Abstract
Objective:
To evaluate the management of malperfusion in acute type B aortic dissection (ATBAD) with endovascular fenestration/stenting.
Methods:
From 1996–2018, 182 patients with an ATBAD underwent fenestration/stenting for suspected malperfusion based on imaging, clinical manifestations, and lab findings. Data were obtained from medical record review and the National Death Index database.
Results:
The median age was 55-years-old. Signs of malperfusion included abdominal pain (61%), lower extremity weakness (27%), non-palpable lower extremity pulses (24%), and abnormal lactate, creatinine, liver enzymes, and creatine kinase levels. Confirmed hemodynamically significant malperfusion affected the spinal cord (2.7%), celiac (24%), superior mesenteric (40%), renal (51%), and iliofemoral (43%) arterial distributions. Of the 182 patients, 99(54%) underwent aortic fenestration/stenting, 108(59%) had one or multi-branch vessel fenestration/stenting, 5(2.7%) had concomitant TEVAR, 17(9.3%) had additional thrombolysis or thromboembolectomy, and 48(26%) received no intervention. Following fenestration/stenting, 24(13%) required additional procedures for necrotic bowel or limb and 9(4.9%) had subsequent aortic repair (TEVAR, open repair) before discharge. The new-onset paraplegia was 0%. The in-hospital mortality was 7.7% over 20+ years, 0% in the last 8 years. The 5- and 10-year survival was 72% and 49%, respectively. The significant risk factors for late mortality were age and acute paralysis (HR=3.5), both p<0.0001. Given death as a competing factor, the 5- and 10-year cumulative incidence of reintervention was 21% and 31% for distal aortic pathology.
Conclusions:
ATBAD patients with malperfusion can be managed with endovascular fenestration/stenting with excellent short- and long-term outcomes. This approach is particularly helpful to patients with static malperfusion of aortic branch vessels.
Graphical Abstract
INTRODUCTION
Malperfusion, a feared complication of aortic dissection, is present in around 20% of type B aortic dissections1,2 and is a risk factor for mortality2 (mortality ranging from 17–64%)2–5. An International Registry of Acute Aortic Dissection (IRAD) study showed 28% mortality in ATBAD with malperfusion compared to 9.6% in those without malperfusion2. Malperfusion is defined as inadequate flow to a vascular territory, while malperfusion syndrome (MPS) is decreased flow to a vascular territory resulting in tissue/organ necrosis and end-organ dysfunction, both because of dissection-related obstruction of the aorta and its branch vessels. Patients with malperfusion more often undergo thoracic endovascular aortic repair (TEVAR) than open repair6–8 to alleviate the end-organ ischemia. However, TEVAR in ATBAD cannot reliably resolve static malperfusion of aortic branch vessels which results from thrombosis of the false lumen and compression of the true lumen of the aortic branch vessels, has the potential risk of acute paraplegia due to false lumen thrombosis of the descending thoracic aorta and its intercostal arteries when the entire descending thoracic aorta is covered, and carries approximately a 2%−5%9,10 risk of retrograde type A dissection.
Since 1996, we have adopted the approach of endovascular reperfusion via fenestration/stenting by interventional radiology (IR) of the critically malperfused organ systems for patients with ATBAD and malperfusion, which can resolve both dynamic and static malperfusion of aortic branch vessels. Previously we reported our 10-year experience of treating malperfusion in ATBAD11. In this study, we report the short- and long-term outcomes of endovascular fenestration/stenting to treat malperfusion in ATBAD over the past 20 years.
MATERIALS AND METHODS
This study was approved by the Institutional Review Board at the University of Michigan, Michigan Medicine (Ann Arbor, MI).
Study Population
From February 1996 to May 2018, 182 patients presented with spontaneous ATBAD and suspected malperfusion and went to angiography for diagnosis and fenestration/stenting. Patients with ATBAD and malperfusion due to trauma (n=4) or malperfusion treated with isolated TEVAR (n=8) or open surgical repair were excluded. ATBAD was defined as onset within 14 days of admission with dissection confined to the aorta distal to the left subclavian artery. Investigators utilized medical record review to obtain pre-, intra-, and post-procedural characteristics. Reinterventions included open or endovascular aortic repair of the aorta distal to the left subclavian artery and were collected from a thorough medical record review. The National Death Index database through December 31, 201512 and medical record review were utilized to determine survival. Loss of follow-up was treated as a censor during the time to event analysis.
