Can pain on palpation rule out PE?

Presence of chest wall tenderness reduces the likelihood of PE but CANNOT be used to rule out the diagnosis (1)

Chest wall tenderness in the presence of a PE could be explained by:

• pulmonary infarct causes irritation and inflammation of the parietal pleura
• intercostal skin is also supplied cutaneous branches of the intercostal nerves that supply the parietal pleura
• palpation of the chest wall could theoretically:
  • a) apply pressure to the already inflamed and stretched parietal pleura
  • b) and/or put pressure on a hyperalgesic area of skin supplied by the same intercostal nerve

Can lack of desaturation on exercise rule out PE?

There is no published evidence to support the use of measuring oxygen saturations after exercise in diagnosing PE (2)

Pulmonary embolisms cause a range of abnormalities in gas exchange:

• V/Q mismatch
• Reduced arterial PO2
• Increased alveolar-arterial O2 tension gradient

With increasing exercise intensity arterial PO2 decreases.
Therefore theoretically a change to lung structure caused by PE would cause a greater drop in arterial PO2 on exercise.

BUT...there is currently no evidence for using this in our diagnostic workup for PE (2)

How do we diagnose PE?

Canterbury Hospital Health Pathways recommends:

ALL patients with suspected PE should have:

• their pre-test probability assessed using the Revised Geneva scoring system
• AND have blood taken for a D-dimer assessment

Patients with signs of right ventricular dysfunction should have:

• urgent investigations with a CTPA and/or echo, as they may benefit from thrombolytic therapy using the standard tPA protocol

Out of normal working hours, and if it is clinically safe to delay establishing the diagnosis, consider anticoagulation overnight and investigate the following morning.

The patient in the case had a Revised Geneva Score of 8 - intermediate risk - and a D dimer of 2050.

The patient was admitted to medicine and had a CTPA which showed an isolated subsegmental PE (ISSPE) in his right upper lobe.
He was commenced on warfarin and treated for his cellulitis.

To treat, or not to treat, that is the other question…

There is much discussion as to whether patients with an isolated subsegmental PE (ISSPE) should be treated with anticoagulation as the risk/benefit in this cohort is unclear (3)

Studies appear to show that people with ISSPE have:

• a lower rate of mortality, morbidity and recurrence than those with larger PE
• comparable outcomes between those receiving anticoagulation and those who are not
• in some studies the outcomes of those not treated are the same as those who have not had a PE

However, there is not currently enough evidence to stop treating ISSPE patients.

Andy Neil, Emergency Medicine Ireland and Ryan Radecki, EM Literature of Note have also discussed this subgroup of PE patients.

Massive PE

In this group it is not a question of whether to treat or not, but how aggressively to treat.

This diagnosis should be considered in patients with severely compromised oxygenation or haemodynamics without other clear cause. (4)

It’s the THROMBUS part of the 4Hs and 4Ts of reversible causes of cardiac arrest.
Patients often present with severe dyspnoea, chest pain or syncope.
They can have non-specific examination features, tachypnoea, tachycardia and hypotension
+/- symptoms of right ventricular failure (increased JVP, parasternal heave, ECG showing S1Q3T3)
T wave inversion in precordial leads indicates severe RV dysfunction.

Management of Massive PE

• ABC
• Supplemental O2, intubation if indicated
• Fluid/pressor support
• CTPA
• Thrombolysis
• Clot retrieval
• Consider IVC filter

Suspected PE in Pregnancy

PE should be considered in all pregnant patients who present with chest pain and/or dyspnoea.

• Wells score and Revised Geneva score are not validated in pregnancy
• CTPA should be avoided in pregnant women if possible due radiation risk to the developing breast and foetus.
• A perfusion-only scan may be undertaken instead, depending on the gestation.
• A normal D-dimer level makes the diagnosis of PE very unlikely, but there is discussion around what the normal values should be during each trimester.
• A chest X-ray involves minimal radiation to both mother and fetus.

Canterbury Hospital Health Pathways for Suspected PE in Pregnancy:

References

1) Chest wall tenderness: a useful discriminatory sign for PE? Hyun Choi 2003/2011, published in: Best Bets
2) Exercise induced oxygen desaturation as a rule out tool for acute pulmonary embolism? Hyun Choi 2015, published in: Best Bets
3) Do patients with a clinically suspected subsegmental pulmonary embolism need anticoagulation therapy? Chris Morgan, Hyun Choi 2015, published in: Best Bets
4) Massive Pulmonary embolism. Victor F Tapson MD 2005 from: UpToDate