Pulmonary Embolism

Pulmonary embolism is the sudden blockage of a major blood vessel (artery) in the lung, usually by a blood clot. In most cases, the clots are small and are not deadly, but they can damage the lung. But if the clot is large and stops blood flow to the lung, it can be deadly.

Differential diagnosis of acute Dyspnea

Respiratory

Airway COPD exacerbation, asthma exacerbation, acute bronchitis, infectious exacerbation of bronchiectasis, foreign body obstruction

Parenchyma pneumonia, cryptogenic organizing pneumonia, ARDS, acute exacerbation of interstitial lung disease

Vascular pulmonary embolism, pulmonary hypertension

Pleural pneumothorax, pleural effusion

Cardiac

Myocardial HF exacerbation, myocardial infarction

Valvular aortic stenosis, acute aortic regurgitation, endocarditis

Pericardial pericardial effusion, Tamponade

Systemic sepsis, metabolic acidosis, anemia

Others neuromuscular, psychogenic, anxiety

Pathophysiology

Virchow’s Triad risk factors for venous thrombo embolism

Injury fracture of pelvis, femur, or tibia

Hypercoaguability obesity, pregnancy, estrogen, smoking, cancer (high suspicion of occult malignancy in patients who develop pulmonary embolism while on anticoagulation), autoimmune dis orders (anticardiolipin antibody syndrome, lupus anticoagulant, IBD), genetics (history of DVT/PE, factor V Leiden, antithrombin III deficiency, protein C/S deficiency, prothrombin G20210A mutation, hyperhomocysteinemia)

Stasis surgery requiring >30 min of anesthesia, prolonged immobilization, CVA, HF

Clinical Features

History dyspnea (sudden onset), pleuritic chest pain, cough, hemoptysis, pre/syncope, unilateral leg swelling/ pain, past medical history (previous DVT/PE, active cancer, immobilization or surgery in last 4 weeks, miscarriages), medications (birth control pill, anticoagulation)

Physical vitals (tachycardia, tachypnea, hypotension, fever, hypoxemia), respiratory examination (pulmonary hypertension if chronic PE), cardiac examination (right heart strain), leg swelling

Investigations

Basic

Labs CBCD, electrolytes, urea, Cr, PTT, INR, troponin/CK 3, D dimer (if low probability for PE or outpatient), βhCG in women of reproductive age

Imaging CXR, duplex U/S of legs, V/Q scan, CT chest (PE protocol)

ECG may see normal sinus rhythm (most common), sinus tachycardia (most common abnormality), atrial fibrillation, right ventricular strain (T wave inversion in anterior precordial leads), non specific ST T wave changes, right axis deviation, right bundle branch block and/or S1Q3T3 (tall S wave in lead I, Q wave and inverted T wave in lead III)

ABG if respiratory distress

Special

Echocardiogram to check for right heart strain (dilated RV and elevated RVSP). Particularly important if hemodynamic changes

Pulmonary Angiogram gold standard

Thrombophilia Workup factor V Leiden, pro thrombin G20210A, anticardiolipin antibody, lupus anticoagulant, protein C, protein S, antithrombin III, fibrinogen; consider homocysteine level and workup for paroxysmal nocturnal hemoglobinuria and antiphospholipid syndrome in cases of combined arterial venous thrombosis.

Diagnostic Issues

CXR Findings in Pulmonary Embolism normal, atelectasis, unilateral small pleural effusion, enlarged central pulmonary artery, elevated hemidiaphragm, Westermark’s sign (abrupt truncation of pulmonary vessel), Hampton’s hump (wedge infarct)

D DIMER (sens 85 96%, spc 45 68%, LR+ 1.7 2.7, LR 0.09 0.22) can rule out PE if low clinical suspicion

V/Q Scan (sens high, spc high) useful but result often not definitive (intermediate probability) because of other intraparenchymal abnormalities

CT PE PROTOCOL (sens 57 100%, spc 78 100%) can be very helpful as it provides clues to other potential diagnoses/pathologies as well. Not good for subseg mental pulmonary emboli

Leg Vein Doppler (sens 50%, spc moderate) serial dopplers may be used for diagnosis of DVT if CT or V/Q scan failed to demonstrate PE but clinical suspicion still high

