+100%-

Geoff’s Narration

The GIST

 

Here we are with the blood vessels again! The blood vessel saga in ME/CFS started about 20 years ago and then quickly folded (after one small negative result), and then opened up again with long COVID. Now it’s become a major theme.

 

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blood vessels

Back to the blood vessels we go!

Now we’re looking at microclots, activated platelets, narrowed blood vessels, senescent blood vessels, thickened basement membranes, deformed red blood cells, issues with hemoglobin – the list of possible blood vessel problems just seems to go on and on.

There’s also the evidence that we have reduced brain and microvascular blood flows. Indeed, two of the big questions raised by David Systrom’s invasive exercise studies are why oxygen from the blood is not being extracted by the muscles, why the blood seems to be disappearing, and where the heck it’s going.

While most of the studies remain quite small – a big bugaboo in these fields – there seems to be a lot going on, and new researchers are joining the fray.

Two more blood vessel studies just popped up. One of them, not surprisingly, is from Germany, and the other is from Yale and Johns Hopkins in the U.S. This blog deals with the Yale/Johns Hopkins study.

The Gist

  • It’s amazing how the blood vessel issue has grown in long COVID and ME/CFS. The list of possible blood vessel problems (microclots, activated platelets, narrowed blood vessels, senescent blood vessels, thickened basement membranes, deformed red blood cells, issues with hemoglobin) seems to go on and on.
  • The “Vascular inflammation in neuropsychiatric long COVID” study started off on a nice note: “LC is a pressing public health issue that patients, providers, and researchers are eager to understand“. I don’t remember seeing such a blatant display of enthusiasm before, and it was good to see.
  • This study examined markers of blood vessel inflammation in people with an acute COVID-19 infection, people who’d had long COVID for 1 or 3 years, and recovered COVID-19 patients.
  • It found, as suspected, that acute coronavirus infection triggers a cytokine storm that pummels the endothelial cells lining blood vessels. A year later, the storm has died down, but a different kind of immune activation is present.
  • The small blood vessels are still under considerable stress and are fighting back with repair mechanisms that are trying to limit the damage.
  • It doesn’t entirely seem to be working. The study found clear correlations between markers of blood vessel inflammation and cognitive problems such as verbal learning, fluency, memory, depression, and anxiety.
  • In the end, this was not a surprise. The authors noted that small blood vessel disease in the brain is strongly associated with, and predictive of, cognitive issues.
  • They proposed that a “microvascular endotheliopathy,” which refers to an injury to the endothelial cells lining the body’s smallest blood vessels, was contributing to the cognitive problems and depression/anxiety.
  • They believe their study provides “compelling evidence that… LC mental health symptoms likely have a neuroimmune and neuro-oxidative origin”.
  • Three years later, an entirely different situation has developed. All signs of blood vessel inflammation, yet the long COVID persisted.
  • The authors proposed that blood vessel healing may have taken place. It’s also possible that the small blood vessel problems may remain; i.e., the extracellular matrix and microvascular damage, and perhaps, most importantly, blood-brain barrier damage (from leaky endothelial cells) may all still be present, but the immune response died down over time.
  • It’s also possible that the small blood vessels are in a senescent state that prevents them from operating normally and producing normal blood flows.
  • It’s also possible that the brain – faced with blood flow problems – has rewired itself and that it’s now in a neuroinflammatory steady state. It’s perhaps notable that many of the brain regions associated with ME/CFS appear particularly vulnerable to inflammation in the blood vessels.
  • More blood vessel studies have recently been published, and this team reported that they’re continuing to study their long-COVID patients – so we should continue to learn about the possibly vital blood vessel connection in long COVID and ME/CFS.

 

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The Study

The “Vascular inflammation in neuropsychiatric long COVID” study started off on a nice note: “LC is a pressing public health issue that patients, providers, and researchers are eager to understand“. I don’t remember seeing such a blatant display of enthusiasm before, and it was good to see. The study examined markers of blood vessel inflammation and added a nice twist: they assessed whether these markers affected cognition.

