Online
Clinical Case Study (January 2004)
Clinical
Cardiology Series
臨床心臟科個案研究
The
content of the Clinical Cardiology Series is provided by:
Dr. Wong Shou Pang, Alexander
F.R.C.P., F.H.K.A.M.(Med.), F.H.K.C.P., Specialist in Cardiology
Dr. Li Siu Lung, Steven
M.B.,B.S.(H.K.), M.R.C.P.(U.K.), F.H.K.A.M., F.H.K.C.P., F.R.C.P.(Glasg.),
F.R.C.P. (Edin.), Specialist in Cardiology
臨床心臟科個案研究之內容誠蒙王壽鵬醫生及李少隆醫生提供。
A 45 year old gentleman
with paroxysmal atrial fibrillation (PAF) comes to your office for control of
his symptoms. Previous investigations with echocardiography and exercise stress
test were normal. He wonders if treatment with amiodarone will be helpful.
Answers
| 1. |
Is
amiodarone useful in treating PAF?
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Yes. In the
Canadian Trial of Atrial Fibrillation (CTAF), more patients were successfully
maintained in sinus rhythm in the amiodarone group than in the conventional
group with sotalol/propafenone (69% vs 39% at 1 year).
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| 2. |
What
are the usual doses of amiodarone therapy?
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Amiodarone
is a lipid soluble drug with a very slow absorption and clearance rate.
The onset of action is also delayed and a steady drug effect may not be
established till several months later. Protocol varies and initial loading
dose may be from 600mg daily to 1200mg daily in divided doses for 1-2
weeks. The dose is then gradually titrated down to the maintenance dose
over a few weeks, which is usually lower (200mg daily) for PAF when compared
with that for ventricular arrhythmias.
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| 3. |
What
are the contraindications for amiodarone therapy?
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Severe sinus node dysfunction, second or third degree
heart block and known hypersensitivity to the drug.
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| 4. |
What
are the side effects of amiodarone?
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The most important
side effects are those cardiac, pulmonary and thyroid ones. Amiodarone
may cause sinus node dysfunction (up to 5%) and may cause torsades de
pointes especially in patients with hypokalemia and digoxin toxicity.
Pulmonary fibrosis may occur in around 10% of patients receiving high
maintenance dose (e.g. 400mg daily) but is less common in patients receiving
a lower dose of 200mg daily. If recognized early with termination of the
drug therapy, the pulmonary complications might be reversible. Amiodarone
has a complex side effect profile on the thyroid function and may cause
hyperthyroidism as well as hypothyroidism in up to 10% of patients, although
some of them may be subclinical.
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| 5. |
What
are the common drug interactions of amiodarone?
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Amiodarone
causes an additive effect on QT prolongation with Class IA and III antiarrhythmic
drugs and psychiatric drugs like phenothiazines and tricyclic antidepressants
and such combinations are best avoided. Amiodarone potentiates the effect
of warfarin, digoxin and phenytoin. Dose reduction is needed in these
patients if they receive concurrent amiodarone therapy.
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Note
of caution:
Baseline ECG, lung function,
thyroid function and renal/liver function tests are essential. Lowest effective
dose should be used. With long-term therapy, half-yearly ECG (to look for QT
prolongation and SA/AV node dysfunction), CXR, thyroid/liver function tests
monitoring are recommended. Drug levels of those drugs that may interact with
amiodarone should also be monitored.
Dermatology Series
皮膚科病例研究
A 64 year old Australian
pilot presented with asymptomatic skin rash over face, anterior neck and upper
limbs for few years. There had been an increasing number and size of the skin
lesions but no bleeding or ulceration was noted. His past health and family
history was unremarkable. Physical examination revealed several erythematous
plaques with adherent scales (arrow) over the site mentioned. There were also
freckles over sun-exposed areas.
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The
content of the Dermatology Series is provided by:
Dr. Chan Loi Yuen and Dr. Tang Yuk Ming, William
Specialist in Dermatology & Venereology
皮膚科病例研究之內容誠蒙陳來源醫生及鄧旭明醫生提供。 |
Answers
| 1. |
What
is the clinical diagnosis? |
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The diagnosis
is actinic keratosis (AK), also known as solar keratosis. It is a common
skin condition induced by chronic sun exposure. The lesion presents as
erythematous scaly plaques measuring 3 to 10 mm in size over sun-exposed
areas. It is more easily recognised by palpation as a roughening rather
than visualization.
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| 2. |
What
is the clinical differential diagnosis?
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The differential
diagnosis for AK includes seborrhoeic keratosis, Bowen's disease, squamous
cell carcinoma, basal cell carcinoma, and discoid lupus erythematosus.
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| 3. |
What
are the risk factors for this skin condition? |
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People who
are fair-skinned, burn easily and tan poorly, with excessive sun exposure
are at risk of developing AK. Immunosuppressed patients are also at a
higher risk.
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| 4. |
What
are the possible complications? |
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About 5-10%
of active lesions may progress into squamous cell carcinoma. Actinic cheilitis
of the lower lip is a high risk area for malignant change. Patients with
AK are also more prone to develop melanoma.
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| 5. |
What
is the treatment?
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Suspicious
lesions should be excised and sent for histology to rule out malignant
transformation. Topical 5-flourouracil cream applied to the affected areas
will induce inflammation and subsequent removal of the lesions. Other
treatment modalities include cryotherapy, curettage, shave removal, excision,
chemical peels and photodynamic therapy. Regular monitoring of other lesions
for early detection of malignant transformation is important. Patients
should be advised to limit sun exposure, wear broad brimmed hats and long-sleeve
clothings for sun protection and use of sunscreens. Their hobby or profession
should be modified to decrease sun exposure.
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