EXPERT ANALYSIS FROM THE AMERICAN ASSOCIATION FOR THORACIC SURGERY AORTIC SYMPOSIUM 2016
TEVAR is the best procedure.
At Cedars-Sinai Medical Center, 70% of the aortic operations are performed in open fashion, but in patients with chronic type B aortic dissection, thoracic endovascular repair (TEVAR) is the preferred option. Goals of TEVAR in the setting of chronic type B dissection are to seal off the intimomedial tears, re-route blood to the true lumen, and induce false lumen thrombosis in the descending thoracic aorta, promoting reverse aortic remodeling and reducing future reinterventions.
TEVAR in patients with chronic type B aortic dissection has the best results if the following five rules apply: the patient should be older than 40 years of age and not have connective tissue disorder; there should be a proper proximal landing zone; the distal landing zone at the celiac artery should be smaller than 4 cm to allow for reverse remodeling; most of the large intimomedial tears should be in the descending aorta; and at least three visceral vessels should come off the true lumen. With this clinical scenario, the majority of centers will have excellent results with TEVAR.
TEVAR for chronic type B aortic dissection comes with three usual concerns: short-term outcomes; reverse aortic remodeling; and long-term outcomes.
In evaluating short-term outcomes of TEVAR in chronic type B aortic dissection, many large, single-center studies, including ours, have documented the superior results.1,2 The VIRTUE study reported an operative mortality and 30-day hospitality mortality of zero and spinal cord ischemia rate of 3.8% in a prospective, multi-center review.3 A meta-analysis of TEVAR for chronic dissection that involved 567 patients reported a 30-day mortality rate of 3.2%, paraplegia rate of 0.45%, a stroke rate of 1.5%, and retrograde type A dissection rate of 0.7%.4
These outcomes are far better than those reported in a meta-analysis of open repair for chronic dissection (771 patients): post-1997 mortality of 8.8% (the overall 30-day mortality rate was 12.5%); paraplegia of 6%; and renal failure with hemodialysis of 4%.5 A statewide analysis of elective open repair for thoracoabdominal aortic aneurysm, including chronic dissections, in California had a 30-day mortality rate of 19.7%.6
With regard to reverse aortic remodeling, acceptable results with TEVAR have been reported. The INSTEAD-XL study reported that at 5 years, 73% of patients had reverse aortic remodeling, with absolute risk reduction of 12.4%, compared with optimal medical therapy.7 A systematic review reported an 85.7% median rate of false lumen thrombosis.4 In the past some surgeons were concerned about a thick septum and whether it would give way and allow reverse remodeling; these studies confirmed that it does. The radial force of a stent graft over time will enlarge to the size that you would expect and it will cause the false lumen thrombosis.
Our group has provided anatomical indicators to achieve reverse remodeling in chronic type B dissection, including the location and size of intimomedial tears above the celiac artery.8 A patient with this anatomy has a great chance of not requiring any future reinterventions if the tears are mostly within the thoracic aorta upper fit.
Large multicenter studies also provide answers to the third concern about TEVAR for chronic aortic dissection – long-term outcomes – and found that they are comparable to open surgery. A study of the Medtronic Thoracic Endovascular Registry (MOTHER) database, a prospective, multicenter, adjudicated registry, looked at three types of aortic pathology: chronic aortic dissection (CAD); acute aortic dissection (AAD); and thoracic aortic aneurysm (TAA). The 195 patients with CAD had the best all-cause mortality outcomes: 3.2 per 100 patient years.9 Aortic-related mortality was also lowest in the CAD group: 0.4 per 100 patient years vs. 0.6 for TAA and 1.2 for AAD.
The reintervention rates for patients with aortic dissection were high, compared with TAA in the MOTHER registry. INSTEAD XL revealed all-cause and aortic-related mortality, respectively, at 11.1% and 6.9% in patients with chronic type B dissection treated with TEVAR at 5 years.
Last but not least, TEVAR is the first choice for many elderly or frail patients with type B aortic dissection. Recovery after the open procedure is much more difficult for this population. Our specialty frequently underappreciates quality of life after an aortic operation.
