Purpose Type A aortic dissection (TAAD) results in an intimal tear that redirects blood flow into the media, splitting the aorta into two channels – the true lumen (TL) and false lumen (FL). Following emergency surgical repair, 50% of patients will remain with a patent false lumen and chronically dissected descending aorta. This is associated with aortic expansion, reoperation and increased mortality. Inflammation and coagulopathy are associated with the pathogenesis of TAAD, with the latter proposed to be caused by the contact of blood with the non-endothelialised walls of the false lumen. We aimed to determine if preoperative coagulopathy a risk factor for postoperative false lumen thrombosis. Methodology We conducted a single-centre, retrospective, case-controlled study of patients with TAAD between January 1, 2015, and June 30, 2024. Patient demographics, preoperative characteristics, operative details, postoperative complications, and follow-up computed tomography scans at one year were compared between patients who presented with patent FL and thrombosed FL. Coagulopathy was evaluated using standard laboratory tests on admission, post-operatively, and discharge. Results Of 125 patients with TAAD, 64.8% (n=81) had patent FL and 35.2% (n=44) had thrombosed FL. Patent FL was associated with higher in-hospital (46.9% vs 4.8% p<0.05) and mid-term mortality (53.2% vs 9.1%, p<0.05), renal failure (12.5% vs 2.4 %, p=0.04) and gastrointestinal ischaemia (30.6% vs 7.5%, p<0.05) compared to the thrombosed FL group. Patients with patent FL had significantly higher preoperative (41.2 vs 33.3, p<0.05), postoperative day 1 (54 vs 40.4, p<0.05) and discharge (38.9 vs 35, p<0.05) APTT and lower levels of fibrinogen at discharge (5.1 vs 6.4 p<0.05). Conclusion TAAD patients with a patent FL have a higher risk of short and mid mortality, and post-operative morbidity. Development of a patent FL is associated with abnormalities in the coagulation cascade which represents a novel therapeutic target.