Current Management of Chronic Type B Aortic Dissection
This study was approved by the Institutional Review Board of Duke University, and the need for individual patient consent was waived. We retrospectively reviewed the records of all patients at our institution who underwent descending or thoracoabdominal aortic intervention for the treatment of CTBAD (>2 weeks from symptom onset) between June 2005 and December 2013. Patient records were identified from the prospectively maintained Duke Thoracic Aortic Surgery Database. The patient cohort included only patients with CTBAD who had previously been managed medically. Patients who had undergone prior interventions for acute type B aortic dissection, or descending or thoracoabdominal aortic interventions at outside institutions were excluded. However, patients treated for residual CTBAD following acute type A aortic dissection repair (repaired DeBakey type I dissection) were included in the analysis. Reinterventions were coded as all subsequent aortic procedures performed following the index descending or thoracoabdominal aortic intervention. Comorbid conditions and postoperative complications were defined using the Society of Thoracic Surgeons definitions (www.sts.org). Aortic arch landing zones were defined using the Ishimaru classification. Long-term follow-up and survival were assessed from medical records and the Social Security Death Index.
Indications for elective intervention included aneurysmal degeneration with an absolute aortic diameter of ≥5.5 cm, rapid aneurysm enlargement (>5 mm in 6 months) or saccular aneurysm protruding ≥2 cm beyond the aortic wall. Indications for non-elective intervention included symptomatic aneurysm with impending rupture (n=18), aortoesophageal fistula (n=1), ruptured aneurysm (n=1) or dynamic iliofemoral malperfusion (n=1). Interventions were classified as one of five principal procedures: (I) isolated descending TEVAR with or without left subclavian artery coverage; (II) hybrid arch repair with descending TEVAR; (III) hybrid thoracoabdominal aortic aneurysm (TAAA) repair; (IV) open descending repair; and (V) open TAAA repair. TEVAR, hybrid arch and hybrid TAAA repairs were considered endovascular-based procedures and open descending and open TAAA repairs were considered open procedures.
Our institutional preference is to perform endovascular repair of CTBAD for all non-CTD patients with suitable anatomy. Our technique for TEVAR in CTBAD has recently been described in detail. We recommend isolated descending thoracic aortic TEVAR only for patients with an isolated descending thoracic aneurysm arising adjacent to the primary tear. Specifically, a thoracoabdominal aneurysm should not be present, and we prefer the diameter of the distal descending thoracic aorta at the level of the celiac axis to be ≤42 mm when utilizing TEVAR for CTBAD with aneurysm.
As previously described, hybrid arch procedures were performed for patients with inadequate proximal landing zone, including zone 1 coverage with carotid-carotid bypass, zone 0 coverage with complete arch debranching or stented elephant trunk completion following prior total arch replacement. Hybrid TAAA procedures with complete visceral debranching were performed for patients with TAAA secondary to CTBAD and deemed poorly suited to conventional repair; this usually required open infrarenal aorto-bi-iliac Dacron graft replacement in conjunction with visceral debranching, to create adequate distal landing zone given the presence of chronic dissection within the infrarenal aorta +/– iliac arteries.
Conventional open surgery was reserved for CTBAD patients with CTD or anatomy unsuitable for TEVAR or hybrid repair due to inadequate stent graft landing zones. Our institutional preference is to perform open descending and TAAA repairs utilizing cardiopulmonary bypass and deep hypothermia for central nervous system and visceral organ protection. Direct aortic cannulation for cardiopulmonary bypass is preferred over femoral arterial cannulation to prevent retrograde embolization of debris from the FL. Preoperative lumbar drains are placed in all open TAAA repairs and open descending thoracic aortic repairs with planned distal anastomosis below the level of T6; drains are managed as previously described.
All patients had lifelong aortic surveillance follow-up at the Duke Center for Aortic Disease. Patient follow-up protocols were previously published for patients undergoing endovascular-based and open repairs.
Categorical variables were represented as numbers and percentages, and continuous variables were represented as medians and interquartile ranges. Continuous and categorical variables were compared between groups using the Mann-Whitney rank sum test and the Chi-squared test, respectively. Estimates of long-term survival and freedom from reintervention were calculated for all patients using the Kaplan-Meier method. Calculations were performed using STATA 11.1 (StataCorp, College Station, TX, USA).