Two groups of long-COVID patients were included: 28 patients with COVID-19, 50 long-COVID patients who had been ill for about a year (Yale), and 114 long-COVID patients who had been ill for about 3 years (Johns Hopkins).

First, Though, a Rant about Criteria – Feel Free to Skip Forward

Missing the target

Six years later, still no standard, interim diagnostic criteria for long COVID? Really?

It’s amazing, disturbing, ridiculous – use what adjective you will, that 6 years later, we still do not have standardized criteria for diagnosing long COVID. For some who’ve been immersed in the ME/CFS field for decades, this is a stunning lapse.

The need to develop criteria to determine which patients could participate in an ME/CFS study was immediately recognized as a major problem, and considerable efforts went into addressing it. Over time, the Fukuda, Canadian Consensus, International Consensus Criteria, the IOM SEID Criteria, and others were put forth.

By 1994, the fledgling field came up with a faulty – but standardized – criteria (Fukuda criteria) which, honestly, largely worked. Post 1994, virtually every ME/CFS study used it. By 2003, the still very small ME/CFS field had picked itself up by its bootstraps, and – successfully challenging the Fukuda criteria – came up with a better criteria called the Canadian Consensus Criteria (CCC). By the mid 2000s, I would hazard to guess that most researchers (Bernard Wyller and the CDC excepted :)) were using the CCC.

The point is that the ME/CFS field recognized that developing good criteria was essential. Throughout this saga, it was lucky to have a crack epidemiological researcher in Lenny Jason, who kept pushing the issue.

Six years after long COVID showed up on the scene, though, the much larger and better-funded long-COVID field is still using nebulous and even unstated symptom criteria to assess a very heterogeneous disease.

Avindra Nath, Jonas Bergquist and others recently decried the diagnostic situation in Lyme Disease and other post-infectious illnesses. Jacqueline Becker, a neuropsychologist and coauthor on the paper, said, “If we want clinical trials that actually lead to treatments, we have to get the fundamentals right: we must confirm diagnoses, choose the right comparison groups, and treat patient populations as distinct rather than lumping everyone together. Patients deserve that rigor.”

They sure do. Getting the diagnostic rigor down is not sexy, but it sure is important. Ultimately, uncovering a biologically based diagnostic criteria is going to take time, but there’s no excuse for not having an international group of long-COVID experts meet to create interim criteria that researchers and doctors can use.

This blood vessel paper, for instance, said that the 50 individuals with neuropsychiatric Long COVID (LC) in the Yale part of the study were “carefully selected.”

They had to have at least one (one?) new, self-reported neuropsychiatric symptom (cognitive dysfunction, headache, etc.) for greater than 3 months, plus a confirmed COVID-19 test (nice touch), and had to take a “formal survey”. How little attention is given to this subject is evident in the fact that the name of the survey, if it has a name, is not even stated.

I’ll bet the researchers did, in fact, pluck out a good neuropsychiatric set of long-COVID patients, but the fact that the long-COVID field, after six years, still hasn’t taken the time and trouble (an international consortium could do it) to create a standardized definition of “neuropsychiatric long COVID”, or even long COVID in general, which guides patient selection across studies, just seems baffling.

At the very least, at the symptom level, let’s be able to compare apples to apples. While one study may have more Fuji apples, another more Granny Smith apples, and another more Honeycrisp apples, at least symptomatically, we know they’re all apples.

One would have assumed that with its huge sample sets, the RECOVER project would have been on this like bees on honey. In fact, it is making some progress, but, boy is it taking a long time.

The closest we’ve come is a 2023 RECOVER study, which listed the most common long-COVID symptoms. While the paper did highlight 12 “signature” symptoms (PEM, fatigue, brain fog, dizziness, GI symptoms, palpitations, sexual dysfunction, smell/taste loss, thirst, chronic cough, chest pain, abnormal movements), it did not provide a simple criterion clinicians could use.

Neither did a 2024 Update. It modified the signature symptoms a bit (post‑exertional malaise, fatigue, brain fog, dizziness, palpitations, change in smell or taste, thirst, chronic cough, chest pain, shortness of breath, and sleep apnea). Using its weighted symptom scores, it found that a remarkable 20% of COVID-19 patients met their criteria for long COVID (!).

