see also: [[Pulmonary embolism ECG]], [[D-dimer]], [[radiation in pregnancy and diagnostic imaging#CTPA vs VQ scan in pregnancy table]], [[PE clinical prediction scores]], [[TPA|thrombolysis]], [[Fat embolism]], [[DVT]], [[thrombophilia]] see: [Dunn - Management of PE](x-devonthink-item://8B5017FD-DFF4-479E-888D-AB7B814DAFC5), [Dunn - investigation in PE](x-devonthink-item://C2291077-3FBC-4AF0-9032-34B76AE7AE51) #haem > note that the commonest symptom of PE is *dyspnoea* which unfortunately is also the commonest symptom of early tamponade (and pulm HTN, among other things). In an ambiguous clinical context, this shared symptom further supports the value of POCUS as an early differentiating test. > [!key points]- Honorary Comment > ![[Pasted image 20241107224643.png]] > As an homage to the prolific Dr. James Hayes, whose legendary Fellowship notes invariably begin with learned musings about everything from Vitruvian architecture to Captain Picard's deference in seeing his home planet from space, I will begin these notes with a circumlocutory prologue. > > Although mythologist Joseph Campbell's 1949 book *The Hero with a Thousand Faces* notoriously transcribed the basic structure of "The Hero's Journey" observed in various classical myths into a protocol for how everything from Star Wars to Rick and Morty can monetise addictive entertainment pabulum along an infinite corporate assembly line, Pulmonary Embolism is more of a villain with a thousand horns: a familiar enemy who is at once eminently recognisable yet often disguised, common yet hard to find, and (especially as it pertains to Star Wars) initially interesting yet progressively tiring the more it conforms itself to fit any situation and imposes its relevance on every facet of your life. > > In this protean respect, the better polycephalic metaphor for a PE is the *chiliagon*, a 1,000-faced polygon often invoked in the Philosophy of Mind to illustrate the dichotomy between what we can imagine and what we can understand. Whereas a triangle can be both understood and visualised, a chiliagon is a shape that one can still understand as a shape with angles just shy of 180º, yet it is impossible to actually visualise it as discrete from a 10,000-sided shape or circle. > > PE is the chiliagon of emergency medicine. We all have a sense of what it is, what it causes, and what some of those things look like when they are bad or obvious. Yet it is also difficult to visualise PE as a discrete entity when it masquerades as virtually every presenting concern. All ED patients are short of breath when asked. All ED patients have chest pain. All ED patients are on some medication or have some historical feature that puts them at risk for PE. How is something so sinister that we understand so deeply so impossible to identify if it is staring us in the face? > > 17th century parent to the Scientific Revolution *Francis Bacon* identified four common intellectual fallacies -- which he called "Idols" to emphasise that they are fundamentally embedded in our consciousness -- that humans succumb to in our pursuit of knowledge. One category of idol, *Idola specus*, or "Idols of the Cave," are the cognitive errors that arise from within the den of our minds "refracting and discolouring the light of nature" as a result of the influences, experiences, and fixations that become effect-modifying biases for how the true world appears from the limited vantage point of our perceptual oubliette. > > In this regard, each of us has many Idols in our respective brain-caves that distort our assessment of PE. Everyone has a colleague with a "bad PE" story; no one wants to miss a PE; everyone knows the heart-sinking feeling of ordering a CTPA on a young patient whom you do not believe actually has a PE. And everyone has heard a chiliagon's worth of conflicting opinions about the use of D-dimer as part of the assessment. > > If you peel away these biases and apply a rigid assessment framework to PE, the issue becomes less oblique. If the patient is very sick and the question is "could this be PE?" there are usually signs to point you towards this diagnosis. If the patient is not very sick and the question is "could this be PE?" there are a host of validated decision tools to invoke. > > Of course, there are many cases that will still be difficult, especially if the patient is sick. In these instances, it is important to reflect on some of our most basic [[Cognitive biases#Types of cognitive bias|biases]]: fears of *errors of commission* and *errors of omission*. Many PE workups in ED invoke a sentiment that we are commissioning unnecessary testing and time in ED, so it is important to overcome that bias and recognise the cases when treatment with anticoagulation (or thrombolysis or embolectomy or even ECMO) is time critical and indicated. %% Time and time again, coroner reports suggest that therapeutic anticoagulation is indicated for treatment in most cases. It would never be an error of commission to give thrombolysis for cardiac arrest from PE, although regardless of this treatment, the mortality is unfortunately still very high. Here is a cognitive aide: ask yourself "would I have any reservation in giving 5000 IU of heparin if this was ACS?" It isn't a perfect analogy so please don't take this literally, but as Douglas Hofstadter asserts, [analogy is the core of cognition](https://shc.stanford.edu/stanford-humanities-center/news/analogy-core-cognition). %% > > On an optimistic note, PE is such a frustrating differential diagnosis that there is no shortage of research about PE assessment