Pulmonary Embolism (PE): Causes, Symptoms, Diagnosis & Treatment | Complete Guide 2026
Pulmonary Embolism
Intensive care unit (ICU) patients typically have multiple risk factors for deep vein thrombosis (DVT) and pulmonary embolism (PE), including acute illness, comorbidities, immobilization, advanced age, and hypercoagulable states. Venous thromboembolism (VTE) is a frequent diagnosis in the ICU. Patients are often classified into:
Submassive PE: Right ventricular (RV) dysfunction without arterial hypotension or cardiogenic shock.
Massive PE: RV dysfunction with arterial hypotension or cardiogenic shock.
Signs and Symptoms: Frequently nonspecific and include tachycardia, tachypnea, dyspnea, pleuritic chest pain, hemoptysis, hypoxemia, presyncope, syncope, and hypotension.
Differential Diagnosis: Includes sepsis, hypovolemia, acute lung injury (pneumonia, aspiration, TRALI), heart failure, acute coronary syndrome, cardiac tamponade, decompensated pulmonary arterial hypertension, constrictive cardiac disease, valvular heart disease, and aortic dissection.
Diagnostic Modalities
Pretest Probability: Tools like the Wells Score, Geneva Score, and PESI are used, though ICU patients often trend toward intermediate-to-high probability.
D-dimer: Low accuracy in the ICU due to many false positives.
Imaging & Tests: CXR, ECG, and ABG are useful for ruling out other causes but do not confirm PE.
CT Scan: Multidetector helical CT with PE protocol is the gold standard. It assesses RV dysfunction and clot burden.
Echocardiography (ECHO): Essential for unstable patients. Findings suggestive of PE include RV dilation, hypokinesis, tricuspid regurgitation, and McConnell’s sign (hypokinesis of the RV free wall with normal apex motion).
Diagnostic Evaluation
For a patient with suspected acute PE, the first step is to assess hemodynamic stability.
If Hemodynamically Stable: The clinician should perform a Multidetector CT. If the CT is positive, treatment begins. If the CT is negative, the clinician should seek alternative diagnoses, though additional testing may be required if suspicion remains high.
If Hemodynamically Unstable: The clinician should perform an immediate ECHO (transthoracic or transesophageal).
If no RV dysfunction is found, PE is unlikely seek alternative diagnoses.
If RV dysfunction is present, it suggests PE. If the patient is too unstable for CT, a portable V/Q scan or proximal lower extremity venous compression ultrasonography (CUS) should be performed.
A positive CUS or V/Q scan confirms VTE and leads to treatment. A negative result requires seeking alternative diagnoses.
Treatment Strategies
Treatment is based on hemodynamic status, RV dysfunction, bleeding risk, and prognosis.
Anticoagulation:
Acts to prevent new clot formation. Options include Unfractionated Heparin (UFH), Low-Molecular-Weight Heparin (LMWH), and Fondaparinux. LMWH is generally preferred over UFH for non massive PE, but UFH is often used in the ICU due to its short half-life and reversibility.
Thrombolytic Therapy:
Agents like alteplase, reteplase, and tenecteplase convert plasminogen to plasmin to lyse clots. These are primarily indicated for massive PE with associated hypotension or shock.
Treatment of Confirmed Acute PE:
Once acute PE is confirmed, again assess stability:
Hemodynamically Stable Patients: Start anticoagulation (or an IVC filter if anticoagulation is contraindicated). Next, assess for RV dysfunction using ECHO or CT and assess for RV injury using biomarkers (Troponin, BNP).
If there is no dysfunction/injury, continue standard anticoagulation.
If dysfunction/injury is present, continue anticoagulation but "cautiously consider" advanced therapies like thrombolysis or embolectomy.
Hemodynamically Unstable Patients: Immediate resuscitation (fluids, vasopressors) and anticoagulation (or IVC filter if contraindicated) are required. Assess for RV dysfunction and injury.
If no dysfunction is found, continue standard treatment.
If dysfunction or injury is present, the clinician should strongly consider thrombolysis, catheter embolectomy, or surgical embolectomy, especially if there is a contraindication to thrombolytics.
Contraindications to Thrombolytic Therapy
Thrombolytic therapy carries a significant risk of major bleeding, and clinicians must strictly evaluate patients for absolute contraindications before proceeding. These include any active internal bleeding, a known bleeding diathesis (predisposition to bleeding), or a history of intracranial hemorrhage. High-risk neurological factors also include known intracranial neoplasms, arteriovenous malformations, or aneurysms. Furthermore, any nonhemorrhagic stroke, significant head trauma, or intracranial/intraspinal surgery within the past 3 months constitutes an absolute contraindication. Lastly, severe uncontrolled systemic hypertension and suspected aortic dissection must be ruled out, as these conditions significantly increase the risk of a catastrophic vascular event during thrombolysis.
Beyond these, there are relative contraindications where the benefits must be carefully weighed against the risks on a case-by-case basis. These include recent internal bleeding, recent major surgery or organ biopsy, and recent trauma (including cardiopulmonary resuscitation, especially if prolonged). Clinicians should also be cautious if there has been a recent blood vessel puncture at a noncompressible site or if the patient’s platelet count is less than 100,000/mm^3.
Other relative factors include diabetic retinopathy or other hemorrhagic ophthalmic conditions, pregnancy, acute pericarditis, endocarditis, or significant hemostatic defects. The patient’s current medication status is also vital, particularly the use of long-acting anticoagulants at therapeutic doses. Patient demographics and history also play a role; advanced age (greater than 75 years) or a prior allergic reaction to streptokinase/anistreplase (if administered more than 5 days prior) are considered relative risks. Finally, any other medical condition in which bleeding would be difficult to manage should give the clinician pause before initiating therapy.
Risks of Treatment
Bleeding: The most significant risk. Major bleeding requires immediate discontinuation of anticoagulants and may require blood products or reversal agents.
HIT (Heparin-Induced Thrombocytopenia): If HIT is suspected, stop all heparin products and switch to a direct thrombin inhibitor like argatroban or lepirudin.