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Information ⬇

Author(s): Roshan Navin and Kevin O'Kane

Consider pulmonary embolism in any patient with:

One or more predisposing factors for venous thromboembolism (Table 56.1) are present in most patients, but only 15% have clinical evidence of deep vein thrombosis (DVT).

The clinical classification of the severity of acute pulmonary embolism is based on the clinical status at presentation, with high-risk pulmonary embolism defined by the presence of shock or persistent hypotension: this determines management (Figures 57.1 and 57.2).

Suspected pulmonary embolism with shock or persistent hypotension (Figure 57.1)Suspected pulmonary embolism with shock or persistent hypotension (Figure 57.1)

 

Priorities ⬆ ⬇

Outline

  • If peri-arrest, call the resuscitation team (see Chapter 6 for further management of cardiorespiratory arrest).
  • Give high-flow oxygen. Place an IV cannula. Attach ECG and oxygen saturation monitors. Check oxygen saturation. Make a rapid clinical assessment (see Chapters 1 and 2). Clinical judgement supplemented by a prediction rule (Table 57.1) should be used to assess the probability of pulmonary embolism.
  • Obtain an ECG, chest X-ray and arterial blood gases. These are principally of value in excluding alternative diagnoses (e.g. myocardial infarction, severe pneumonia, tension pneumothorax).
    • In pulmonary embolism with shock/hypotension, the ECG may show evidence of right ventricular strain (right axis deviation, right bundle branch block, T wave inversion in V1–3).
    • The chest X-ray is often normal, or may show non-specific abnormalities (Table 57.2).
    • A normal ECG and chest X-ray do not exclude pulmonary embolism.
  • If pulmonary embolism is the working diagnosis or must be excluded, CT pulmonary angiography (CTPA) should be done if immediately available. If CTPA cannot be done immediately, echocardiography should be performed.
  • If pulmonary embolism is confirmed by CTPA, or is highly likely on echocardiography (Table 57.3), give systemic thrombolysis if no contraindication (Table 57.4). Surgical embolectomy or local endovascular thrombolysis (with unfractionated heparin infusion as a bridging measure) should be considered if systemic thrombolysis is contraindicated.
  • If systolic BP remains <90 mmHg, give dobutamine (2.5–10μgm/kg/min IV) aiming for systolic BP ≥90 mmHg. Consider adding noradrenaline if a systolic BP ≥90 mmHg (mean arterial pressure >65 mmHg) is still not achieved.
  • Transfer the patient to ICU or HDU. Mechanical ventilatory support may be required. Pulmonary vasodilators such as inhaled nitric oxide or nebulized iloprost may have a role (though available data are limited).
  • Further management (anticoagulation, investigation for cause of pulmonary embolism) is given below.
Suspected pulmonary embolism without shock or hypotension (Figure 57.2)Suspected pulmonary embolism without shock or hypotension (Figure 57.2)

 

Review the physiological observations and make a focused clinical assessment. Obtain an ECG and chest X-ray (and arterial blood gases if arterial oxygen saturation is <94% breathing air. In pulmonary embolism without shock or hypotension, the ECG may be normal or show only sinus tachycardia or minor ST/T wave abnormalities. The chest X-ray is often normal or may show non-specific abnormalities (Table 57.2). A normal ECG and chest X-ray do not exclude pulmonary embolism.

Assess the probability of pulmonary embolism, using clinical judgement supplemented by a prediction rule (Table 57.1).

If Pulmonary Embolism is Clinically Unlikely!!navigator!!

Check the plasma D-dimer. The commonly used assays have high sensitivity (95%) but only low specificity (50%) for venous thromboembolism; the normal range will depend on the assay. Plasma D-dimer levels increase with age. Causes of a raised plasma D-dimer other than venous thromboembolism include renal failure, aortic dissection, infection and malignancy.

