Abstract
Mortality during follow-up after acute Type B aortic dissection is substantial with aortic expansion observed in over 59% of the patients. Lumen pressure differential is considered a prime contributing factor for aortic dilation after propagation. The objective of the study was to evaluate the relationship between changes in vessel geometry with and without lumen pressure differential post propagation in an ex vivo porcine model with comparison with patient clinical data. A pulse duplicator system was utilized to propagate the dissection within descending thoracic porcine aortic vessels for set proximal (%circumference of the entry tear: 40%, axial length: 2 cm) and re-entry (50% of distal vessel circumference) tear geometry. Measurements of lumen pressure differential were made along with quantification of vessel geometry (n = 16). The magnitude of mean lumen pressure difference measured after propagation was low (~ 5 mmHg) with higher pressures measured in false lumen and as anticipated the pressure difference approached zero after the creation of distal re-entry tear. False lumen Dissection Ratio (FDR) defined as arc length of dissected wall divided by arc length of dissection flap, had mean value of 1.59 ± 0.01 at pressure of 120/80 mmHg post propagation with increasing values with increase in pulse pressure that was not rescued with the creation of distal re-entry tear (p < 0.01). An average FDR of 1.87 ± 0.27 was measured in patients with acute Type B dissection. Higher FDR value (FDR = 1 implies zero dissection) in the presence of distal re-entry tear demonstrates an acute change in vessel morphology in response to the dissection independent of local pressure changes challenges the re-apposition of the aortic wall.
Highlights
The current treatment for Type B dissection which always includes best medical, treatment, and eventually endovascular or surgical intervention or a combination of both, aims to stabilize the hemodynamics and restore blood flow to end organs, and reduce the risk of rupture
To systematically understand the spontaneous antegrade Type B dissection, we have recently shown the relationship between initial tear geometry and pulse pressure magnitude for initiation and propagation of dissection.[20]
The magnitude of the lumen pressure difference after propagation was consistent across the three spatial locations with mean value of 4.6 (2.1) mmHg with higher pressure measured within the false lumen (FL) (Fig. 3)
Summary
The current treatment for Type B dissection which always includes best medical, treatment, and eventually endovascular or surgical intervention or a combination of both, aims to stabilize the hemodynamics and restore blood flow to end organs, and reduce the risk of rupture. Mortality from Type B aortic dissection is substantial, varying between 10 and 29%24,29,32 with follow-up mortality rates approaching 1 in every 4 patients at 3 years.[34]. Aortic expansion during follow-up was reported in 59% of patients with average rate of 1.7 ± 0.7 mm/year.[5,13] Computed tomography show the acute enlargement of dissected aorta of almost 25% from its baseline.[23]. The criteria for repair of aneurysmal dissection are a diameter > 5.0 to 6.0 cm, or rapid expansion in a chronic aneurysmal dissection > 1 cm/year.[8,30] In a clinical study[27] performed across 101 patients with Type B acute dissection without complications, a maximum aortic diameter of > 4 cm and a patent false lumen during the acute phase served as important predictors for aortic enlargement in the chronic phase
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