Superior Survival With TEVAR vs Open Aortic Aneurysm Repair

Batya Swift Yasgur MA, LSW

February 21, 2019

Thoracic endovascular aortic repair (TEVAR) confers a survival rate superior to that of open surgical repair of intact descending thoracic aortic aneurysms, a new study suggests.

A team of investigators from the Department of Cardiothoracic Surgery and Department of Health and Research, Stanford University School of Medicine, California, used a Medicare database to conduct a retrospective study comparing 2470 patients who underwent TEVAR with 1235 matched patients who underwent open surgical repair between 1999 and 2010, with follow-up continuing through 2014.

They found that open surgical repair was associated with increased odds of early postoperative mortality but reduced late hazard of death. In contrast, mean survival was greater in patients who had undergone TEVAR.

"The superior survival observed in patients undergoing TEVAR compared with open surgical repair suggests that TEVAR ought to be considered first-line among Medicare beneficiaries with open surgical repair restricted to high-volume centers and patients with low risk of perioperative mortality," the authors, with first author Peter Chiu, MD, and corresponding author Michael D. Dake, MD, conclude.

The study was published in the February 19 issue of the Journal of the American College of Cardiology.

Previous Studies Imprecise

Since its approval by the US Food and Drug Administration (FDA) in 2005, the use of TEVAR has been expanding as an alternative to open surgical repair for the treatment of descending aortic aneurysms as a result of "excellent perioperative outcomes with TEVAR reported in small prospective nonrandomized trials," the authors write.

However, larger studies have suggested that the survival advantage of TEVAR might end at about 2 years, suggesting that open surgical repair might have superior midterm outcomes, they note.

Previous efforts to examine short- and long-term results using data from the Nationwide Inpatient Sample and the Medicare database have been "limited, due to the reliance on imprecise diagnostic and procedural codes" of ICD-9, which "fail to distinguish between ascending, arch, and descending thoracic aortic aneurysms."

These differences are relevant because each type requires a different approach and has a different expected survival time.

Failure to distinguish between these different disease processes may "introduce substantial bias," the authors point out.

The current study therefore utilized Current Procedural Terminology (CPT) codes, which are able to distinguish among operations of different segments of the thoracic aorta.

Additionally, these CPT codes are able to compare midterm outcomes of TEVAR and open surgical repair.

Pre- and Post FDA Approval

To look at this question, the researchers retrospectively reviewed Medicare data from 1999 to 2010 with follow-up through 2014, obtaining data regarding demographics, survival, comorbidities, and diagnostic codes from several additional databases.

Patients were excluded if they underwent concomitant procedures or had aortic dissection, ruptured thoracic aortic aneurysm, trauma, or aortoenteric fistulae.

Abrupt change in practice pattern after the introduction of TEVAR in 2005 was used in a regression discontinuity design.

Patients undergoing surgery prior to FDA approval were encouraged toward open surgical repair (100% compliance), whereas virtually all patients were compliant with treatment encouragement toward TEVAR (94.4% compliance) once it became available.

The analysis then "proceeded as an 'intent to treat'" — that is, patients in the second half of the study period undergoing open surgical repair were treated in a manner similar to noncompliers in a randomized trial and analyzed as part of the TEVAR group.

"This approach was used due to the inability to identify patients who were anatomically ineligible for TEVAR in the early phase of the study," the authors explain.

The introduction of TEVAR increased the pool of patients clinically eligible for aortic repair, leading to an imbalance in baseline covariates, which the researchers addressed using a nonparsimonious logistic regression model and a standardized difference approach between matched patients.

The primary end point was all-cause mortality, and the secondary end point was reintervention (either open or endovascular) or the descending thoracic aorta.

9-Year Survival Advantage

The researchers identified 16,955 Medicare patients with specific codes for endovascular or open surgical repair of the descending thoracic aorta (n = 11,411 and n = 5544, respectively).

After the exclusion of patients who did not meet the inclusion criteria prior to matching, the cohort consisted of 1235 open surgical repair and 4580 TEVAR patients.

After the introduction of TEVAR, there was a decrease in the frequency of open surgical repair and a "substantial increase" in the overall frequency of descending thoracic aortic aneurysms treated in Medicare beneficiaries.

Prior to matching, TEVAR patients tended to be older and have a greater burden of chronic diseases than open surgical repair patients. They were also less likely to be treated at a high-volume open surgical center.