Diagnosis of Dynamic and Static Malperfusion
Malperfusion, inadequate blood flow to the end organs, could be diagnosed with radiographic findings consistent with reduced or absent flow to an end organ or complete true lumen collapse on computed tomography (CT), including disappearance of the aortic double lumen indicating elimination of the true lumen with the dissection flap being pushed against the aortic wall causing obstruction of flow to branch vessels, continuation of dual lumen patency with absent flow in a branch vessel (dynamic malperfusion), and dissection into a branch vessel or a thrombosed false lumen in a branch vessel (static malperfusion), with or without clinical evidence of end-organ dysfunction (Figure 1). Malperfusion syndrome involves tissue/organ necrosis and end-organ dysfunction as a result of inadequate blood flow (malperfusion) and requires clinical features (abdominal pain, bloody diarrhea, tenderness to palpation, decreased urine output, absence of peripheral pulses, motor or sensory deficit of the lower extremity) and laboratory findings (elevated lactate, liver enzymes, metabolic acidosis, elevated creatinine) in addition to radiographic findings. The etiology of the malperfusion can be static, dynamic, or both static and dynamic obstruction of a branch vessel13. Dynamic malperfusion results from the dissection flap of a collapsed true lumen prolapsing across the origin of the branch vessel and obstructing flow and can vary in severity depending on variations of pressure in the false lumen. Dynamic obstruction can usually be resolved with restoration of the true lumen with a TEVAR endograft covering the intimal tear or aortic fenestration/stenting. Static obstruction results from extension of the dissection flap into a branch vessel, frequently accompanied by false lumen thrombosis due to no or very small re-entry tear and occlusion of the true lumen, and is present throughout the cardiac cycle. Total occlusion of a vessel, like the superior mesenteric artery (SMA), by a thrombosed false lumen can lead to thrombosis of the true lumen distal to the dissection. Furthermore, collateral flow to an obstructed SMA is often compromised by dissection-related compromise of the celiac trunk or inferior mesenteric artery. Static obstruction usually requires stenting or other intervention (fenestration/thromboembolectomy/thrombolysis) of the affected branch vessel to restore flow. Both static and dynamic obstruction can be resolved with endovascular reperfusion via fenestration/stenting. In contrast to our management in type A aortic dissection, where MPS is the indication for IR procedures, in type B aortic dissection suspected malperfusion (not MPS) is an indication for IR.
Figure 1:
Computed tomography (CT) angiogram of a 55-year-old man with an acute type B aortic dissection and static malperfusion of the celiac and superior mesenteric arteries before and eight years after endovascular fenestration/stenting. Axial CT at the level of the superior mesenteric artery (SMA) (A) shows thrombosed false lumen (arrowhead) just beyond the SMA origin. Sagittal CT of the upper abdomen through the false lumen of the aorta (B) again shows thrombus in the terminal portion of the false lumen of the celiac trunk and the SMA, resulting in arterial occlusion. 3D reconstruction of the abdominal aorta (C) shows the dissection flap cleaving the celiac and SMA origins with thrombosed false lumen (red), with the inferior mesenteric artery (IMA) supplied by the false lumen. Superior mesenteric arteriogram (D), approximately 28 hours after symptom onset, shows proximal occlusion of the SMA trunk (arrowheads), absent filling of jejunal and ileal branches, and retrograde filling of the celiac distribution through pancreatic collaterals. Following stenting of the SMA and celiac trunk, distal SMA pressure was 57/43 mmHg, 32 mmHg lower than aortic true lumen pressure. Sheath injection at the celiac origin after stenting (E) fills hepatic and splenic arteries and refluxes into the abdominal aorta, filling stented SMA (arrowhead) with jejunal and ileal branches (asterisks). CT with 3D-reconstruction 8 years later (F) shows the celiac artery (C) stent extending into the common hepatic artery (H) with jailed but patent splenic artery (S). The SMA stent (arrowhead) is patent down to the ileocolic artery. Several small jejunal and ileal branches continue to fill through stent interstices. A prominent IMA (not shown) supports flow through the middle colic artery (MC). T= true lumen, F = false lumen, H = hepatic artery, IMA = inferior mesenteric artery, MC = middle colic artery, S = splenic artery.
Endovascular Techniques
Angiography was completed a median of one day following hospital admission. The angiographic evaluation of malperfusion has been previously described in detail13–16. In angiography, treatable malperfusion was indicated by ongoing arterial obstruction and was confirmed by a systolic blood pressure gradient >15 mmHg between the ascending aorta and the branch vessel. If a branch artery is dissected, branch artery manometry is performed distal to the dissection (confirmed by intravascular ultrasound [IVUS]). The gradient of 15 mmHg was chosen as the criterion for malperfusion based on the customary acceptance of a blood pressure differential of >20 mmHg as indicating hemodynamic significance in patients with aortic coarctation17. Fenestration and stenting were performed by creating a tear in the dissection flap 2–4 cm above the celiac artery using a 16 mm diameter balloon, thereby permitting flow between the true and false lumens, followed by deployment of a 16–18 mm diameter closed-cell self-expanding stent (Wallstent, Boston Scientific Corporation, Marlborough, MA, off-label application) exclusively in the aortic true lumen (Central Picture), as previously described13,16,18,19 if the true lumen remains collapsed or a gradient between the aortic root and abdominal aorta persists following aortic fenestration. Blood pressure gradients between the aorta and the branch vessels were determined both before and after fenestration/stenting (Wallstents). If after aortic fenestration/stenting a significant gradient persisted between the aorta and a branch vessel, then branch vessel fenestration/stenting, thrombolysis, or thromboembolectomy was performed as appropriate, based on angiographic and IVUS findings. (Central Picture) Complete resolution of malperfusion was defined as blood pressure gradient decreased to <15 mmHg. In dissected vessels with thrombosed false lumens, gradients after stenting might exceed 15 mmHg, defined as partial resolution of malperfusion, but as long as absolute perfusion pressure was viable, i.e., >60 mmHg, post-dilation of stents was not performed.
