Welcome to a new season of TheCase.Report! We're kicking off Season 3 with a very special episode on VTE, ahead of the VTE Dublin Conference.

Deirdre is at the helm for this episode and is joined by Leah and Bibi.

Our Adult in the Room Dr Tomás Breslin brought along his colleagues Prof John Moriarty and Dr Cian McDermott to comment on the case.

And finally, Bibi sat down with Prof Fionnuala Ní Áinle and Dr Barry Kevane for our segment where they discuss VTE prophylaxis, Covid-19 and pulmonary embolism in pregnancy.

Many thanks once again to IAEM for supporting this podcast and making all of this possible.

The case

So, we’ve got a 35yr old lady who presented today with chest pain and shortness of breath. At triage she was a little tachycardic at 105bpm but otherwise her vitals were fine. She had Covid a few weeks ago, and takes the OCP. What’s the plan?

Chest pain differentials

Here we’ve got both the heart and the lungs to consider. Pericarditis, myocarditis, infection, and don’t forget musculoskeletal. In this patient, however, the Big Bad we need to consider is pulmonary embolus.

Well’s score

So sometimes, we have a low pre-test probability, but we are still concerned for PE. This is where we can use our pulmonary embolus rule out criteria (PERC).

The Pulmonary Embolism Rule Out Criteria (PERC)

The Pulmonary Embolism Rule Out Criteria (PERC) rule should only be applied in those with a low clinical probability of pulmonary embolism. If such a patient meets all eight criteria, the likelihood of PE is deemed to be low, and no further testing is needed.

If all of the criteria are met, and the wells score is low, we can confidently say that PE is not a consideration in this patient as the probability is <2 %.... So NO D-DIMER.

If though, PERC is (+), meaning one of the criteria are met, then we roll the DIMER DICE!

The Role of D-dimers

The negative predictive value of D-dimer testing is high – so a normal D-dimer means an acute PE or DVT is unlikely. BUT, the positive predictive value of elevated D-dimer levels is low, so we cannot confirm a PE based on its result.

So in low to intermediate risk patient, where the Wells is low, Perc (+) and Dimer is normal: you can safely exclude PE as cause of the patient’s symptoms. But if the Dimer is positive, you require a CTPA to confidently exclude a PE.

The current ESC guidelines recommend D-dimer cut-off values adjusted for age as an alternative to the fixed cut-off value. This is because the specificity of D-dimer in suspected PE decreases steadily with age to < 10% in patients >80 years of age, so age-adjusted cut-offs improves the outcome of D-dimer testing in the elderly.

So, Pulmonary Embolus. Let’s break it down.

Stable vs Unstable

Unstable patients are those with an acute high-risk PE and present either in cardiac arrest, obstructive shock or persistent hypotension. There is often a high index of suspicion for PE in these patients based either on POCUS or ECG – here we risk adapt and don’t waste time. If emergency CTPA is not possible, we treat for PE.

In the stable patient, we can use the Pulmonary Embolism Severity Index (PESI) (30 day mortality risk indicator) in combination with POCUS findings and troponin levels to stratify the patient’s mortality risk as low, intermediate or high - this will guide the level of care the patient needs (HDU, ICU) and alert us for the potential for the patient to deteriorate.

So, D-dimers are positive, Well’s score is high. Who ya gunna call?

The radiologist - it’s time for a CTPA

In an acute PE, CT pulmonary angiogram will show filling defects.

The role of POCUS

Acute PE can lead to right ventricular pressure overload and dysfunction. In other words…

Increasing afterload — increased RV wall tension — increased RV O2 demand — RV ischaemia — decreased RV output — decreased LV preload — decreased systolic BP.

An unstable patient with a high clinical probability of PE and signs of RV pressure overload with no other obvious cause justifies thrombolysis — whilst we are managing this BP, all other hands must be getting your thrombolytic agent of choice ready and making sure ICU are on the way!

Why thrombolysis?

In PE, the hypoxaemia is due to a V/Q mismatch. In these patients, we aim to be as non-invasive as possible. Remember, the intubation process can further drop the blood pressure, and PPV can reduce venous return.

If there’s a delay or failure to thrombolise successfully, the next step is to intubate. Get ICU/anaesthetics involved ASAP, choose drugs that won’t drop the blood pressure and know exactly how to set the ventilator to keep the TV low.

The impact of Covid

Covid presents quite the conundrum. The scoring tools we use to predict the probability of PE are not validated in Covid populations, so clinical judgement and senior input are heavily relied upon in these cases when deciding whether or not to proceed with diagnostic testing.

COVID-19 is a risk factor for VTE. Bottom line is, all patients with Covid-19 should be risk assessed for VTE, and they should all be prescribed some form of pharmacological thromboprophylaxis unless there are contraindications.

PERT model of care

There are huge complexities in the presentation and treatment options of PE. It’s not a one-size-fits-all diagnosis. The Pulmonary Embolism Response Team model comprises bringing together ED consultants, critical care, cardiology, respiratory, haematology etc for a rapid real-time discussion of the clinical scenario, competing risks, patients background and likelihood of VTE.

Having this broad senior level engagement is paramount so that a decision can be made balancing all these risks.

References and further reading

Well’s score: https://emed.ie/Haematology/Wells.php

Pulmonary Embolism Rule Out Criteria (PERC): https://www.uptodate.com/contents/image?imageKey=PULM%2F94941

ESC guidelines on diagnosis and management of acute PE: Stavros V. Konstantinides, Guy Meyer, et al., 2019 ESC Guidelines for the diagnosis and management of acute pulmonary embolism developed in collaboration with the European Respiratory Society (ERS), European Respiratory Journal 2019

Case courtesy of Dr Jeremy Jones: https://radiopaedia.org/cases/pulmonary-embolism-saddle-embolus?lang=gb

The Pulmonary Embolism Response Team Model: https://journals.sagepub.com/doi/full/10.1177/1076029619853037

Sensitivity, specificity, positive and negative predictive values: https://geekymedics.com/sensitivity-specificity-ppv-and-npv/

Prospective Trial on PE rule out criteria from 2008: Kline JA, Courtney DM, Kabrhel C, et al. Prospective multicenter evaluation of the pulmonary embolism rule-out criteria. J Thromb Haemost 2008; 6:772.

S3E1: VTE