The paper did produce 5 possible symptom clusters. Remarkably, 4 of the 5 clusters clearly denote ME/CFS-like subsets characterized by post-exertional malaise and fatigue.

The good news is that RECOVER’s next steps are to accumulate more data, including incorporating symptom trajectories (getting better, worse, or staying the same over time) and associating symptom types with immunologic signatures, viral persistence, autoantibodies, and autonomic and cardiopulmonary measures.

(Unfortunately, the observational side of the RECOVER project, which is driving the symptom typing, doesn’t appear to be gathering much, if any, multi-omic information).

In the end, it’s clear we will get better criteria, but, again, why not produce interim criteria for long COVID as a whole, and for the different subsets, to help guide researchers and clinicians?

This long rant was occasioned by the fact that this study involved two different cohorts, which produced very different results. That may well have been due to different durations, but since we don’t have good criteria, it could also have been due to different patient sets. Rant over! Back to a very interesting study.

Study Results

The results appeared to support a hypothesis that emerged in a previous study, which suggested that a cytokine storm during the initial infection hits the blood vessels really hard. After the infection was resolved (at least in the blood vessels), a different kind of inflammatory response set in. After some time, that died down as well, but the blood vessels may or may not have been left with long-term damage.

The Initial Big Blood Vessel Hit

Blood clots

Blood clots and inflammation gave the blood vessels a big hit during the initial infection.

The dramatically increased levels of acute-phase proteins AGP (p = 0.0005), CRP (p < 0.0001), and haptoglobin (p = 0.0003) in the COVID-19 group vs the long-COVID group indicated that a classic systemwide inflammatory response had occurred, which may have damaged the endothelial lining of blood vessels. This indicated that the endothelial cells lining the blood vessels have become activated and that clotting is occurring.

Struggling Blood Vessels A Year Later

A year later, things had changed. One group had recovered, and another had not. That big pro-inflammatory cytokine spike had largely disappeared in both groups. Now, the long-COVID group exhibited increases in different immune factors. They included elevated SAP (p=.0005), fetuin (p = 0.001), sp-selectin (p = 0.0001), sl-selectin (p=.03), and ADAMTS13 (p < 0.0001).

(Notice the huge probability factors (p = 0.0005, p < 0.0001) often found. They indicate there’s an extremely low probability (1 in 10,000 or 5,000) that the findings were due to random chance; i.e., these are really solid results.

Driving the Dysfunction?

trigger

Could activated platelets be driving the blood vessel inflammation?

The high p-value regarding the sp-selectin (p=0001) provides a very clear indication that while platelet/endothelial activation may have died down, it’s still present in long COVID. Several studies suggest that low-grade inflammation is keeping the platelets in long-COVID patients in an activated state.

Those activated platelets could be producing a lot of mischief. They could be sticking to the endothelium and releasing a host of pro-inflammatory factors that, in turn, activate the endothelial cells, increase blood vessel permeability (causing the blood loss/preload failure Systrom sees?), and cause microvascular damage.

One study suggested that an as-yet unidentified factor in the plasma is hyperactivating the platelets in long COVID. While microclots, NETs (see the last blog), autoantibodies, and damaged bits of the extracellular matrix weren’t assessed in this study, they could be activating the platelets.

A Short Treatment Interlude

Because platelet activation appears to be present and may be driving inflammation and vascular remodeling, platelet inhibitors seem a possibility.

Pretorius and colleagues found benefit from triple antiplatelet and anticoagulant therapy in long COVID, but dual or triple antiplatelet/anticoagulant therapy (except for aspirin) appears to be pretty serious business, and the field will likely need compelling evidence before it embarks on these trials.

On the supplement and diet side, omega‑3 fatty acids (fish oil, EPA/DHA), polyphenols/flavonoids (resveratrol, quercetin, grape seed extract, green tea catechins), garlic, ginger, ginkgo, turmeric, cinnamon, and Vitamin E could have modest effects.

The increased sL‑selectin (soluble L‑selectin) suggests that immune cells called leukocytes are being drawn to damage in the endothelium. Instead of producing a cytokine storm, however, they’re creating a kind of smoldering infection.

