Thoracic Endovascular Aortic Repair for Type B Aortic Dissection

Hemodynamic parameters that may predict false-lumen growth in type-B aortic dissection after endovascular repair: A preliminary study on long-term multiple follow-ups

Thoracic endovascular aortic repair (TEVAR) is commonly applied in type-B aortic dissection. For patients with dissection affects descending aorta and extends downward to involve abdominal aorta and possibly iliac arteries, false lumen (FL) expansion might occur post-TEVAR. Predictions of dissection development may assist in medical decision on re-intervention or surgery. In this study, two patients are selected with similar morphological features at initial presentation but with different long-term FL development post-TEVAR (stable and enlarged FL). Patient-specific models are established for each of the follow-ups. Flow boundaries and computational validations are obtained from Doppler ultrasound velocimetry. By analyzing the hemodynamic parameters, the false-to-true luminal pressure difference (PDiff) and particle relative residence time (RRT) are found related to FL remodeling. It is found that (i) the position of the first FL flow entry is the watershed of negative-and-positive PDiff and, in long-term follow-ups, and the position of largest PDiff is consistent with that of the greatest increase of FL width; (ii) high RRT occurs at the FL proximal tip and similar magnitude of RRT is found in both stable and enlarged cases; (iii) comparing to the RRT at 7days post-TEVAR, an increase of RRT afterwards in short-term is found in the stable case while a slight decrease of this parameter is found in the enlarged case, indicating that the variation of RRT in short-term post-TEVAR might be potential to predict long-term FL remodeling.

Aneurysmal Degeneration in Patients with Type B Aortic Dissection

BACKGROUND

The optimal management of type B aortic dissection (TBAD) remains controversial in the era of endovascular therapies. This study reports the outcomes and complication rates of different treatment paradigms for TBAD.

METHODS

A retrospective review was undertaken of all patients with TBAD from June 2006 to June 2012. Demographics, hospital course, and follow-up visits were analyzed. Patients who underwent surgical interventions were compared to those with medical therapy. Survival rates and predictors of outcome were determined using the Kaplan-Meier method with Cox proportional hazards.

RESULTS

Of 261 consecutive patients who were hospitalized during this period with a confirmed thoracic dissection, 134 (51%) had TBAD. Sixty-two (46%) were women, and the mean age was 66.4 ± 14.9. Median follow-up was 22.4 (0, 184) months. Thirty-five patients underwent surgical intervention with 20 thoracic endovascular aortic repair (TEVAR) and open surgery in 15. The overall 30-day mortality was 7%, and cumulative survival rates at 1, 3, and 5 years were 85% (95% confidence interval [CI], 79-91), 68% (95% CI, 59-78), and 57% (95% CI, 47-69) with no difference between medical versus surgical groups (P = 0.8) and TEVAR versus open surgery group (P = 1.0). Sixty-six (50%) patients developed aneurysmal expansion, which required surgical intervention in 26 (hazard ratios [HR], 0.99; P = 0.96). Malperfusion and rupture only occurred in 5 (HR, 1.57; P = 0.54) and 5 (HR, 3.64; P = 0.01) patients, respectively. Multivariate analysis for overall survival found renal insufficiency (HR, 2.6; P = 0.004) and age (HR, 1.06; P < 0.0001) and rupture (HR 3.3, P = 0.04) were independent predictors of mortality. Intramural hematoma was not a significant predictor of survival (HR, 0.49; P = 0.11).

CONCLUSIONS

Medical therapy remains the mainstay of treating TBAD with low morbidity. Surgical interventions are indicated in selected patients with malperfusion or aneurysmal expansion with comparable survival rates.

Systematic review of outcomes of combined proximal stent-grafting with distal bare stenting for management of aortic dissection

OBJECTIVE

Available data on outcomes of combined proximal stent-grafting with distal bare stenting for management of aortic dissection are limited. The objective of this study was to provide a systematic review of outcomes of this approach.

METHODS

Studies involving combined proximal stent-grafting with distal bare stenting for management of aortic dissection were systematically searched and reviewed through MEDLINE databases.