Overall, TEVAR for chronic type B aortic dissection is feasible, reproducible, and less invasive than open repair. It has acceptable early results, rate of reverse aortic modeling, and late mortality, and although its reintervention rate can be significant, that can be reduced with experience and a careful algorithmic approach.
Dr. Ali Khoynezhad is a professor of cardiovascular surgery, director of aortic surgery, and co-director of the atrial fibrillation program at Cedars-Sinai Heart Institute, Los Angeles. He disclosed receiving research grants from Medtronic, Gore, and Vascutek.
Open repair is the better procedure.
It’s my contention that open repair is still the gold standard for chronic thoracoabdominal aortic dissection. It has a record of outstanding results in high-volume centers of excellence with low morbidity and mortality and very good long-term survival. It has no anatomical constraints. It’s a durable repair and there are no device- or procedure-related proximal and/or distal aortic complications. Reintervention on the operated segment is very rare.1-6
Thoracic endovascular repair (TEVAR), despite having very good procedural results, has challenges in the successful treatment of chronic aortic dissection. Morbidity is low, as are rates of spinal cord ischemia, stroke, and renal failure. However, thoracic remodeling at the level of the endograft is in the 70%-88% range, which means that 12%-30% of patients do not have protection in the form of reverse aortic remodeling. In the abdominal aorta, remodeling is uncommon, with 11%-23% thrombosis of the false lumen even with advantageous anatomy. Survival in several series is in the 60%-80% range at 3 and 5 years. TEVAR creates new challenges for chronic thoracoabdominal aortic dissection: retrograde type A dissections have been as high as 2%-7%; 15%-30% of cases require intervention; and stent graft-induced new entry (SINE) has been reported as high as 36%.
Specific anatomical features are not suitable for TEVAR. They include multiple visceral vessels off of the false lumen; multiple fenestrations, especially in the abdominal aorta; dissection within the dissection; and pseudocoarctation. The durability of the endovascular graft for chronic aortic dissection is unknown; it’s a relatively new procedure so the long-term data is lacking.
Success of the endovascular approach depends on aortic remodeling, and it’s my contention that the thoracic devices now available cannot effectively treat a chronic thoracoabdominal aortic dissection. There are steps surgeons can take to improve their success, but procedures specifically addressing the false lumen are not time-tested and thoracoabdominal-specific devices are not widely available in the United States. And of course, morbidity and mortality will increase with the complexity of the endovascular repair.
Our in-hospital outcomes with open repair of chronic thoracoabdominal aortic dissection using deep hypothermia and circulatory arrest have been excellent: mortality rate of 3.6%; a stroke rate of 1%; permanent spinal cord ischemia rate 2.6%; and a 0% rate of patients on permanent hemodialysis. Our hospital length of stay is approximately 12 days. Blood product transfusion is reasonable with a mean blood product transfusion of 9 units for the hospital admission. The reintervention rate is 1% for infected grafts, 3.1% for anastomotic pseudoaneurysm and 3.6% for growth of a distal aneurysm. Long-term survival is very good: 93% at one year; 79% at five years; and 57% at 10 years.
There’s no denying that mortality rates for endovascular repair are excellent. There’s no denying that open repair is much more invasive. And if the patient is of advanced age, is frail and has comorbidities, the endovascular repair can have a certain advantage.
But for false lumen obliteration, the advantage goes to open repair. With regard to reintervention, certainly the advantage is with open repair. For durability, from what we know currently, open repair has the advantage. There are no stent-induced new entries in open repair; and open repair can address any and all anatomy. A successful endograft repair requires fixation and seal in the appropriate aortic anatomy; it demands good proximal and distal landing zones. However, in chronic dissection, there is the added complexity of having to address the false lumen flow from an untreated abdominal aortic segment.
For patients with connective tissue disorders, open repair is still the gold standard. As for long-term survival, the advantage goes to open only because the endovascular approach is relatively new. If it’s done in high-volume centers with great experience, open repair has a mortality advantage as well.
Dr. Joel Corvera is an assistant professor of surgery and director of thoracic and vascular surgery at Indiana University, Indianapolis. He had no relationships to disclose.