Pathology predicts midterm outcome after endo repair

Endovascular repair of the thoracic aorta appears to offer good protection from aortic-related mortality in patients with aneurysm or dissection, according to a study published Jan. 1 in Circulation. But the high rate of nonaortic-related deaths suggests that more attention needs to be paid to modifiable risk factors in aneurysm patients, according to researchers, while the authors of an accompanying editorial questioned whether aneurysm patients should be treated in the first place.

Matt M. Thompson, MD,  of the division of cardiovascular sciences at St. George’s Vascular Institute in London, and colleagues collated data from five Medtronic trials and one institution to create the Medtronic Thoracic Endovascular Registry. Their goal was to use the registry to investigate midterm outcomes of patients treated with thoracic endografts (Talent and Valiant stent-graft systems, Medtronic) to determine the durability of thoracic endovascular aortic repair (TEVAR). They noted that physicians increasingly favored TEVAR as a treatment for thoracic aortic conditions because of its early mortality advantage over open surgery.

“Given the spectrum of different pathologies that affect the descending thoracic aorta, it is important to define whether the outcome of TEVAR is pathology specific to refine procedural technique and endograft design,” they wrote. “Careful analysis of long-term results will be required to define which subsets of patients benefit most from endovascular therapy and to modify management algorithms according to the pathology treated.”

They identified 670 patients with thoracic aortic aneurysm (TAA), 195 with chronic type B aortic dissection (more than two weeks after symptom onset) and 114 with acute type B aortic dissection (less than two weeks after symptom onset). Mean follow-up for the TAA groups was 3.1 years; for the chronic type B aortic dissection group, 2.4 years; and for the acute type B aortic dissection group, 2.2 years.

Their analysis showed that TAA patients were older with significantly higher rates of comorbidities than the other patient groups. Acute type B aortic dissection patients all were treated nonelectively.

Using regression modeling, Thompson et al found that age, emergency admission, American Society of Anesthesiologists grade and pathology were independent predictors of 30-day death. Of those patients who underwent elective surgery, the TAA group had more deaths compared with the chronic type B aortic dissection group (5 percent vs. 3 percent); more strokes (5 percent vs. 2 percent); and more acute spinal cord injuries (5 percent vs. 3 percent) after TEVAR.

Midterm mortality was higher in the TAA group, mostly due to nonaortic death. The all-cause mortality rate was 8, 4.9, and 3.2 deaths per 100 patient-years for TAA, acute type B aortic dissection and chronic type B aortic dissection, respectively. The rate of aortic-related death was 0.6, 1.2 and 0.4 deaths per 100 patient-years for TAA, acute type B aortic dissection and chronic type B aortic dissection, respectively.

The TAA group was more likely to remain free of aortic reintervention. At six years, 84 percent of the TAA group was reintervention-free vs. 71 percent in the chronic type B dissection and 46 percent in the acute dissection groups. The researchers found no association between the need for aortic reintervention and midterm death.

Their results demonstrated that TEVAR outcomes are pathology-specific, they wrote. “The midterm results revealed considerable differences in mortality and reinterventions with reference to aortic pathology.”

Their midterm analysis also demonstrated that patients with acute and chronic aortic dissection had low rates of aortic-related deaths after TEVAR, “which suggests that endovascular therapy has the potential to confer prevention of aortic dissection and rupture over a reasonable time period. This effect appears to be dependent on aortic surveillance and subsequent intervention because rates of aortic reintervention in patients with acute and chronic type B aortic dissection were higher than those described for patients with TAA.”

They pointed out that only 53 percent of patients in the TAA group took statins, and that more attention should be paid to medical management of cardiovascular risk factors in these patients.

Editorialists Joseph S. Coselli, MD, Susan Y. Green, MPH, Scott A. LeMaire, MD, all of Baylor College of Medicine in Houston, praised Thompson et al's study design for stratifying patients into groups based on presenting pathology and providing supplementary data on midterm outcomes. They observed that the number of patients now being treated has increased, “perhaps because many patients previously considered at prohibitive risk for open repair, as well as patients with acute aortic dissection who were once treated by medical management alone, are now being treated endovascularly,” they wrote.

They described the long-term survival data as “sobering,” with aneurysm-related deaths a reflection of the high burden of comorbidities in this patient group. “This result … raises the question of whether these patients should be treated at all, because aneu­rysms tend to grow slowly,” the editorialists wrote. “This question is particularly impor­tant when elective TEVAR is being considered for patients deemed unsuitable for open repair, because TEVAR in such patients is associated with extremely poor midterm survival.”

Thompson and colleagues listed several limitations in the study, including the inability in some cases to accurately determine the cause of death, which may have led to underreporting; care that may no longer reflect current practice; and the use of high-volume centers, which may not make the results generalizable.