Yes, part X, and not at the end… yet. Before trying to sum up I thought I should discuss calcification of the arteries. This is an area I have tended to shy away from in the past, because I am not sure exactly where to place it. Association, end-result, cause… Ignore.
Firstly, what is calcification? It is generally accepted, and I think it is true, that calcification represents the final stage of atherosclerotic plaque development, or growth – or whatever word fits most accurately. The best way of looking at calcification, within the spectrum of CVD, would be to define it as the end stage of plaque development.
Having said that, this is not always the case. Not all plaques calcify. Some do, some don’t, and there are many other factors that have a key role in calcification. Various vitamins, such as Vitamin K(K2) and vitamin D are important. Warfarin, which blocks the effects of vitamin K, increases plaque calcification. The picture is complex.
You may have heard of a condition called fibrordysplasia ossificans progressiva, where muscle turns to bone. Not nice, but it does demonstrate that, in certain circumstances, various other tissues can also calcify – to one extent or another.
The main reason for mentioning calcification is that the Calcium artery score (CAC) has become the latest way of frightening people about CVD. You do a CT scan, count of the amount of calcium you can see, and score it. The more the calcium, the worse things are.
In truth, despite my slightly sceptical tone, measuring calcification seems to be one of the most accurate ways of assessing overall plaque burden, and your true risk of dying of CVD. Like everything else in this area, the CAC score is far from perfect. However, even with many provisos in place, if you have a high CAC then you are definitely at a higher risk of dying of CVD. Equally, if you have a zero calcium score, you can pretty much relax. So it is important.
I suppose you may be wondering, at this point, why would plaques calcify? What is the body doing here? Well, you might find these quotes interesting:
“Atherosclerotic calcification is an organized, regulated process similar to bone formation that occurs only when other aspects of atherosclerosis are present.” L Wexler, et al., American Heart Association Writing Group
In short – and, by the way, I fully agree with the above quote, calcification is not an accident, or an unwanted effect. It seems to be an organised, and regulated process. But organised, and regulated, for what purpose…
‘This chapter will show that vascular calcification is a physiologic defense against active, progressive atherosclerotic disease, that it is produced by physiologic mechanisms similar to those required for normal bone formation and that it is potentially reversible.’ 1
You might well then ask the following. If calcification is a physiologic defense mechanism… why would you want to reverse it? You might just be making things worse. It is certainly true that plaques pass through several different phases. The most dangerous of which seems to be the ‘unstable’ plaque. This is when the central core of the plaque is a kind of liquid goo which, if it ruptures, stimulates a massive – and potentially fatal – blood clot. Plaques in this state are sometimes called ‘vulnerable.’
On the other hand, once a plaque calcifies, it appears to become more stable, and less likely to rupture… and kill you. Which means that reversal of calcification may look good on a scan, and your doctor may smile with pleasure at your reduced CAC. But… it is all good? I have seen an argument used (by the pro-statin camp) that statins accelerate calcification – but this might be a good thing, because the plaque is less likely to rupture. Is this true? [It would by a nice irony].
Perhaps, here, you can see why I struggle a bit with the whole calcification thing. Is it a natural progression of the plaque? It is a way that the body closes down further damage, and stops further plaque progression. Does calcification help to strengthen the artery wall to prevent it rupturing? Should we be trying to reverse calcification… would we simple be turning a calcified plaque back into a vulnerable plaque?
Calcification is certainly not a new thing. CT scans of mummies – from a number of different cultures – have demonstrated that many/most mummified bodies have large areas of arterial calcification. Ergo, CVD is most certainly not a disease of modern humanity. The mummies from Egypt are well over two thousand years old.
As you can probably tell I am not sure exactly what to make of calcification. However, I think you can probably make the following statements:
- If you do a CT scan and have no demonstrable calcification – after the age of about forty to fifty – you are at very low risk of dying of CVD
- If you have a high CAC score this means that you have been developing plaques for quite a while, and therefore (unless you change something) you are at high risk of dying of CVD. [However, bear in mind that CAC represents your history, not necessarily your future].
- Calcification can reverse. Vitamin K2s (Menaquinones) seem to be more protective/able to reverse calcification than Vitamin K1. Menaquinones are primarily found in meat and dairy-based foods and fermented soybeans (known as natto, commonly consumed in Japan)
- Calcification is not a cause of CVD, it is (or seems to be) the final stage of plaque development. It may be a protective mechanism to stabilise plaques.
- There is no evidence, that I am aware of, that if you reverse calcification you improve CVD risk. But it seems likely there would be benefit.
Sorry, I am not sure if that is very helpful, but I thought I had to discuss calcification in this series.