Pulmonary Embolism Presentation to Diagnosis

Objectives Review the incidence, symptoms and presenting signs of PE Learn about clinical prediction models Learn about different diagnostic methods and diagnostic algorithms.

Incidence The true incidence of PE is unknown and is suspected to be underestimated It is estimated to be between 0.5% to 3% in the general population Mortality from PE is estimated to be 0.1%

Risk Factors Previous or current DVT Immobilization Surgery within the last 3 months Stroke/paralysis Central venous instrumentation within the last 3 months Malignancy CHF Autoimmune diseases Air travel * Thrombophillias In Women Obesity (BMI ≥29) Pregnancy Heavy cigarette smoking (>25 cigarettes per day) Hypertension * Optional Info: Air travel for > 4 hours doubles your risk for a venous thromboembolism Most of these patients had an undiagnosed underlying thrombophillia such as Factor V Leiden or other risk factor Incidence in healthy individuals of VTE due to air travel is 1:6000

Presentation Most Common Symptoms Most Common Signs Tachypnea (54 %) Dyspnea at rest or with exertion (73 %) Pleuritic pain (44 %) Cough (34 %) >2-pillow orthopnea (28 %) Calf or thigh pain (44 %) Calf or thigh swelling (41 %), Wheezing (21 %) Rapid onset of dyspnea within seconds (46 %) within minutes (26 %) Tachypnea (54 %) Tachycardia (24 %) Rales (18 %), Decreased breath sounds (17 %), Accentuated pulmonic component of the second heart sound (15 %) Jugular venous distension (14 %)

Case A 63-year-old woman with stage IV lymphoma calls 911 for acute shortness of breath (SOB). At baseline, the patient is mobile and does not have SOB. She is also taking hormone replacement therapy. On the day of admission, she develops a sudden SOB and new pleuritic chest pain. She does not improve with nebulizer treatment on the way to the hospital. In the ER, her pulse is 115 bpm, RR = 36/min, temp = 100.1oF and O2 sat = 88% on room air. On exam, her lungs are clear, and her extremities are normal. A chest x-ray (CXR) shows mild right-sided atelectasis. An ABG shows ph = 7.48, PCO2 = 32 mm Hg and PO2 = 50 mm Hg on room air. What is this patient’s pretest probability for having a pulmonary embolism? What diagnostic method would you use to confirm this? Patient presenting with classic symptoms, signs and risk factors of possible PE. These are the questions we will be addressing during this talk, and by the end we will review the answers.

Clinical Decision Rules Models for assessing clinical Probability of Pulmonary Embolism Well’s Criteria Geneva Score

Wells’ Score Clinical symptoms of DVT (leg swelling, pain with palpation) 3.0 Other diagnosis less likely than pulmonary embolism Heart rate >100 1.5 Immobilization (≥3 days) or surgery in the previous four weeks Previous DVT/PE Hemoptysis 1.0 Malignancy Traditional clinical probability assessment (Wells criteria) High >6.0 Moderate 2.0 to 6.0 Low <2.0 Simplified clinical probability assessment (Modified Wells criteria) PE likely >4.0 PE unlikely ≤4.0

Simplified Geneva Score Variable Score Age >65 1 Previous DVT or PE Surgery or fracture within 1 month Active malignancy Unilateral lower limb pain Hemoptysis Pain on deep vein palpation of lower limb and unilateral edema Heart rate 75 to 94 bpm Heart rate greater than 94 bpm +1 Score of less than 2 is low probablility for PE, score of less than 2 plus a negative D-dimer results in a likelihood of PE of 3%

Diagnostic tests

D-Dimer Elevated in thrombosis, malignancy, pregnancy, elderly, hospitalized patients Role in low or moderate probability for PE Normal results can rule out PE Estimated 3 month risk of thromboembolism with negative D-dimer is 0.14% Role in high probability patients  proceed to CT, negative d-dimer can miss up to 15% of patients in this group

EKG in Pulmonary Embolism Most commonly sinus tachycardia, with possible nonspecific ST/T wave changes Only 10% of patients can have the S1Q3T3 so not reliable Other EKG abnormalities including atrial arrhythmias, right bundle branch block, inferior Q-waves, and precordial T-wave inversion and ST-segment changes, are associated with a poor prognosis.

Chest Radiography Not a sensitive or specific test for the diagnosis of PE. Atelectasis, Pleural effusion, or a pulmonary parenchymal abnormality is noted most commonly Only a small portion of patients with PE have a normal CXR.

