Pulmonary embolism: Clinical sciences

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Introduction0:00–1:02

Pulmonary embolism, or PE, is a blockage of the pulmonary artery or one of its branches by an embolus, which is a traveling blood clot, tumor, fragment of fat, or air, that originates from somewhere else in the body.
In most cases, the embolus originates from a thrombus in the iliac, femoral, or popliteal veins that broke loose. Once the embolus reaches the pulmonary circulation, it blocks alveolar blood flow and increases dead space ventilation.
This causes ventilation perfusion mismatch, eventually reducing blood oxygenation and causing damage to lung tissue. In addition, there’s increased pulmonary vascular resistance and right ventricular afterload, which can lead to right ventricular heart failure.
Because of this, patients who are unstable need immediate management, and those who are stable should be evaluated quickly with the Wells criteria.
When assessing a patient with a suspected pulmonary embolism, first do an ABCDE assessment to determine if your patient is stable or unstable.

Unstable branch1:02–3:41

An unstable presentation is commonly caused by a large embolus in the main pulmonary artery. Because of the high mortality-risk in these patients, it’s essential to stabilize their airway, breathing, and circulation first.
You should establish intravenous access for fluids or vasopressors, and attach an automatic blood pressure cuff, chest leads, and digital pulse oximeter to monitor blood pressure, cardiac rhythm, and oxygen saturation.
Additionally, provide supplemental oxygen to maintain the oxygen saturation above 90%. On examination, unstable patients typically present with severe hypotension, tachypnea, and tachycardia.
They might also have dyspnea, pleuritic chest pain, hemoptysis, fatigue, and weakness. Additional physical findings found in physical examination might reveal rales, JVD, a loud P2, calf tenderness and swelling, and pedal edema.
In severe cases, the patient can progress to bradycardia, which can be associated with right ventricular strain and impending shock.
The most common ECG finding in PE is sinus tachycardia, but a less common finding is the S1Q3T3 pattern where there’s a large S wave in lead I, and a Q wave and inverted T wave in lead III.
Next, order an emergent CT pulmonary angiography, or CTPA, to assess for intraluminal filling defects in the pulmonary circulation.
If there are filling defects in the pulmonary blood flow, the CTPA is considered positive, and the diagnosis is confirmed.
You can often rule out PE if it’s negative, but on rare occasions, CTPA can be inconclusive because of interference from motion, patient body habitus, or lung parenchymal disease.
Now, if you diagnose PE and the patient has no bleeding risk, like bleeding disorders, uncontrolled hypertension, or recent major trauma or surgery, immediately initiate thrombolytic therapy with medications such as alteplase to quickly break down the embolus.
If there’s a high risk of bleeding, then surgical embolectomy or percutaneous catheter-directed therapy are the best options.
Alright, now let’s discuss how to manage stable patients. You should start with acute management, like obtaining IV access, and monitoring cardiac rhythm, blood pressure, and oxygen saturation.

Acute management3:41–4:00

You should also provide supplemental O2 as needed. Once you initiate acute management, you should do a focused history and physical.
Stable patients often have mild symptoms, or might even be asymptomatic. They typically present with dyspnea, pleuritic chest pain, hemoptysis, and leg pain or swelling if a DVT is present.

History and Physical4:00–5:08

Additionally, past medical and family history might reveal risk factors for PE, such as recent prolonged immobilization, recent orthopedic surgery, malignancy, indwelling catheter, obesity, pregnancy, smoking, or oral contraceptive use.
Family history of PE or DVT can also indicate possible familial inherited genetic disorders that predispose to PE. Now, a physical examination might reveal elevated body temperature, tachypnea, tachycardia, or calf swelling with tenderness and erythema, pedal edema, and palpable cords.
Chest auscultation often reveals rales, wheezing, and decreased breath sounds. If you suspect PE, your next step is to order a D-dimer and coagulation profile, which might be needed for clinical decision making later on.
After the history and physical, the next step is to use the Wells criteria to determine the probability of PE in your patient.
This is important because a low Wells score may help the patient avoid a more costly or risky workup. The Wells criteria scores seven parameters.

