Friday, 3 October 2008

Pulmonary Embolism - A New Way To Look At An Old Problem

Dear Bloggers

The European Society of Cardiology has recently updated the guidelines for the diagnosis and treatment of pulmonary embolism (PE).

There has been much research in this field and there are now new ways to look at the severity of PE and with more defined criteria for therapeutics derived from studies on prognostic factors.

One area that has developed is with the use of cardiac biomarkers of severity which now include measuring the BNP and Troponin ( I or T ) in addition to measuring the D-Dimer. The BNP and especially Troponin levels give prognostic information and may help to guide treatment.

The guidelines make it more clear with regards to those patients who ultimately require thrombolysis / surgery based on their risk of early death in PE rather than by pure CT criteria. This is a major advance in the field of PE -- the guidance advises that even if PEs do not look 'massive', they can nevertheless still cause significant haemodynamic compromise and hence, such PEs should be regarded as potentially causing a high early mortality rate if they result in hypotension or shock.

Hence, the terms 'massive', 'submassive', 'catastrophic', 'minor' should probably no longer be used. It does not matter so much with regards to the anatomical shape, distribution or burden of the PEs on a scan, but more from the haemodynamic consequences of this disorder. The newer terminology of High Risk for early death and Non-High Risk are being adopted instead to replace the above misleading terms that are heavily dependent on imaging interpretation rather than how the PE actually affects the patient's cardiovascular system.

The European Society of Cardiology guidelines on PE are some 32 pages in length (including 400 references!!) and they are very detailed and complete. Moreover, they provide a template on how to effectively stratify patients at presentation and how to workup the patients according to specific algorithms.

If you wish to read the current guidelines, they can be downloaded from the European Society of Cardiology website here.

The major concern for me is in those patients who have a high risk PE score either via the Well's Score or Modified Geneva Score and have a negative scan for PE, but are nevertheless at high risk. The guidelines intonate that further investigations can be performed but do not go further to elucidate what these tests should be.

It is indeed worthwhile checking the D-Dimer, Troponin and BNP in such high risk patients and performing ultrasonography of the pelvic and lower limb veins. Remember that PE can occur from the deep veins of the upper limbs (Paget-Shroetter Syndrome) so a hunt for thrombosis of the upper limbs can sometimes be fruitful. Ventilation Perfusion (V/Q) scanning is less sensitive than that of multi-detector CT but in terms of those patients who have multiple subsegmental PEs which the CT scanner may not be able to pick up, this test might still be useful in the 5% of cases of CT negative - PE positive patients. Ultimately, despite extensive testing, the patient may still have PE and hence, it may be considered of greater benefit to treat than to withold therapy. Remember the risk of death from PE can be as high as 30-45% whereas the risk of a major bleed on warfarin is about 3%, at least a 10 times difference.

The other area of concern is in those patients who have a confirmed single subsegmental PE with a negative ultrasound scan of the deep veins. These patients are apparently at low risk of subsequent death. Do we anticoagulate such patients??

I think the answer to the above questions will only come with future studies.

I hope you enjoy the above guidelines as much as I did.

Have a great weekend!

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