  • If plasma D-dimer is negative, pulmonary embolism is effectively excluded. A negative D-dimer test in a patient with a modified Wells score of <4 makes PE highly unlikely (0.14–0.5% probability); the negative predictive value of this combination is at least 99.5% and comparable to the most sensitive imaging such as CT pulmonary angiography. Pursue other diagnoses.
  • If this is positive, request CT pulmonary angiography or ventilation/perfusion (V/Q) scan (see below). If this is negative for pulmonary embolism, pursue other diagnoses. If positive for pulmonary embolism, start anticoagulation (see below).

If Pulmonary Embolism is Likely!!navigator!!

  • Request CT pulmonary angiography (CTPA), or alternative imaging if indicated (see below).
  • If imaging is negative for pulmonary embolis/deep vein thrombosis, pursue other diagnoses. If positive for pulmonary embolism, start anticoagulation (see below).
  • Thrombolysis may be indicated for some patients with sub-massive pulmonary embolism (defined as acute PE without systemic hypotension (systolic blood pressure >90 mmHg) but with either right ventricular dysfunction or myocardial necrosis): see Problems below.

Alternatives to CT Pulmonary Angiography!!navigator!!

CT pulmonary angiography (CTPA) is the investigation of choice if the chest X-ray is abnormal, or there is underlying respiratory disease (including chronic obstructive pulmonary disease (COPD) and asthma). It also gives information on lung parenchyma, aorta, mediastinum, pleural spaces, bones and chest wall, and can reveal alternative diagnoses if PE is excluded. It carries considerably higher radiation exposure than a V/Q scan.

Ventilation/perfusion scan (V/Q scan)

A ventilation/perfusion scan (V/Q scan) is the investigation of choice if the chest X-ray is normal, and there is no underlying respiratory disease such as COPD or asthma. It is also preferable to CTPA in renal failure or previous contrast reaction.

A normal perfusion (Q) scan or ventilation/perfusion (V/Q) scan excludes pulmonary embolism if pulmonary embolism is unlikely on clinical grounds.

A ‘high-probability’ scan confirms the diagnosis if pulmonary embolism is likely on clinical grounds.

Further diagnostic testing is needed if the scan shows a low or intermediate probability result, or if the scan findings and clinical probability are discordant.

Duplex scan of leg veins

Duplex scan of the leg veins is the first imaging of choice in pregnancy for suspected pulmonary embolism without shock or hypotension, as a positive finding eliminates the need for investigation involving radiation. See Problems below.

Further Management ⬆ ⬇

Outline

Anticoagulation!!navigator!!

Anticoagulation is discussed in detail in Chapter 103. Anticoagulation for pulmonary embolism can be with rivaroxaban, heparin or warfarin (preceded by and overlapping with heparin).

Rivaroxaban

Rivaroxaban (a direct factor Xa inhibitor) is licensed in the UK for the treatment of pulmonary embolism (without the need for adjunctive heparin).

Rivaroxaban is contraindicated in pregnancy, breastfeeding, renal failure, significant liver disease, concomitant use of cytochrome P-450 inhibitors, and is not currently recommended in patients with active cancer.

Low-molecular-weight heparin (LMWH)

LMWH is indicated in patients with active cancer (particularly if undergoing chemotherapy) or who are pregnant.

Unfractionated heparin

Unfractionated heparin by infusion (UFH) should be used if there is:

  • Renal failure (eGFR <30 mL/min)
  • Increased risk of bleeding
  • Peri-operative state
  • Peri-partum state

Warfarin

Warfarin should be used if rivaroxaban is contraindicated and in the absence of active cancer or pregnancy.

  • Warfarin loading is given in Table 103.11.
  • It is initially pro-thrombotic, so is co-administered with LMWH or unfractionated heparin. During this period, check both the activated partial thromboplastin time (APTT) and International Normalized Ratio (INR) daily.
  • Heparin can be stopped after five days provided the INR is >2.0.
  • The target INR is usually 2.0–3.0.

Duration of anticoagulation

In provoked PE (those with a transient, reversible risk factor), treatment is usually for three months. In unprovoked PE, treatment is usually extended for as long as the underlying risk factor (if identified) is present. If no cause is identified, treatment duration is determined on a case-by-case basis: seek advice from a haematologist.