Wells Criteria5:08–5:56

Clinical signs and symptoms that point to DVT and PE as the most likely diagnosis are scored 3 points each. Previous PE or DVT, heart rate above 100, and recent surgery or immobilization are scored 1.5 points each.
Lastly, hemoptysis and malignancy are given 1 point each. These scores are added up and used to categorize the patient’s risk into one of three probability groups.Alright, a Wells score below 2 indicates a low probability of PE.
For these individuals, you can use a clinical tool called the PE rule-out criteria, or PERC, to further rule out PE. The PERC criteria is composed of eight elements, including the patient’s age, heart rate, oxygen saturation, prior history of PE or DVT, and history of recent trauma or surgery, as well as the presence of hemoptysis, unilateral leg swelling, and the use of exogenous estrogen.

Low probability5:56–6:52

If all eight elements are negative, the criteria are fulfilled and you can rule out PE. On the other hand, if the criteria are not fulfilled, you should check the patient’s D-dimer level.
If the D-dimer level is less than 500 ng/mL, consider alternative diagnoses. However, if the D-dimer is 500 ng/mL and above, proceed with CTPA.
Alright, let’s go back to the Wells criteria. A score between 2 and 6 indicates a moderate probability of PE.
In this case, your next step is to check the patient’s D-dimer levels. As before, D-dimer levels less than 500 ng/mL mean you should consider alternative diagnoses, while levels of 500 ng/mL and above require CTPA.

Moderate probability6:52–7:18

Finally, a Wells score above 6 indicates a high probability of PE. For most patients in this group, you can immediately start anticoagulation therapy with direct oral anticoagulants, or DOACs, unless severe hepatic impairment is present, as DOACs are contraindicated in that setting.
If you suspect larger emboli, heparin or fondaparinux might be a better choice. Once you start anticoagulants, the next step is CTPA.Okay, if the Wells score indicates that you should order a CTPA, you can use the results to determine your next management steps.

High probability7:18–7:52

A negative CTPA effectively rules out PE, so you should consider an alternative diagnosis. On the other hand, a positive CTPA confirms PE and requires immediate anticoagulation therapy if not already initiated.

CTPA7:52–9:25

Finally, if the findings are inconclusive, order a ventilation-perfusion scan, or VQ scan for short. If there’s normal ventilation but poor perfusion, it’s suggestive of a PE.
Now let's take a closer look at how we assess the results of the V/Q Scan. The imaging result is combined with the Wells score to increase predictability.
A low-probability VQ scan result and a Wells score less than 2 require no further investigation, while a high-probability VQ scan result and a Wells score above 6 is considered diagnostic for PE, and DOACs should be continued.
All other combinations are considered moderate probability, and you should assess further with a lower extremity compression ultrasonography with doppler.
This test cannot diagnose PE, but can diagnose DVT in the leg, which in combination with active pulmonary symptoms can establish a presumptive diagnosis of PE, and anticoagulation therapy should be started.
Anticoagulation treatment should continue for 3 months.Alright, as a quick recap… PE is a life threatening condition that needs to be diagnosed quickly.
Unstable patients require emergent CTPA and thrombolytic therapy, surgical embolectomy or percutaneous catheter-directed therapy.
On the other hand, stable patients should be assessed using the Wells criteria to predict the probability of PE. Low probability patients should be further evaluated using the PERC criteria and D-dimer levels to rule out PE.
Moderate probability patients should have a D-dimer level checked to rule out PE. If you can’t rule out PE, the next step is a CTPA.

Review9:25–10:34

High probability patients should start an anticoagulant unless it’s contraindicated, followed by a CTPA. A negative CTPA rules out PE and a positive CTPA confirms the diagnosis, while inconclusive results require further evaluation using a VQ scan.
All patients with confirmed PE should be treated with anticoagulants. perc criteria and D dimer levels to rule out pe moderate probability patients should have ad dimer level checked to rule out P if you can't rule out P The next step is a CT P High probability patients should start an anticoagulant unless it's contraindicated Followed by a CT P A negative CT P rules out pe and a positive CT P confirms the diagnosis While inconclusive results require further evaluation Using a VQ scan All patients with confirmed pe should
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