptake
Fine Needle Aspiration
Non- Specific
CRP/ESR – Raised in type 2
ECG – Atrial fibrillation?
Treatment Options
Medical
Antithyroid Drugs
Potassium percholate?
Beta blockers – for control of symptoms
Steroids
Radioactive iodine
Surgery
Subtotal/total thyroidectomy
Medical Treatment
If possible withdraw amiodarone
treatment
Amidarone will remain in the blood following
cessation due to its long half life.
In type 1 AIT
Antityhroid drugs
Potassium percholate
In type 2 AIT
Steroids
Type 1 AIT
1st 6 weeks
Carbimazole 45mg/day for 6 weeks – I/c with
Potassium percholate? 0.6-1.2g/day.
> 6 weeks
Carbimazole ~ 30-45mg/day for 12-18
months
Radioactive iodine
Subtotal thyroidectomy/total thyroidectomy
Type 2 AIT
Steroids
Prednisolone 30-40 mg/day for 1-2 weeks
Gradually weaned off of steroids following
normalisation of serum T3 and serum T4
levels.
If required antithyroid drugs can also be used
 Mixed Type 1 and Type 2 AIT
In these types of case of AIT both treatment
regimes are combined.
Therefore treatment is Antityroid
drugs/potassium percholate and steroids.
Radioactive iodine
Usually NOT FEASIBLE
In AIT:
Low thyroid radioactive iodine uptake
High stable iodine content in the gland
This reduces the efficacy of radioactive
iodine
Radioactive iodine can be used to treat
underlying graves disease following
medical treatment of AIT.
Surgery
Normally want patient euthyroid pre-op
Subtotal/Total thyroidectomy
Patient is started on thyroxine
replacement due to hypothyroid state
following subtotal or total thyroidectomy.
Patient can then remain on Amiodarone to
treat cardiac arrythmia