Pulmonary Thromboendarterectomy for CTEPH

KEY LEARNING POINTS

Part 1

• CTEPH (Class 4 pulmonary hypertension) results from organised, non-resolving thromboembolic material in the pulmonary vasculature causing progressive right heart failure. Between 1 and 9% of patients with acute PE will develop CTEPH; approximately 30–50% have no recalled prior PE. New Zealand should be diagnosing approximately 20 new cases per year — currently only 4–7 are referred annually.

• Diagnosis requires three months of anticoagulation followed by confirmation of pre-capillary pulmonary hypertension (mean PA >20 mmHg, normal PCWP) on right heart catheter, with ventilation-perfusion mismatch on V/Q scan. V/Q scintigraphy remains the gold standard; dual-energy CT is emerging. There is almost always more surgical disease than imaging suggests.

• PTE surgery is the only potentially curative treatment for CTEPH. Medical therapy (riociguat — the only FDA-approved agent, a soluble guanylate cyclase stimulator) and balloon pulmonary angioplasty have important roles for non-surgical patients and as adjuncts, but surgery offers the best long-term survival for accessible disease.

• Patient selection requires expert MDT review. Auckland reviews all candidates at the Alfred Hospital MDT in Melbourne before local confirmation — a validated model for small-volume centres. The distinction between surgical (proximal/segmental) and non-surgical (sub-segmental) disease is critical but often imprecise, and there is always more surgical disease than initially apparent.

• Surgical technique uses bicaval cannulation, CPB, cooling to 18°C, and repeated deep DHCA (maximum 20 minutes per arrest, maximum three arrests). The dissection plane is the intima of the media. The operation requires efficiency and constant situational awareness of DHCA time.

• Primary pulmonary haemorrhage (from perforation of a segmental or sub-segmental artery) carries 50–60% mortality. Complete disease clearance is the primary determinant of long-term outcome. Auckland has invested in a camera system enabling remote mentoring during the arrest intervals to shorten the learning curve.

Part 2

• Risk stratification in PTE surgery is uniquely demanding: those with the most to gain (highest PVR, worst RV function) are at highest operative risk. The most important 90-day mortality predictors are PVR, cardiac index, mean PA pressure, 6-minute walk distance, and age. Approximately 60% of Auckland’s PTE patients have severe pre-operative RV dysfunction — a near-universal finding in this population, not a contraindication to surgery.

• DHCA is the standard technique for distal dissection. The PEACOG trial showed ACP offered no cognitive advantage over DHCA, and 15–20% of ACP patients required conversion to DHCA for inadequate visualisation — effectively confirming DHCA as the preferred approach.

• Neurological monitoring uses NIRS cerebral oximetry: time below 40% saturation correlates with injury and informs decisions to curtail arrest. Stroke remains the most significant morbidity; cumulative arrest time should be kept under 60 minutes. Pre-operative steroid administration (≥6–8 hours before surgery) is used in Auckland following major centre practice, but clinical benefit has not been demonstrated in RCTs.

• In severe pulmonary hypertension, right coronary artery perfusion reverses to a predominantly diastolic pattern — making diastolic systemic pressure the key determinant of RV perfusion. Induction must be cardio-stable: maintain systemic diastolic pressure, avoid hypoxia and hypercarbia, prevent tachycardia. The specific inotrope matters less than achieving the haemodynamic endpoint.

• Separation from bypass in PTE patients can produce the ‘pulmonary steal phenomenon’ — newly unobstructed pulmonary segments divert blood flow without effective gas exchange, causing hypoxia and reperfusion pulmonary oedema. Management requires gentle re-perfusion, controlled cardiac output, and avoidance of pulmonary vasodilators (which worsen the steal). Minimal inotrope use at separation has been associated with a 15% mortality reduction.

• Post-operative care requires early therapeutic anticoagulation (4–6 hours post-operatively), aggressive negative fluid balance, and heightened vigilance for two PTE-specific complications: pericardial effusion (occurring at substantially higher rates than in other cardiac surgery, regardless of drain dwell time) and subdural haematoma (under-recognised in this population).

Part 3

• The standard approach to PE management — anticoagulation for most, systemic thrombolysis only for haemodynamic collapse — rests substantially on a 1995 eight-patient study with significant methodological limitations. The last two years have produced more thrombectomy publications in PE than any preceding period, signalling a genuine shift in the evidence base.

• Systemic thrombolysis carries a 10% risk of major bleeding and approximately 3% risk of disabling intracranial haemorrhage, and is significantly more hazardous in patients over 75 (PEITHO data). The risk profile of PE thrombus (fibrin-rich, older clot with poor fibrinolytic substrate) differs materially from arterial thrombus in stroke or MI, making dose translation unreliable.

• Risk stratification has evolved from massive/submassive categories to the current ESC/ERS and AHA/ACC framework distinguishing high-risk, intermediate-high, intermediate-low, and low-risk PE. Catheter-directed mechanical thrombectomy now has Class 2B evidence for intermediate-high and high-risk groups; systemic thrombolysis has 1B evidence.

• The STORM-PE randomised trial of large-bore mechanical thrombectomy (Inari FlowTriever) versus anticoagulation demonstrated significant RV/LV ratio improvement and better 6-minute walk distance at 90 days with a good safety profile. PEERLESS (2024) showed large-bore thrombectomy reduced ICU admission compared with EKOS (ultrasound-assisted catheter-directed thrombolysis). PEERLESS 2 (1,200 patients, 1:1 randomisation) has completed recruitment and is expected to report by late 2026.

• Pulmonary embolism response teams (PERTs) — MDTs providing real-time guidance on PE management — improve outcomes even independently of increased interventional therapy, through structured decision-making. Dunedin’s PERT (122 consecutive cases, including high-risk patients taken for thrombectomy due to thrombolysis contraindications) achieved 30-day survival above 85% across an unselected population.

• Geographic isolation and limited interventional radiology resource are key constraints to equitable PE care in regional New Zealand. Reduced-dose systemic thrombolysis remains a viable bridge in rural hospitals. Regional PERT networking — shared imaging, video MDT — offers a scalable model for extending specialist decision-making without requiring physical co-location.