Concomitant (n=5) or post-IR TEVAR (n=4) or open aortic repair (n=5) were indicated for pending rupture, refractory back pain, uncontrollable severe hypertension, and aortic aneurysm. Concomitant TEVAR includes patients who initially had TEVAR for back pain/impending rupture with persistent post-operative static malperfusion subsequently treated by fenestration/stenting. All open procedures were performed before 2004. Post-procedure management consisted of aspirin therapy, blood pressure control, standard management of end-organ dysfunction, and adequate analgesia and sedation. When bowel ischemia or extremity ischemia was present, general or vascular surgery was consulted, respectively, to determine if exploratory laparotomy or fasciotomies were indicated.
Statistical Analysis
Continuous variables were summarized by median (25%, 75%) and categorical variables were reported as n (%) in frequency tables. Crude survival curves since admission were estimated using the non-parametric Kaplan-Meier method. Multivariable logistic regression was performed to calculate the odds ratio (OR) of risk factors for in-hospital mortality adjusting for age, gender, coronary artery disease (CAD), acute myocardial infarction (MI), acute renal failure on dialysis, acute paralysis, celiac malperfusion, mesenteric malperfusion, renal malperfusion, and extremity malperfusion. Cox proportional hazard regression was performed to calculate the hazard ratio (HR) for late mortality by stepwise selection of variables including age, gender, coronary artery disease, chronic renal failure on dialysis, acute myocardial infarction, acute paralysis, acute renal failure requiring dialysis, malperfusion syndrome found, bowel resection, amputation, and fasciotomy. As patients may experience death before reintervention was indicated, cumulative incidence curves adjusting for death as the competing risk were generated to assess cumulative incidence of reintervention over time. Cox regression was used to calculate the risk factors of reintervention adjusting for age, gender, connective tissue disease, aortic flap fenestration without TEVAR or open aortic repair, and hypertension. All statistical calculations used SAS 9.4 (SAS Institute, Cary, NC) and were considered significant at p<0.05.
RESULTS
Demographics and Pre-procedural Data
The median age was 55-years-old and most patients (88%) had hypertension. The majority (93%) of patients were transferred from another hospital. Patients frequently presented with abdominal pain (61%), lower extremity weakness (27%) with non-palpable pulses (24%), and elevated creatinine and liver enzymes. Some already had certain vascular procedures for limb ischemia prior to presentation (Table 1).
Table 1.
Demographics and Characteristics before Procedures by Interventional Radiology
| Variables | Total (n=182) |
|---|---|
| Patient age (years) | 55 (48, 65) |
| Sex (male) | 139 (76) |
| BMI | 30 (26, 33.5) |
| Hypertension | 160 (88) |
| Hyperlipidemia | 47 (26) |
| Diabetes | 15 (8.2) |
| COPD | 23 (13) |
| CAD | 40 (22) |
| PVD | 18 (9.9) |
| History of Smoking | |
| None | 61 (34) |
| Former | 43 (24) |
| Current | 78 (43) |
| History of MI | 17 (9.3) |
| History of Stroke | 12 (6.6) |
| History of Renal Failure | 20(11) |
| On Dialysis | 3 (1.6) |
| Connective Tissue Disorder | 12 (6.6) |
| Acute MI | 25 (14) |
| Acute Stroke | 1 (0.5) |
| Worsening Renal Function | 91 (50) |
| Requiring Dialysis | 5 (2.7) |
| Acute Paralysis | 12 (6.6) |
| Prior Cardiac Surgery | 30 (16) |
| Prior Aortic Intervention | 29 (16) |
| Location of Initial Admission | |
| University of Michigan | 12 (7) |
| Outside Hospital | 170 (93) |
| Admission to IR (days) | 1 (0, 2) |
| Presenting Signs and Symptoms | |
| Abdominal Pain | 111 (61) |
| Lower Extremity Weakness | 49 (27) |
| Lower Extremity Pulses Non-palpable | 43 (24) |
| Lab Values | |
| Creatinine on Admission (mg/dL) | 1.2 (0.9, 1.6) |
| Maximum Creatinine before IR (mg/dL) | 1.5 (1.0, 2.1) |
| Maximum lactate before IR (mmol/L) | 1.5 (1.0, 2.2) |
| Elevated AST/ALT | 66 (37) |
| Max CK (U/L) | 124 (58.5, 232) |
| Procedures During Hospital Stay before IR | |
| Exploratory Laparotomy for Suspected Ischemia | 0 (0) |
| Vascular Surgery for Suspected Ischemia | 6 (3.3) |
| Thrombolysis/Stenting of SMA | 1 (0.5) |
| Thrombectomy/Embolectomy | 2 (1.1) |
| Fem-Fem Bypass | 4 (2.2) |
| Fasciotomy | 2 (1.1) |
| Amputation | 0 (0) |
| Aortic Surgery | 3 (1.6) |
| TAVR | 1 (0.5) |
| Median Sternotomy* | 1 (0.5) |
| Open TAA | 1 (0.5) |
Data presented as median (25%, 75%) for continuous data and n (%) for categorical data. ALT = alanine aminotransferase; AST = aspartate aminotransferase; BMI = body mass index; CAD = coronary artery disease; CK = creatine kinase; COPD = chronic obstructive pulmonary disease; MI = myocardial infarction; PVD = peripheral vascular disease; SMA = superior mesenteric artery; TAVR = transcatheter aortic valve replacement; TAA = thoracic aortic aneurysm.
