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What causes heart disease? – part 49 (nearly there)

15th June 2018

Many years ago, whilst I was at University, a doctor called Elspeth Smith was giving a small group tutorial on cardiovascular disease. I did not know it at the time, but she was doing detailed research into the process of atherosclerosis itself. During the tutorial she made this statement ‘cholesterol cannot get past the endothelium.

At the time I had no idea what the endothelium was, and in truth, not much idea about cholesterol. However, those six words changed my life. At least my medical life. It was as if a door had opened onto a hidden world. No-one else in the group reacted, but I knew from the way those words were spoken that this was someone who was thinking something very differently. Very differently indeed.

Here is the conclusion of one of her talks, reproduced in the book: ‘Factors in formation and regression of the atherosclerotic plaque.’ Yes, the usual jargon filled stuff, but the bit at the end is most interesting.

‘In this talk I have concentrated mainly on the factors that may be involved in the progression of the early, low-lipid gelatinous lesion into the typical fibrous plaque with lipid-rich centre that is generally accepted as the significant lesion in occlusive vascular disease and have tried to emphasize the key role that may be played by fibrin.

Fibrin, the key component of blood clots. How strange, how completely whacky. Is this woman mad. In the tutorial, she moved on quickly, almost as if being caught in an act of disloyalty. Which, I have come to realise, she was.

I now believe that, if she had been bolder, Dr Smith would have got it. The answer as to what really causes cardiovascular disease. I have since read many of her papers, and her contributions to various books. To my mind she was right over the target, looking straight down at the answer – bomb doors open.

Unfortunately, to fit in with mainstream consensus whereby everything must rotate around cholesterol (LDL/cholesterol), she kept looping back to cholesterol, and LDL, constantly trying to crowbar them into her research. Where they did not, and do not, fit.

She also made it too complicated, falling into the trap of ultra-reductionism. A trap that becomes almost impossible to avoid if you travel down and down, further and further, into biological systems. A point will be reached whereby, as physiological systems become smaller, they also multiply endlessly in all directions, and it becomes virtually impossible to see how they link together to create disease.

If you want to see the bigger picture, you must keep moving up and down between the levels. Just as a work of art cannot be understood by an analysis of the molecular structure of the paint, human physiology cannot be understood by tracking down individual biochemical pathways looking for the tiny, essential, lever that starts it all. The single snowflake that triggers an avalanche.

Anyway, getting back to her comment ‘cholesterol cannot get past the endothelium.’ Once you come to recognise that this is true, you are forced to accept that the cholesterol hypothesis, or LDL hypothesis is wrong, because it makes no sense. This does not necessarily mean that LDL does not have any role to play, but it cannot be the necessary factor. The ‘if and only if’ factor.

Which means that, if you want to understand cardiovascular disease, you must strip everything apart and start looking at the whole thing again. If not LDL, then what? Unfortunately, the moment you do this, a number of different problems emerge. The trickiest one is trying to find absolutely agreed facts to build a hypothesis on. Which is far more difficult than you would imagine.

Some facts may seem like bedrock, but when you start to press down on them, they can begin to crack and splinter, and turn to quicksand. For example, the fact that – at a younger age – women have a lower mortality rate from cardiovascular disease than men. This ‘fact’ is quoted endlessly but is it true? Not universally. Younger Brazilian women have an almost identical rate of death from heart disease as the men. At least it was, last time I looked

So, do women really have a lower rate of cardiovascular disease due to a biological difference? Or it is all to do with environmental differences, or psychological differences, or something else?

[By the way I am not referencing much of this blog, this time. You can simply Google most of this stuff yourself. I hope by now readers of this blog will accept that when I make a statement it is not plucked from thin air].

So, do we actually know? Really and truly know? Where are the foundation facts? At one point I reached a little island of despondency where I felt that there was no fact that I could rely on. It seemed that there was nothing that could not be contradicted.

For example, heart attacks are caused by blood clots in the coronary arteries. Surely that is certain? Well, I can find you solid evidence to contradict this, and several people I communicate with will argue that the blood clot follows the heart attack/myocardial inflation (MI). Not the other way around. You think this is mad?

What is certain is that you can find people who suffer from myocardial infarctions with no evidence of any blood clot, in any coronary artery, anywhere. It even has a name. Myocardial Infarction With Nonobstructive Coronary Arteries (MINOCA). To quote from an article in Circulation:

‘Myocardial infarction with nonobstructive coronary arteries (MINOCA) is clinically defined by the presence of the universal acute myocardial infarction (AMI) criteria, absence of obstructive coronary artery disease (≥50% stenosis), and no overt cause for the clinical presentation at the time of angiography (eg, classic features for takotsubo cardiomyopathy)’

This, I should add, is not rare. Maybe 25% of all heart attacks.

Yet, and yet. If you give drugs designed to break down blood clots (clots busters) you can reduce the risk of death from a myocardial infarction (MI). So, clearly, many myocardial infarctions are caused by blood clots. Equally if you use a device to clear out an obstruction from the coronary artery and put in a stent to keep the artery open this does reduce the risk of death following an MI.

