Lecture 9 (VTE)-Exam 3 Flashcards
(87 cards)
1
Q
Pulmonary Vessels
* What is the pressure and resistance system?
A
- Low pressure and Low resistance system
- PVR 10x less than SVR
2
Q
Venous Thromboembolism (VTE)
* What are the types?
A
- Pulmonary Embolism (PE)
- Deep Venous Thrombosis (DVT)
- Lower extremity deep venous thrombosis (DVT) and pulmonary embolism (PE) are two manifestations of venous thromboembolism.
3
Q
DVT
* What is it?
A
Obstruction from a thrombus in the deep venous system, most commonly occurring in the legs
4
Q
What is a distal DVT? High or low rates of PEs?
A
Distal DVT
* Isolated to the deep veins below the knee (aka in the calf)
* Lower rates of recurrence and pulmonary embolism
5
Q
Proximal DVT
* Where is it?
* High or low chances of PE?
A
- Most will fall under this category
- Extends into the popliteal vein or more proximally
- More than 50% of patients with proximal vein thrombosis have a concurrent PE at presentation
6
Q
Pulmonary Embolism
* Occurs in the absence of what?
* Patients often have underlying what?
* What is a common scenairo?
A
- Occurs in the absence of surgery or trauma
- Patients often have an underlying hypercoagulable state, although a specific thrombophilic condition may not be identified
- Common scenario is a clinically silent tendency towards thrombosis, precipitated by a stressor such as a prolonged immobilization, recent surgical procedures, oral contraceptives, pregnancy, or hormone replacement
7
Q
Pulmonary Embolism
* What are the risks of VTE?
* “Secondary” pulmonary embolism among what?
A
- Risks of VTE among patients with medical illness, including cancer, congestive heart failure and COPD and infectious diseases like COVID-19
- “Secondary” pulmonary embolism among types of surgery patients may occur as late as a month after discharge from the hospital (they do not want to move around at home)
8
Q
Pulmonary Embolism
* Why is it difficult to diagnose?
* Acute pulmonary embolism can manifest clinically as what?
* Pulmonary Embolism is a life-threatening condition resulting from what?
A
- Pulmonary embolism is difficult to diagnose due to its variable clinical presentation
- Acute pulmonary embolism can manifest clinically as high risk, intermediate risk, intermediate-low risk or low-risk based on severity of clinical presentation
- Pulmonary Embolism is a life-threatening condition resulting from dislodged thrombi occluding the pulmonary vasculature; right heart failure and cardiac arrest may ensue if not aggressively treated
9
Q
Pulmonary Embolism
* High risk PE is life-threatening condition characterized by what?
* Many pulmonary emboli are not discovered until when?
* What is important?
A
- High risk PE is life-threatening condition characterized by sudden onset of chest pain/pressure, hypotension (blockage of BF), hypoxemia, and distended neck veins
- Many pulmonary emboli are not discovered until postmortem examination
- Appreciation of clinical settings that may make patients susceptible to PE and maintenance of a high degree of clinical suspicion are of paramount importance
10
Q
Pulmonary Embolism
* Most common what?
* 3rd most common cause of what?
* What do 66% of hospitalizations result from?
* Who is higher risk?
* High what?
A
- Most common preventable cause of hospital related death
- 3rd most common cause of hospital related death
- 66% of all VTE events result from hospitalizations
- Medical>surgical pts at risk
- High morbidity/mortality
11
Q
Pulmonary Embolism
* 40-50% of patients with DVT develop what? Some PE never have what?
* When does PE present after DVT? Fatal when? What are some other sxs?
* Most fatalities occur in who?
* Perfusion defects completely resolve in who?
A
12
Q
What are the most common risk factors for VTE? (genetic and acquired?
A
13
Q
Virchow Triad
* Major theory delineating the pathogenesis of venous thromboembolism (VTE), proposes that VTE occurs because of what?
A
- Alterations in blood flow, stasis
- Vascular endothelial injury
- Alterations in the constituents of the blood, inherited or acquired hypercoagulable state
14
Q
Virchow Triad:
* What does endothelial injury cause? What are examples?
* What is an unprovoked DVT/PE?
* What is a Provoked DVT/PE?
A
Endothelial injury: endothelial cell damage promotes thrombus formation, usually at the venous valves
* Surgery
* Trauma
Unprovoked DVT/PE: no identifiable provoking event or risk factors present
Provoked DVT/PE: known risk factors and/or caused by known events
15
Q
Virchow’s Triad:
What are the hypercogulability states?
