What is the underlying cause of Mr. Chan's loss of consciousness?
a) Vasovagal attack
b) Atrial fibrillation
c) Asystole
d) Polymorphic VT

d. Mr. Chan has a polymorphic VT attack. It was started with an increase of QT interval (0.46 sec) and there was a ventricular ectopic (VE) which caused a pause. The spontaneous sinus rhythm that followed the VE had an R on T phenomenon by the subsequent VE and the whole polymorphic VT was started.

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What is your management plan?
a) Check the electrolytes
b) Check the drugs
c) IV lignocaine
d) Pacing

a,b and d. Because of the long QT interval, we should try to correct any disturbance in the electrolytes including those of potassium, magnesium and calcium. A temporary pacemaker to accelerate the spontaneous sinus rhythm would be very useful as it corrects the QT interval and suppresses the ventricular ectopics. The whole ventricular event can then be stopped. This patient was on tricyclic anti-depressants (TCA) and the drug had caused the QT interval prolongation. His electrolytes were normal. His VT storm was finally stopped by pacing and his TCA was stopped. QT intervals should be monitored regularly in patients who were put on TCA.

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What are the clinical diagnosis and differential diagnoses?

The most likely diagnosis is a malignant melanoma arising from a pre-existing mole. The differential diagnoses are pigmented basal cell carcinoma, pyogenic granuloma, haemagioma, and cutaneous secondary metastasis.

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What are the predisposing factors?

The predisposing factors for malignant melanoma include the presence of precursor lesions like dysplastic nevi, congenital nevomelanocytic nevi; family history of melanoma in parents, children and siblings; light skin type with inability to tan easily; and excessive sun exposure, especially during childhood. The estimated life-time melanoma risk for congenital nevomelanocytic nevi smaller than and bigger than 10 cm in diameter are 0-4.9% and 4.5-10% respectively.

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How would you confirm the diagnosis?

Total excisional biopsy should be performed. However, in case of a large lesion, an incisional biopsy can be performed to establish the diagnosis but this may result in sampling error and false negative finding.

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What are the prognostic factors?

The prognosis depends on the clinical staging. Tumor thickness as denoted by the Clark level and the Breslow thickness are important prognostic factors.

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What is the management and what are the important investigations for evaluating the disease?

Wide margin re-excision remains the mainstay of treatment. Extensive work-up including sentinel lymph node biopsy, positron emission tomography scan should be performed for staging of the disease. Depending on the clinical stage, further interventions like single or combination chemotherapy, systemic interferon, biologics, chemo-immunotherapy, gene therapy or radiotherapy for palliative treatment of metastasis may be tried.

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