Dr. Monish Raut discusses key excerpts from the 2019 European Society of Cardiology (ESC) guidelines on the treatment of acute phase of pulmonary embolism (PE).

The recent pulmonary embolism guidelines 2019 by European Society of Cardiology (ESC) helps clinicians in decision making while using their judgement. The salient features of treatment in the acute phase of pulmonary embolism are briefly discussed here.

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Haemodynamics and respiratory stabilisation

Mismatch between perfusion and ventilation in severe pulmonary embolism leads to hypoxaemia. Administration of conventional oxygen supplementation should be used in such patients with oximetry saturation <90%. If not improving, high-flow nasal cannula oxygenation can help.

In patients with severe hypoxaemia, refractory to oxygen supplementation, possibility of right-to-left shunt through atrial septal defect or patent foramen ovale should be suspected.

Mechanical ventilation should be considered in patients with extreme haemodynamic instability. However it should be kept in mind that oxygen saturation would not improve without pulmonary reperfusion. Anaesthesia induction, intubation, and positive-pressure ventilation can be deleterious in patients with right ventricular failure exacerbating hypotension. Tidal volumes of about 6 mL/kg keeping end-inspiratory plateau pressure <30 cm H₂O should be used. Avoid anaesthesia drugs that are prone to decrease blood pressure.

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Management of acute right ventricular (RV) failure

In patients with high-risk pulmonary embolism, acute RV failure is the most important cause of mortality.

Even short term use can be associated with high incidence of complications e.g. increased risk of bleeding. Recent case reports have suggested improved outcomes after using Impella® catheter in patients with acute PE induced shock. Cardiopulmonary resuscitation with advanced life support should be used in cardiac arrest caused by acute PE.

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Anticoagulation therapy

Anticoagulation should be commenced in patients with high or intermediate clinical probability of PE.

Parenteral anticoagulation:

• Subcutaneous low-molecular weight Heparin (LMWH)
• SC Fondaparinux
• IV unfractionated Heparin (UFH)

Advantages of LMWH and Fondaparinux include not having to monitor anti-Xa levels and lower risk of major bleeding and heparin-induced thrombocytopenia.

Unfractionated heparin is mainly preferred in patients with decompensated haemodynamics, or severe kidney dysfunction (creatinine clearance below 30 ml/min) or morbid obesity. Activated partial thromboplastin time guides the dosing of unfractionated heparin .

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Non-vitamin K antagonist oral anticoagulants (NOACs): Dabigatran, apixaban, edoxaban, and rivaroxaban

Dabigatran directly inhibits thrombin and apixaban, edoxaban, and rivaroxaban inhibit factor Xa. The advantages include:

• Predictable bioavailability and pharmacokinetics
• Fixed-dose regimen without routine laboratory monitoring
• Fewer drug interactions as compared with VKA.

NOACs have been found equally efficacious as the combination of LMWH with VKA in phase III trials on the treatment of acute venous thromboembolism. NOACs have demonstrated significantly decreased incidence of major bleeding.

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Vitamin K antagonists (VKAs)

Vitamin K antagonists have been the age-old, gold-standard and time-tested oral anticoagulation therapies. As the desired clinical effect of VKAs is observed after a substantial time period. It is always preferred to continue anticoagulation with parenteral anticoagulation such as LMWH or UFH along with VKAs for more than 5 days until the international normalised ratio (INR) value is 2.0 to 3.0 for 2 consecutive days.

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Reperfusion treatment

Systemic thrombolysis is effective if started within 48 hours of symptom onset. Patients with symptoms for 6 to 14 days can still be benefitted with thrombolysis. The contraindications include:

• Active bleeding
• Major trauma, surgery, or head injury in the previous 3 weeks
• Central nervous system neoplasm
• Ischaemic stroke in the previous 6 months
• History of haemorrhagic stroke
• Bleeding disorders

Significant decrease in the combined outcome of mortality and recurrent pulmonary embolism have been demonstrated in a meta-analysis of thrombolysis trials. Recombinant tissue-type plasminogen activator (RTPA- 100 mg over 2 hours) is recommended for intravenous administration for thrombolysis. It is preferable to extend infusions of 1st generation thrombolytic agents such as urokinase and streptokinase. Unfractionated Heparin (UFH) should not be continued during infusion of urokinase or streptokinase, however it can be administered during continuous infusion of RTPA. The impact of early thrombolysis for acute PE on clinical symptoms and chronic thromboembolic pulmonary hypertension (CTEPH) at follow-up is still not clear.

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Percutaneous catheter-directed treatment

This involves the insertion of a catheter into the pulmonary arteries through femoral artery and catheter-guided thrombus aspiration, mechanical fragmentation route or in situ reduced-dose thrombolysis. Although procedural success rate has been reported approximately 87% in some studies comprising small number of patients, data from randomised control trials are still lacking on clinical efficacy outcomes.

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Surgical embolectomy

Surgical embolectomy in acute PE is generally performed with cardiopulmonary bypass without cardioplegic cardiac arrest. Clots are removed after incision of the two main pulmonary arteries. Combined extracorporeal membrane oxygenation (ECMO) with surgical embolectomy has been recently reported in patients with high risk pulmonary embolism with or without the need for cardiopulmonary resuscitation.

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Multidisciplinary pulmonary embolism teams

Recent guideline encourages the formation of pulmonary embolism response teams (PERTs). It constitutes specialists from different clinical areas such as, pulmonology, cardiology, haematology, anaesthesiology, vascular medicine, intensive care, interventional radiology and cardiothoracic surgery. Such teams are useful in making appropriate clinical decisions.

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Vena cava filters

A vena cava filter placed inside the inferior vena cava aims to prevent dislodged venous clots reaching the pulmonary circulation. It is broadly indicated in patients with recent proximal deep venous thrombosis and absolute contraindications to anticoagulation therapy with anticipated high risk of recurrent pulmonary embolism.

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To read Dr. Monish Raut's other article on acute PE diagnosis and risk assessment, click here.

Disclaimer- The views and opinions expressed in this article are those of the author's and do not necessarily reflect the official policy or position of M3 India.

The author, Dr. Monish S Raut is a Consultant in Cardiothoracic Vascular Anaesthesiology. His area of expertise is perioperative management and echocardiography with numerous publications in various national and international indexed journals.