Acute type B aortic dissection noted intraoperatively during aortic root repair.
Procedural Data
Renal, extremity, and mesenteric malperfusion were the most frequently suspected and confirmed malperfusion in ATBAD. Frequently, multiple vascular beds were affected. Overall, 74% of patients had interventions in the angiography suite, including aortic fenestration/stenting (54%), branch vessel fenestration/stenting (59%), or thrombolysis/thrombectomy/embolectomy (9.3%) for static malperfusion. (Table 2, Figure 1) Branch artery stenting was performed in the iliac, renal, superior mesenteric, and celiac arteries 56, 47, 37, and 8 times, respectively. Overall, 93% of malperfusion was completely resolved and 5% was partially resolved (Table 3). Following endovascular fenestration/stenting, 13 patients required laparotomy for suspected bowel ischemia, including 9 patients who had bowel resection, and 12 patients required additional vascular procedures during the current hospital stay. Nine patients required additional TEVAR (n=4) or open aortic repair (n=5) due to aortic aneurysm, pending rupture, and persistent symptoms. (Table 2)
Table 2.
IR Indications and Procedures and Subsequent Procedures During Hospital Stay
| Variables | Total (n=182) |
|---|---|
| IR Indications | |
| Malperfusion Suspected | 182 (100) |
| Spinal Cord | 8 (4.4) |
| Celiac | 22 (12) |
| Mesenteric | 81 (45) |
| Renal | 119 (65) |
| Extremity | 71 (39) |
| Malperfusion Found | 140 (77) |
| Spinal Cord | 5 (2.7) |
| Celiac | 43 (24) |
| Mesenteric | 73 (40) |
| Renal | 93 (51) |
| Extremity | 79 (43) |
| IR Procedures | |
| No Intervention in IR | 48 (26) |
| Aortic Fenestration/Stenting | 99 (54) |
| Branch Vessel Fenestration/Stenting | 108 (59) |
| Concomitant TEVAR | 5 (2.7) |
| Additional Procedures* | 17 (9.3) |
| Subsequent Procedures During Hospital Stay | |
| Exploratory Laparotomy for Suspected Ischemia | 13 (7.1) |
| Bowel Resection | 9 (4.9) |
| Vascular Surgery for Suspected Ischemia | 12 (6.6) |
| Thrombectomy/Embolectomy | 6 (3.3) |
| Fem-Fem Bypass | 2 (1.1) |
| Fasciotomy | 5 (2.7) |
| Amputation | 3 (1.6) |
| Aortic Surgery | 9 (4.9) |
| TEVAR | 4 (2.2) |
| Open TAA/A | 4 (2.2) |
| Open AAA | 1 (0.5) |
| Time from IR (days) | 12 (9, 14) |
Data presented as n (%).
Thrombolysis, thrombectomy, embolectomy of aortic branch vessels.
AAA = abdominal aortic aneurysm; IR = interventional radiology for fenestration/stenting; TAA/A = thoracic aortic aneurysm (TAA) or thoracoabdominal aortic aneurysm (TAAA); TEVAR = thoracic endovascular aortic replacement. TEVAR was performed by both IR faculty and cardiac surgeons together.
Table 3.
