Pulmonary Embolism: Pathophysiology, Virchow's Triad, and Genetic Factors

BOTH blood flow and ventilation

the mechanical and humoral reflex consequences of embolic obstruction cause alterations in

stasis, hypercoagulability, enothelial injury

Virchow's triad

it has a mutation that causes resistance to protein C which normally inactivates clotting factors V and VIII

How does Factor V Leiden relate to PE and DVT

increased plasma prothrombin concentrations, inherited hypercoagulability

prothrombin gene mutation leads to

It increases. pulmonary embolism creates a ventilation-perfusion (V/Q) mismatch, where blood clots block blood flow to parts of the lung. As a result, oxygenated air reaches the alveoli, but deoxygenated blood cannot pass through those areas to pick up oxygen, leading to a larger-than-normal difference between the oxygen levels in the alveoli and the arterial blood.

what happens to the A-a gradient in PE

lung ischemia/infarct (blood supply cut off)

increase vascular resistance/RV afterload

may lead to RV dilation, hypokinese, tricuspid insuff/failure

hemodynamic effects of PE

in a patient with low moderate likelihood of DVT. can rule out but cannot rule in (nonspecific)

when to use d-dimer test

can ID DVT (assoc with PE)

can visualize the thombus directly, otherwise relies on loss of vein compressability

detects change in venous flow

how can ultrasound help diagnose DVT/PE

90% cases have hypoxia, hypocapnia, and respiratory alkalosis

Increased A-a gradient (most >20)

how can ABG help diagnose

PE (hamptoms hump and westermark sign)

most often normal, but when not it looks like this

lack of vascular markings downstream of clot

westermark sign

pleural based opacities with convex medial margins, wedge-shaped, suggest infarct

hamptom hump

sinus tachy most often

complete/incomplete RBBB

Right axis deviation

famous "s1-q3-t3"

EKG findings in PE

RBBB, seen in PE

Right axis deviation, seen in PE

new standard of diagnosis for PE, neg predictive value of 99%. accurate as invasive angiography

CT chest with contrast

this is V/Q scan. use if renail impairment or IV contrast allergy

low prob (2% have), high probability (96% have)

intermediate, correlate with U/S for DVT

when would you use this instead of CT with iv contrast

clinical signs of DVT

alternative diagnosis less likely than PE (look at CXR, ABG, and EKG)

wells criteria - 3 pointers

HR > 100 (tachy)

surgery/immobilization in past 4 weeks

previous DVT/PE

wells criteria - 1.5 pointers

hemoptysis

malignancy

wells criteria - 1 pointers

0-1 low

2-6 mod

6+ high

0-4 unlikely, >4 likely

wells low, mod, high prob scores

4

malignancy: 1

surgery in past 4 weeks: 1.5

tachy: 1.5

A 67 year old female with history of stage II lung cancer with resection 3 weeks ago presents to office with cough and shortness of breath. her CXR is clear and EKG demonstrates sinus tachy. ABG shows mild hypoxia. What is her wells score?

based on hemodynamic stability

elevated biomarkers like troponin, bnp?

RV strain on EKG?

risk stratification of PE

non-massive (70-75%)

Sub-mmassove (20-25%)

Massive (5-10%)

categories for PE

Sys BP >= 90 with NO signs of cardiac instability. excellent prognosis

non-massive PE

sys BP >= 90 with right ventricular strain pattern on EKG/echo and possible elevations in troponin/bnp

more likely to be detected clinically

submassive PE

sys BP <90 (obstructive/cardiogenic shock)

thrombosis affecting at least half of the pulmonary vasculature

dyspnea, syncope, hypotension, cyanoisis

massive PE

fondaparinux

can be used in HIT in pregnancy

II, VII, IX, X

what factors are prevented from being activated in heparin

life threatening or intracranial hemorrhage due to UFH or LMWH

what is protamine sulfate used for

dabigatran

idarucizumab neutralizes which anticoag

acitvated charcoal if last dose was recent

andexxa is a reversal agent.

Kcentra is a 4 factor complex concentrate

how to treat factor Xa inhibitor complications

3-6 months

duration of anticoag treatment for provoked DVT/PE

use LMWH or DOAC as monotherapy indefinitely

PE patients with cancer anticoagulants