The VIRTUE Registry of Type B Thoracic Dissections – Study Design and Early Results

Preliminary findings in quantification of changes in septal motion during follow-up of type B aortic dissections

OBJECTIVE

To quantify longitudinal changes in intra-arterial septum (IS) motion with two-dimensional (2D) phase-contrast magnetic resonance imaging (2D pcMRI) in type B aortic dissections (AD) to improve the understanding of AD and its midterm development.

METHODS

From a database of 42 patients who underwent a dynamic magnetic resonance imaging (MRI) examination at the Acute Aortic Treatment Center of The Methodist DeBakey Heart & Vascular Center, 2D pcMRI image data was available from 10 patients with type B AD for both short-term (mean, 6.6 days; range, 1-10 days; n = 7) and midterm follow-up (mean, 155 days; range, 60-324; n = 5). IS motion was quantified as motion of IS boundary points averaged over the cardiac cycle. Relative change in IS motion was expressed as percent change compared with initial presentation. Maximum IS extension (true lumen [TL] expansion) and contraction (TL compression), IS fraction in phase with aortic flow and correlation of IS motion with aortic flow (IS compliance) were quantified.

RESULTS

IS motion at initial presentation was 0.68 ± 0.2 mm and was reduced at short-term (0.48 ± 0.3 mm; P = .07) and midterm (0.5 ± 0.2 mm; P = .1) follow-up. Trend in relative change of IS motion was variable during short-term follow-up: reduced in three subjects (-75% ± 6%) and elevated in four subjects (48% ± 23%). During midterm follow-up, relative change in IS motion was reduced in four subjects (28% ± 19%) and slightly elevated in one (6.2%). IS contraction decreased with follow-up while IS extension slightly increased. Fraction of IS moving in phase with aortic flow increased but IS compliance decreased, suggesting increasing IS stiffness.

CONCLUSIONS

Reduction of IS motion in AD is seen with short-term and midterm follow-up. Intersubject variability of this trend is high at short-term follow-up but low at midterm follow-up. Detailed analysis of IS motion parameters indicate reduction of IS contraction and IS compliance with time. This has potential implications for endovascular management of type B aortic dissections, as expansion of aortic stent grafts can be limited by a stiff IS.

Predictors of outcome after endovascular repair for chronic type B dissection

OBJECTIVES

To assess the durability of endovascular repair (TEVAR) in chronic type B dissection (CD) and identify factors predictive of outcome.

DESIGN

Retrospective analysis of a prospective database.

MATERIALS

Patients undergoing TEVAR for CD at a tertiary referral centre 2000-2010.

METHODS

Analysis of pre-operative characteristics, operative outcome, false lumen thrombosis, aortic diameter and survival.

RESULTS

58 consecutive patients were included (49 elective, 9 urgent, mean age 66 years). Mean aortic diameter was 6.4 cm (Standard deviation SD 1.3 cm). Three patients died perioperatively (5%, 1 urgent, 2 elective). Complications included retrograde type A dissection (n = 3), paraplegia (1), and transient ischaemic attack (1). Estimated survival (Kaplan-Meier) was 89% (1-year) and 64% (3-years). Forty-seven patients had mid-term imaging follow-up at mean 38 months. Reintervention rate was 15% at 1-year and 29% at 3-years. Aortic diameter decreased in 24, was stable in 15 and increased in 8. Mid-term survival was higher in patients with aortic remodelling (reduction of aortic diameter >0.5 cm; 3-year 89%) than without (54%; Log Rank p = 0.005). Remodelling occurred with extensive false lumen thrombosis.

CONCLUSION

Satisfactory mid-term outcome after TEVAR for CD remains a challenge. Survival is associated with aortic remodelling, which is related to persistence of flow in the false lumen.