Coronary Calcium Scanning

The latest generation of fast CT scanners has given us the ability to freeze the heart in motion, and so we can finally look at calcium deposits in the walls of the coronary arteries. This deposition of calcium is something like the furring on the inside of a kettle that occurs over time.

In general a higher calcium score on this scan is consistent with a greater risk of future heart disease. This can help us to decide which patients need aggressive management of risk factors, such as elevated cholesterol. And we know that treatment can regress the calcification - so it's worth knowing too.

I've done about 2000 of these scans since they became available to me in 2003 , and I've had some surprises. We see patients who smoke and have raised cholesterol, but have a coronary calcium score of 0. In other patients who are fit and well in their 30s, but perhaps have a family history of premature coronary artery disease, the calcium load has occasionally been very high indeed.

In one or two patients the calcium load has been so high that the cardiologists have thought it wise to proceed to an angiogram. Here we directly image the coronary arteries, using dye pumped in through a tiny catheter in the femoral artery. If because of this we discover an incipient block in one of the arteries, then perhaps we have stopped that patient having an unexpected heart attack! You hear about these - they usually happen right after the patient has been given a clean bill of health by their doctor at a check up.

 A low or zero coronary calcium score seems also to be a good indicator of a low risk of having a stroke – it seems that the cerebral arteries mirror the coronary arteries.

Now, like most medical tests, this isn't fool proof. But we have a powerful new tool for the assessment of coronary risk. I don't usually advocate statins in patients who have a raised cholesterol but a zero coronary calcium score - so this simple test could save you a life time of medication.

Coronary CT angiography

Coronary calcium scoring isn't fool proof - it is possible to have soft plaque narrowing a coronary artery which just doesn't show up on the scan. Happily we can now directly visualise the arteries to look for narrowing, and even measure flow of blood across any narrowing that we find - this is called fractional flow reserve. If the narrowing is causing significant disturbance of blood flow to part of the heart muscle then a "stent" - a tiny coil - can be place across the narrowing to improve blood flow. I usually reserve this test for patients with suspicious symptoms or very high risk factors such as diabetes.

A new worry is the realisation that although stents can alleviate angina they might not actually prolong life expectancy - I’ll keep you posted on this one.

Chest CTs in smokers.

A recent paper has suggested that routine chest CTs in those with a significant smoking history can find early lung cancers and that these may be surgically removed at a stage when they would not have otherwise declared themselves. The study was performed in those smoking around 20 a day for 20 years or more - we just don't know whether you can extend this benefit to lesser smokers. Lung cancer can often declare itself too late for surgery - we really need this strategy to work.

Now there is a problem here. It took years for us to establish that irradiating the breasts with a mammogram in those with a high risk of breast cancer didn't actually cause breast cancer. I have no way of knowing whether an annual chest CT in this group may increase the risk by irradiating the lung fields so frequently. So for now I am discussing this with patients, but I can't convince myself to do it routinely yet.

However on four occasions now I have discovered a very early lung cancer on these scans - removed it and probably saved a life. So I’m becoming more enthusiastic about these scans not surprisingly. Feel free to discuss this with me if you have been a smoker.

Why don't we advocate total body scanning?
This is one of the most contentious areas in health screening; do we keep our heads in the sand, or do we scan everything in sight, and risk worrying the patient entirely without justification? We now have the scanning technology to produce exquisite three-dimensional pictures of most of your internal organs - and there is no doubt that some patients love the idea of having this sort of screening, and ask for it. 

These scans often detect tiny lesions in the lungs, kidneys and other organs. But we often don't know if these will go on to become cancer, or will remain benign. An example is pulmonary nodules. We just don't know which of these tiny shadows will remain benign for ever, and which will go on to become a lung cancer. So if we find one you will have to be prepared for regular scans perhaps at six-monthly intervals so that we can watch for any change. It's that concept of "outcome data" again. We simply don't have the proof that these scans are helpful.

Not surprisingly, centres that perform these scans are highly enthusiastic about them - what a money-spinner if we have to repeat them twice a year! But next time somebody boasts to you over the dinner table that their doctor organized total body scans, you can tell them from me; the pictures may be pretty, but the benefits to health are exceedingly dubious.