Pulmonary Embolism

Say what?

Virchow’s triad (stasis, endothelial injury, hypercoagulability) leads to thrombosis in your patient’s deep venous system. Part of the formed thrombus breaks loose, and gets stuck in your patient’s pulmonary vasculature.

Your patient will report (in decreasing order of frequency)1:

  • Dyspnea
  • Pleuritic chest pain
  • Cough
  • Hemoptysis
  • Diaphoresis
  • Nonpleuritic chest pain
  • Syncope (massive PE)
  • Nothing (asymptomatic)

You will see and hear (in decreasing order of frequency)1:

  • Tachypnea (RR>16/min)
  • Rales
  • Accentuated S2
  • Tachycardia (HR>100/min)
  • Hyperthermia (T>37.8)
  • Diaphoresis
  • S3 or S4 gallop
  • Clinically evident thrombophlebitis
  • Decreased breath sounds
  • Lower extremity edema
  • Cardiac murmur
  • Cyanosis
  • Hypotension (massive PE)
  • A normal exam – absence of physical findings does not rule out a PE

Is this really it?

Clinical scoring systems

One of the most important steps in the work up of your patient is to determine how likely it is that your patient has a PE. Low risk indicates you think that the patient has a 0-20% risk of having a PE, intermediate indicates a risk of 20-80% and high is a risk of 80-100% of PE.2 ED docs have been pretty good at the guessing game, but unfortunately not good enough with an accuracy of pretest probability of PE between 71-78%. As we do not want to send a patient home with a PE a bunch of clinical scoring systems have been proposed, two will be discussed here as they are most frequently used and have been prospectively validated.

First, the Wells score is used to risk stratify our patient.3 The patient will be given a score according to the criteria below.

  • Suspected DVT – 3.0 points
  • An alternative diagnosis is less likes than PE – 3.0 points
  • Heart rate >100/min – 1.5 points
  • Immobilization or surgery in the previous 4 weeks – 1.5 points
  • Previous DVT/PE – 1.5 points
  • Hemoptysis – 1.0 points
  • Malignancy (current treatment, treated in last 6 months or palliative) – 1.0 points

A score of 0-1 indicates a low risk, 2-6 is an intermediate risk and a score greater than 6 is a patient at high risk. If your patient is at low risk, the Pulmonary Embolism Rule out Criteria (PERC) can be used to assess if your low risk patient can be safely discharged home without ancillary testing.4  The following questions need to be answered with “no” in order to discharge without additional testing:

  • Is the patient >49 years of age?
  • Is the pulse rate > 99/min?
  • Is the pulse oximetry reading <95% while the patient breathes room air?
  • Is there a history of hemoptysis?
  • Is the patient receiving exogenous estrogen?
  • Does the patient have a prior diagnosis of venous thromboembolism?
  • Has the patient had recent surgery or trauma requiring endotracheal intubation or hospitalization in the previous 4 weeks?
  • Does the patient have unilateral leg swelling?

ECG

There is no evidence that ECG alone has sufficient sensitivity or specificity to rule out PE.5  It is mainly used to exclude alternative causes of your patient’s symptoms. It will be normal in 30% of cases.6,7

Most common ECG findings in patients with PE include:

  • Sinus tachycardia (36%)
  • Right axis deviation
  • (In)complete right bundle branch block (6-67%)
  • Non-specific T-wave inversions (68-80%)
  • S1Q3T3 – even though S1Q3T3 has been traditionally thought of as pathognomonic for PE, it only occurs in 20% of patients.

Labs

D-dimer – aids in excluding PE if your patient has a low pre-test probability. If your patient’s Wells score is 2 or less the D-dimer assay has a negative predictive value of 99%.8 A D-dimer assay is not indicated if your patient has an intermediate or high risk of having a PE.

  • “False” positive D-dimer in: your patient is elderly or has myocardial infarction, DIC, trauma, postoperative states, infection, malignancy, sickle cell crisis, pre-eclampsia, atrial fibrillation, aortic dissection, stroke or a superficial thrombophlebitis
  • False negative D-dimer in: small clot burden, older thrombus, fibrinolysis disorder

Troponin and pro-BNP – an elevated troponin is associated with adverse outcomes and hemodynamic instability in non-massive PE. A low pro-BNP indicates your patient will probably do well.

ABG – not helpful in making diagnosis, as multiple studies have shown that a normal ABG does not exclude PE. Do not routinely violate your patient’s radial artery when evaluating for PE.6

Imaging

CXR – mainly used to exclude alternative causes of your patient’s symptoms. Commonly seen abnormalities in PE include cardiomegaly, elevated hemidiaphragm and pleural effusion.9  Westmark’s sign (peripheral oligemia) and Hampton’s hump (pleural wedge-based density) are classically described in PE, but occur in less than 20% of patients with PE and have low sensitivity and specificity.10

CTA – indicated if your patient has a high probabilty or is a low or indeterminate risk patient with a positive D-dimer. CTA has a false negative rate of 15-20%, even with multidetector scanners.11 Subsegmental PE’s are most likely to be missed, and it has been debated if these subsegmental PE’s are clinically relevant.12

V/Q scan – performed if your patient has a contra-indication to CTA. Results will be reported as low, intermediate or high probability of PE. If your patient has a high pretest probability and a high-probability V/Q scan a PE is reliably diagnosed. It is more complicated if your patient has a low or intermediate risk. The American College of Emergency Physicians has attempted to help you out here by leaving their recommendations.13 They state that if your patient has a low or intermediate risk of PE and has a non diagnostic V/Q, a negative D-dimer or a bilateral venous ultrasonographic scan will exclude a clinically significant PE. In low risk patients a single bilateral venous ultrasound will suffice, if your patient has an intermediate risk serial ultrasound scans are indicated.

