Pulmonary Venous Thromboembolism Flashcards
Pulmonary embolism (PE) is the ____ leading cause of death among hospitalized patients
3rd
Less than __% of patients with fatal emboli have received specific treatment for the condition
10
What substances can embolize to the pulmonary circulation?
- air
- amniotic fluid
- fat
- foreign bodies
- parasite eggs
- septic emboli
- tumor cells
What is the most common embolus?
thrombus
Where do thrombi most commonly originate?
In the deep veins of the LEs
__% of calf thrombi propagate proximally to the popliteal and ilieofemoral veins, at which point they may break off and embolize to th pulmonary circulation
20
Pulmonary emboli with develop in __-__% of patients with proximal DVT
50-60
Approximately __-__% of patients who have symptomatic pulmonary emboli will have LE DVT when evaluated
50-70
The risk factors for PE are the risk factors for thrombus formation within the venous circulation. What are these 3 risk factors? What are they referred to as?
- venous stasis
- injury to the vessel wall
- hypercoagulability
Virchow’s triad
What does venous stasis increase with?
- immobility
- hyperviscosity
- increased central venous pressures
What 3 things can cause injury to the vessel wall?
- prior episodes of thrombosis
- orthopedic surgery
- trauma
What can cause hypercoagulability?
- medications
- disease
- inherited gene defects
- defieincies or dysfunction of protein C, protein S, and antithrombin
- prothrombin gene mutation
- hyper-homocysteinemia
- the presence of antiphsopholipid antibodies (lupus anticoagulant and anticariolipin antibody)
What is the most common inherited cause in white populations?
Resistance to activated protein C, aka factor V Leiden
Factor V Leiden is present in approximately _% of healthy American men and in __-__% of patients with idiopathic venous thrombosis
3
20-40
Physical obstruction of the vascular bed and vasoconstriction from neurohumoral reflexes both increase what?
Pulmonary vascular resistance
Massive thrombus may cause _____ _____ failure
right ventricular
Vascular obstruction _____ physiologic dead space and leads to what?
increases
hypoxemia
What symptoms of PE are fairly sensitive?
- dyspnea (75-85%)
- pain (65-75%)
What is the only sign reliably found in more than half of patients?
tachypnea
97% of patients in the original prospective investigation of pulmonary embolism diagnosis (PIOPED I) proved pulmonary emboli have one or more of what 3 findings?
- dyspnea
- chest pain with breathing
- tachypnea
ECG is abnormal in __% of patients with PE
70
What are the most common ECG abnormalities? These abnormalities are seen in __% of patients
- sinus tachycardia
- nonspecific ST and T wave changes
40%
What do arterial blood gases usually reveal?
acute respiratory alkalosis due to hyperventilation
What lab fidnings are highly suspicious for PE?
Profound hypoxia with a normal chest radiograph in the absence of preexisting lung disease
Plasma levels of D-dimer are ____ in the presence of thrombus
elevated
A D-dimer less than ___ ng/mL provides strong evidence against venous thromboembolism
500
What are 6 imaging and special examination studies performed to help diagnose PE?
- chest radiograph
- CT
- ventilation-perfusion (V/Q) lung scanning
- venous thrombosis studies
- pulmonary angiograph
- MRI
When are chest x-rays the most suggestive of PE?
When normal in the setting of hypoxemia
Chest radiographs are normal in __% of patients with confirmed PE
12
What are the 3 most frequent radiograph findings?
- atelectasis
- parenchymal infiltrates
- pleural effusions
What is used as the initial diagnostic study in North America for suspected PE?
Helical CT pulmonary angiography
__% of patients with DVT will have PE on angiography
50
What are 3 commonly available diagnostic venous thrombosis studies?
- venous US
- impedance plethysmography
- contrast venography
What venous thrombosis study is the test of choice to detect proximal DVT?
venous ultrasonography
What is diagnostic of first-episode DVT?
inability to compress the common femoral or popliteal veins in symptomatic patients
How does impedance plethysmography work?
