Snapshot A 36-year-old woman presents to the emergency department with worsening shortness of breath and pleuritic chest pain. She recently returned to the United States from a business meeting. She takes an oral contraceptive and a daily multivitamin. Her temperature is 98.6°F (37°C), blood pressure is 135/82 mmHg, pulse is 112/min, respirations are 24/min, and oxygen saturation is 89% on room air. A CT angiogram demonstrates a filling defect in the pulmonary vasculature. She is started on supplemental oxygen and heparin. Introduction Definition mechanical obstruction of the pulmonary vasculature secondary to a blood clot typically, a thromboembolism from a deep vein thrombosis (DVT) Epidemiology Risk factors prolonged immobilization malignancy thrombophilia / hypercoagulability (factor V Leiden, antithrombin III deficiency, protein C/S deficiency) high estrogen states (pregnancy, hormonal contraceptives) autoimmune conditions (lupus) nephrotic syndrome (including HIV which can cause a nephrotic syndrome) Etiology DVT (most common) from the veins of the proximal thigh (iliac, femoral, or popliteal) Phlegmasia cerulea dolens a progression from a DVT massive thrombus that can embolize from the proximal ileofemoral vein enlarged, blue, and tender lower extremity Septic embolism from right-heart endocarditis Fat embolism Amniotic fluid embolism Pathophysiology occlusion of the pulmonary vasculature results in hypoxemia and subsequent pulmonary vasoconstriction the increased pulmonary constriction causes an increase in pulmonary vascular resistance, which decreases right ventricular stroke volume leading to increased ventricular oxygen demand right ventricular dilatation decreased left ventricular preload poor blood flow to the lung, leading to a ventilation-perfusion mismatch hypoxemia leads to compensatory tachypnea, hyperventilation, and a respiratory alkalosis Presentation Symptoms dysnea (most common) chest pain palpitations hemoptysis extremity swelling (suggestive of DVT) syncope in cases of a large PE Physical exam tachypnea tachycardia loud P2 findings of DVT fever hemodynamic instability in cases of a large PE Imaging CT angiography of the chest indication most appropriate confirmatory test indicated if moderate/high risk via Wells' score or if D-dimer is positive Chest radiography (typically normal and neither sensitive nor specific) pleural effusions Hampton hump (wedged-shaped infarct) Westermark sign (avascularity distal to the PE) V/Q scan indication performed if patient cannot undergo a CT angiogram interpretation (not a specific test) normal = rules out PE high-probability with a positive V/Q scan = treat with blood thinners low or intermediate probability = consider angiography vs empiric treatment Venous duplex ultrasound of the lower extremities indication to evaluate if there are DVTs (if positive, can start anticoagulation) Echocardiography larger PEs may cause right ventricular dysfunction and dilatation Studies ECG findings sinus tachycardia tachydysrhythmias right ventricular strain S1Q3T3 (neither sensitive nor specific) presence of S wave in lead I and Q wave and inverted T wave in lead III T-wave inversions in V1-V4 Arterial blood gas findings hypoxemia hypocapnia respiratory alkalosis alveolar-arterial gradient may be elevated D-dimer has a high sensitivity but poor specificity for PE used to rule-out PE if there is a low pre-test probability via Wells' score a positive D-dimer in a low risk patient must be followed by a confirmatory study (CTA chest) Differential Acute coronary syndrome differentiating factors ST elevation in a vascular distribution in a STEMI troponin elevation in STEMI or NSTEMI (but can also be elevated in PE) Costochondritis differentiating factors pain with palpation or movement of the arms Aortic dissection differentiating factors sudden tearing pain that radiates to the chest, back, and/or abdomen CTA can differentiate between these diagnoses Treatment Medical anticoagulation indication initial therapy in patients with PE in order to prevent further clot formation medication options (best initial step in high risk patient with obvious PE) low-molecular weight heparin do not give in renal failure unfractionated heparin dose by monitoring aPTT preferred in kidney injury/failure direct Xa inhibitors (apixaban, rivaroxaban) easy dosing, no need to monitor INR warfarin must monitor INR and ensure stable vitamin K consumption (diets high in vegetables may alter INR) typically need to bridge to warfarin until INR is therapeutic (goal = 2-3) thrombolytic therapy indication performed in patients with PE who are hemodynamically unstable or in cardiac arrest from a PE Operative embolectomy indication performed in patients with massive/sub-massive PE IVC filter indication performed in patients with PE who have a contraindication or failure of anticoagulation Prognosis High mortality without treatment Wells' criteria used to assess for risk of pulmonary embolism signs and symptoms of DVT +3 pulmonary embolism (PE) is the most likely diagnosis +3 pulse is 100/min or greater +1.5 surgery within the past 4 weeks or immobilization for the past 3 days + 1.5 previously diagnosed PE or DVT + 1.5 hemoptysis +1 malignancy with treatment in the past 6 months < 2 points low risk consider using D-dimer 2-6 points moderate risk consider D-dimer or CTA > 6 points high risk imaging required