gemini://thfr.info/hi/2023-06-07-schoener-thrombus.gmi

Blood clots... some patients know about them, and have a sense that blood clots can mean trouble. On the other hand healthcare workers, especially those dealing with acute illness, are on average positively horrified by this entity.

There are arterial and venous clots. The former is something like what happens with many types of heart attacks and strokes, but can also travel to and block arterial blood flow in the kidneys, spleen, other organs, or the arms and legs. I will leave those for other discussions and the pertinent specialists (cardiologists, neurologists, vascular surgeons...).

Venous clots are the actual topic of this post. The med-speak terms for talking about the different types of problems caused by the venous clots include:

"venous thromboembolism" (VTE), the umbrella term for all of the following,

"deep vein thrombosis" (DVT, as opposed to the potentially painful, but much less dangerous thromboses in superficial veins), and

"pulmonary embolism" (PE), where the veins carrying blood to the lungs are partially or sometimes completely blocked by a clot.

So what makes this an entity that scares even hardened emergency and intensive care physicians?

It's the obscure nature of many clots, usually vague and non-specific symptoms, and the risk that is generally proportional to the size of the clot, up to and including sudden cardiac arrest and death.

There are decent tests and treatments for pulmonary emboli, but they come with high cost, inconvenience, radiation exposure, and bleeding risk.

When it comes to clinicians dealing with the possibility of VTE, my observation has been that it amounts to a /test of character/, or at least a test of your conflict resolution style...

For example, high anxiety and uncertainty about one's clinical skills and judgment can easily reflect in a practice of treating every patient as having a pulmonary embolism until proven otherwise, even if the presenting symptoms are perfectly well explained by another obvious disease process: e.g. asthma exacerbation with wheezing, lobar pneumonia, clinically obvious heart failure with weight gain, shortness of breath, bibasilar crackles, leg edema, and jugular venous distension...

Another example might be a provider with a more avoidant personality and conflict resolution style who might develop an elaborate inventory of justifications not to check the studies for PE or DVT when several findings point to the possibility of a blood clot.

It should not be surprising that in a healthcare system with limited time to hone and use one's clinical skills (as opposed to the ever growing time spent in the electronic health record) and high-profile million-dollar malpractice lawsuits, the trend has been going in the direction of more testing. This would seem justifiable if the result was safer care, but the trends over time don't justify it:

The main wrinkle is that the increase in testing over time has 1) not decreased mortality from VTE over time, and 2) has mainly led to diagnosis of more small, likely clinically insignificant VTEs.

(There is a resemblance of this overdiagnosis problem to the problem of detecting incidental lung nodules on imaging. Many of those also resolve on their own over time.)

Here are some of my thoughts around this topic, to serve as food for thought when wrestling with the question whether to test or not to test:

1. The first step is the clinical judgment - in a potential high-stakes condition like this one, often people abbreviate it to: "if you think of it at all, then rule it out".

2. In many situations there is doubt, especially when other conditions explain the abnormalities in heart rate, breathing, oxygenation etc. Then it may be sufficient to have evidence or data to merely support the decision to not escalate testing: PERC, age-adjusted D-dimer, Well's score, revised Geneva score, or the YEARS algorithm.

3. If there are other reasons to run a chest CT, doing it with contrast as a CT angiography adds cost and radiation, but of course less than if the only reason to obtain a CT at all is the need to rule out the PE.

4. Size and context matter: a small subsegmental pulmonary embolism in a patient with virtually no symptoms paints a very different threat picture than a patient with clots in multiple veins and active, raging cancer likely driving ongoing hypercoagulability.

5. If doing a contrast CT right away is deemed too risky, typically based on the kidney function (debatable in many situations), the patient usually is ill enough to be admitted to the hospital anyway, where empirical anticoagulation and later CT angiography can be considered.

PS: The title of this post is from watching a German documentary about Covid-19 patients in Berlin, with one of them developing a large pulmonary embolism that was exciting enough for the physician to speak of a: "Schöner Thrombus", or "beautiful blood clot" when they reviewed the CT angiogram... Likely because it was so visible to leave no doubt about the finding on the CT.