4.2 Entry tear
Entry tears are to be considered based on their size, whether they are located at the outer (convexity) or inner (concavity) circumference of the distal aortic arch, and their proximity to the LSA. Entry tears >10mm have been shown to have a greater aortic growth rate and incidence of dissection-related complications (HR = 5.8) than patients with an entry tear of < 10mm (16). Intuitively, larger entry tears mean more blood flow in the FL (discussed later) which is a well-documented predictor of wall growth (12-14, 18, 24, 25). A single entry tear produces a more pressurised avenue than multiple tears for blood which accelerates aortic growth (21). Specifically, patients with one entry tear showed an aortic growth rate of 5.6 ± 8.9mm/year versus those with two tears (2.1± 1.7 mm/year) and three tears (2.2 ± 4.1 mm/year) (21). The actual mechanism for this finding is misunderstood, although a haemodynamic ex-vivo study suggested that inner tears (IT) (Fig. 2A ) cause significant elevation of the diastolic pressure (DP) in the FL (26).
Greater FL volumes are more likely to retrogradely propagate and manifest as acute coTBAD. Literature suggests that this manifestation is more common with ITs (Fig. 2A ) than outer tears (OT) (Fig. 2B ) (21, 26-29). Loewe et. al (27) reported 61% (IT; n = 23) vs 21% (OT; n = 42) incidences of primary coTBAD (p = 0.003). Tolenaar et. al (21) similarly compared differences in aortic growth rates. Growth rates in the IT group (n = 53) was 4.6 ± 9.6 (SD) mm/yr versus 2.9 ± 5.1 mm/yr in the OT group (n = 187) (21). Nonetheless, OTs appear to be of particular risk when within 5cm of the LSA based on the likelihood of forming an additional false lumen (30). Patients with 1 entry tear located within 5 cm of the LSA showed significantly more growth than their counterparts (5.8 ± 7.7 versus 2.5 ± 2.7 mm/yr; p = 0.003) (30). LSA coverage is a significant independent risk factor for dissection related death (HR = 5.6) (25) and more recently, for failing OMT (16, 31). Codner et. al (31) showed that aortic growth (n = 72) versus non-aortic growth (n = 49) patients had their median entry tears respectively located 27mm [9 to 66 mm] versus 77mm [26 to 144 mm] from the LSA; 53% of the growth group required open surgical repair/TEVAR vs 0% in the non-growth group (31).