Well’s Criteria for Pulmonary Embolism Scoring signs/symptoms of DVT (+3), alternative diagnosis less likely (+3), HR >100 (+1.5), immobilization or surgery in last 4 weeks (+1.5), previous DVT/PE (+1.5), hemoptysis (+1), active cancer (+1)

Low Suspicious (sum 0 1, <10% chance) D dimer ͢if positive, CT or V/Q scan  Intermediate SUSPICION (sum 2 6, 30% chance) D dimer ͢  CT or V/Q scan ͢  if negative but suspicious, leg doppler ͢  if negative but still sus picious, pulmonary angiogram

High Suspicious (sum >6, >70% chance) CT or V/Q scan ͢  if negative but suspicious, leg Doppler ͢   if negative but still suspicious, pulmonary angiogram

Management

Acute ABC, O2 to keep sat >94%, IV, consider thrombolysis (must be done in ICU) for massive PE (hemodynamic instability, right ventricular strain)

Anticoagulation if moderate to high risk of developing PE, consider initiating anticoagulation while waiting for investigations. Heparin (unfractionated heparin 5000 U IV bolus, then 1000 U/h and adjust to 1.5 2.5 normal PTT), LMWH (enoxaparin 1 mg/kg SC BID or 1.5 mg/kg SC daily), or fondaparinux 5 mg SC daily (<50 kg), 7.5 mg SC daily (50 100 kg), or 10 mg SC daily (>100 kg). Start warfarin 5 mg PO daily within 72 h and continue heparin/LMWH/fondaparinux until INR is between 2 and 3; ensure overlap of heparin and coumadin with therapeutic INR for at least 48 h

Thrombolytics controversial as increased risk of intracranial bleed and multiple contraindications (see below). Consider only if hemodynamically unstable or life threatening pulmonary embolism. TPA 100 mg IV over 2 h, or streptokinase 250,000 IU over 30 min, the 100,000 IU/h over 12 24 h or 1.5 million IU over 2 h. Unfractionated heparin may be used concurrently

Surgical embolectomy. Consider if thrombolysis failed or contraindicated or if hemodynamically unstable

IVC Filter if anticoagulation contraindicated

Treatment Issues

Contraindications to Thrombolytic Therapy Absolute Contraindications history of hemorrhagicstroke or stroke of unknown origin, ischemic stroke in previous 3 months, brain tumors, major trauma in previous 2 months, intra cranial surgery or head injury within 3 weeks

Relative Contraindications TIA within 6 months, oral anticoagulation, pregnancy or within 1 week postpartum, non compressible puncture sites, traumatic CPR, uncontrolled hypertension (SBP >185 mmHg, DBP  > 110 mmHg), advanced liver disease, infective endocarditis, active peptic ulcer, thrombocytopenia

Anticoagulation Duration

First Pulmonary Embolism with reversible or Time-limited Risk Factor anticoagulation for at least 3 months

Unprovoked PE at least 3 months of treatment. If no obvious risk factors for bleeding, consider indefinite anticoagulation

PE and malignancy treatment with SC LMWH better than oral warfarin. Treatment should be continued until eradication of cancer as long as there are no significant contraindications to anticoagulation

PE and Pregnancy SC LMWH is preferred for outpatient treatment. Total duration of therapy should be 6 months unless patient has risk factors for hypercoagulable state

Specific Entities

Fat Embolism

Pathophysiology embolism of fat globules to lungs, brain, and other organs  metabolized to fatty acids leading to inflammatory response. Commonly caused by closed fractures of long bones, but may also occur with pelvic fractures, orthopedic procedures, bone marrow harvest, bone tumor lysis, osteomyelitis, liposuction, fatty liver, pancreatitis, and sickle cell disease

Clinical Features triad of dyspnea, neurological abnormalities (confusion), and petechial rash (head and neck, chest, axilla). May also have fever, thrombocytopenia, and DIC

Diagnosis clinical diagnosis (rash is pathognomonic). Investigations may include CXR, V/Q scan, CT chest, and MRI head

Treatments supportive care as most patients will fully recover. Mortality is 10%. Primary prophylaxis includes early mobilization and maybe steroids