Which means that you can – on the face of it – have MIs caused by blood clots, and MIs not caused by blood clots. Apart from the missing blood clot, they are both the same thing, with damaged heart muscle, raised cardiac enzymes and suchlike. So, what the bloody hell is going on?

Equally, you can find people who die of an MI and when you examine their coronary arteries you can find that a blood clot had formed days, or weeks, before the MI occurred. So, again, what the bloody hell is going on here? The blood clot did, or did not cause the MI? Surely not if there is a gap in time, of weeks, between the clot and the MI.

At which point you find yourself asking, or at least I did, how many people have the classic MI. By which I mean a blood clot forms in a coronary artery, then the person gets immediate central crushing chest pain and a myocardial infarction. More than half, less than half? In truth I do not know, and nor does anyone else.

In fact, just to throw more confusion into the ring, it is clear that the vast majority of MIs do not actually cause any symptoms at all. Or at least not symptoms that make anyone think they were having a heart attack.

Deep coal miners in Russia die the very earliest from heart attacks, at least I am pretty sure that they do. Average age of death is less than fifty. If you examine the hearts of these coal miners they will have had, on average, six previous MIs before the final one that got them. None of which were identified at the time. So, why do some MIs cause terrific pain whilst others do not? I have no idea. Nor, as far as I can ascertain, does anyone else.

Perhaps you now have some idea of my difficulty in trying to study CVD. At times it is like trying to pick mercury up off a flat table top. Or, asking questions of someone who will only answer your questions with another question. Frustrating.

I came to realise, eventually, that I could not rely on evidence, then work backwards. Instead I had to look at the metabolism, the physiology, the anatomy and suchlike, and attempt to work out what was going on. Then create a working hypothesis and see if facts fitted into it. Alternatively, find facts that completely blow it out of the water.

So, here we go, again. My working hypothesis as to the cause of CVD is, currently, the following:

  • The first step in the development of atherosclerosis is damage to the endothelium (layer of cells that lines all blood vessels). No damage to the endothelium = no atherosclerosis.
  • After the endothelium has been damaged a blood clot forms over the area
  • The blood clot is mainly broken down and removed – on site
  • Any remaining blood clot is covered over by new endothelial cells, effectively drawing the clot into the artery wall.
  • Further repair systems, such as macrophages, then break up and remove any blood clot remnants, so nothing remains….

Unless.

Unless clots form more rapidly than they can be got rid of, at which point a plaque starts to develop, and grow. When it reaches a critical point, the final deadly blood clot occurs. [I will deal with the issues of MINOCA and suchlike, in the future].

Essentially, therefore, we are looking at a dynamic process whereby, if damage > repair, problems occur. However, if repair > damage, all is well. My analogy is with road repairs. [A major issue in the UK at the moment]. All roads are being damaged by car tyres, rain, ice and suchlike, all the time. If they are regularly repaired, then potholes will not form. However, if the damage outstrips repair, you end up with potholes all over the place.

In a similar sort of way if damage > repair in our arteries we develop atherosclerotic plaques. There are three things that can lead to accelerated atherosclerotic plaque development:

  • Increased rate of endothelial damage
  • Bigger, and more difficult to remove, blood clots forming
  • Impaired healing systems

What this ‘three stage process’ hypothesis can immediately explain is why atherosclerotic plaques never develop in veins. The blood flow in veins in much slower, the blood pressure is around thirty times lower, and the biomechanical strain is much lower. Ergo, the endothelial cells in veins have a lot less ‘strain’ to deal with in their day to day lives. So, there is less endothelial damage going on.

It also explains why, if you take a vein, and use it in a coronary artery bypass (CABG) atherosclerosis very rapidly develops. It further explains why atherosclerosis never develops in the blood vessels in the lungs (pulmonary blood vessels). The blood pressure here is, again, far lower. Although, people with pulmonary hypertension (high blood pressure in the lungs) can develop plaques.

What else does it explain? Well, it explains how smoking increases the risk of CVD. Smoking has no impact on the classic risk factors such as LDL levels, or blood pressure, or diabetes. However, smoking does cause rapid and significant damage to endothelial cells.

Smoking a single cigarette causes mayhem. Endothelial cells die, as measured by a rise in endothelial microparticles in the blood, Endothelial Progenitor cells (EPCs) are released from the bone marrow to repair the damage. At the same time platelets (the key component of all blood clots) are activated. In fact, all hell breaks loose.1

When you look at the damage smoking does, it amazes me that anyone who smokes lasts longer than a week. But they do. Which just demonstrates that the repair systems in the body are extremely efficient.

Anyway, what is clear is that smoking causes CVD through endothelial damage. Precisely the same thing happens with air pollution. It is increasingly recognised that air pollution increases the risk of CV death, and that the primary mechanism is endothelial damage.

