PARTNER Substudy Looks at Echocardiographic Differences Between TAVR, Surgery

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Both surgical and transcatheter aortic valve replacement (TAVR) lead to lasting reductions in transaortic gradient and gains in effective orifice area (EOA), according to a new analysis of the PARTNER trial scheduled for online publication April 23, 2013, ahead of print in the Journal of the American College of Cardiology. But differences emerge in other echocardiographic findings as well as in predictors of death between the 2 treatments, suggesting possibilities for better patient selection.

Rebecca T. Hahn, MD, of Columbia University Medical Center (New York, NY), and colleagues looked at 636 patients with severe aortic stenosis enrolled in cohort A of the PARTNER trial who underwent their assigned treatment and received a valve implant. In all, there were 326 patients from the TAVR arm (97 transapical and 229 transfemoral) and 310 from the surgery arm. A core laboratory managed the process of image acquisition and analysis and centrally analyzed echocardiographic findings.

Baseline echocardiographic parameters related to LV size, geometry, and function as well as valvular hemodynamics and levels of mitral and aortic regurgitation all were similar between the 2 treatment groups.

Sustained Changes at 2 Years

Immediately post-procedure, TAVR and surgery patients showed reductions in transaortic gradients and increases in EOA (P < 0.0001 vs. baseline for all); these changes were retained over 2 years. Both treatments resulted in similar LV mass regression. Over 2 years, TAVR provided larger indexed EOA than surgery (P = 0.038) but also greater total aortic regurgitation (P < 0.0001; table 1).

Table 1. PARTNER Cohort A: Echocardiographic Findings

Abbreviations: AV, aortic valve; EOA, effective orifice area; LV, left ventricular.

In addition, prosthesis-patient mismatch was lower with TAVR than with surgery through 2 years (P = 0.0193; table 2).

Table 2. PARTNER Cohort A: Prosthesis Patient Mismatch

Univariate predictors of mortality differed between TAVR and surgery.

For TAVR patients, the only baseline echocardiographic factor to predict death was peak gradient (HR 0.94; 95% CI 0.90-0.99 per 5 mm Hg increase; P = 0.010). Post-implantation predictors included paravalvular aortic regurgitation that was more than mild (HR 2.11; 95% CI 1.43-3.10; P = 0.0002) in addition to larger LV diastolic volume, LV systolic volume, and indexed EOA and lower LVEF. Patient-prosthesis mismatch, meanwhile, was associated with lower mortality (HR 0.74; 95% CI 0.57-0.96; P = 0.024)

For SAVR patients, there were several baseline echocardiographic predictors of mortality, the strongest of which was mitral regurgitation (HR 1.49; 95% CI 1.17-1.90 per grade; P = 0.001). Post-implantation of predictors were stroke volume of 35 mL/m² or less (HR 1.97; 95% CI 1.16-3.33; P = 0.0012) and prosthesis-patient mismatch (HR 1.43; 95% CI 1.11-1.84; P = 0.0005) as well as small LV diastolic volume, LV systolic volume, EOA, and stroke volume.

Core Lab a Key Component

The current study “documents early and sustained hemodynamic improvements with both therapies and freedom from structural valve deterioration, while highlighting the differences in therapeutic groups and presenting echocardiographic determinates of outcome,” Dr. Hahn and colleagues conclude, adding, “A complete understanding of these differences may allow future refinement in patient selection.”

Brian D. Hoit, MD, of Case Western Reserve University (Cleveland, OH), points out in an accompanying editorial that “the acquisition and interpretation of echocardiographic data is highly patient- and operator-dependent, which introduces variability and bias and lowers reproducibility.”

Though the new findings are primarily “hypothesis generating,” PARTNER “is important because of its multicenter, randomized design that uses core laboratory principles to maximize the accuracy and prediction of echocardiographic data,” he concludes.

In a telephone interview with TCTMD, Josep Rodés-Cabau, MD, of Laval University (Quebec City, Canada), said that while the results are in line with what is known about TAVR and surgery, they deserve praise for being “very detailed” and originating from a core lab.

TAVR Still Evolving

Dr. Rodés-Cabau added that the disparate echocardiographic outcomes and mortality predictors between TAVR and surgery may present an opportunity.

“Maybe there are some groups that benefit from these better antegrade hemodynamics—better gradients and less mismatch—and then maybe other groups benefit more from having zero aortic insufficiency,” he noted. “At this point, it’s difficult to say which [patients are in] these groups, and it will be important to identify them.”

According to Dr. Rodés-Cabau, aortic regurgitation is a known limitation of TAVR. However, better sizing and evolving technology will change the situation, he predicted, adding, “I don’t think we can say that in 5 years this problem will be solved and the results will be equivalent to surgery, but I am sure the results will improve.”

Importantly, outcomes being obtained now through post-dilation and other techniques are likely even better than those seen in the original PARTNER trial, he said.

Note: Study coauthors Martin B. Leon, MD, and Susheel K. Kodali, MD, both of Columbia University Medical Center, are faculty members of the Cardiovascular Research Foundation, which owns and operates TCTMD.

1. Hahn RT, Pibarot P, Stewart WJ, et al. Comparison of transcatheter and surgical aortic valve replacement in severe aortic stenosis: A longitudinal study of echo parameters in cohort A of the PARTNER trial. J Am Coll Cardiol. 2013;Epub ahead of print.

2. Hoit BD. Evaluating the results of transcatheter versus surgical aortic valve replacement: The value of a core echocardiographic laboratory. J Am Coll Cardiol. 2013;Epub ahead of print.

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