A
Under slide: Thrombus formation is usually a result of a combination of Virchow’s triad and Inherited thrombophilia: Factor V Leiden mutation, prothrombin gene mutation, Protein C and S deficient, antithrombin deficient and antiphospholipid antibody syndrome
16
Q
Virchow’s Triad
* What are the hypercoagulability (thromophilia)?
A
- Factor V Leiden mutation
- Prothrombin gene mutation
- Protein S deficiency
- Protein C deficiency
- Antithrombin deficiency
17
Q
Virchow’s Triad
* What are some drugs that affect the virchow’s triad?
A
- HRT
- Testosterone
- Tamoxifen
- Steroids
- Antidepressants
SHATT
18
Q
Virchow’s Triad
* What is venous statsis?
* What is the most common cause?
A
- Venous stasis: Poor blood flow and stasis promote the formation of thrombi
- More than 48 hours of immobility in the preceding month – 45 percent, most common
19
Q
What are some other examples of venous stasis states?
A
- Hospital admission in the past three months – 39 percent
- Surgery in the past three months – 34 percent
- Malignancy in the past three months – 34 percent
- Infection in the past three months – 34 percent
- Current hospitalization – 26 percent
- Previous VTE
- Prolonged traveling
- Heart failure
20
Q
What are the CV risk factors of VTE?
A
- Obesity 2.3 (95% CI 1.7-3.2)
- Hypertension 1.5 (95% CI 1.2-1.8)
- Diabetes mellitus 1.4 (95% CI 1.1-1.8)
- Smoking 1.2 (95% CI 0.95-1.5)
- Hypercholesterolemia 1.2 (95% CI 0.67-2.0)
- VTE
- CHF
21
Q
⭐️⭐️⭐️⭐️
Signs and Symptoms of PE:
* Sudden what?
* Life threathening or high risk present with that?
* Should be suspected in who?
* What type of chest pain? Why?
A
- Sudden onset shortness of breath
- Life threatening or high-risk present with dyspnea, syncope, or cyanosis rather than chest pain
- Should be suspected in hypotensive patients with evidence of VTE and clinical findings of acute right failure – distended neck veins, tachycardia, or tachypnea
- Pleuritic chest pain (Pleuritic pain = distal emboli pulmonary infarction and pleural irritation)
22
Q
Signs and Symptoms: PE
* What does it mean when pt has Isolated dyspnea of rapid onset ?
* Cough or no cough?
* What does hemoptysis iwht severe chest pain mean?
* Lungs will be what?
* Normal or low O2?
A
- Isolated dyspnea of rapid onset = central pulmonary embolism with hemodynamic sequala
- Cough
- Hemoptysis with severe chest pain – anatomically small PE near the periphery of the lung – leads to pulmonary infarct
- Lungs will be clear on auscultation
- Hypoxia
23
Q
What are the sxs of DVT?
A
- Unilateral leg swelling
- Erythema
- Pain
- Positive Homan’s sign
- Calf pain upon dorsiflexion of the ankle
24
Q
Diagnostic Testing of VTE
* The most important thing to do when evaluating a DVT/PE is to what?
* What is the clinical scoring system? What is the max points?
* Greatest emphasis is on presence of what?
A
- The most important thing to do when evaluating a DVT/PE is to risk stratify the patient (determine pre-test probability)
- Widely used clinical scoring systems is Wells index
- Maximum of 12.5 points
- Greatest emphasis is on presence of signs or symptoms of DVT and whether an alternative diagnosis is unlikely
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# ⭐️⭐️⭐️⭐️⭐️
Electrocardiogram:
* What will be the HR?
* What is a sign present?
* What else is present?
* S1Q3T3 sign – a prominent S wave in Lead I, a Q wave in Lead III, and an inverted T wave in Lead III
* Finding is relatively specific but insensitive
* RV strain and ischemia cause the most common abnormality, T- 0wave inversion in leads V1 to V4
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# ⭐️⭐️⭐️
What does the EKG show on a pt with PE?
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Diagnostic Testing of PE
* Low risk = ≤ 4 points – likelihood of PE is less than 8%: What should you order and then what do you do if it positive or negative?