The researchers report that their matching algorithm "successfully matched" each open surgical repair patient with two TEVAR patients, with balance achieved across all available covariates.

In the matched group, the median duration of follow-up was 5.6 years (interquartile range [IQR], 0.7 - 10.0 years) for open surgical repair and 4.7 years (IQR, 2.5 - 6.4 years) for TEVAR.

Mortality was significantly lower among TEVAR patients than among open surgical repair patients (log-rank test P < .001).

There was "clear evidence" that the hazard of open surgical repair did not remain consistent, but rather varied over time, with an early phase of increased risk and a later phase of lower risk for death compared with TEVAR, the authors report.

Mortality at 180 days was greater among open surgical repair patients than among TEVAR patients (23.8% [95% CI, 21.4% - 26.1%] vs 10.2% [99.0% - 11.4%]).

Late hazard of death was reduced in the open surgical repair group (hazard ratio [HR], 0.86; 95% CI, 0.77 - 0.95; P = .004).

The difference in restricted mean survival time (RMST) was −209.2 days (95% CI, −298.7 to −119.7 days; P < .001), "revealing a substantial survival disadvantage with open surgical repair compared with TEVAR at 9 years," the authors comment.

Among those patients treated after the introduction of TEVAR, patients who were matched had a significantly lower comorbidity burden and lower mortality during follow-up than patients who were unmatched (HR, 0.70; 95% CI, 0.65 -0.76; P < .001).

Sensitivity analyses teasing out factors such as institution differences and time period "did not affect the inference from the main analysis," the authors state.

Despite a reduction in perioperative mortality for open surgical repair in the second half of the study period, there was no difference in the risk for midterm death.

Hospital Volume

Matched regression discontinuity analysis found that, of 293 first-time reinterventions on the descending thoracic aorta, 90.7% were performed endovascularly.

A "substantial risk" was found to be associated with reintervention, they note.

Patients who had originally undergone open surgical repair and required reintervention had higher 180-day mortality than those originally treated with TEVAR (23.5% vs 19.3%).

In contrast, open surgical repair patients experienced a significantly lower likelihood of reintervention at 9 years than TEVAR patients (5.3% [95% CI, 3.9% - 6.6% vs 10.1% [95% CI, 8.8% - 11.5%]; HR, 0.45; 95% CI, 0.34 - 0.60; < .001).

"Despite the potential improved durability of open surgical repair, the initial mortality advantage of TEVAR over open surgical repair persisted until 9 years postoperatively, resulting in a significant survival benefit associated with TEVAR," the authors conclude.

However, "the late hazard of death and risk of reintervention were lower among patients who underwent open surgical repair."

They note that hospital volume significantly affected perioperative outcome and, in fact, was one of the major driving forces for the difference between TEVAR and open surgical repair.

"Regionalization of care by limiting open surgical repair to a group of high-volume and high-performing centers should be considered, given the superior outcomes seen at centers of excellence," the authors advise.

"Referral to an aortic center may further improve the likelihood of appropriate treatment selection after weighting the risks and benefits of each approach," they add.

Novel Statistical Methods

Commenting on the study for theheart.org | Medscape Cardiology, Fenton McCarthy, MD, MS, New Mexico Heart Institute and the University of New Mexico, Albuquerque, who was not involved with the research, said that it "makes a number of important contributions to the field of aortic surgery, as well as surgical outcomes research, although with some limitations, especially in potentially younger and healthier patients."

The researchers are able to "show a significant survival advantage to TEVAR over open surgery for aneurysms in the descending thoracic aorta" using "relatively novel statistical methods, at least to the field of cardiac surgical outcomes research, that are worth highlighting," said McCarthy, who is coauthor of an accompanying editorial.

The study's most significant contribution to the field "is the demonstration of long-term survival benefits of TEVAR," since the majority of previous studies focused on short-term outcomes.

"For clinicians, the important message is that TEVAR can potentially provide long-term survival advantage to patients, particularly Medicare patients," he said.

"Consideration should be given to referring to high-volume centers for the management of descending aortic pathology in patients of all ages to offer the most appropriate therapies and to concentrate this expertise and experience so as to optimize outcomes," he added.

This work was conducted with support via several awards to researchers from the National Institutes of Health. The study authors' disclosures are listed on the original paper. McCarthy reports no conflicts of interest. His coauthor's disclosures are listed on the original editorial.

J Am Coll Cardiol. 2019;73:643-51, 652-653. Abstract, Editorial

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