COMPUTERISED X-ray Tomography, or CT scanning, is a medical imaging technology which uses X-rays to create cross-sectional images of parts of the body.

When compared to traditional X-rays, CT scanning is more sensitive for picking up abnormalities and its use has increased dramatically over decades. CT imaging can be used to evaluate cardiac structure and function. The initial use case was in looking for calcification in the coronary arteries as a marker of cardiac disease. Further development has resulted in the ability to perform angiography (evaluation of the coronary arteries), assessment of heart function, and assessment of valve function. Our topic for today, however, will focus on the clinical importance of calcification in the heart that is picked up incidentally on CT imaging for other indications. A CT scan of the chest can be done for many indications, including further evaluation after an abnormal chest X-ray, the evaluation of symptoms such as coughing up blood and chest pain, screening for tumours in smokers, evaluation of the extent of cancer, etc. In almost all of these studies the heart and large blood vessels in the chest are seen as part of the study. Calcium is seen to be laid down in the heart arteries on between 26 and 93 per cent of CT chest studies done for non-cardiac indications, depending on the population that is studied. Calcium is noted in the aortic valve about five per cent of the time and in and around the mitral valve about eight per cent of the time.

What does calcium laid down in the coronary arteries mean?

There are several processes by which calcium can be laid down in arteries; however, for the heart arteries the most common reason for calcium to end up in the arterial wall is a consequence of cholesterol deposition or atherosclerosis. As we have discussed previously, laying down of cholesterol is a process that occurs over decades, often starting in young adulthood in western countries. It begins with disruption of the normal processes that prevent arterial damage. Fat deposition, chronic inflammation, cellular infiltration, scarring, abnormalities in clotting, local hormonal changes, and vessel spasm all play important roles. The deposition of calcium is often the endpoint of this process. Therefore, when calcification is seen in the location of the heart arteries this is a marker for cholesterol deposition or atherosclerosis. People with coronary calcification thus have coronary artery disease. This finding can be very useful as we know that many patients with coronary artery disease are asymptomatic, that is, have no chest pain or other concerning symptoms. The initial presentation of coronary artery disease can be sudden death or a large heart attack. In cardiology we will often use CT scanning to look for coronary calcification in patients that we are unable to adequately classify as low risk. Seeing calcium deposition in these patients signifies a group of patients who need aggressive medical management, lifestyle therapy, and potentially further evaluation. In patients who have calcium in the coronary arteries diagnosed incidentally this is an opportunity to improve outcome.

Does seeing calcium in the heart arteries change management?

There is currently a large body of data looking at the significance of finding calcium in the heart arteries. These data have come predominantly from studies in which the CT scan was ordered for cardiac evaluation. There is a strong association with the deposition and extent of calcium in the heart arteries and subsequent risk of heart attack and cardiac death. Most national cardiac bodies have guidelines that suggest lifestyle measures, risk factor modification, and cholesterol lowering therapy for those found to have significant amounts of calcium in heart arteries. Some of these patients will need further testing to see if the cholesterol that is laid down is serving as an obstruction to the flow of blood down the artery.

What does calcification in the valves of the heart mean?

Calcification of the valves of the heart is somewhat more complicated. Cholesterol deposition does play a role; however, degenerative change, repeated low level trauma from valve opening and closing, abnormalities in valve structure, abnormalities in flow across the valve are likely more significant factors. Importantly, calcium deposition in valves reduces the flexibility of the leaflets which can progress over time. For example, in a patient with severe narrowing of the aortic valve the initial change in a significant proportion of patients is leaflet calcification. Calcification of the mitral valve and its supporting structures with ageing is common and can lead to both narrowing and leakage of the valve over time. An interesting point to note is that in contrast to calcium deposition in the heart arteries, cholesterol-lowering therapy has not been demonstrated to lower the risk of needing valve replacement for the aortic or mitral valves. For the aortic valve, the amount of calcium that is seen on a CT scan can be used to diagnose severe narrowing of the valve and the need for valve replacement.

What should be done if calcium is noted in the heart arteries or valves on a CT scan performed for non-cardiac indications?

This question needs to be looked at from several perspectives. The first is that of the radiologist who is reading the study. A CT scan report will generally comment on all the structures that are in the field of view. Many imaging societies are suggesting that if coronary calcification is seen it should be qualitatively assessed and reported as mild, moderate, or severe, and this can be done with good accuracy when compared to a formal CT scan that is done specifically for a cardiac indication. Some societies have suggested that recommendations be made for cholesterol lowering therapy and lifestyle measures as part of the formal CT scan report.

From the point of view of the physician who has ordered the study, it is important that he/she recognises the significance of calcification in the heart structures. Even if the test was ordered for a more urgent clinical problem, that is, pneumonia, the presence of coronary calcification suggests an additional cardiac issue which will need treatment and possibly further testing. In my practice, if a new patient has had a CT scan of the chest previously, I will review the report to see if any cardiac abnormalities are noted and if time permits and they are available, I will review the images personally. For a patient who is seen acutely in the emergency room for chest pain, the knowledge that there has been coronary calcification noted previously can change the management strategy.

If as a patient you have had a CT scan of the chest for any indication, it is often a good idea to ask your primary care physician if your heart was OK on the study as this is often an opportunity to identify heart disease that is asymptomatic. Treatment at this stage may involve lifestyle measures of a low-salt, low-fat diet with adequate intake of fruits and vegetables; regular exercise; trying to avoid weight gain; good sleep hygiene, avoiding smoking, alcohol, and drugs of abuse. For most patients we would recommend cholesterol-lowering therapy to reduce the risk of further cholesterol deposition and the risk of heart attack. Some patients will require further testing of the heart. For patients with heart valve calcification there does not appear to be any benefit from cholesterol-lowering therapy in preventing progression of valve disease, although there may be other benefits. We would, however, recommend lifestyle measures as noted above and, in some scenarios, an ultrasound of the heart for evaluation of valve function.

Dr Ernest Madu, MD, FACC and Dr Paul Edwards, MD, FACC are consultant cardiologists for Heart Institute of the Caribbean (HIC) and HIC Heart Hospital. HIC is the regional centre of excellence for cardiovascular care in the English-speaking Caribbean and has pioneered a transformation in the way cardiovascular care is delivered in the region. HIC Heart Hospital is registered by the Ministry of Health and Wellness and is the only heart hospital in Jamaica. Send correspondence to info@caribbeanheart.com or call 876-906-2107.