Detailed IR Procedures
| Level of aortic fenestration/stenting |
Aortic Fenestration (n=87) |
Aortic Stenting (n=89) |
Branch Vesse Fenestration (n=2) |
Branch Vessel Stenting (n=105) |
Malperfusion in Vascular Bed (n=182) |
Malperfusion Completely Resolved+ |
Malperfusion Partially Resolved+ |
|---|---|---|---|---|---|---|---|
| Descending thoracic | 6 | 5 | - | - | - | - | - |
| Supraceliac | 22 | 12 | - | - | - | - | - |
| Celiac | 17 | 2 | 0 | 8 | 43 | 42 | 1 |
| Supramesenteric | 17 | 45 | - | - | - | - | - |
| Mesenteric | 15 | 0 | 0 | 37 | 73 | 65 | 8 |
| Suprarenal | 1 | 0 | - | - | - | - | - |
| Renal* | 7 | 5 | 0 | 47 | 93 | 87 | 2 |
| Infrarenal | 44 | 62 | - | - | - | - | - |
| Iliac* | - | - | 2 | 56 | 79 | 74 | 4 |
IR = interventional radiology for fenestration/stenting. In the columns 2 −5, n means number of patients. In column 6, n means the total malperfusion found in different vascular beds, including celiac artery, superior mesenteric artery, renal arteries, and common iliac arteries and their branches (external iliac arteries, femoral arteries).
Aortic stenting: If there was a compression of the true lumen by the thrombosed false lumen in the descending aorta, we placed a 16 mm self-expanding bare stent in the descending aorta (Descending thoracic aortic stenting). After fenestration of aortic dissection flap, we place the same self-expanding bare stent in the distal descending thoracic aorta if needed to keep the true lumen open. The distal descending thoracic aortic stent was placed frequently above the superior mesenteric artery (Supramesenteric aortic stenting). If we had to place stents in the superior mesenteric artery, then we place the aortic stent above the celiac artery (Supraceliac aortic stenting). The goal of aortic stenting is to achieve adequate expansion of the true lumen of dissected aorta and eliminate blood pressure gradient between distal aorta and ascending aorta.
Among 47 patients receiving renal artery stenting, 38 (81%) received unilateral stenting (right renal, 38% and left renal, 43%) and 9 (19%) had bilateral renal artery stenting. Among 56 patients receiving iliac stenting, 42 (75%) had aorto-iliac stenting, 32 (57%) had common iliac artery stenting, 33 (59%) had external iliac artery stenting, and 7 (12.5%) had common femoral artery stenting. Four renal artery and one iliac malperfusion were unable to be treated due to an inability to cannulate the specific branch vessel (n=1, renal artery), anatomy unsuitable for stenting (n=3, renal artery), or a significant gradient without symptoms of malperfusion (n=1, iliac).
Complete resolution of malperfusion was defined as the systolic blood pressure gradient between the branch vessel and ascending aorta is < 15 mmHg after endovascular fenestration/stenting. Partial resolution of malperfusion was defined as systolic blood pressure gradient was still > 15 mmHg.
Postoperative Outcomes
Post-procedural new-onset paraplegia (0%), retrograde type A dissection (0%), and new-onset acute renal failure requiring dialysis (1.6%) were low. In five patients with spinal cord malperfusion, two had complete resolution and one had partial resolution of paraplegia. Overall in-hospital mortality was 7.7% over 20 years, 11.3% in the first decade (1996–2007), 3.5% in the second decade (2008–2018), and 0% in the last 8 years. (Table 4) The significant risk factors for in-hospital mortality were age (OR=1.15), acute MI (OR=8.6), acute paralysis (OR=11.5), and extremity malperfusion (OR=8.8) (Table 5). Detailed causes of death included aortic rupture, extensive necrotic intestine, arrhythmia, and stroke. (Supplemental Table 1)
Table 4.
Post-procedural Outcomes
| Variables | Total (n=182) |
|---|---|
| Stroke | 10 (5.5) |
| Continued Acute Renal Failure Requiring New Dialysis | 14 (7.7) |
| New-onset Renal Failure | 10 (5.5) |
| Requiring Dialysis | 3 (1.6) |
| Dialysis at Discharge | 2 (1.1) |
| New-onset Paraplegia | 0 (0) |
| Preoperative Paraplegia resolved* | 3 (60) |
| GI Bleed | 1 (0.5) |
| Groin Hematoma | 8 (4.4) |
| Length of Stay (days) | 11 (8, 18) |
| In-hospital Mortality | 14 (7.7) |
Data presented as median (25%, 75%) for continuous data and n (%) for categorical data.
Five patients had preoperative paraplegia due to spinal cord malperfusion, two patients’ paraplegia resolved completely and one patient’s resolved partially.
Table 5.