Fighting Back

A host of factors suggest that a year after the infection, the blood vessels are fighting back and trying to repair themselves.

Fetuin-A – The increased fetuin-A levels indicate the blood vessels are under stress and are attempting to stop calcium from being dumped into them. Calcium in our blood vessels is a no-no because it stiffens them, which disrupts the smooth flow of blood through them. That loss of elasticity and fine-tuning can, by itself, result in low oxygen conditions and reduced blood flow to the brain, muscles, and organs.

α2 macroglobulin – a protease‑inhibitor and extracellular matrix remodeler, α‑2 macroglobulin was the most elevated endothelial factor found in the long-COVID patients. A-2 macroglobulin tries to limit extracellular matrix damage – which was featured in a recent blog.

The elevation of α-2 macroglobulin suggests, as some studies have found, that extra collagen deposition may have occurred in the blood vessel lining. German studies have recently found increased collagen deposition in the basement membranes associated with ME/CFS patients’ endothelial cells. Increased collagen deposition may also be inhibiting blood from getting to the muscle tissues.

ADAMS13 – Because ADAMS13 supports microvascular blood vessel production and repair, increased ADAMS13 levels indicate the microvasculature is under stress.

An inflammatory environment, then, appears to be present in patients with long COVID. It’s much lower than in COVID-19 patients but much higher than in healthy controls. The demonstrates the stress the blood vessels are under a year after the acute infection has triggered several efforts to repair and maintain microvascular flows.

Importantly, once again, we have findings that jive with each other. If high SP levels are present, we might expect elevated fetuin, selectin, and ADAMTS13 levels. At times in ME/CFS, we’ve seen disjointed findings that were hard to know what to make of (and which were discarded), but there doesn’t appear to be any mystery here. The blood vessels have taken a hit.

Brain Fog, Depression, and Anxiety

brain fog

The study suggested that inflammation in the blood was contributing to the brain fog, depression and anxiety found in long COVID.

The brain fog (reduced verbal learning, memory, fluency) and depression/anxiety that were associated with markers of inflammation in the blood vessels (sP-selectin, fetuin-A, AGP (α1‑acid glycoprotein) may have been the most important finding. Note that this study assessed inflammation in the blood, not the brain. The brain receives the same blood that circulates in the body, with one key exception: the blood-brain barrier filters out some substances.

Several of these substances, though, can weaken the blood-brain barrier, and a leaky BBB that allows sP-selectin and activated platelets to cross into brain tissue could produce or exacerbate neuroinflammation, and ultimately, brain fog.

Indeed, the authors noted that “chronic vascular inflammation, particularly in the context of cerebral small vessel disease, is strongly associated with and predictive of cognitive decline”. They proposed that a “microvascular endotheliopathy”, which refers to an injury to the endothelial cells lining the body’s smallest blood vessels, was at least contributing to the cognitive problems.

Given that, it was no surprise that the authors saw a clear biological foundation for both the cognitive problems and the depression/anxiety found in long COVID. They stated that the study evidence thus far provides “compelling evidence that … LC mental health symptoms likely have a neuroimmune and neuro-oxidative origin”.

They didn’t even get to the reduced blood flows to the brain! So we have some more ways to explain the brain fog present in long COVID and ME/CFS. Besides reduced blood flows to the brain and impaired metabolism, the inflammation associated with endothelial cell damage in the blood vessels could be weakening the blood brain barrier, allowing inflammatory substances to penetrate the brain and produce neuroinflammation. Combine that with the sticky, sludgy blood, and damaged small blood vessels in the brain, and you have a nice explanation for brain fog and a host of other problems.

Three Years Later: Healing, Chronic Damage, ????

Three years later, an entirely different situation has developed. All signs of platelet activation and endothelial disruption are gone (!), yet the long-COVID patients with their high rates of fatigue (95.5%), poor memory (90.2%), poor concentration (81.3%), headache (80.4%), post-exertional malaise (78.6%), and word finding difficulty (77.7%) remain.

Immune Exhaustion?

