Aortic aneurysms represent the most common and dangerous aortic diseases. Although conventional aortic repair techniques cure the disease, there is a high risk of paraplegia particularly in extensive thoracoabdominal aneurysms due to impaired blood supply to the spinal cord.

The PAPA-ARTiS trial will assess the clinical safety and efficacy of the MISACE (Minimally-Invasive Segmental Artery Coil-Embolization) procedure, a novel therapeutic concept to reduce the risk of paraplegia due to aneurysm repair.

The study investigates the MISACE procedure as a potential pre-treatment prior to open or endovascular aneurysm repair in patients with thoracoabdominal aortic aneurysms. Patients will be randomized to one of the two treatment strategies: a) aneurysm repair without MISACE pre-treatment, or b) aneurysm repair with MISACE pre-treatment.

Chronic aortic aneurysms are permanent and localized dilations of the aorta that remain asymptomatic for long periods of time, but continue to increase in diameter before they eventually rupture. Left untreated, the patients' prognosis is dismal, since the internal bleeding of the rupture brings about sudden death. Although successful treatment cures the disease, the risky procedures compromise spinal cord blood supply acutely and permanently, frequently leading to paraplegia, particularly for aneurysms involving crucial segmental arteries, i.e. thoracoabdominal aortic aneurysms of Crawford type II & III. Although various strategies have achieved a remarkable decrease in the incidence of paraplegia, it is still no less than 10-20%.

However, it has recently been found that the deliberate staged occlusion of the segmental arteries to the paraspinous collateral network finally supplying the spinal cord can trigger arterial collateralization, thus stabilizing blood supply from alternate inflow sources and preventing ischaemia.

This has been translated to a clinically available therapeutic option, 'minimally invasive staged segmental artery coil embolization' (MISACE), which proceeds in a 'staged' manner to occlude groups of arteries under highly controlled conditions, after which time must be allowed for arteriogenesis to build a robust collateral blood supply.

PAPA-ARTiS is a multi-national, prospective, open-label, two-arm, randomized controlled trial to demonstrate, that a minimally invasive staged treatment approach can reduce paraplegia and mortality in patients undergoing thoracoabdominal aortic aneurysm (TAAA) repair.

Patients with planned aneurysm repair will be included in the study and will be randomized 1:1 in the control group or the MISACE-group. The control group receives treatment as per standard institutional protocol - open or endovascular repair without MISACE. In the MISACE-group, segmental arteries will be occluded in one to three sessions some weeks before the definite repair. Segmental arteries are occluded with coils or plugs.This induces arteriogenesis and the building of a robust collateral network ultimately supplying the spinal cord. During aneurysm repair, these new arteries provide an alternate blood supply to the spinal cord and thereby help prevent paraplegia.

Inclusion Criteria:

• TAAA, Crawford type II or III
• planned open or endovascular repair of aneurysm within four months
• ≥ 18 years old

Exclusion Criteria:

• complicated (sub-) acute type B aortic dissection
• ruptured and urgent aneurysm (emergencies)
• untreated aortic arch aneurysm
• bilaterally occluded iliac arteries or chronic total occlusion of left subclavian artery
• pre-operative neurological deficits or spinal cord dysfunction
• major untreated cardio-pulmonary disease
• life-expectancy of less than one year
• high risk for segmental artery embolism
• severe contrast agent allergy, severe reduction in glomerular filtration rate (CKD stage 4)
• expected lack of compliance
• pregnant or nursing women
• impaired thyroid function, if not under stable treatment
• women of child bearing potential without highly effective contraceptive measures
• current participation in other interventional clinical trial
• patients under legal supervision or guardianship
• patients placed in an institution by official or court order