Echocardiography – echo may reveal right ventricular dilatation, decreased ventricular wall contractility or ventricular filling if your patient has a (sub)massive PE. Worry about your patient if you find that their right ventricle is dilated, as that is a predictor of poor early outcome. A dilated right ventricle will also help you with decision making regarding thrombolytics (see below).14

Venous compression ultrasonography – use if your patient is pregnant and has an elevated D-dimer and you worry about the radiation risk.15 It can also be used in patients with a intermediate to high clinical risk of PE and a negative or inconclusive CTA or V/Q scan. In these intermediate to high risk patients it is necassary to repeat the US in 5 – 7 days to assess for clot progression.11

Is there a cure, doc?

Anticoagulation – indicated if your patient is hemodynamically stable. Start with low molecular weight heparin (LMWH) or unfractionated heparin. LMWH is just as effective as unfractionated heparin.11 Monitor partial thromboplastin. Recent studies support the initiation of oral warfarin on day one. Contra-indications to anticoagulation include active bleeding, vascular trauma, drug sensitivity, recent major surgery, lumbar puncture, history of GI bleed, severe hypertension or bleeding tendencies.

Thrombolysis – only indicated in hemodynamically unstable patients, even though there is limited data that thrombolytics lead to improved mortality rates.11 There is no consensus on the use of thrombolytics in patient who are hemodynamically stable but have signs of right ventricular dilatation on echocardiography. Some data suggests that in hemodynamically stable patients with right ventricular dilatation on echocardiography might benefit from thrombolysis: your patient might have lower all cause mortality (if your patient is <75 years old), but at the cost of higher bleeding rates.16

Inferior vena cava filter – indicated if your patient has: a contraindication to anticoagulation, has had a complication from the use of anticoagulation or if they have failed to attain adequate anticoagulation while undergoing treatment.6

Surgical embolectomy – use is limited, ill defined indications, mostly used in critically ill with unsuccesful, prolonged resuscitation, high mortality rate.11

Congrats, you got your life vest, now dive into the FOAM:

Beginner

Intermediate

Advanced

References

1. Dr. Carol Rivers’ Preparing for the Written Board Exam in Emergency Medicine Paperback, 6th edition (2011) Ohio Chapter, American College of Emergency Physicians.

2. The PIOPED Investigators. Value of the ventilation/perfusion scan in acute pulmonary embolism diagnosis. Results of the prospective investigation of pulmonary embolism diagnosis (PIOPED). JAMA. 1990;263:2753-2759.

3. Wells PS, Anderson DR, Rodger M, et al. Derivation of a simple clinical model to categorize patients probability of pulmonary embolism: Increasing the models utility with the SimpliRED d-dimer. Thromb Hamemost. 2000;83(3):416-420.

4. Kline JA, Courtney DM, Kabrhel C, et al. Propsective multicenter evaluation of the pulmonary embolism rule-out criteria. J Thromb Haemost. 2008;6(5):722-780.

5. BestBets “Diagnostic utility of ECG for diagnosing pulmonary embolism.”

6. Rogers RL, Winters M, Mayo D. Pulmonary Embolism: Remember That Patient You Saw Last Night? Emergency Medicine Practice 2004 Jun;6(6):1-20.

7. Stein PD, Terrin ML, Hales CA, et al. Clinical, laboratory, roentgenographic and electrocardiographic findings in patients with acute pulmonary embolism and no pre-existing cardiac or pulmonary disease. Chest 1991;100(3):537-543.

8. Wells PS, Anderson DR, Rodger M, et al. Excluding pulmonary embolism at the bedside without diagnostic imaging: management of patients with suspected pulmonary embolism presenting to the emergency department by using a simple clinical model and d-dimer. Ann Intern Med. 2001 Jul 17;135(2):98-107

9. Elliott CG, Goldhaber SZ, Visani L, et al. Chest radiographs in acute pulmonary embolism. Results from the International Cooperative Pulmonary Embolsim Registry. Chest 2000; 118 (1): 33-38.

10. Worsley DF, Alavi A, Aronchick JM, et al. Chest radiographic findings in patients with acute pulmonary embolism: observations from the PIOPED Study. Radiology 1993 Oct;189(1):133-136.

11. Church A, Matthew T. The Emergency Medicine Approach To THe Evaluation And Treatment of Pulmonary Embolism. Emergency Medicine Practice Dec 2012;14(12):1-24.

12. Carrier M, Righini M, Wells PS, et al. Subsegmental pulmonary embolism diagnosed by computed tomography: incidence and clinical implications. A systematic review and meta-analysis of the management outcome studies. J Thromb Haemost. 2010;8(8):1716-1722

13. American College of Emergency Physicians Clinical Policies Committee; Clinical Policies Committee Subcommittee on Suspected Pulmonary Embolism. Clinical policy: critical issues in the evaluation and management of adult patients presenting with suspected pulmonary embolism. Ann Emerg Med 2003 Feb;41(2):257-270

14. Ten Wolde M, Sohne M, Quak E, et al. Prognostic value of echcardiographically assesed right ventricular dysfunction in patients with pulmonary embolism. Arch Intern Med. 2004;164:1685-1689.

15. Wang PI, Chong ST, Kielar AZ, et al. Imaging of pregnant and lactating patient: Part 2, evidence based review and recommendations. AJR Am J Roentgenol. 2012;198(4):785-792.

16. Chatterjee S, Chakraborty A, Weinbert I, et al. Thrombolysis for pulmonary embolism and risk of all-cause mortality, major bleeding, and intracranial hemorrhage: a meta-analysis. Jama. 2014 Jun 18;311(23)2414-2421

 

Written by: Maite Huis in ‘t Veld, M.D. | Peer reviewed by: Michael Bond, M.D. | August 4th, 2014

 

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