Partial thrombosis of the false lumen in patients with acute type B aortic dissection

Abstract

Conclusion: After hospital discharge, patients with acute type B aortic dissection and partial thrombosis of the false lumen are at increased risk of death compared with patients with complete patency of the false lumen. Summary: The International Registry of Acute Aortic Dissection (IRAAD) tracks patients with acute aortic dissection at 22 aortic centers in 11 countries. This is a registry, and treatment during hospitalization is not standardized but is conducted at the discretion of each patient’s physician and institution. Patients with acute aortic type B dissection have low in-hospital mortality but survival rates after discharge range from 92% at 1 year to 48 to 82% at 5 years. It has been suggested that patients with complete thrombosis of the false lumen have improved outcomes compared with patients who have a patent false lumen, with the patent false lumen thought to place the patient at increased risk of aortic expansion and death (Am J Card 2001;87:1378-82). The authors sought to determine the influence on mortality of partial thrombosis of the false lumen. They defined partial thrombosis of the false lumen as both flow and thrombus present in the false lumen. Between 1996 and 2003, 201 patients with type B aortic dissection were enrolled in IRAAD and survived to discharge from the hospital. The authors developed mortality curves according to the status of the false lumen (complete thrombosis vs partial thrombosis vs patent). False lumen status was determined during the initial hospitalization. They used Cox proportional hazard analysis to identify independent predictors of death on follow-up. There were 114 patients (56.7%) who, during the index hospitalization, had a patent false lumen. Sixty-eight patients (33.8%) had partial thrombosis of the false lumen, and 19 (9.5%) had complete thrombosis of the false lumen. At 3 years, the mortality rate for patients with a patent false lumen was 13.7%. The mortality rate for patients with partial thrombosis of the false lumen was 31.6%, and mortality for those with complete thrombosis was 22.6% ± 22.6% (median follow-up, 2.8 years; P = .003, log-rank test). Postdischarge mortality was independently predicted by partial thrombosis of the false lumen (relative risk, 2.69; 95% confidence interval [CI], 1.45 to 4.98; P = .002), a history of atherosclerosis (relative risk, 1.87; 95% CI, 1.01 to 3.47; P < .05), and a history of aortic aneurysm (relative risk, 2.05; 95% CI, 1.07 to 3.93; P = .03). Comment: The authors postulate their findings may reflect that a patent false lumen is perfused by a proximal entry tear and then decompressed through re-entry tears distally. When thrombus partially occludes the lumen, these distal re-entry tears may be occluded, impeding outflow and leading to an increase in mean arterial and diastolic pressure that results in increased wall tension in the false lumen and increases the risk of aneurysm expansion, with increased risk of rupture and redissection.