Pulmonary Embolism

• Pulmonary embolism (PE) is a common and often fatal form of venous thromboembolism (VTE)
• Clinical presentation of PE is highly variable and non-specific, making diagnosis challenging
• Diagnosis of PE requires a high level of suspicion and efficient evaluation for quick therapy administration
• Search for risk factors contributing to PE development is essential for treatment and determining optimal therapy duration
• Thrombus: A solid or semisolid mass formed from circulating blood constituents within the vascular system
• Embolus: Undissolved material carried by the blood stream and impacting part of the vascular tree
• Venous Thromboembolism (VTE): Formation of thrombotic material in the systemic venous system with the potential to embolise to distant sites, usually the lungs
• PE: Obstruction of the pulmonary artery or its branches by material originating elsewhere in the body
• PE can be classified by the type of material embolised, temporal pattern of presentation, haemodynamic stability, anatomic location, and presence of symptoms
• PE incidence in the general population has increased with CT pulmonary angiography introduction
• PE is slightly more common in males and incidence rises with age
• Deaths from confirmed PE have declined, but overall mortality remains high with 30-day and 1-year mortality rates
• Thrombus generation involves risk factors classified by Virchow’s Triad: venous stasis, endothelial injury, and hypercoagulable state
• Most pulmonary emboli arise from lower extremity proximal veins
• PE diagnosis involves clinical suspicion, pretest probability assessment, and definitive testing
• Clinical suspicion for PE is determined by the presentation consistency with PE
• Clinical features include dyspnoea, pleuritic chest pain, cough, and occasionally haemoptysis
• Laboratory investigations for PE include arterial blood gas showing hypoxaemia and hypocapnoea
• Assessment of a patient’s pretest probability for PE involves using scoring systems like the Well’s score
• High probability patients (Well’s > 4) should undergo definitive diagnostic testing
• Low to intermediate probability patients (Well’s 4 or less) may need further assessment before testing
• 1. dimers are breakdown products of thrombus and can help rule out PE in low to intermediate probability patients
• Elevated D-dimer alone is insufficient for PE diagnosis
• Definitive diagnostic testing for PE includes CT pulmonary angiogram (CTPA) or ventilation perfusion (V/Q) scan
• CTPA is the imaging modality of choice for PE diagnosis with good sensitivity and specificity
• CTPA may assist in discovering alternate diagnoses and is more widely available than V/Q scan
• Empiric parenteral anticoagulation is reasonable while awaiting definitive diagnostic testing results to avoid therapeutic delay
• V/Q scanning is preferred when CT scanning is contraindicated
• V/Q scanning may be preferred over CT scanning when CTPA is indeterminate or negative and suspicion for PE remains high
• V/Q scan is highly sensitive but not very specific, good for ruling out pulmonary emboli
• V/Q scan is safer than CT as it does not expose the patient to radiation or contrast
• V/Q scan is better for visualizing smaller peripheral emboli
• V/Q scan requires a normal chest X-ray for positive findings to be interpreted correctly
• Doppler ultrasound can be used for DVT evaluation when CTPA or V/Q scan is not available
• Echocardiography can be used for visualizing PE in the proximal pulmonary arteries
• Patients with massive or high-risk PE are hemodynamically unstable
• Supportive therapies for confirmed PE include supplemental oxygen, analgesia, intravenous fluids, and inotropic support
• Low-risk patients should be prioritized for early discharge on oral anticoagulation therapy
• Intermediate-risk patients require an initial period of parenteral anticoagulation
• Anticoagulation strategies include initiation phase, treatment phase, and extended phase