Pulmonary Embolism: Risk Stratification and Emergency Management

Pulmonary embolism is a time-critical emergency that is still too frequently missed or recognized too late in clinical practice. Clinical presentation ranges from nonspecific symptoms such as dyspnea and tachycardia to obstructive shock with cardiac arrest. It is precisely this wide spectrum that makes diagnosis challenging – and structured risk stratification the decisive tool. Whether you work in the emergency department, the intensive care unit, or in prehospital emergency medicine: a clear understanding of scoring systems, D-dimer interpretation, and therapeutic algorithms determines your patients' outcomes.

Pathophysiology in a Nutshell

Pulmonary embolism most commonly results from thrombotic material originating in the deep venous system of the lower extremities or the pelvis. The thrombus travels through the right atrium and right ventricle into the pulmonary arteries, where it partially or completely occludes the vascular lumen.

The hemodynamic consequences depend on the extent of obstruction and the cardiopulmonary reserve capacity:

• Increased pulmonary arterial pressure → acute right heart strain
• Decreased left ventricular preload → drop in cardiac output
• Ventilation-perfusion mismatch → hypoxemia and increased dead space
• Release of vasoactive mediators → additional pulmonary vasoconstriction

In massive obstruction (> 50% of the vascular cross-section), the right ventricle cannot compensate for the sudden pressure increase – resulting in obstructive shock progressing to pulseless electrical activity (PEA).

Clinical Presentation: What You Need to Consider

Pulmonary embolism is a chameleon. Typical symptoms and findings include:

• Sudden onset dyspnea (most common symptom)
• Chest pain (often pleuritic; retrosternal in central PE)
• Tachycardia (heart rate > 100/min)
• Tachypnea
• Hemoptysis (rare but specific)
• Syncope (warning sign of hemodynamic significance)
• Signs of deep vein thrombosis (unilateral leg swelling)
• Jugular venous distension, hypotension, cyanosis in massive PE

Important: A normal oxygen saturation does not rule out pulmonary embolism. An unremarkable chest X-ray is also not an exclusion criterion. Clinical pretest probability is the key to guiding further diagnostics.

Risk Stratification: Clinical Scores

Wells Score

The Wells Score is the most widely used tool in clinical practice for estimating the pretest probability of pulmonary embolism. It comprises seven criteria:

Criterion	Points
Clinical signs of deep vein thrombosis	3.0
Pulmonary embolism more likely than alternative diagnosis	3.0
Heart rate > 100/min	1.5
Immobilization (> 3 days) or surgery within the past 4 weeks	1.5
Previous DVT or PE	1.5
Hemoptysis	1.0
Malignancy (active or treated within the last 6 months)	1.0

Interpretation (three-tier model):

• 0–1 points: low probability
• 2–6 points: intermediate probability
• ≥ 7 points: high probability

Interpretation (two-tier model, simplified):

• ≤ 4 points: PE unlikely
• > 4 points: PE likely

The simplified two-tier model has proven practical in many emergency departments and is recommended as an equivalent option in the European guidelines.

Revised Geneva Score

The Revised Geneva Score eliminates the subjective parameter "PE more likely than alternative diagnosis," making it more standardizable:

Criterion	Points
Age > 65 years	1
Previous DVT or PE	3
Surgery or fracture within the past month	2
Active malignancy	2
Unilateral leg pain	3
Hemoptysis	2
Heart rate 75–94/min	3
Heart rate ≥ 95/min	5
Pain on deep palpation of lower extremity and unilateral edema	4

Interpretation:

• 0–3 points: low probability
• 4–10 points: intermediate probability
• ≥ 11 points: high probability

Both scores serve exclusively to estimate pretest probability. They are not diagnostic proof and do not replace imaging – but they determine whether and how you proceed with further diagnostics.

D-Dimer: When Useful, When Misleading?

D-dimers are fibrin degradation products that are elevated in thrombosis but also in a wide variety of other conditions (infection, malignancy, pregnancy, postoperative state, trauma, advanced age). Therefore, D-dimer testing is only useful when pretest probability is low to intermediate.