Methods
Patient Population and Data Collection
This study was approved by the Institutional Review Board of Duke University, and the need for individual patient consent was waived. We retrospectively reviewed the records of all patients at our institution who underwent descending or thoracoabdominal aortic intervention for the treatment of CTBAD (>2 weeks from symptom onset) between June 2005 and December 2013. Patient records were identified from the prospectively maintained Duke Thoracic Aortic Surgery Database. The patient cohort included only patients with CTBAD who had previously been managed medically. Patients who had undergone prior interventions for acute type B aortic dissection, or descending or thoracoabdominal aortic interventions at outside institutions were excluded. However, patients treated for residual CTBAD following acute type A aortic dissection repair (repaired DeBakey type I dissection) were included in the analysis. Reinterventions were coded as all subsequent aortic procedures performed following the index descending or thoracoabdominal aortic intervention. Comorbid conditions and postoperative complications were defined using the Society of Thoracic Surgeons definitions (www.sts.org). Aortic arch landing zones were defined using the Ishimaru classification. Long-term follow-up and survival were assessed from medical records and the Social Security Death Index.
Patient Selection and Operative Technique
Indications for elective intervention included aneurysmal degeneration with an absolute aortic diameter of ≥5.5 cm, rapid aneurysm enlargement (>5 mm in 6 months) or saccular aneurysm protruding ≥2 cm beyond the aortic wall. Indications for non-elective intervention included symptomatic aneurysm with impending rupture (n=18), aortoesophageal fistula (n=1), ruptured aneurysm (n=1) or dynamic iliofemoral malperfusion (n=1). Interventions were classified as one of five principal procedures: (I) isolated descending TEVAR with or without left subclavian artery coverage; (II) hybrid arch repair with descending TEVAR; (III) hybrid thoracoabdominal aortic aneurysm (TAAA) repair; (IV) open descending repair; and (V) open TAAA repair. TEVAR, hybrid arch and hybrid TAAA repairs were considered endovascular-based procedures and open descending and open TAAA repairs were considered open procedures.
Our institutional preference is to perform endovascular repair of CTBAD for all non-CTD patients with suitable anatomy. Our technique for TEVAR in CTBAD has recently been described in detail. We recommend isolated descending thoracic aortic TEVAR only for patients with an isolated descending thoracic aneurysm arising adjacent to the primary tear. Specifically, a thoracoabdominal aneurysm should not be present, and we prefer the diameter of the distal descending thoracic aorta at the level of the celiac axis to be ≤42 mm when utilizing TEVAR for CTBAD with aneurysm.
As previously described, hybrid arch procedures were performed for patients with inadequate proximal landing zone, including zone 1 coverage with carotid-carotid bypass, zone 0 coverage with complete arch debranching or stented elephant trunk completion following prior total arch replacement. Hybrid TAAA procedures with complete visceral debranching were performed for patients with TAAA secondary to CTBAD and deemed poorly suited to conventional repair; this usually required open infrarenal aorto-bi-iliac Dacron graft replacement in conjunction with visceral debranching, to create adequate distal landing zone given the presence of chronic dissection within the infrarenal aorta +/– iliac arteries.
Conventional open surgery was reserved for CTBAD patients with CTD or anatomy unsuitable for TEVAR or hybrid repair due to inadequate stent graft landing zones. Our institutional preference is to perform open descending and TAAA repairs utilizing cardiopulmonary bypass and deep hypothermia for central nervous system and visceral organ protection. Direct aortic cannulation for cardiopulmonary bypass is preferred over femoral arterial cannulation to prevent retrograde embolization of debris from the FL. Preoperative lumbar drains are placed in all open TAAA repairs and open descending thoracic aortic repairs with planned distal anastomosis below the level of T6; drains are managed as previously described.
All patients had lifelong aortic surveillance follow-up at the Duke Center for Aortic Disease. Patient follow-up protocols were previously published for patients undergoing endovascular-based and open repairs.
Statistical Analysis
Categorical variables were represented as numbers and percentages, and continuous variables were represented as medians and interquartile ranges. Continuous and categorical variables were compared between groups using the Mann-Whitney rank sum test and the Chi-squared test, respectively. Estimates of long-term survival and freedom from reintervention were calculated for all patients using the Kaplan-Meier method. Calculations were performed using STATA 11.1 (StataCorp, College Station, TX, USA).