It relies on changes in electrical impedance between patent and obstructed veins to determine the presence of thrombus
What does contrast venography reveal?
a filling defect and the “railroad sign”
What imaging technique is the reference standard for the diagnosis of PE?
Pulmonary angiography
What angiography finding establishes a definitive diagnosis of PE?
intraluminal filling in more than one projection
What secondary angiograph findings are highly suggestive of PE?
- abrupt arterial cutoff
- asymmetry of blood flow
- prolonged arterial phase with slow filling
What limits the use of MRI in the diagnosis of PE?
Artifacts introduced by respiration and cardiac motion
Most American centers use what kind of diagnostic algorithm?
A rapid D-dimer and helical CT pulmonary angiogram
A clinical prediction rule score greater than 4.0 indicates what? What does a score less than or equal to 4.0 indicate?
PE is likely
PE is unlikely
The incidence of proximal DVT in untreated patients undergoing hip fracture is __-__%.
10-20%
The incidence of PE in untreated patients undergoing hip fracture is __-__%.
4-10%
The incidence of fatal PE in untreated patients undergoing hip fracture is __-__%.
0.2-5%
What are 2 treatment options for PE?
- Anticoagulation drugs
- Thrombolytic therapy
What anticoagulation drug is used as a secondary prevention method?
Heparin
How does heparin work?
It beinds to and accelerates the ability of antithrombin to inactivate thrombin, factor Xa, and factor IXa, which retards additional thrombus formation
The appropriate duration of anticoagulation therapy needs to take what 4 things into consideration?
- patient’s age
- potentially reversible risk factors
- likelihood and potential consequences of hemorrhage
- preferences for continued therapy
Continued anticoagulant therapy result in a lower rate of recurrence at the cost of an increased risk of what?
hemorrhage
It is recommended that anticoagulation therapy should last how long after a first episode provoked by a surgery or a transient nonsurgical risk factor?
3 months
When is extended (6-12 months) therapy recommended?
For unprovoked or recurrent episode with a low to moderate risk of bleeding
Describe anticoagulant therapy in cancer patients
Extended therapy with low molecular weight heparin is recommended regardless of bleeding risk
It is reasonable to continue therapy for how long after a first episode when there is a reversible risk factor?
6 months
It is reasonable to continue therapy for how long after a first-episode of idiopathic thrombosis?
12 months
It is reasonable to continue therapy for how long in patients with nonreversible risk factors or recurrent disease?
6-12 months
What is the major complication of anticoagulation therapy?
hemorrhage
What risk factors increase the risk for hemorrhage?
- concomitant drugs such as aspirin that interferes with platelet function
- increased patient age
- previous GI hemorrhage
- coexistent chronic kidney disease
What are the 3 drugs used for thrombolytic therapy?
- streptokinase
- urokinase
- recombinant tissue plasminogen activator (rt-PA; alteplase)
How does thrombolytic therapy work?
Those 3 drugs increase plasmin levels and thereby directly lyse intravascular thrombi
What are the major disadvantages of thrombolytic therapy compared with heparin?
Its more expensive and there is a significant increase in major hemorrhagic complications
When should thrombolytic therapy be used?
In PE patients at high risk for death in whom the more rapid resolution of thrombus may be lifesaving
What are the absolute contraindications to thrombolytic therapy?
active internal bleeding and stroke within the past 2 months
What are the major contraindications to thrombolytic therapy?
- uncontrolled hypertension
- surgery or trauma within the past 6 months
What are 2 other additional measures that can be taken to treat PE?
- Inferior vena cava filter
- Mechanical or Surgical extraction of thrombus
Under what 3 circumstances is an inferior vena cava filter recommended?
- for recurrent thromboembolism despite adequate anticoagulation
- for chronic recurrent embolism with a compromised pulmonary vascular bed
- with the concurrent performance of surgical pulmonary thromboendarterectomy
PE is estimated to cause more than _____ deaths annually
50,000
What contributes to this high mortality rate?
PE is not recognized antemortem or death occurs before specific treatment can be initiated
The outlook for patients with diagnosed and appropriately treated PE is generally ____
good
Death from recurrent thromboemboli develops in approximately _% of patients
3
