Randomized Trial on Acutely Dissected Aorta Repair With Hemiarch Replacement With or Without Stent Implantation (RADAR Trial)

Project Objectives

1. To compare the occurrence of Distal Anastomosis New Entry (DANE) after conventional hemiarch replacement group (Hemiarch-C) and the hemiarch replacement plus AMDS implantation group (Hemiarch-AMDS).
2. To compare the rate of all-cause mortality and aortic related mortality (at 30 days, 3-6, 12 months follow-up) between the study groups
3. To compare the rate of patients who are free from the following Major Adverse Events (MAEs) (new permanent disabling stroke, new permanent (> 30 days) paraplegia or paraparesis, reintervention, all-cause mortality) (at 12 months follow-up)
4. To compare radiological outcomes in terms of the rate of stenosis in supra-aortic head vessels, increasing (≥ 5 mm), stable or decreasing (≥ 5 mm) in true lumen in in both groups (at 3-6, 12 months follow-up).
5. To compare the radiological outcomes in terms of obliterated, completely thrombosed, partially thrombosed, or patent false lumen at various segments of aorta in both groups (at 3-6, 12 months follow-up).Thoracic aortic aneurysms (TAAs) and their complications (i.e. dissection, rupture, etc.) cause more than 1400 hospital admissions and 300 deaths every year in Hong Kong. Acute aortic dissection involving the ascending thoracic aorta is a highly lethal surgical emergency that warrants immediate surgical intervention. It can be classified according to DeBakey classification (DeBakey Type I, II, or III). The ascending thoracic aorta is involved in DeBakey Type I and II aortic dissections. In DeBakey Type I (ATAD), the aortic arch and descending thoracic aorta are also involved in the dissection process, therefore conventional hemiarch replacement is only considered "palliative".

Data from international registries showed the mortality of surgically treated ATAD was around 17-26% and those with mal-perfusion had even higher mortality. A significant number of patients of ATAD after conventional hemiarch replacement still have a persistent pressurized false lumen and this is related to the presence of distal anastomotic new entry (DANE).The presence of DANE leads to persistent pulsatile flow and pressurization of the false lumen in 70% of cases after hemiarch replacement.The persistently patent FL will in turn cause mal-perfusion, the need for aortic re-intervention involving the aortic arch, and, most importantly, reduced long-term survival by up to 50%.

To avoid the occurrence of DANE and downstream aortic mal-perfusion, Bozso and colleagues advocated the use of a novel Ascyrus Medical Dissection Stent (AMDS; Artivion, Atlanta, Georgia, US) hybrid prosthesis which comprises a proximal sewing collar and a distal self-expanding nitinol un-covered stent. From a prospective trial utilizing AMDS in ATAD, the Dissected Aorta Repair Through Stent Implantation (DARTS) trial, by Boszo and colleagues, the positive remodeling of the aortic arch occurred in 100% of cases with complete obliteration or thrombosis of the false lumen in 74%. In their series of 47 patients, there was no DANE after the AMDS implantation.

Work done by the principal investigator's unit is a major referral center for acute and complex aortic disease in Hong Kong, with more than 100 cases of operated aortic cases and 200 aortic referrals each year. The investigator's unit also operated on an average of 40-50 cases of ATAD each year.