Order D-dimer
* Normal D-dimer virtually excludes a pulmonary embolism
* If the D-dimer is positive, get a CT angiogram (CT PE Protocol)
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PE
* What is the best diagnostic accurary of all noninvasive imaging?
* What is the jury out on?
* CT angiogram has the best diagnostic accuracy of all noninvasive imaging
* Jury is out on VQ scan being a preferred study if the patient is pregnant
## Footnote
Under slide:
* Chest x-ray must be normal for the VQ scan to be properly interpreted
* If the CTA or VQ scan can’t be done (contraindicated) or if the results are indeterminate, then a lower extremity duplex US can also be ordered.
* US is also indicated if the patient is presenting with signs of DVT.
* A positive DVT with a good pretest probability = pulmonary embolism.
30
What do you need to do if wells score over 4 points?
likelihood of PE confirmed with testing is 41%
* Order CT angiogram
* Diagnosis confirmed by direct visualization of the thrombus in pulmonary artery; appears as a partial or complete intraluminal filling defect
31
What is the PERC?
*The PERC Rule is a “rule-out” tool - all variables must receive a “no” to be negative.
*The test is unidirectional: while PERC negative typically allows the clinician to avoid further testing, failing the rule doesn't force the clinician to order tests.
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# Clinical Setting – Outpatient Clinics/Emergency Departments
* Where overall prevalence of PE is low, but symptoms present such as what? What criteria should you use?
* Eight factors included are what?
* If none apply, what can be excluded?
33
D-Dimer
* What does it measure?
* Specific or no?
* What test is highly sensitive?
* What are another things that increase d-dimer?
* Normal D-dimer virtually excludes a PE in who?
34
What are some inflammation, surgery, liver disease, kidney disease, vascular disorders, malignancy, therapy, pregnancy causes of increase D-dimer
35
# ⭐️⭐️⭐️
V/Q Scan (ventilation- perfusion scan)
* how does it work?
* Used to evaluate what?
* What is the sensitivity and specificity?
* Who should you use this in?
* Nuclear medicine scan that uses radioactive material to examine airflow (ventilation) and blood flow (perfusion) in the lungs
* Used to evaluate for pulmonary embolism
* High sensitivity (96%) and high specificity (97%)
* During pregnancy: The toxicity of radioactive agent has been reported to be equivalent as the radiation exposure to fetus in CT
36
# ⭐️⭐️⭐️
V/Q Scan (Ventilation- perfusion lung scan)
* What is injected and what does that do?
* The patienr breathes what?
* A defect on perfusion scanning represents what?
* Defects in the perfusion scan are interpreted in conjunction with what?
* Injection of radiolabeled microaggregated albumin into the venous system, allowing the particles to embolize to the pulmonary capillary bed
* The patient breathes a radioactive gas or aerosol while the distribution of radioactivity in the lungs is recorded
* A defect on perfusion scanning represents diminished blood flow to that region of the lung
* Defects in the perfusion scan are interpreted in conjunction with the ventilation scan to give a high, low, or intermediate (indeterminate) probability for PE.
37
# ⭐️⭐️⭐️⭐️
V/Q Scan
* Normal perfusion scan excludes what?
* Provides probabilities of what?
* High-probability V/Q scan is what?
* Normal perfusion scan excludes the diagnosis of clinically significant PE
* Provides probabilities of PE, not the diagnosis of PE (low, moderate, high)
* High-probability V/Q scan is two or more segmental perfusion defects in the presence of normal ventilation
38
V/Q Scan
* What does gravity affect? ⭐️
radiotracer distribution
39
# ⭐️
CT Angiogram
* What is it the gold standard of?
* What does it do?
* Allows for what?
* Gold standard modality for diagnosing pulmonary embolism
* Direct visualization of emboli-> true diagnosis of PE (not based on probabilities)
* Visualization of intraluminal pulmonary arterial filling defect surrounded by contrast
* Allows for direct visualization of thrombus, estimation of thrombus burden, identification of high venous filing pressures and RV distention suggestive of RV failure
40
CT Angiogram
* What is the issue?
* Optimally used when?
* Dye load and large radiation dose (kidney disease, contrast allergy)
* Optimally used when incorporated into a validated diagnostic decision tree
41
This algorithm allowed for a management decision in 98% of patients presenting with symptoms suggestive of PE
42
MRI
* MRIhasarelativelylimitedrolein pulmonary imaging but is preferred over CT in specific circumstances, such as assessment of what? (4)
* MRI can sometimes identify what?