RESULTS

A TOTAL OF FOUR STUDIES WERE INCLUDED: 108 patients treated for management of acute (n=54) and chronic (n=54) aortic dissection. The technical success rate was 95.3% (range, 84-100%). The 30-day mortality rate was 2.7% (range from 0% to 5%). The morbidity rate occurring within 30 days was 51.8% (range from 0% to 65%) and included stroke (2.7%), paraplegia (2.7%), retrograde dissection (1.8%), renal failure (14.8%), severe cardiopulmonary complications (5.5%) and bowel ischemia (0.9%). The incidence of type I endoleak was 9.2% (10/108). During follow-up, 5 (4.6%) deaths were related to aortic rupture or aortic repair. Mean re-intervention rate was 12.9%. Two cases (1.9%) of delayed retrograde type A dissection and one case of aortobronchial fistula (0.9%) were reported. The most common delayed complication was thoracic stent-graft migration (4.7%). The rate of device failure was 9.2%. Favorable aortic remodeling was observed: studies reporting midterm follow-up of the true lumen demonstrated a high rate of both false lumen regression and true lumen expansion. At 12 months, complete false lumen thrombosis was observed at the thoracic level in 70.4% and at the abdominal level in 13.5% of patients.

CONCLUSIONS

Combined proximal stent-grafting with distal bare stenting appears to be a feasible approach for the management of Type B aortic dissection. Although this approach clearly improved true lumen perfusion and diameter, it failed to completely suppress false lumen patency. However, it should be acknowledged that contemporary data on this approach is limited to small studies with variable results.

Computational fluid dynamics investigation of chronic aortic dissection hemodynamics versus normal aorta

OBJECTIVES

To evaluate hemodynamic changes during aneurysmal dilatation in chronic type B aortic dissections compared to hemodynamic parameters in the healthy aorta with the use of computational fluid dynamics (CFD).

METHODS

True lumen (TL)/false lumen (FL) dimensional changes, changes in total pressure (TP), and wall shear stress (WSS) were evaluated at follow-up (FU) compared to initial examination (IE) with transient CFD simulation with geometries derived from clinical image data and inflow boundary conditions from magnetic resonance images. The TL/FL pressure gradient between ascending and descending aorta (DAo) and maximum WSS at the site of largest dilatation was compared to values for the healthy aorta.

RESULTS

Hemodynamic changes at site of largest FL dilatation included 77% WSS reduction and 69% TP reduction. Compared to the healthy aorta, pressure gradient between ascending and DAo was a factor of 1.4 higher in the TL and a factor of 1.5 in the FL and increased at FU (1.6 and 1.7, respectively). Maximum WSS at the site of largest dilatation was a factor of 3 lower than that for the healthy aorta at IE and decreased by more than a factor of 2 at FU.

CONCLUSIONS

The FL dilatation at FU favorably reduced TP. In contrast, unfavorable increase in pressure gradient between ascending and DAo was observed with higher values than in the healthy aorta. Maximum WSS was reduced at the site of largest dilation compared to healthy aorta.

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.

Complicated acute type B thoracic aortic dissections: endovascular treatment for visceral malperfusion and pseudoaneurysms

PURPOSE

Morbidity and mortality of acute type B thoracic aortic dissections remain alarmingly high. Endoluminal options are promising.

METHODS

A single-center 5-year review of 17 acute type B aortic dissections complicated by visceral malperfusion (11) or pseudoaneurysm formation (6) treated with endovascular intervention. Interventional techniques included endografting (15) and/or percutaneous fenestration (4). Median follow-up is 28 months (range 0-76 months).

RESULTS

Median age was 55 years; 30-day death, stroke, and paraplegia rates were 0%, 17.6%, and 5.9%. Success reversing visceral ischemia or sealing a pseudoaneurysm was 100%. Cross-sectional imaging demonstrated that the false lumen was thrombosed in 9 patients, partially thrombosed in 6 patients. Late events include 1 delayed proximal type I endoleak, 1 delayed rupture of the thoracic aorta requiring successful emergent open surgical repair, and 2 unrelated late deaths.

CONCLUSION

Endovascular approaches to type B dissections presenting with visceral malperfusion and/or pseudoaneurysm can achieve acceptable early results.