TAVR was associated with similar and stable valve hemodynamics and improved hemodynamic burden on both left and right ventricular function at five years compared with SAVR in low-risk patients with severe aortic stenosis (AS), according to a new echocardiographic analysis from PARTNER 3 published April 16 in JACC: Cardiovascular Imaging. Furthermore, among common echo parameters, only high valvulo-arterial impedance (Z_va) and low rates of ventricular-to-pulmonary artery coupling (RV-PA) were associated with the primary composite endpoint of death, stroke or rehospitalization.

In the multicenter study, low-risk patients with severe AS were randomized to either SAVR (n=453) or transfemoral TAVR with the balloon-expandable SAPIEN 3 valve (n=495). Transthoracic echocardiograms were taken at baseline, 30 days and annually for five years. Among patients, 79% of both arms had echocardiograms available for this analysis.

Results showed that TAVR patients compared with SAVR patients had higher rates of mild-to-severe aortic regurgitation (24.5% vs. 6.3%, p<0.001), as well as a higher mean transaortic gradient (12.8 vs. 11.7 mm Hg, p<0.001), stroke volume index (SVI) (44.6 vs. 41.1, p<0.0001) and aortic valve area (1.87 vs. 1.82, p=0.895). In addition, low-flow SVI and left ventricular hemodynamic burden were less common with TAVR, while tricuspid annular plane systolic excursion (TAPSE) was lower and RV-PA coupling was higher.

Of note, 33.0% of SAVR patients had Z_va ≥4 mm Hg/mL/m² compared with 25.2% of TAVR patients (p<0.01). Rates of RV-PA uncoupling – when TAPSE/PASP is <0.50 mm/mm Hg – were 59.1% among SAVR patients and 33.9% among TAVR patients (p<0.0001).

In both treatment groups, RV-PA uncoupling and high Z_va at 30 days were the only two measured echo parameters associated with an increased risk of the primary endpoint at five years. On the other hand, 30-day moderate to severe prosthesis-patient mismatch, mild-to-severe aortic regurgitation and stroke volume index had no association.

"Our results contribute to the published reports suggesting that RV-PA coupling using TAPSE/PASP may be an important measure of outcomes in low-risk patients undergoing intervention," write study authors Rebecca T. Hahn, MD, FACC, et al. "Given these findings, it is possible that a high Z_va or low TAPSE/PASP seen at 30 days warrants closer follow-up and possible improvement in medical management. Better blood pressure control or aggressive management of comorbidities could potentially improve Z_va, but this requires further study."

The authors note that, due to a well-defined patient population, results might not be generalizable to larger populations or applicable to other transcatheter valve systems. Additionally, they recommend longer-term echocardiographic follow-up to continue observing the effects of TAVR beyond five years. Follow-up for the PARTNER 3 trial is planned at 10 years.