Specific circumstances:
* Superior sulcus tumors (Pancoast tumor)
* Possible cysts
* Lesions that abut the chest wall
* Any condition where contrast or radiation of absolutely contraindicated
MRI can sometimes identify large proximal emboli but usually is limited in this disorder
43
What are the advantages and disadvantages of MRI?
* Advantages include absence of radiation exposure, excellent visualization of vascular structures, lack of artifact due to bone, and excellent soft-tissue contrast.
* Disadvantages include respiratory and cardiac motion, the time it takes to do the procedure, the expense of MRI, and the occasional presence of contraindications, which include many implanted devices and certain metallic foreign bodies. Gadolinium contrast may be harmful to the fetus, so use of contrast is usually avoided in pregnancy.
44
Additional Diagnostic Testing
* how might the EKG show if a pt has ACUTE cor pulmonale?
S1Q3T3 pattern is classic, yet rarely seen
* S wave in lead I
* Q wave in Lead 3
* Inverted T-wave in Lead 3
New incomplete RBBB
Right axis deviation
Right ventricular strain with ST-segment depressions
45
Chest x-ray for PE
* Specific or no?What is most commonly shown?
* What are the signs in late findings? ⭐️⭐️⭐️
46
Diagnostic Testing
* What was the previous golf standard for dx? What is the new one?
*Pulmonary angiogram Previously considered the GOLD standard for diagnosis
* Most diagnostic questions can be resolved with new generation CT scanners
47
Bedside echocardiogram
* Excellent tool for what?
* What strongly suggests PE?
* What can sometimes be ID by echo?
* What type of strain?
* Excellent tool for risk stratification
* Imaging a normal left ventricle in the presence of a dilated, hypokinetic right ventricle strongly suggests PE
* Occasionally clot in transits can be identified by echo, helping identify acute risk for further embolism
* Right ventricle strain
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49
Saddle PE
* What it is? What can it lead to?
* What does it do to the heart? What is elevated?
* txt?
50
txt of PE
* What is the initial therapy?
* Respiratory support – oxygenation target greater than 90%, may require securing airway such as intubation
* Hemodynamic support – fluid resuscitation, vasopressor support as well
51
Strong clinical suspicion of acute PE, empiric treatment with what?
a parenteral anticoagulation agent should be started while waiting for tests results to arrive
52
# ⭐️⭐️⭐️⭐️⭐️
What are the three parenteral anticoagulation agents? (why must some be prefered, what are unique things about them?)
53
* Thrombolysis: Never shown to do what? Given to who?
* Embolectomy: Who gets this?
* Mechanical circulatory support such as with what
* What are IVC filters for?
* Thrombolysis – never shown to improve mortality, given the hemorrhage risk of systemic thrombolytic therapy, bleeding risk should be assessed prior to administration
* Embolectomy – if adverse outcome with anticoagulation alone should be considered for such->Catheter based procedure conducted in IR
* Mechanical circulatory support such as with ECMO
* Inferior vena cava filters (IVC) – when can not use anticoagulants such as due to cerebral bleed
54
Treatment: warfarin
* Needs to be started with what?
* Never given how?
* what should the INR be?
* You must overlap the two medications for how long? WhY?
* Needs to be started with heparin or LMWH.
* Never given as monotherapy
* After 5 days, a therapeutic INR (2-3) should be achieved, and heparin may be discontinued.
* You must overlap the two medications for 5 days, as it takes a few days for warfarin to take effect.
* Also, warfarin inhibits protein C and S initially, and might increase the risk for clot formation during the first few days.
## Footnote
Under slide: DOAC recommended, approved 2010 first one
Dabigatran (Pradaxa) - binds to clotting factor IIa (thrombin)
Rivaroxaban (Xarelto), Apixaban (Eliquis), Edoxaban -directly to clotting factor Xa (the clotting factor responsible for activating prothrombin to thrombin)
Warfarin 1954 approved
Reduces the total amount of clotting factors in the circulation. Specifically, by inhibiting the C1 subunit of vitamin K epoxide reductase enzyme complex, the liver is unable to produce vitamin K-depending clotting factors II, VII, IX, X and the endogenous anticoagulants proteins C and S
55
# ⭐️⭐️⭐️
Treatment
* DOAC’s have shown comparably reliable pharmacokinetics and pharmacodynamics to what? **Who can get the meds?**
* What are adjunctive measures?