and management. Although keeping up with the literature can be tedious and translating it into practice slow, hopefully someday soon we will meet the *Hero with 1,000 Citations*: a perfectly coherent and validated study or ACEM-endorsed guideline that everyone embraces as the capital R Right way to approach PE in the future. **Symptoms** | Feature | % | | -------------------- | --- | | dyspnoea | 85 | | pleuritic chest pain | 75 | | apprehension | 60 | | cough | 50 | | sweats | 25 | | syncope | 15 | | non-pleuritic CP | 15 | | haemoptysis | 10 | ↑ look at how infrequent haemoptysis is! # Treatment ## indication for thrombolysis - cardiac arrest from suspected PE - no absolute contraindications to thrombolysis in setting of cardiac arrest from PE (mortality is already 66-95%) - high risk PE presenting with cardiogenic shock ankd/or persistent hypotension not responsive to IV fluid bolus or persistent hypoxia with respiratory distress unresponsive to max O2 therapy > optimal doses are unknown; therefore likely no major wrong answers on an exam unless off by an order of magnitude **Dose** - r-tPA - 10mg IV bolus folled by 40-90mg IV over 2 hours (likely only need 40 gm) - *Cardiac arrest* up to 50 mg Iv bolus in cardiac arrest → repeat in 15 min if no ROSC - ==CPR 30 minutes up to 90 min ongoing==. - tenectoplase - 30-50mg IV bolus for pts 60-90 kg - withhold heparin during thrombolytic infusion in contrast to treatment for MI ## embolectomy **indications** - high risk PE in whom thrombolysis is absolutely contraindicated - "rescue embolectomy" after failed thrombolysis - patient foramen ovale and intracardiac thrombus **contraindications** - chronic thromboembolic [[Pulmonary Hypertension]] - no ROSC following cardiac arrest ## PE treatment tables | Type of PE | Treatment | Disposition | | ------------------------------------------- | ------------------------------------------- | ----------- | | *Subsegmental* | | | | ↑ recurrence risk | DOAC | discharge | | ↓ recurrence risk | ?observation | discharge | | *Size* | | | | small/low risk | DOAC | d/c | | intermediate /<br>submassive | - DOAC<br>- UFH if considering thrombolysis | admit | | massive - ↓ bleeding risk | [[TPA\|thrombolysis]] then UFH | ICU | | massive - ↑ bleeding risk | UFH prior to embolectomy | ICU | | cardiac arrest | tPA 50mg IV stat | ICU | | *special situations* | | | | Pregnancy | LMWH | | | lupus anticoagulant | LMWH then warfarin | | | malignancy | LMWH / DOAC | | | ↑ bleeding risk | UFH | | | Valvular AF or mechanical prosthetic valuve | - warfarin<br>- LMWH if INR sub-therapeutic | | ![[Pasted image 20230801112141.png]] # Special situations ## PE in patients already anti-coagulated - [PE risks in patients anticoagulated for AF (PREFER)](https://pubmed.ncbi.nlm.nih.gov/30928922/) - [OpenEvidence chat regarding pe risks in anti-coagulated patients](https://www.openevidence.com/ask/ca8c0595-fed0-4647-a185-f8b64d8ad327) - [performance of wells in predicting DVT in hospitalised patients](https://pubmed.ncbi.nlm.nih.gov/33749393/) - the Wells score performed poorly for the discrimination of risk for proximal deep vein thrombosis (DVT) in hospitalized patients on anticoagulation but performed reasonably well among patients without anticoagulation. This suggests that the presence of anticoagulation therapy may lower the pre-test probability of PE as assessed by the Wells score, potentially leading to underestimation of the actual risk. ## pulmonary embolism in pregnancy See [[PE clinical prediction scores#Pregnancy-adapted YEARS]] - 5x increased risk during pregnancy and post-partum - DVT risk 3x risk of PE - *strong left leg predominance of DVT is unique to pregnancy* due to compression o fL common iliac vein by crossing R iliac artery - risk increased equally in all trimesters - contributing factors: hyperemesis, venous stasis, hypercoagualability, decrsed fibrinolysis, bed rest - pregnancy-related risk factors: assisted reproduction, post partum haemorrhage, [[Pre-eclampsia]], c-section - ==pregnancy-specific decision rules not yet developed== as of Aug 2023 (note pregnancy-adjusted YEARS) ### Ix [[D-dimer]] - concentration rises gradually during pregnancy - drops in first 3 days postpartum, normal 4-6 weeks postpartum - specificity of d-dimer testing in pregnancy and postpartum period lower than normal - **negative predictive value still high** so a negative D-dimer usually does not require further investigation - no prospectively validated "pregnancy adjusted d-dimer" yet; upper limit of normal 1st T 0.95, 2nd 1.3, 3rd 1.7 > topic of debate; according to tintinalli, ACOG, Royal college of obstetricians and gynaecologists recommend against the use of D-dimer alone to rule out PE in pregnant women. > [[Pregnancy-Adapted YEARS algorithm]] is promising but needs external validation before entering prime-time (as of March 2024) imaging -- see [[radiation in pregnancy and diagnostic imaging#CTPA vs VQ scan in pregnancy table]] - concern about exposure to radiation should not outweigh use of CTPA or VQ when indicated - mortality a/w untreated PE >> risk to fetus from exposure to diagnostic imaging ### management - same as initial approach in non-pregnant patients - **LMWH** preferred over unfractionated heparin - long-term anti-coagulation with LMWH until 6 weeks post partum - *warfarin is a teratogen* - safety of DOACs is uncertain, however, are known to cross placenta and may cause birth defects # controversies - isolated subsegmental emboli - clinical significance controversal - lack of evidence for islated subsegmental in absence of DVT