The value of Ca score is directly proportional to the degree of lumen obstruction.

False. Ca score is an index which reflects the degree of coronary calcification, which is in turn associated with the degree of plaque burden. A higher Ca score indicates a higher plaque burden and a higher risk of cardiac events. However, a higher Ca score and a higher plaque burden is not necessarily equivalent to a higher degree of lumen obstruction. Further functional tests or angiographic studies are needed to ascertain the degree of ischemia and lumen obstruction. For example, a Ca score of 300 with the calcifications evenly distributed in all three major coronary arteries is likely associated with less lumen obstruction than a Ca score of 300 with all the calcifications concentrated in a discrete calcified plaque in the mid left anterior descending artery.

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The image quality in patients with low or high Ca score is about the same.

False. Heavy calcifications often cause suboptimal images. The calcium plaques obscure the X-ray penetration and render precise lumen obstruction difficult. They also cause a blooming effect which may exaggerate the plaque size and lumen obstruction. Indeed in patients with exceptionally high Ca score, CT coronary angiogram would not be helpful to evaluate any lumen obstruction.

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True. Cardiac structures are in constant motion and accurate timing of imaging to capture images during the segment of the R-R interval with relatively slow cardiac motion is essential for a good image quality. Therefore, synchronization of data acquisition to the cardiac cycle is important. A constant heart rate with minimal variability is essential and in patients with atrial fibrillation and premature beats, the variable and unpredicted R-R intervals often render image quality suboptimal.

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True. A lower heart rate provides a longer diastolic window of minimal cardiac motion for image acquisition and image quality is usually better. Beta blockers are usually used to lower heart rates if there no contraindications such as asthma, active heart failure, heart block etc.

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True. CT coronary angiogram involves the use of iodinated contrast agent, which may have an adverse effect on renal function. Diabetic patients who are on metformin should stop the drugs one day before and two days after the examination. Adequate hydration is essential for those patients with pre-existing renal insufficiency.

What are the differential diagnoses?

The differential diagnoses are eczema herpeticum, folliculitis, chickenpox, impetigo, insect bite reactions and rarely Mucha-Habermann disease.

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What is the most likely clinical diagnosis?

The most likely diagnosis is eczema herpeticum (also known as Kaposi varicelliform eruption). Eczema herpeticum is an extensive, disseminated cutaneous infection with Herpes Simplex virus (HSV). It occurs most commonly as a complication of a localized herpes infection in patients with atopic dermatitis, Darier’s disease, pemphigus, severe seborrhoeic dermatitis and psoriasis. Immune dysfunction in these groups of patients is believed to play a role in the pathogenesis.

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How can you establish the diagnosis?

The clue to clinical diagnosis is the presence of monotonous discrete 2-3 mm haemorrhagic crusts. Further laboratory tests include Tzanck smear, HSV culture and serology. Polymerase chain reaction for HSV viral DNA sequences may also be performed.

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What other cutaneous manifestations does the agent also cause?

HSV also causes herpetic whitlow of the digits, erythema multiforme and HSV folliculitis. Herpes gladiatum, which is a disseminated cutaneous HSV infection occurring in contact sports players, may also occur.

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What is the treatment?

Systemic antiviral therapy such as acyclovir, valaciclovir or famciclovir is indicated. Intravenous administration is necessary for severe cases. Secondary bacterial infection should be treated if present.

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