Risk Factors for In-hospital Mortality (Multivariable Logistic Regression)
| Variables | Odds Ratio (95% Confidence Interval) | p-value |
|---|---|---|
| Age | 1.15 (1.06, 1.25) | 0.0009 |
| Male Gender | 3.31 (0.68, 16.09) | 0.14 |
| CAD | 0.65 (0.10, 4.43) | 0.66 |
| Acute MI | 8.59 (1.35, 54.42) | 0.02 |
| Acute Renal Failure Requiring Dialysis | 1.80 (0.11, 28.88) | 0.68 |
| Acute Paralysis | 11.5 (1.83, 72.38) | 0.009 |
| Found Celiac Malperfusion | 1.38 (0.20, 9.61) | 0.74 |
| Found Mesenteric Malperfusion | 3.16 (0.43, 23.05) | 0.26 |
| Found Renal Malperfusion | 2.88 (0.58, 14.28) | 0.19 |
| Found Extremity Malperfusion | 8.83 (1.43, 54.78) | 0.02 |
CAD = coronary artery disease; MI = myocardial infarction.
Long-term Outcomes
The 5- and 10-year survival was 72% (95% CI: 64%, 78%) and 49% (95% CI: 39%, 58%) respectively. (Figure 2A) The significant risk factors for late mortality were age [HR=1.04, (95% CI: 1.02, 1.06)] and acute paralysis [HR=3.5, (95% CI: 1.8, 6.8)], p<0.001.
Figure 2A:
Kaplan-Meier survival analysis of patients with an acute type B aortic dissection and malperfusion syndrome undergoing endovascular fenestration/stenting. The 5- and 10-year survival was 72% (95% CI: 64%, 78%) and 49% (95% CI: 39%, 58%) respectively.
Of the 182 patients, 14 patients died in the hospital before discharge and 12 (6.6%) were lost to follow-up for reintervention. The mean follow-up time was 6.2 years. The 5- and 10-year cumulative incidence of reintervention for pathology of the descending or thoracoabdominal aorta adjusted for death as a competing factor was 21% (95% CI: 15%, 28%) and 31% (95% CI: 23%, 40%) (Figure 2B). The significant risk factors for reintervention were connective tissue disease [HR=3.4 (95% CI: 1.4, 8.3), p=0.007] and male gender [HR=3.2, (95% CI: 1.3, 8.0), p=0.014]. Fenestration without TEVAR or open repair was not a significant risk factor [HR=0.8, (95% CI: 0.4, 1.5), p=0.49]. The 5- and 10-year cumulative incidence of reintervention for patients undergoing fenestration/stenting only, without TEVAR or open repair during the hospital stay, was 20% (95% CI: 13%, 28%) and 31% (95% CI: 21.5%, 41%) (Figure 2C). The primary indication for reintervention was aortic aneurysm (91%) and was primarily done through open repair (76%). The median interval time to reintervention was two years.
Figure 2B:
The cumulative incidence of reintervention of the whole cohort (n=182) for pathology of the descending thoracic or thoracoabdominal aorta following hospital discharge, adjusting for death as the competing event. The 5- and 10-year cumulative incidence of reintervention was 21% (95% CI: 15%, 28%) and 31% (95% CI: 23%, 40%) respectively.
Figure 2C:
The cumulative incidence of reintervention for patients who had only fenestration/stenting (n=125) following hospital discharge, adjusting for death as the competing event. The 5- and 10-year cumulative incidence of reintervention was 20% (95% CI: 13%, 28%) and 31% (95% CI: 21.5%, 41%) respectively.
DISCUSSION
In this study, we managed ATBAD complicated by malperfusion with endovascular fenestration/stenting, which enables resolution of both dynamic and static malperfusion. The in-hospital mortality was 7.7% over 20+ years and 0% in the last 8 years; the cumulative incidence of reintervention was 21% at 5 years and 31% at 10 years; and the 5- and 10-year survival was 72% and 49% respectively.
Aortic dissection, both type A and B, can be complicated by malperfusion due to dissection-related obstruction of aortic branch vessels. In acute type A aortic dissection, because of the risks of aortic rupture, acute heart failure and aortic insufficiency, acute myocardial infarction, pericardial effusion and tamponade, and neurologic complications20,21, we pursue upfront angiography with endovascular reperfusion only for patients with malperfusion syndrome (malperfusion with tissue/organ necrosis and end-organ dysfunction). In ATBAD patients, we extend this strategy to patients with malperfusion unresponsive to blood pressure and heart rate control and patients with a documented history of poor compliance with anti-hypertensive medication in addition to patients with MPS. Patients with acute type B aortic dissection have a lower risk of aortic rupture with adequate blood pressure management11,22 and a small risk of the proximal aortic complications commonly seen with type A dissections23. Malperfusion due to dynamic obstruction, which is generally corrected by proximal aortic repair in ATAAD patients, may persist in ATBAD patients unless dealt with directly by fenestration/stenting or TEVAR. In summary, malperfusion, in addition to malperfusion syndrome, is an indication for angiography for diagnosis and potential treatment in ATBAD patients. Because clinical manifestation of mesenteric and renal malperfusion may lag their CT demonstration and unsuspected vascular beds with malperfusion are frequently identified when we investigate malperfusion of suspected vascular beds, we consider the endovascular evaluation of ATBAD patients an angiographic emergency and have a low threshold for performing it. The angiographic evaluation of these patients typically involves manometry, IVUS examination, and hand injection of 7 ml of contrast material diluted 1: 1 with normal saline into the SMA, bilateral renal arteries, and external iliac arteries. In the case of SMA or renal artery dissection associated with a significant pressure deficit, IVUS examination is performed to determine radiographic landmarks of the dissection terminus, in order to aid in stent placement.
