Pulmonary Embolism

Clinical Spectrum of PE

1. Small PE causes pleuritic pain ± haemoptysis
2. Shortness of breath ± central chest discomfort in a hypoxaemic patient with normal CXR and acute right heart strain on ECG is classic presentation of a large PE
3. Many patients with PE do not fit neatly into these categories & as a result, PE is both overdiagnosed & underdiagnosed
4. Most patients with PE are nevertheless breathless and/or tachypnoeic >20/min. In the absence of these, symptoms are usually due to another cause
5. The differential diagnosis of pleuritic pain presenting acutely to medicine is PE, pneumonia, pneumothorax, rib fracture and musculoskeletal pain including costochondritis.
6. The differential diagnosis of acute onset central chest discomfort includes ACS, large PE and aortic dissection

Predictive Risk Scores

1. The 2 tier Wells score is the most commonly used score to evaluate for pulmonary embolism
2. Some physicians prefer the Revised Geneva score because of its objectivity, and because the Wells criteria assign a high score to the subjective ‘PE as likely as any other diagnosis’
3. If Wells ≤4 or revised Geneva ≤2 then request D-dimer.  If Wells >4 or revised Geneva >2 go straight to CTPA.
4. Consider ambulatory care for patients with low risk of PE – See Ambulatory Care Pathway for Clinical Suspicion PE  

Wells Score

Revised Geneva Score

1. As accurate as the Wells Score, and is less reliant on the experience of the doctor applying the rule

Pulmonary Embolism Rule Criteria (PERC)

1. Patients with PERC =0 and a low Wells Score (≤4) have a very low risk group of PE and may safely be discharged without further investigation for PE.
2. PERC =0 and Wells ≤4 means that fewer young people <50 years will have unnecessary D-dimers and CTPAs

Age adjusted D-dimer

1. D-dimer is a fibrin degradation product that reflects the degree of activation of the coagulation system.
2. The upper limit of the normal range for plasma D-dimer in Dumfries is 500ng/ml.
3. D-dimer rises with age which means that older patients will have unnecessary CTPAs if a single D-dimer threshold is used.
4. It has been shown that use of an age adjusted D-dimer in patients with low clinical risk (Wells ≤4, Revised Geneva ≤2) can reduce the number of unnecessary CTPAs without missing any PEs.
5. The upper limit of age adjusted D-dimer is 10x patient’s age for patients who are over 50 years eg upper limit for an 80 year old is 10×80 = 800

The ECG in Pulmonary Embolism

1. A number of ECG changes have been reported to occur more commonly in PE and when present usually reflect large clot load.
2. Up to 30% patients with PE will have normal ECGs ie wont even have a sinus tachycardia.
3. The most useful change when present is probably RV strain pattern which is recognised by simultaneous T wave inversion (TWI) in the inferior (II, III, avF) and right precordial leads (V1-4).
4. NB in ACS you may have TWI in VI-4 but it would be very unusual to have TWI in the inferior leads as well.
5. The ECG below shows both S1Q3T3 and RV strain pattern from a patient with a large PE

CT Pulmonary Angiogram

1. This is now the investigation of choice for suspected PE
2. Large clot load means embolisation of either the pulmonary trunk or main pulmonary arteries and embolisation of either the lobar arteries or remote branches.
3. Small clot load means embolization of the lobar arteries or remote branches only.
4. Clot load can also be estimated by determining the ratio of RV to LV diameter on CT, typically based on an RV/LV cut off ratio of 0.9.
5. A normal CTPA does not exclude a subsegmental PE, but the risk of a larger PE is so low that the British Thoracic Society say that there is no need to request VQ scan or to anticoagulate.
6. CTPA can be done out of hours for seriously ill patients in whom thrombolytic therapy would be indicated if exam positive – discuss with Consultant Radiologist on call.

