SM_169a: Pulmonary Embolism Flashcards
Virchow’s triad for pulmonary embolism includes ______, ______, and ______
Virchow’s triad for pulmonary embolism includes venous stasis, vascular injury, and alterations in coagulation
Describe some risk factors for PE
- Venous stasis: immobility, age > 60
- Alterations in coagulation: hereditary thrombophilias, estrogen therapy, malignancy
- Vascular injury: surgery, trauma, post-partum, indwelling vascular access, history of VTE
Most PEs are from a ______ vein in the ______ ______ extremity
Most PEs arise from a deep vein in the proximal lower extremity
Most PEs result from _____, with risk highest at the _______
Most PEs result from embolized deep vein thrombosis, with embolization risk highest with the proximal deep veins
DVTs can become ______, ______, or ______ PEs
DVTs can become saddle, segmental, or sub-segmental PEs
Obstruction of a pulmonary artery causes ______, and hypoxemia in PE is caused primarily by ______
Obstruction of a pulmonary artery causes dead space, and hypoxemia in PE is caused primarily by V/Q mismatch
Describe the impact of a PE on the respiratory system
In PE
- Fundamental defect = dead space
- Sudden increase in dead space in a ventilated patient -> think of PE
- Hypocapnia more common than hypercapnia
- Main mechanism of hypxemia is V/Q mismatching
A sudden increase in _______ in a ventilated patient should make you think of a PE
A sudden increase in dead space in a ventilated patient should make you think of a PE
Main mechanism of hypoxemia in PE is ______
Main mechanism of hypoxemia in PE is V/Q mismatching
What are the mechanisms of CV collapse in PE?
- Increased RV afterload -> RV dilation -> septal shift -> decreased LV preload -> decreased CO
- Myocardial O2 supply/demand mismatch -> coronary perfusion decreases RV ischemia -> progressive RV dysfunction
(these can feed off each other to cause rapid decompensation)
What is the picture in the right showing?
Acute PE w/ “D” sign
(RV much bigger so septum looks like a “D” in systole - IV septal bowing and LV compression)
Additional diagnostic testing is ______ needed for PE
Additional diagnostic testing is almost always needed for PE
(almost no constellation of findings is sufficiently specific for VTE to obviate the need for additional diagnostic testing)
What are the signs and symptoms of PE?
PE
- Symptoms: pleuritic chest pain +/- hemoptysis, isolated dyspnea, circulatory collapse
- Signs: hypoxemia, tachypnea, tachycardia, crackles on exam
A normal chest x-ray in patient with significant respiratory symptoms should _____ suspicion for PE
A normal chest x-ray in patient with significant respiratory symptoms should raise suspicion for PE
(CXR helpful to identify alternative diagnoses)
What are the problems with using invasive angiography/venography to diagnose PE?
- Invasive
- Contrast
- Poor test characteristics for small clots
- Requires specialty expertise
(prior gold standard)
A negative lower extremity compression ultrasound ______ exclude diagnosis of PE
A negative lower extremity compression ultrasound does not exclude diagnosis of PE
Describe the pros and cons of using CT pulmonary angiography for diagnosing PE
Most frequent test obtained
- Pros: fast, widely available, high diagnostic accuracy
- Cons: radiation, contrast, less accurate for small sub-segmental thrombi
Wells score ____ means PE is likely, while ____ means PE is unlikely
Wells score > 4 means PE is likely, while ≤ 4 means PE is unlikely
Describe the algorithm for PE diagnostic testing
- High pre-test probability: straight to CTPA
- Lower pre-test probability: D-dimer
- If positive, CTPA
- If negative, no further testing