Management options for ATBAD complicated with malperfusion have generally included open surgical repair and more recently TEVAR. Although TEVAR has reduced early mortality to around 10% in all ATBAD1,7,24–26, we still use fenestration/stenting as our main stream treatment for malperfusion in ATBAD for the following reasons: (1) TEVAR has risks of retrograde type A dissection27 (1.6% in large registry10) and spinal cord ischemia and paraplegia (2–10%28–30), (2) TEVAR alone cannot reliably resolve static malperfusion, (3) TEVAR sometimes has to cover the left subclavian artery to cover the primary intimal tear, which requires additional procedures (such as left carotid artery-subclavian artery bypass) to preserve blood flow to the left subclavian artery, and (4) When patients suffer from necrotic bowel or limb and sepsis, TEVAR has a higher risk of graft infection. With endovascular fenestration/stenting, we can avoid all the risks from TEVAR and adequately treat static malperfusion with branch vessel stenting, fenestration, thromboembolectomy, or thrombolysis.
In this study, 59% of patients had fenestration/stenting of an aortic branch vessel and 9.3% had thrombolysis or thromboembolectomy for static malperfusion which could not be resolved by TEVAR alone. Since we did not cover any intercostal arteries, protecting the spinal cord from ischemic injury, our post-procedural new-onset paraplegia due to ischemic spinal cord injury was 0%, which is lower than those treated with TEVAR alone (2–10%28–30). The in-hospital mortality rate was 7.7% with this approach in this sick sub-population (ATBAD with malperfusion) with 0% mortality in the last 8 years as we became more experienced with fenestration/stenting and with utilization of TEVAR for aortic pending rupture or rupture, which is lower than that seen with open repair and with TEVAR alone1,6,7,24–26,31, possibly because TEVAR alone does not reliably correct static obstruction. Other reasons for improved mortality include better imaging, prompt diagnosis, treating suspected malperfusion in an acute dissection as an angiographic emergency, and better ICU management (blood pressure control). Endovascular fenestration/stenting of ATBAD with malperfusion combined with TEVAR and open repair achieved favorable survival (5-year and 10-year survival: 72% and 49%) which was better than or similar to those treated with TEVAR or open repair alone7,8,24,25,31,32. The significant risk factors for late mortality were age and acute paralysis (HR=3.5). By decreasing the risk of new- onset paraplegia, endovascular fenestration/stenting could potentially decrease the late mortality.
Our approach is based on risk stratification to determine best management. In the setting of ATBAD with malperfusion without signs of rupture (persistent or increasing back pain), we think the malperfusion is the most immediate concern and elect to treat the malperfusion with percutaneous fenestration/stenting. This approach accomplishes the goal of resolving the malperfusion and essentially “converts” a complicated ATBAD to an uncomplicated ATBAD and allows patients to recover with medical management afterwards. If patients had rupture/pending rupture, refractory back pain, uncontrollable hypertension, or large aortic aneurysm, a concomitant or delayed TEVAR or open aortic repair was performed as is seen in a small portion of this cohort (n=14, 7.7%) (Table 2). Managing ATBAD with malperfusion via fenestration/stenting does not prevent aortic rupture, as would open surgery or TEVAR. In this study, seven patients (3.8%) possibly died from aortic rupture a median of 3 days (IQR: 2, 4.5 days) following angiography with fenestration/stenting, which all happened before 2011 when TEVAR was not commonly used at our institution. Aortic rupture may have been prevented in these patients if they had undergone TEVAR, although cases of rupture have been reported during24 and following TEVAR1,24,25,33. After 2010, we applied endovascular fenestration/stenting, combined with TEVAR and open repair as appropriate, to all patients with ATBAD and malperfusion, with a 0% aortic rupture rate and 0% in-hospital mortality. In summary, endovascular fenestration/stenting is a very effective tool to treat malperfusion (dynamic and static) in ATBAD and is a valuable adjunct to both medical and surgical therapy (TEVAR and open repair). The fenestration/stenting approach does not exclude TEVAR or open repair of the aorta. If needed, all three approaches can be used to treat ATBAD with different complications.