Basic rules:

• Low/intermediate pretest probability + negative D-dimer: Pulmonary embolism can be ruled out with high confidence (negative predictive value > 99%)
• High pretest probability: Do not order D-dimers – proceed directly to CT pulmonary angiography (CTPA). A negative D-dimer does not reliably exclude PE when pretest probability is high.
• Age-adjusted cut-off: In patients over 50 years of age, the cut-off value is calculated using the formula age × 10 µg/L (e.g., 700 µg/L for 70-year-old patients). This increases specificity without significantly reducing sensitivity.

Imaging: CTPA as the Gold Standard

CT pulmonary angiography (CTPA) is the standard investigation for confirming or ruling out pulmonary embolism. It is available almost everywhere, can be performed quickly, and simultaneously provides information about the extent of obstruction and the condition of the right ventricle (RV/LV ratio).

Point-of-care echocardiography has particular importance in the emergency setting:

• Detection of acute right heart strain (RV dilation, septal kinetics, D-sign, reduced TAPSE)
• McConnell's sign (akinesia of the free RV wall with preserved apical contractility)
• In hemodynamically unstable patients who cannot be transported, echocardiography can justify the treatment decision (thrombolysis) even without CTPA

Hemodynamic Classification and Risk Stratification by Severity

Classification into risk groups follows the ESC classification and determines the therapeutic approach:

High-Risk PE (Massive PE)

• Definition: Hemodynamic instability – systolic blood pressure < 90 mmHg for > 15 minutes, or vasopressor requirement, or cardiac arrest
• Mortality: > 15% in the early phase
• Management: Immediate reperfusion therapy (systemic thrombolysis)

Intermediate-High Risk (Submassive PE)

• Definition: Hemodynamically stable, BUT signs of right ventricular strain (echocardiography/CTPA) AND elevated cardiac biomarkers (troponin and/or NT-proBNP)
• Mortality: 3–15%
• Management: Anticoagulation, close monitoring in ICU/IMC, rescue thrombolysis if deterioration occurs

Intermediate-Low Risk

• Definition: Hemodynamically stable, right ventricular strain OR elevated biomarkers (not both)
• Management: Anticoagulation, inpatient monitoring

Low Risk

• Definition: Hemodynamically stable, no right ventricular strain, normal biomarkers, sPESI = 0
• Mortality: < 1%
• Management: Anticoagulation, outpatient treatment possible under certain conditions

The simplified Pulmonary Embolism Severity Index (sPESI) helps with risk stratification in stable patients:

• Age > 80 years: 1 point
• Malignancy: 1 point
• Chronic heart failure or pulmonary disease: 1 point
• Heart rate ≥ 110/min: 1 point
• Systolic blood pressure < 100 mmHg: 1 point
• SpO₂ < 90%: 1 point

sPESI = 0: Low risk. sPESI ≥ 1: Intermediate or high risk – further stratification required.

Emergency Therapy: Anticoagulation

Anticoagulation is the cornerstone therapy for every confirmed pulmonary embolism and should be initiated before diagnostic workup is complete when clinical probability is high.

Initial Anticoagulation

• Unfractionated heparin (UFH): Bolus 80 IU/kg IV, then 18 IU/kg/h as continuous infusion, target aPTT 60–80 seconds. Preferred in hemodynamic instability, planned thrombolysis, or high bleeding risk (short half-life, reversible with protamine).
• Low-molecular-weight heparin (LMWH): e.g., enoxaparin 1 mg/kg subcutaneously every 12 hours. Standard for hemodynamically stable patients without renal impairment (GFR > 30 mL/min).
• Fondaparinux: Weight-adjusted subcutaneous injection once daily (5 mg if < 50 kg, 7.5 mg if 50–100 kg, 10 mg if > 100 kg).

Ongoing Anticoagulation

Transition to oral anticoagulation occurs after stabilization. Direct oral anticoagulants (DOACs) such as rivaroxaban or apixaban can be used from the outset in eligible patients without initial heparinization (rivaroxaban: 15 mg twice daily for 21 days, then 20 mg once daily; apixaban: 10 mg twice daily for 7 days, then 5 mg twice daily).

Systemic Thrombolysis: Indications and Administration

Systemic thrombolysis is the reperfusion therapy of choice in high-risk pulmonary embolism. It leads to a rapid reduction in pulmonary arterial pressure and improvement of right ventricular function.