This pattern may fit with the idea – first elucidated by an ME/CFS Hornig/Lipkin paper – that these diseases change over time. Hornig/Lipkin observed a dramatic upregulation of the immune system followed by a dramatic reduction over time. At no time was the immune system in a normal state: it was either overly activated or under-activated.

The authors suggested that healing may have taken place, but it’s also possible that the blood vessel problems may remain; i.e., the extracellular matrix and microvascular damage, and perhaps, most importantly, blood-brain barrier damage (from leaky endothelial cells) may all still be present, but the immune response died down over time.

A Senescent Blood Vessel State?

Another possibility is that some blood vessels – perhaps existing in different parts of the body in different patients – have entered into senescent or SASP steady state (SASP). These blood vessels, perhaps located deeper in the body, are pumping out some cytokines, producing microclots, and having trouble opening and closing properly. This study would not have captured that state, but a recent study suggests it may be present.

SASP blood vessels tend to have thicker, stiffer walls (increased stiffness index, reduced pulse wave velocity), have damaged extracellular matrices, and may contain calcium deposits.

Because they’re not elastic enough, these blood vessels tend to pound blood into the microvasculature, potentially damaging the smaller blood vessels. This seems like it could nicely explain a PEM state that occurs after exercise. The small blood vessels get hammered, go hypoxic, and it takes some time for them to return to baseline.

The presence of SASP blood vessels could also help explain the neurovascular coupling problems observed in the brain. If they are present, the blood vessels may not be pliable enough to quickly deliver blood to different parts of the brain. Likewise, their inability to open properly may be impairing their ability to deliver blood to the muscles during exertion. SASP blood vessels have been described as “aged, inflamed, stiff, leaky pipes” (a nice portrayal of what it feels like to have ME/CFS!).

With its pulse wave velocity measurement, the Oura ring provides a coarse estimate of arterial stiffness, which it then translates into a “cardiovascular age”. My cardiovascular age according to Oura is usually 1-3 years younger than my real age, so it doesn’t appear that my larger blood vessels have stiffened. Because the Oura ring would not pick up stiffened blood vessels in the microvasculature, though, it’s possible that my small blood vessels have become stiffened.

Going Deeper?

It’s also possible that the problems have migrated deeper into the tissues, have rewired the brain, put the microglial cells on a knife’s edge, and destabilized the autonomic nervous system.

Senescent blood vessels can cause a leaky blood-brain barrier, which can let unwanted proteins, complement, and pro-inflammatory cytokines into the brain. The reduced capillary density and damaged capillaries that result could prevent the blood from smoothly and easily moving to different parts of the brain.

That introduces “noise” into the system, which can impair brain networking. It’s perhaps notable that the parts of the brain most at risk from immune factors coming from the body appear to have been most affected in ME/CFS.

In response to the altered blood flows, the brain begins to prune its synapses, resulting in a new hardwired state. At this point, you need to find a way to rewire the brain.

This situation – damaged capillaries, poor brain blood flows, hypoxia, etc., would put the immune cells of the brain – the microglia – on high alert. The inflammatory cytokines they produce would, then, exacerbate the situation.

The increased white matter hyperintensities found in ME/CFS (40 years ago!) and, more recently, in both ME/CFS and long COVID appear to fit this picture very well, as they’re now understood to be a signature of small-vessel disease and chronic microvascular injury.

Whatever the case, the good news is that researchers in general are digging deeper than ever into the blood vessels in both long COVID and ME/CFS, and this team reported that it continues to study its cohort of long-COVID patients.  We can expect more out of them.

Finally, if this study is accurate, we now have two new subsets: early long COVID and later COVID that must be taken into account. The plot thickens!

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Health Rising’s Quickie Summer Donation Drive is On!

Keeping up with the latest research in ME/CFS, long COVID, fibromyalgia, and allied diseases. Exploring new treatment possibilities. Learning how others have recovered. All in as thoroughly and comprehensively as we can. 

Please support Health Rising during our quickie summer donation drive. Our goal is to raise $15,000. 

 Find out more here.

Please support Health Rising in our Quickie Summer Donation Drive! Our goal is $15,000.Click here for more.

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