Radiographic Signs – Westermark Sign The sign results from a combination of: dilation of the pulmonary arteries proximal to the embolus collapse of the distal vasculature creating the appearance of a sharp cut off on chest radiography The Westermark sign has a low sensitivity (11%) and high specificity (92%) for the diagnosis of pulmonary embolus

Radiographic Signs – Hamptons Hump Wedge-shaped infarct sensitivity (21) and specificity (82%) for the diagnosis of pulmonary embolus

Ventilation-Perfusion Scans Useful if Normal (negative predictive value of 97%) Also useful if High probability (positive predictive value of 85 to 90%) Unfortunately, only diagnostic in 30 to 50% of patients Optional Info: PIOPED I looked at the accuracy of diagnosing PE compared with gold standard of pulmonary angiography Normal V/Q scan and high probability V/Q scans were helpful in ruling out or in PE but indeterminate category required additional testing Venous ultrasonography can diagnose thromboembolism in 4% of patients with a non-diagnostic V/Q scan

CT Angiography

CT Angiography Studies have shown sensitivity of close to 95% with an experienced observer One of the most commonly cited benefits of CTA is its ability to detect alternative pulmonary abnormalities that may explain the patient's symptoms and signs In 67% of patients without PE, CT provided additional information for alternate diagnosis May predispose patients to further unnecessary testing

CT Agiogram Acute pulmonary embolism and deep venous thrombosis (DVT) in a 48-year-old woman. Multifocal low-attenuation emboli (arrows) in segmental and subsegmental arteries in the right lower lobe. 

Pulmonary Angiography

Pulmonary Angiography in PE The “gold standard” A negative pulmonary angiogram excludes clinically relevant PE. The risk of embolization in patients with a negative angiogram is extremely low 

Diagnostic Pathways

Is it important to use clinical decision rules? In the setting of no thromboembolic risk factors, it is extraordinarily unlikely (0.95% chance) to have a CT angiogram positive for PE. With the combination of a negative D- dimer test result, this risk is even lower.

Diagnostic Algorithm When PE is suspected, the modified Wells criteria should be applied to determine if PE is unlikely (score ≤4) or likely (score >4). The modified Wells Criteria include the following: Patients classified as PE unlikely should undergo D-dimer testing with a quantitative rapid ELISA assay or a semiquantitative latex agglutination assay. The diagnosis of PE can be excluded if the D-dimer level is <500 ng/mL or negative. Patients classified as PE likely and patients classified as PE unlikely who have a D-dimer level >500 ng/mL should undergo CT-PA. A positive CT-PA confirms the diagnosis of PE. Alternatively, a negative CT-PA excludes the diagnosis of PE. In those rare instances in which the CT-PA is inconclusive, either pulmonary angiography or the diagnostic approach intended for institutions without experience in CT-PA can be used.

Lower Extremity US indicated? Depends on pre-test probability High pretest probablity for PE and negative CT may require additional testing Good initial test to evaluate for pulmonary embolism in patients with contrast allergy, renal insufficiency, pregnancy, or critically ill patients. Inexpensive test without radiation exposure Can avoid additional testing if positive

Case Presentation Reminder: A 63-year-old woman with stage IV lymphoma with acute shortness of breath (SOB) and pleuritic chest pain. At baseline, the patient is mobile and does not have SOB. She is also taking hormone replacement therapy. In the ER, her pulse is 115 bpm. On exam, her lungs are clear, and her extremities are normal. A chest x-ray (CXR) shows mild right-sided atelectasis. An ABG shows ph = 7.48, PCO2 = 32 mm Hg and PO2 = 50 mm Hg on room air.

Case Presentation Applying the Wells’ Scoring system, the patient has a moderate likelihood of having a PE with a score of 5.5 for high clinical suspicion for PE, tachycardia, and cancer. Considering the patient’s score is >4, may proceed to CT angiography for PE rule out. This patient did have CTA performed, which confirmed presence of PE. She was subsequently started on anticoagulation

Summary and Recommendations Consider your patient’s risk factors for pulmonary embolism The clinical presentation of acute pulmonary embolism is variable and nonspecific The major diagnostic tests employed in the evaluation of a patient with suspected PE include d-dimer testing, CTPA, V/Q scanning, venous ultrasonography, and conventional pulmonary angiography Follow a diagnostic algorithm that combines CTPA, d-dimer and clinical assessment