VQ Scans

1. No longer investigation of choice but can be considered if patient has allergy to contrast.
2. Shouldn’t be done if patient has abnormal CXR, chronic cardiac or respiratory disease, as impossible to interpret.
3. Arrange by phoning Nuclear Medicine, Glasgow Royal, on 0141 211 4762 – will usually do scan same or following day. Patient will require to go to Glasgow with recent (within 12 hours) CXR.
4. Phone 0141 211 4762 for provisional report after 1600 hours. The options are:
   1. multiple mismatched defects indicating high probability PE
   2. normal lung scan which means PE effectively excluded
   3. indeterminate lung scan – the majority of reports

Other Investigations

1. Blood gases – look for hypoxaemia with normal PaCO₂. Normal PaO₂ does not exclude PE
2. Echo – first choice for cardiovascular collapse. PE Likely if RV dilatation present
3. Leg Ultrasound – an alternative to lung imaging in patients with clinical signs of DVT

Unprovoked PE

1. The concern here is that patients may have an underlying cancer.
2. The risk is not high but has led some to suggest patients with unprovoked PE should have CT chest abdo pelvis
3. Bear in mind that CTPA will show cancers that affect lung and liver (because the top half of the liver is included in the scan).
4. NICE make the following recommendations for patients with unprovoked PE:
   • review the medical history and baseline blood tests including FBC, renal and hepatic function
   • offer a physical examination for people who are not known to have cancer
   • do not offer further investigations for cancer unless they have relevant clinical symptoms or signs.

Patients with Very High D-dimer but CTPA negative for PE

1. The common causes of raised D-dimer are VTE and infection eg pneumonia
2. Less common but important not to miss are cancer and aortic dissection/aneurysm
3. In our experience there will be clues to a new diagnosis of cancer eg bony, liver or lung tumour on the CTPA
4. CTPA will also show evidence of aortic dissection/aneurysm which can then be confirmed by CT aortogram

Anticoagulation

1. DOACs are  treatment of choice for a first episode of VTE in Dumfries & Galloway.
2. DOACs are at least as effective and no more likely to cause bleeding when compared to warfarin for treatment of PE.
3. Apixaban can be used as a single-drug regimen without the need for an LMWH lead-in period and is preferred in Dumfries.
4. Edoxaban can also be used to treat PE but requires a 5 day lead in with LMWH.
5. Treatment of PE with apixaban may allow outpatient management of PE and be associated with a shorter LOS in hospital.
6. Warfarin remains a perfectly acceptable alternative and should be considered in prerference to a DOAC under certain circumstances. For more information see page on Treatment of VTE

Outpatient Management of PE

1. Patients with suspected PE should, where reasonably practical, undergo investigation on the same day of presentation to exclude a diagnosis of PE.
2. An alternative strategy of anti-coagulation followed by OP imaging within 24hours may be considered in patients with suspected PE, who have been deemed low risk and eligible for OP care.
3. All patients with confirmed acute PE or on an outpatient pathway for suspected acute PE should have their clinical risk determined by the simplified Pulmonary Embolism Severity Index (sPESI) for patients without cancer and by the Hestia criteria for patients with cancer
4. Only those with sPESI =0 or with no risk factors using the Hestia criteria are eligible for OP management
5. All patients managed via an outpatient PE pathway should be reviewed by a senior clinical decision-maker prior to going home.
6. All patients managed via an outpatient PE pathway should receive verbal and written information containing details of potential complications of the disease process, its treatment and a point of contact.
7. Patients undergoing outpatient management following diagnosis of an acute PE should have an initial review within 7 days of discharge. Subsequent follow-up by a senior clinician with a special interest in PE should take place within a formal pathway.

Simplified Pulmonary Embolism Severity Index (sPESI)

Hestia Criteria

PE and Cancer

1. Please visit Lothian Oncology Online Quality System (OOQS) for full information

Follow up

1. Provide patients with confirmed PE who are eligible for OP care with verbal and written information on the signs and symptoms of recurrence and complications such as bleeding.
2. Provide an appropriate point of contact in the event of complications or concerns, both in and out of hours.
3. Telephone patient or review face to face at least once during the first week after discharge to ensure therapeutic compliance along with the absence of complications. The ANPs will generally do this in Dumfries but important to make sure it happens
4. Thereafter refer patients with large clot load to the respiratory clinic for follow up
5. Follow up for patients with small clot load can safely be undertaken in primary care
6. Consider providing Patient Information Leaflet on PE [pdf]

Links

• Nice Clinical Guideline 158 – Venous thromboembolic diseases: diagnosis, management and thrombophilia testing – March 2020 [pdf]
• BTS Guideline for initial outpatient management of pulmonary embolism [pdf]
• Patients Who May be Suitable for Outpatient Management of PE [pdf]