56
# ⭐️
Treatment
* What is the long term therapy?
* A first unprovoked pulmonary embolism warrants what?
* All provoked pulmonary embolisms (reversible causes) are treated for how long?
* Longer treatment times can be considered in who?
* Long term therapy (minimum of 3 months):
* A first unprovoked pulmonary embolism warrants lifetime anticoagulation.
* All provoked pulmonary embolisms (reversible causes) are treated for 3-6 months.
* Longer treatment times can be considered in the active cancer patient.
57
Inferior Vena Cava (IVC) Filters
* Who are they indicated for?
* Retrievable vena cava filters should be what?
* Patients with inferior vena cava (IVC) filters in place require what?
* Vena cava filters are indicated for the prevention of pulmonary emboli (PE) in patients who are unable to receive anticoagulation.
* Retrievable vena cava filters should be removed once the indication for PE prevention is no longer present.
* Patients with inferior vena cava (IVC) filters in place require close follow-up to ensure timely removal.
58
IVC Filter
* May provide what?
* Unclear what?
* What are the complications (3)?
* Use when there are absolute contraindications to what?
* Who should be considered?
* Optimal duration of retrievable filters is unclear, generally should be removed beyond how long?
* May provide lifelong protection against PE
* Complications:DVT (20%), Post thrombotic syndrome (40%), IVC thrombosis (30%)
* Use when there are absolute contraindications to anticoagulation and a high risk of VTE recurrence
* Consider in pregnant women with extensive thrombosis
* Optimal duration of retrievable filters is unclear, generally should be removed beyond 3 months
## Footnote
* Unclear effect on overall survival
* Risk/benefit ratio difficult to determine
59
Pulmonary Hypertension
* What is the pathophysio?
* Primary cause of what?
* Most common cause of what?
* Also has a late complication of what?
*
* Involves pathogenic remodeling of the pulmonary vasculature, which increases pulmonary artery pressure and vascular resistance
* Primary cause of PH are left heart or primary lung disease
* Most common cause of PH are left heart or primary lung disease
* Also has a late complication of luminal pulmonary embolism
60
Pulmonary artery hypertension (PAH) is an UNCOMMON subtype characterized by what? What are the sxs?
Pulmonary artery hypertension (PAH) is an UNCOMMON subtype characterized by interplay between molecular and genetic events that cause obliterative arteriopathy (abnormal narrowing) and symptoms of
* Dyspnea, chest pain and syncope
61
Pulmonary Hypertension (pHTN)
* How is defined as?
* Pulmonary Hypertension is defined as a mean arterial pressure (MAP) > 25mm Hg at rest during right heart catheterization (8-20 is normal)
## Footnote
Under slide:
* Normal mean pulmonary arterial pressure = 15 mmHg.
* Hypertension > 25 mmHg
62
What are the four groups of pHTN?
Group 1: pulmonary artery hypertension
* Idiopathic, heritable, drugs, toxins, connective tissue disease.(idiopathic carries a poor prognosis)
Group 2: left heart disease
* Heart failure or valvular disease
Group 3: chronic lung disease and hypoxemia
* COPD or OSA
Group 4: chronic thromboembolic disease
states
* Pulmonary embolism
Group 5: unknown or multifactorial cause
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64
Explain the pathophy of PHTN?
65
Explain the Pathophysiology of pulmonary venous hypertension in valvular heart disease
## Footnote
Key words: LV, left ventricle; LVEDP, left ventricular end-diastolic pressure; LA, left atrial; PVH, pulmonary venous hypertension; LAP, left atrial pressure; PV, pulmonary veins; PA, pulmonary artery; PHT, pulmonary arterial hypertension; RVH, right ventricular hypertrophy; RV, right ventricular; TR, tricuspid regurgitation; RA, right atrium; CHF, congestive heart failure
66
# ⭐️⭐️
Sign and Symptoms of pHTN
* What are the most common sx?
* What are the sx of more advnaced disease?
* What is an unique but rare finding? Why does it happen?
* What are the signs of right ventricular failure?
* What mumers may be present?
67
# RVH in Pulmonary HTN
Diagnostics
* What does Chest x-ray show?
* What does CT scan show?
* What does EKG show?
