What is the difference between septic emboli and pulmonary embolism (Pulmonary Embolism, PE)?

From the Guidelines

Septic emboli and pulmonary embolism are distinct conditions that require different management approaches, with septic emboli necessitating antimicrobial therapy and pulmonary embolism requiring anticoagulation. Septic emboli are infected material that travel through the bloodstream to the lungs, typically originating from infectious sources like endocarditis, infected intravenous catheters, or septic thrombophlebitis, as noted in the European Heart Journal guidelines 1. They contain both clotted material and microorganisms, causing both vascular obstruction and infection in the lungs. Patients often present with fever, cough, chest pain, and may have multiple peripheral nodular infiltrates on imaging.

In contrast, pulmonary embolism results from non-infected blood clots that typically originate from deep vein thrombosis in the legs, as discussed in the Journal of the American College of Radiology 1. These emboli cause pure vascular obstruction without infection, presenting with sudden-onset dyspnea, pleuritic chest pain, and sometimes hemoptysis. Imaging typically shows wedge-shaped perfusion defects. Management focuses on anticoagulation with heparin followed by oral anticoagulants like warfarin, direct oral anticoagulants, or low molecular weight heparin for 3-6 months.

Key considerations in managing these conditions include:

• Identifying the source of the emboli, whether infectious or thrombotic
• Initiating appropriate therapy, either antimicrobial for septic emboli or anticoagulant for pulmonary embolism
• Monitoring for complications and adjusting treatment as necessary
• Considering the use of inferior vena cava filters in select patients with pulmonary embolism, as recommended by the Journal of the American College of Radiology 1
• Recognizing the potential for overlap in clinical presentation and the need for a comprehensive diagnostic approach, as highlighted in the European Heart Journal guidelines 1.

Given the most recent and highest quality evidence, the primary distinction in management between septic emboli and pulmonary embolism lies in the need for antimicrobial therapy in the former and anticoagulation in the latter, with the European Heart Journal providing the most current guidance on pulmonary embolism management 1.

From the FDA Drug Label

The efficacy data are provided in Table 11 and demonstrate that prophylaxis with fondaparinux sodium was associated with a VTE rate of 4.6% compared with a VTE rate of 6.1% for dalteparin sodium ( P = NS). VTE was a composite of venogram positive DVT, symptomatic DVT, non-fatal PE and/or fatal PE reported up to Day 10. In a randomized, double-blind, clinical trial in patients with a confirmed diagnosis of acute symptomatic DVT without PE, fondaparinux sodium 5 mg (body weight <50 kg), 7. 5 mg (body weight 50 to 100 kg), or 10 mg (body weight >100 kg) SC once daily (fondaparinux sodium treatment regimen) was compared to enoxaparin sodium 1 mg/kg SC every 12 hours. The primary efficacy endpoint was confirmed, symptomatic, recurrent VTE reported up to Day 97. In a randomized, open-label, clinical trial in patients with a confirmed diagnosis of acute symptomatic PE, with or without DVT, fondaparinux sodium 5 mg (body weight <50 kg), 7. 5 mg (body weight 50 to 100 kg), or 10 mg (body weight >100 kg) SC once daily (fondaparinux sodium treatment regimen) was compared to heparin intravenous bolus (5,000 USP units) followed by a continuous intravenous infusion adjusted to maintain 1.5 to 2. 5 times aPTT control value.

The difference between septic emboli and pulmonary embolism is not explicitly addressed in the provided drug label.

• Pulmonary embolism (PE) is mentioned as a condition treated with fondaparinux sodium.
• Septic emboli are not mentioned in the provided text. The FDA drug label does not provide a direct comparison between septic emboli and pulmonary embolism 2.

From the Research

Definition and Diagnosis

• Septic emboli and pulmonary embolism are two distinct clinical entities, with septic pulmonary embolism (SPE) being a rare condition characterized by the presence of septic emboli in the lungs 3.
• Pulmonary embolism (PE) is characterized by occlusion of blood flow in a pulmonary artery, typically due to a thrombus that travels from a vein in a lower limb 4.
• The diagnosis of SPE depends on specific radiologic findings, such as multiple, peripheral, nodular, possibly cavitated lesions, while PE is diagnosed using chest imaging and laboratory tests, including D-dimer testing 3, 4.

Clinical Presentation and Management

• Patients with SPE typically present with signs and symptoms of pulmonary involvement, such as acute chest pain, shortness of breath, or syncope, and may have a systemic acute inflammatory reaction or sepsis 3.
• Patients with PE may also present with similar symptoms, and the clinical probability of PE can be assessed using a structured score or clinical gestalt 4.
• Management of SPE involves an immediate search for the primary source of infection and may require invasive treatment, such as anticoagulation and broad-spectrum antimicrobial therapy 3.
• Management of PE involves risk stratification and treatment with anticoagulation, thrombolytics, or mechanical or surgical thrombectomy, depending on the patient's clinical status and risk classification 5, 4, 6, 7.

Treatment Options and Outcomes

• The in-hospital mortality of SPE can range up to 20% in published case series, while the mortality rate for PE can be as high as 3.9% in patients with systolic blood pressure lower than 90 mm Hg 3, 4.
• Treatment options for PE include direct oral anticoagulants, such as apixaban, edoxaban, rivaroxaban, or dabigatran, which have been shown to be noninferior to heparin and warfarin, with a lower rate of bleeding 4.
• Surgical pulmonary embolectomy (SPE) remains a vital option for select patients with PE, particularly those who are not candidates for thrombolysis or have a high risk of recurrence 7.