In healthy, non-smoking, young adults, episodic exposure to PM2.5 [fine particulate air pollution] was associated with elevated circulating endothelial microparticles, indicative of endothelial cell apoptosis [cell death] and endothelial injury’. 2

Sorry, I did reference those two. I thought they might be difficult to find.

In fact, if you look for any ‘factor’ that damages the endothelium, you will find that it increases the risk of CVD. Below is a list of some of the things that I have been looking at, in some detail. Many of which you will never have heard of, but try not to let that put you off:

  • Systemic Lupus Erythematosus
  • Sickle Cell Disease
  • Lead (the heavy metal)
  • Mercury
  • Bacterial infections
  • Kawasaki’s disease
  • Avastin (and any other VEGF inhibitor (vascular endothelial growth factor)
  • Rheumatoid arthritis
  • Proton Pump Inhibitors (used for ulcers and suchlike e.g. omeprazole)
  • Scleroderma
  • Smoking
  • Air pollution
  • Chronic Kidney Disease
  • Vitamin C deficiency
  • Erythema Nodosum
  • Cocaine use
  • Migraine
  • Diabetes

That list is probably long enough for now. On the face of it, most of these factors may seem completely unrelated. But the simple fact is that they all cause significant endothelial damage, and they all greatly increase the risk of CVD. From 100% in the case of omeprazole, to 50,000% in the case of sickle cell disease.

You may be wondering how the hell does Sickle Cell Disease damage the endothelium. Well, sickle cells are sharp, sickle shaped red blood cells (erythrocytes) – that is where the name comes from. It should come as no great leap of the imagination to propose that having sharp sickle shaped red blood cells hammering through your arteries may be rather likely to damage them.

‘A recent study of spleens* resected from Sickle Cell Disease (SCD) patients… has shown that there was consistent vascular lesions affecting large arteries. The same finding was also shown in studies of brains from SCD patients who developed cerebrovascular accidents (strokes). These lesions were attributed to the rigidity of sickled erythrocytes causing mechanical injury to the endothelial cells. The widespread distribution of the lesions was also suspected in other studies, in which it was suggested that the sickled erythrocyte-endothelial adhesion seen in the microvasculature could be occurring in large arteries and contribute to large vessel endothelial injury, vascular intimal hyperplasia and thrombosis.’3

*spleens are often removed from those with sickle cell disease because they become enlarged and liable to rupture

And here, from the paper referenced above, is the case of a fourteen-year-old boy with sickle cell disease. Much jargon, but important jargon.

‘A 14 year-old boy was referred to our vascular unit, with gangrene of the right foot. The condition started about one year prior to this referral with ulceration of the foot which was treated conservatively. The condition of the foot deteriorated until development of gangrene of most of the foot. The boy is a known patient of SCD. His past medical history revealed right sided stroke when he was 8 years old. His parents have SCD. His brother had also SCD and died suddenly at the age of 5 years.

There were no identifiable risk factors for atherosclerosis.

On examination, there were no palpable pulses [no pulses could be felt]. He was found to have heavily calcified femoral and brachial arteries [main arteries of arms and legs]. Plain x ray of both arms showed extensive calcifications of brachial, femoral and popliteal arteries. An X ray of his right foot showed infarction and osteomyelitis of most of the bones [infection in the bones].

Plain CT [detailed x-ray] of the abdomen and pelvis showed calcification of splenic artery and calcifications of both iliacs and inferior mesenteric artery [arteries branching from the aorta, main arteries of legs and artery supplying the bowel]. Digital subtraction angiography [too complicated to explain here] showed occlusion of right external iliac artery and both superficial femoral arteries with extensive collaterals. MRI & MRA of the brain showed left parietal wedge area of infarction with total occlusion of the supraclinioid segment of left internal carotid artery [important bit of the brain] and multiple collaterals. The patient had a right below knee amputation and was discharged home on antiplatelets.3

This fourteen-year-old boy had calcified atherosclerosis in virtually every artery in his body. With, and this should be highlighted again no identifiable risk factors for atherosclerosis.

Now, you can look at every single current hypothesis as to the cause(s) of CVD, and NONE of them can explain why this fourteen-year-old boy has widespread and overwhelming atherosclerotic plaque development. He represents the classic black swan.

On the other hand, if you believe that endothelial damage is the primary driver of CVD, this case history makes perfect sense. It also explains how the other fourteen things on my list increase the risk of CVD, whereas the current ‘LDL hypothesis’ can explain precisely NONE of them.

Which makes it – fourteen-nil to the endothelial damage hypothesis, and we have not even reached half time. Russell Ross – who first proposed the ‘response to injury’ hypothesis would be pleased with this result. As would, I hope, Elspeth Smith. Unfortunately, they are both now dead. But I hope to see that they get the posthumous recognition that they deserve.

They were telling us what truly does cause CVD, but no-one was listening. Everyone else was content to blindly follow the ‘cholesterol hypothesis’ waving flags, cheering, and raking in the money.

1: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0090314&type=printable

2: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5215745/

3: https://www.sciencedirect.com/science/article/pii/S1533316707000192

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