Chest x-ray
* Central pulmonary artery enlargement
CT scan
* Typically, same findings as x-ray with greater detail
EKG
* Normal if there isn’t right ventricular strain
* Right ventricular hypertrophy
68
# RVH in Pulmonary HTN
Diagnostics:
* What does echo show?
* What does PFT show?
* What is the GOLD stardard for dx and severity assessment?⭐️⭐️⭐️⭐️
69
* What is required to confirm the dx of PAH?
* How is PAH defined by?
* What is also required to calulate PVR?
70
Treatment pHTN
* What is the txt?
* What if patient is hypoxic?
* Patients with pulmonary arterial hypertension (Group 1) should undergo what? Why?
* What happens if it is positive?
* What happens if it is negative?
71
Explain how the vasoreactivity test works?
During testing, the patient typically receives pure oxygen for 5 minutes. If PA pressures normalize with supplemental oxygen alone (indicating hypoxic vasoconstriction), further vasoreactivity testing is unnecessary and the patient should be treated with oxygen therapy. If the patient does not respond to oxygen therapy, one should proceed with acute vasoreactivity testing.
72
txt of pHTN
* Diuretics: Why given? Too much can lead to what?
* Those refractory to treatment are candidates for what?
Diuretics
* Given to reduce right ventricular pressure
* Too much diuresis can lead to problems as these patients are preload dependent.
Those refractory to treatment are candidates for a lung transplant.
73
What is the main complication of pHTN and explain the process
Cor Pulmonale is the main complication of pHTN
* Right-sided heart failure as a result of the high pressures in the pulmonary vasculature.
74
Cor Pulmonale
* What is it? What does it produce?
* What happens to the right vent?
* Usually what?
* May be cause by what?
## Footnote
Under slide: Cor pulmonale is right ventricular enlargement secondary to a lung disorder that produces pulmonary artery hypertension.
75
What are the sxs of cor pulmonale? How do you dx and txt?
* Findings include peripheral edema, neck vein distention, hepatomegaly, and a parasternal lift.
* Diagnosis is clinical and by echocardiography.
* Treatment is directed at the cause
76
What is cor pulmonale?
77
# he said FYI but idk lol
What are the acutr and chronic causes of cor pulmonale
78
Cor Pulmonale
* What does it increase?
* What is elevated? What does that cause?
79
Cor Pulmonale Symptoms?
* Asymptomatic at first
*Dyspnea
* Exertional fatigue
* Edema
* Chest pain
* Syncope
80
# ⭐️⭐️⭐️
What are the Cor Pulmonale Signs (4)
* Loud pulmonic component of the 2nd heart sound (S2)
* Murmurs of functional tricuspid and pulmonic insufficiency
* JVD
* Hepatomegaly
81
Cor Pulmonale Diagnosis
* What does EKG show?
* What does CXR show?
82
Cor Pulmonale Diagnosis
* What does the echocardiogram show?
83
Cor Pulmonale Diagnosis
* What does right heart cath show?
Elevation of pulmonary artery, RV and RA pressures
84
Cor Pulmonale Treatment
* how do you txt the cause?
* How do you treat the symptoms?
Treat cause
* Stop smoking
* Recurrent PE-anticoagulation
* Tumor-resection or chemo
Treat symptoms
* Oxygen therapy
* Diuretics for fluid overload
* Calcium channel blockers
85
Cor Pulmonale Prognosis? What is it the marker of?
* In patients with lung disease, the development of cor pulmonale is associated with poor prognosis
* Usually a marker of severe end-stage lung disease
86
35 y.o female presents with dyspnea and pleuritic CP. Hx of recent travel > 4 hours. Hemodynamically stable. Sats 92% on room air. CTA reveals small PE right main. She has close ability to f/u with PCP. No other comorbidities. BNP, TPI, Cr normal. What is the next step?
A.Start heparin gtt
B.Start DOAC
C.Start coumadin
D.Give systemic tPa
E.Consult IR for catheter directed thrombolysis
B.Start DOAC
87
22 y.o G1P0 at 18 weeks gestation is admitted to ICU with acute hypoxic respiratory failure. Afebrile, RR 29, HR 102, BP 100/60, SaO2 95% on 60%. Lungs clear, LE w/o edema/pain. CXR – hazy opacity RLL. What is the most appropriate next step?
A.CTA
B.V/Q
C.Doppler US
D.dimer
E. Warfarin
C.Doppler US