Indications

• Established indication: Hemodynamically unstable pulmonary embolism (high-risk PE)
• Rescue thrombolysis: Initially hemodynamically stable patients with intermediate-high risk who deteriorate under anticoagulation
• Cardiac arrest: When pulmonary embolism is suspected as the cause of cardiac arrest

Agents and Dosing

Agent	Dosing
Alteplase (rtPA) – standard protocol	100 mg IV over 2 hours (10 mg bolus, then 90 mg over 2 h)
Alteplase (rtPA) – accelerated protocol	0.6 mg/kg over 15 minutes (maximum 50 mg)
Tenecteplase	Weight-adjusted single bolus: 30–50 mg IV (increasingly used)

In cardiac arrest: Alteplase 50 mg IV bolus, repeat if necessary after 15 minutes. CPR must be continued for at least 60–90 minutes after thrombolysis before terminating resuscitation efforts.

Contraindications to Thrombolysis

Absolute contraindications:

• Active bleeding or hemorrhagic diathesis
• Ischemic stroke within the past 3 months
• CNS neoplasm
• Major trauma, surgery, or head injury within the past 3 weeks
• Gastrointestinal bleeding within the past month

Relative contraindications:

• TIA within the past 6 months
• Oral anticoagulation
• Pregnancy or first week postpartum
• Non-compressible puncture sites
• Refractory hypertension (> 180/110 mmHg)
• Advanced liver disease

Important: In life-threatening high-risk PE, the only absolute contraindication is active, uncontrollable bleeding. All other contraindications are weighed against the immediate threat to life.

Pulmonary Embolism in Cardiac Arrest

Pulmonary embolism is one of the most common treatable causes of cardiac arrest and belongs to the "4 T's" of reversible causes (thromboembolism). Within the ACLS algorithm, the following considerations apply:

• Most common rhythm: Pulseless electrical activity (PEA), less commonly asystole
• Suspected PE in cardiac arrest: Systemic thrombolysis (alteplase 50 mg IV bolus) during ongoing CPR
• CPR duration after thrombolysis: At least 60–90 minutes
• Epinephrine: Per standard ACLS algorithm, 1 mg IV every 3–5 minutes
• No interruption of CPR for diagnostic procedures – echocardiography performed by a second provider (without interrupting chest compressions) can strengthen the clinical suspicion
• Alternative reperfusion: Catheter-directed interventions or surgical embolectomy are only options in specialized centers with immediate availability

Supportive Measures in Hemodynamic Instability

Beyond causal therapy (anticoagulation/thrombolysis), supportive measures are critical in unstable PE:

• Volume administration: Use caution! The already dilated right ventricle is further compromised by excessive volume loading. Administer a maximum of 500 mL crystalloid solution as an initial bolus, then reassess.
• Vasopressors: Norepinephrine is the first-line vasopressor to maintain systemic perfusion pressure. Dobutamine can be added for inotropic support in severe RV failure.
• Oxygen: Target SpO₂ > 90%. Use non-invasive ventilation if needed. Exercise caution with intubation: induction of anesthesia and positive-pressure ventilation can further reduce venous return and precipitate cardiac arrest.

Pitfalls and Clinical Pearls

• Tachycardia + dyspnea ≠ automatically pneumonia: Especially in postoperative or immobilized patients, always consider PE.
• Syncope as initial symptom: Syncope in the context of pulmonary embolism is a sign of hemodynamic significance and requires immediate risk stratification.
• Pregnancy: D-dimers are physiologically elevated in pregnancy. CTPA is the diagnostic modality of choice (low fetal radiation dose). Anticoagulation is performed with LMWH. DOACs are contraindicated.
• Right heart thrombus: A thrombus visible on echocardiography in the right heart chambers (thrombus-in-transit) is an indication for immediate reperfusion therapy, regardless of hemodynamic status.
• Don't forget differential diagnoses: Aortic dissection, acute coronary syndrome, cardiac tamponade, and tension pneumothorax can present similarly – point-of-care echocardiography helps with differentiation.

Practical Training

Pulmonary embolism – from subclinical incidental finding to obstructive shock with cardiac arrest – requires rapid, structured decision-making under time pressure. Risk stratification, thrombolysis indications, and supportive management are best practiced in the safe environment of realistic simulation scenarios. In the ACLS courses offered by Simulation Tirol, you practice exactly these situations: from recognizing pulmonary embolism as the cause of cardiac arrest, through thrombolysis during CPR, to managing the hemodynamically unstable patient. Hands-on training that makes the difference when it matters most.