Abstract
The hemodynamic and geometric factors leading to propagation of acute Type B dissections are poorly understood. The objective is to elucidate whether geometric and hemodynamic parameters increase the predilection for aortic dissection propagation. A pulse duplicator set-up was used on porcine aorta with a single entry tear. Mean pressures of 100 and 180 mmHg were used, with pulse pressures ranging from 40 to 200 mmHg. The propagation for varying geometric conditions (%circumference of the entry tear: 15–65%, axial length: 0.5–3.2 cm) were tested for two flap thicknesses (1/3rd and 2/3rd of the thickness of vessel wall, respectively). To assess the effect of pulse and mean pressure on flap dynamics, the %true lumen (TL) cross-sectional area of the entry tear were compared. The % circumference for propagation of thin flap (47 ± 1%) was not significantly different (p = 0.14) from thick flap (44 ± 2%). On the contrary, the axial length of propagation for thin flap (2.57 ± 0.15 cm) was significantly different (p < 0.05) from the thick flap (1.56 ± 0.10 cm). TL compression was observed during systolic phase. For a fixed geometry of entry tear (%circumference = 39 ± 2%; axial length = 1.43 ± 0.13 cm), mean pressure did not have significant (p = 0.84) effect on flap movement. Increase in pulse pressure resulted in a significant change (p = 0.02) in %TL area (52 ± 4%). The energy acting on the false lumen immediately before propagation was calculated as 75 ± 9 J/m2 and was fairly uniform across different specimens. Pulse pressure had a significant effect on the flap movement in contrast to mean pressure. Hence, mitigation of pulse pressure and restriction of flap movement may be beneficial in patients with type B acute dissections.
Highlights
Aortic dissection is a life-threatening disease with an incidence of 3.5–14 cases per 100,000 persons per year.[3,18,23,26]. It is characterized by a tear in the intimamedia, where blood enters the layers of the aortic wall to create a false channel, known as the false lumen (FL) in addition to normal endothelialized channel known as the true lumen (TL)
The relation between %circumferential length of entry tear, and axial length of the flap for a thick flap and thin flap are presented in Figs. 4a and 4b, respectively
Flap propagation was dependent upon initial geometry of the entry tear for both the thick and thin flaps
Summary
Aortic dissection is a life-threatening disease with an incidence of 3.5–14 cases per 100,000 persons per year.[3,18,23,26] It is characterized by a tear in the intimamedia, where blood enters the layers of the aortic wall to create a false channel, known as the false lumen (FL) in addition to normal endothelialized channel known as the true lumen (TL). This article is published with open access at Springerlink.com section models[4,29,34] on isolated porcine and human aortas reported mean propagation pressures in nonphysiological ranges (197–579 mmHg). These studies used hydrostatic rather than pulsatile pressure, to propagate the dissection. We hypothesize that the hemodynamic (e.g., pulse pressure) and geometric (e.g., degree of circumferential and axial dissection as well as the depth of dissection) parameters affect the propensity to propagation of dissection To test these hypotheses, a pulsatile flow-loop was created with porcine aorta in a simulated type B dissection. The vessel preparation was finalized by removing any loose adventitial tissue and ligating the major branches of the aorta with silk suture
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