How would you further investigate this gentleman?
a. Treadmill stress test
b. CT coronary angiogram
c. Cardiac MRIU

All tests are useful but as far as non-invasive tests are concerned, cardiac MRI appears to be more useful in this scenario.

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CT coronary angiogram is contraindicated in patients with asthma.

False

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False

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False

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This gentleman presents with a common clinical scenario: Chest pain in a patient
with known coronary artery disease. The clinical questions here are (1) Does this gentleman have progression of his atherosclerosis in RCA or restenosis of his LAD lesion? (2) Does he need a catheter-based coronary angiogram?

For patients with typical exertional angina, direct catheter-based coronary angiogram appears to be the most cost-effective approach. However, for those with atypical symptoms, non-invasive tests should be considered first. A treadmill stress test is easy and convenient. If the test is definitely positive, life would be simple as what he needs then is a cardiac catheterization to confirm any stenosis. However, if the treadmill test result is equivocal or negative and yet the patient has persistent symptoms, one may feel it difficult to leave the patient on simple medical treatment, given that the treadmill stress test has limited sensitivity and specificity.

CT coronary angiogram has a high negative predictive value. However, in this gentleman, its usefulness may be limited because detailed assessment of in-stent restenosis inside the previous stent would be difficult, particularly with small stents. In addition, for known intermediate lesions like this 50% stenosis in RCA, the limited spatial resolution of CT coronary angiogram may render it difficult to differentiate a 60% or a 40% stenosis from a 50% one. Therefore, sometimes a CT coronary angiogram may not be able to give a conclusive result in this scenario unless the progression of the lesions is distinctively obvious. Presence of asthma does not preclude the application of CT, especially if the baseline heart rate is in the range of 60s/min, although steroid cover is recommended. If beta-blocker is to be used due to high baseline heart rate, it may still be used with caution if the asthma is in clinical remission and if it does not need regular maintenance treatment. However, beta-blocker is contraindicated in patients with active asthma.

Perhaps the best non-invasive investigation in this gentleman is cardiac MRI. In cardiac MRI, the anatomy of the coronary arteries is not shown and what it demonstrates is the presence and absence of myocardial ischemia via perfusion defects in adenosine perfusion stress MRI or via wall motion abnormalities in dobutamine stress MRI. In this patient, since there are known coronary lesions, the functional information on presence of ischemia appears to be more important than the anatomical information. If there is ischaemia, one can proceed to cardiac catheterization and if not, one can continue medical treatment. Adenosine is a short acting drug that can cause bronchospasm. In general, it should be safe for patients with mild asthma in remission and for those who do not need regular maintenance treatment. Again, it is contraindicated in patients with active asthma. On the other hand, dobutamine stress cardiac MRI can be safely performed on patients with a history of asthma. Cardiac MRI is not contraindicated in patients with underlying asthma. In a way, adenosine cardiac MRI is similar to thallium perfusion stress test and dobutamine stress MRI is similar to dobutamine stress echocardiogram with cardiac MRI having a higher spatial resolution and specificity.

Most if not all coronary and peripheral vascular stents are MRI compatible. Cardiac MRI may be safely performed a few weeks after stent deployment. In addition, Amplatzer ASD/VSD/PFO/PDA occluders are also MRI compatible.

What are the likely diagnosis and differential diagnoses?

The differential diagnoses include eccrine poroma, other benign adnexal tumours (e.g. hidradenoma or acrospiroma) and pyogenic granuloma. For rapidly enlarging lesion, malignant neoplasm such as squamous cell carcinoma has to be excluded. It is eccrine poroma in this case.

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What investigation(s) is/are necessary to establish a diagnosis?

Diagnosis of eccrine poroma cannot be made on clinical grounds alone. A diagnostic biopsy is necessary to establish the correct diagnosis.

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Where in the body is this type of lesion found?

Eccrine poroma occurs only on skin, and most commonly on palmoplantar type of skin.

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What treatment will you offer to this patient?

Eccrine poroma is a benign skin tumour and does not require any treatment if asymptomatic. Sometimes treatment is required if it is causing a physical problem such as pain or erosion on friction. Treatment is also required if there is any suspicion of malignancy. Surgical excision provides the definitive cure of the condition.

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What is the prognosis of this condition?

The prognosis of eccrine poroma is favourable because the lesion has no known clinical significance. Even poromatosis (multiple poromas) is not known to be associated with other anomalies. The risk of malignant transformation of a poroma is minimal and is thought to be similar to that of normal skin.

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