[3] Due to the nature of the procedure, patients with significant hemodynamic or ventilation complications or impairments may be unable to undergo PTE.

PTEs involve a full cardiopulmonary bypass (CPB), deep hypothermia and cardioplegia (a crystalline fluid which stops the heart from beating).

Actual removal of the embolus is carried out in a standstill operation (deep hypothermia and periods of cessation of circulation).

Cardioplegia is initiated as the approach to the pulmonary arteries is performed through the pericardium, a fibrous sac surrounding the heart.

Furthermore, movement from the heart makes delicate work on the closely attached pulmonary arteries complex.

Hypothermia is necessary as the embolus is very delicate and the risk of disruption is high, in order to appropriately visualize the clot and remove it a bloodless field is required.

This is only feasible if the patient is hypothermic (cooled to 18–20 °C) as metabolism is slowed and the body can better tolerate the resulting lack of blood supply.

[4] There are emerging alternative options available that seek to limit neurologic complications resulting from hypothermia and circulatory arrest.

They include use of moderate hypothermia, antegrade cerebral artery perfusion without total circulatory arrest, and negative pressure application to the left ventricle.

[16] In the UK, PTE is offered only at one centre,[17] Royal Papworth Hospital,[18] led by surgeon Mr David Jenkins.

[21] The footage shows the patient's entire body being drained of blood and cooled to 20 degrees Celsius – half the normal temperature – in order to enable the surgery to occur.