Ambulatory care, discharge planning and follow-up

  • Ambulatory care and outpatient management of patients with low-risk pulmonary embolism is possible. The Pulmonary Embolism Severity Index (PESI) (Table 57.5) score is the most widely validated and used prognostic model for PE, to guide the initial decision to admit to hospital or discharge.
  • Serial/repeat PESI scoring can guide the subsequent timing of safe discharge if originally admitted.
  • A robust system of communication, support and follow-up is required for the ambulatory care approach to be successful.

Why has the patient had a pulmonary embolism?

  • Consider the presence of risk factors (Table 56.1). In many patients, the cause of pulmonary embolism is obvious. Further tests for patients with unprovoked DVT/PE are given in Table 56.3.
  • Patients under 50 with unprovoked DVT/PE or with a strong family history of venous thromboembolism should be screened for a thrombophilic disorder: seek advice from a haematologist.

Problems!!navigator!!

Sub-massive pulmonary embolism

Sub-massive PE is characterized by:

  • Right ventricular (RV) dysfunction (RV dilatation on echo, or raised plasma BNP/NT-pro-BNP)
  • Myocardial necrosis (raised plasma troponin)
  • Worsening hypoxaemia and respiratory insufficiency
  • Extreme tachycardia
  • High clot burden

If sub-massive PE suspected, there may be a role for half-dose thrombolysis. Seek expert advice. The incidence of longer-term complications such as chronic thromboembolic pulmonary hypertension (CTEPH) may be reduced by using this strategy.

Currently, the judgement on thrombolysis in sub-massive PE should be individualised and based on local guidelines or specialist advice. It is not generally recommended for those patients with only minor RV dysfunction or myocardial necrosis, and no clinical deterioration. If there are no features of sub-massive PE, proceed with anticoagulation, p. 563.

Suspected pulmonary embolism in pregnancy

  • The differential diagnoses of breathlessness, chest pain and shock in pregnancy are discussed in Chapter 32.
  • PE is the leading cause of maternal death in the UK, with a mortality rate of 1.56 per 100,000 pregnancies.
  • The risk of undiagnosed maternal PE to a mother and her fetus far outweighs any risk from radiation exposure through diagnostic imaging. The commonly used tests are not associated with high levels of radiation.
  • D-dimer is negative in up to 50% of pregnant patients up to 20 weeks gestation and should be the first test of choice. If D-dimer is negative, the patient is highly unlikely to have a PE, and alternative diagnoses should be sought.
  • If D-dimer is positive, duplex scan of both leg veins should be performed, as confirming the presence of DVT will instigate the same treatment regimen of LMWH as in non-massive PE. If no DVT is found, but there is ongoing suspicion of PE, then a half-dose perfusion (Q) scan, following a (normal) chest X-ray, is the imaging modality of choice and carries a lower maternal radiation exposure than CTPA.
  • If the clinical presentation is with shock or hypotension, and echocardiography shows features of massive pulmonary embolism (Table 57.3), CTPA is not necessary.

When to consider placement of an inferior vena cava (IVC) filter

IVC filter use is generally limited to patients in whom anticoagulation is contraindicated, thrombosis has recurred despite adequate anticoagulation, or if temporary cessation of anticoagulation within one month is anticipated, for example in pregnant patients within one month of the expected date of delivery.

Further Reading ⬆

Kearon C, Akl EA, Ornelas J, et al. (2016) Antithrombotic therapy for VTE disease: CHEST guideline and expert panel report. Chest 149, 315–352.

Raja AS, Greenberg JO, Qaseem A, et al. (2015) Evaluation of patients with suspected acute pulmonary embolism: best practice advice from the Clinical Guidelines Committee of the American College of Physicians. Ann Intern Med . 163, 701–711.

The Task Force for the Diagnosis and Management of Acute Pulmonary Embolism of the European Society of Cardiology (ESC) (2014) 2014 ESC Guidelines on the diagnosis and management of acute pulmonary embolism. http://eurheartj.oxfordjournals.org/content/early/2014/08/28/eurheartj.ehu283