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Outside the United States, a growing number of patients with severe aortic stenosis are undergoing transcatheter aortic valve replacement (TAVR) despite being at only intermediate risk for surgery. Now an observational study comparing the therapies suggests that the choice of TAVR over surgery does not jeopardize early or 1-year survival in this patient subset.

The findings from a registry trial are scheduled to be published in the May 2013 issue of JACC: Cardiovascular Interventions.

Investigators led by Peter Jüni, MD, of the University of Bern (Bern, Switzerland), looked at 3,666 consecutive patients with symptomatic severe aortic stenosis who underwent TAVR (n = 782) or surgery (n = 2,884) at 3 European centers between November 2006 and January 2010. From this cohort, they created 405 propensity score-matched pairs of patients treated with each technique.

The pairs were stratified into 3 groups according to STS score:

• Less than 3% (n = 99)
• 3% to 8% (n = 255)
• More than 8% (n = 51)

The pairs with STS scores of 3% to 8%, deemed to be at intermediate surgical risk, constituted the study population.

The mean STS score of propensity score-matched TAVR patients decreased from 6% to 4.3% from the first to the last quartile of the study period. (P for trend < 0.001), suggesting that practice patterns are evolving toward lower-risk patients.

No Mortality Difference at 30 Days, 1 Year

In the intermediate-risk cohort, 30-day mortality was similar between TAVR and surgery patients (7.8% v. 7.1%; HR 1.12; 95% CI 0.58-2.15; P = 0.74), as was 1-year mortality (16.5% vs. 16.9%; HR 0.90; 95% CI 0.57-1.42; P = 0.64). For the latter endpoint, treatment effects were comparable across several subgroups except for sex, with TAVR being more beneficial relative to surgery in women compared with men (P for interaction = 0.027).

In the overall cohort of propensity score-matched pairs, there were no differences between TAVR and surgery patients for 30-day (HR 1.29; 95% CI 0.76-2.20, P = 0.35) or 1-year mortality (HR 1.02; 95% CI 0.71-1.46; P = 0.93). Likewise, there was little evidence of differences in risk between the 191 pairs with STS scores of 4% or lower (HR 0.75) compared with the 214 pairs with STS scores of greater than 4% (HR 1.26; P for interaction = 0.17). In the subset of 99 propensity score-matched pairs with STS scores of less than 3%, the HR was 0.75 (95% CI 0.17-3.35; P = 0.71) at 30 days and 0.76 (95% CI 0.34-1.75; P = 0.53) at 1 year.

Beware of Imitations

The authors observe that just over one-third of TAVR patients in the overall cohort had STS scores between 3% and 8% and thus would potentially qualify for enrollment in the ongoing randomized SURTAVI trial, which is comparing TAVR and surgery in patients at intermediate surgical risk. 

In fact, Peter C. Block, MD, of Emory University School of Medicine (Atlanta, GA), suggested that the registry study may be trying to approximate the randomized SURTAVI trial by means of propensity matching. But because that strategy is “fraught with hazards” and the analysis is plagued by missing data, “we need to be cautious” in interpreting the results, he said.

“On the positive side, any data that we can gather on TAVR at this point is useful,” Dr. Block noted, “and my guess is that the [ultimate] outcome of SURTAVI will be very similar to this one, because lower-risk patients are commonly treated [with TAVR] in Europe and are doing very well. But we really need [to wait for] the randomized trials, including PARTNER II, which will hopefully be the final arbiters of TAVR’s safety and efficacy in this group.”

‘Intermediate Risk’ Label Questionable 

In a telephone interview with TCTMD, Philippe Généreux, MD, of Columbia University Medical Center (New York, NY), said he was taken aback by the finding that 30-day TAVR mortality in the paper was higher than and 1-year mortality similar to those outcomes in PARTNER I Cohort A, which enrolled only high-risk patients. It renders the characterization of the study group as ‘intermediate risk’ suspect, he asserted.

“[The mortality findings] demonstrate the inability of the STS score to appropriately risk-stratify patients,” he observed, noting that the tool fails to capture many traits known to be tied to a worse prognosis, such as frailty. Also, the inability of the investigators to provide the STS scores of surgery patients is inexplicable, he commented.

“Despite all the shortcomings of this paper, and the fact that these patients seem to be sicker than their STS score projects, I think it’s still a fair anticipation of what [the results] will be in SURTAVI and PARTNER II,” Dr. Généreux continued.  But these data are far from definitive, he stressed, even though some clinicians are likely use them to justify their existing practice of offering TAVR to lower-risk patients.

The heart team takes on added importance in the intermediate-risk population insofar as it can identify prognostic factors that the STS score overlooks, Dr. Généreux said. On the other hand, he commented, if TAVR and surgery are shown to be in equipoise, the heart team may also encounter some strains, as interventionalist and surgeon can both make equally good cases for their therapy.

In addition, as the TAVR field moves toward lower-risk patients, Dr. Généreux predicted that mortality will become less relevant as an endpoint because most patients will survive either procedure Instead, in these younger, healthier patients, attention will shift to reducing TAVR complications like paravalvular leakage and stroke and ensuring prosthesis durability, he noted.

Study Details

For the cohort of intermediate-risk pairs of TAVR and surgery patients, the mean ages were 80.6 years and 79.7 years, respectively, and at baseline, 83.7% and 86.3% were in NYHA functional class III or IV. The mean logistic EuroScore was 17.3% for TAVR patients and 17.6 for surgical patients. Overall, one-tenth or less had severe left ventricular dysfunction (LVEF < 30%).

Piazza N, Kalesan B, van Mieghem N, et al. A 3-center comparison of 1-year mortality outcomes between transcatheter aortic valve implantation and surgical aortic valve replacement on the basis of propensity score matching among intermediate-risk surgical patients. J Am Coll Cardiol Intv. 2013;6:443-451.

Related Stories:

• German Valve Registry Shows Advantage of Surgery in Lower Risk Patients
• No Change Seen in European TAVR Clinical Use Patterns
• Registry Study Explores Potential for TAVR in Low-, Intermediate-Risk Patients