For patients with malperfusion syndrome (late stage malperfusion with tissue/organ necrosis and dysfunction), endovascular fenestration/stenting resolves the malperfusion with minimal operative trauma and provides the opportunity for patients to recover from malperfusion syndrome. Additional intervention may be needed in order to recover from severe malperfusion syndrome. In our study, 24 patients (13%) required general and/or vascular surgery intervention for bowel and extremity necrosis following angiography, including bowel resection, fasciotomy and amputations (Table 2). Of these 24 patients, 20 patients had branch vessel stenting during angiography for static malperfusion, which could not have been treated with open repair or TEVAR alone. This highlights the gravity of the malperfusion syndrome; despite initial reperfusion of affected vascular territories, patients may still suffer complications of the pre-existing malperfusion and subsequent reperfusion. With prolonged static malperfusion, as would be with initial open repair or TEVAR, it is suspected that more patients would suffer from irreversible, unsalvageable end-organ death.
One concern about leaving a patent false lumen after fenestration/stenting is that it could increase the risk of reintervention. TEVAR could facilitate aortic remodeling by thrombosing and stabilizing the size of the thoracic false lumen due to closure of the primary intimal tear with a covered stent graft33. We think the aortic flap fenestration/stenting approach achieves the same goal by creating a distal fenestration as outflow for the false lumen to decompress and prevent the dilation of the false lumen even though the proximal primary intimal tear is open. Burris et al.34 found that in chronic type B aortic dissection the false lumen dilates very quickly with a large proximal primary intimal tear and a small distal re-entry tear due to high pressure in the false lumen during diastole evident as regurgitant blood flow from the false into the true lumen through both proximal and distal intimal tears. If the distal re-entry tear is large, there is no regurgitant flow from false to true lumen and there is minimal growth of the false lumen and the dissected aorta34. Our approach, endovascular fenestration of the distal aortic flap, serves exactly the same purpose. As a result, the 5- and 10-year cumulative rate of reintervention with fenestration/stenting alone was 20% and 31%, respectively, adjusting for death as a competing factor (Figure 2B, 2C), which is similar if not better than that reported with TEVAR24,32,35 and open repair7 alone; and we had longer follow-up than most studies since TEVAR is a more recent technology. Most of the studies using TEVAR in the literature use freedom from reintervention and do not adjust for late death as a competing factor, which could underestimate the rate of reintervention. Taken together, we do not think endovascular fenestration/stenting alone treating malperfusion in ATBAD increases the risk of reintervention compared to TEVAR.
Our study is limited by a single-center and retrospective experience. The management strategy of angiography evaluation and endovascular fenestration/stenting has a learning curve. Because the follow-up of reintervention was 93.4% complete, we could underestimate the rate of reintervention. This study is also limited by lack of a direct comparison group, such as TEVAR alone.
CONCLUSION
In patients with ATBAD complicated by malperfusion, endovascular fenestration/stenting can effectively resolve the malperfusion and achieve favorable short- and long-term results with additional indicated TEVAR or open aortic repair. We recommend endovascular fenestration/stenting when treating ATBAD with malperfusion, especially in patients with static malperfusion.
Supplementary Material
Central Picture Legend:
A) Aortic flap balloon fenestration; B) Thoracic aortic true lumen, and C) SMA stenting.
Central Message:
Endovascular fenestration/stenting can effectively resolve dynamic and static malperfusion in acute type B aortic dissection with favorable short- and long-term outcomes (survival and reoperation).
Perspective Statement:
Endovascular fenestration/stenting effectively and timely resolves dynamic and static malperfusion in acute type B aortic dissection with minimal risk of paraplegia and retrograde type A dissection, and excellent in-hospital mortality, cumulative incidence of reintervention, and long-term survival in this sick patient population as combined with TEVAR or open repair when they are indicated.
ACKNOWLEDGEMENT:
The authors thank Eric Wizauer, Vanessa Allen, and Sarah Abate for their help in composing and annotating the figures.
Sources of Funding: Dr. Yang is supported by the NHLBI of NIH K08HL130614 and R01HL141891, Phil Jenkins and Darlene & Stephen J. Szatmari Funds. Dr. Patel is supported by the Joe D. Morris Collegiate Professorship, the David Hamilton Fund, and the Phil Jenkins Breakthrough Fund in Cardiac Surgery. Dr. Deeb is supported by the Herbert Sloan Collegiate Professorship, Jamie Buhr Fund, and Richard Nerod Fund.
GLOSSARY OF ABBREVIATIONS
- ATAAD
acute type A aortic dissection
- ATBAD
acute type B aortic dissection
- CAD
coronary artery disease
- CI
confidence interval
- CT
computed tomography
- HR
hazard ratio
- IQR
interquartile range
- IR
interventional radiology
- IRAD
International Registry of Acute Aortic Dissection
- IVUS
intravascular ultrasound
- MPS
malperfusion syndrome
- OR
odds ratio
- SMA
superior mesenteric artery
- TEVAR
thoracic endovascular aortic repair
Biography
Footnotes
Conflict of Interest: Dr. David Williams is on the Medical Advisory Board of Boston Scientific and Drs. David Williams and Himanshu Patel are consultants with Gore on an unrelated device.
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