Severe low-flow aortic stenosis after transcatheter aortic valve replacement (TAVR) is unlikely to normalize by 1 year and is linked to mortality, according to a secondary analysis of the PARTNER trial.
Flow was normal within 6 months of TAVR for the moderate low-flow (35.9 mL/m2 from 31.7 mL/m2 at discharge, P<0.001) and normal flow groups (38.8 mL/m2 from 43.1 mL/m2, P<0.001), but the same could not be said for the severe low-flow cohort.
These patients, while improving from their start at a mean of 23.1 mL/m2, maintained their low-flow status at 6 months and 1 year (31.4 mL/m2 and 33.0 mL/m2 respectively, P<0.001 for both), Howard C. Herrmann, MD, of Hospital of the University of the Pennsylvania in Philadelphia, and colleagues reported online in JAMA Cardiology.
The incidence of death by 1 year corresponded with the degree of low-flow as measured by the left ventricular stroke volume index: 26.5% for severe low-flow, 20.1% for moderate low-flow, and 19.6% for normal flow (P=0.045). On multivariable analysis, mortality was more likely in the severe low-flow arm (hazard ratio 1.61, 95% CI 1.17-2.23).
“Severe low-flow at discharge is associated with an increased risk of mortality following TAVR in patients with severe aortic stenosis and preexisting low-flow. The identification of remedial causes of persistent low-flow after TAVR may represent an opportunity to improve the outcome of these patients,” they concluded.
Herrmann’s analysis included echocardiograms from 984 patients with low-flow aortic stenosis at 26 participating sites in the U.S. and Canada.
Besides low flow at discharge, independent predictors of 1-year mortality after TAVR were:
- Male sex (HR 1.59, 95% CI 1.18-2.13)
- Atrial fibrillation (HR 1.41, 95% CI 1.06-1.87)
- High Society of Thoracic Surgeons score (HR 1.03, 95% CI 1.01-1.06)
- Moderate-to-severe mitral regurgitation at discharge (HR 1.65, 95% CI 1.21-2.26)
- Effective orifice area index (HR 1.87, 95% CI 1.09-3.19)
- Pre-TAVR mean transvalvular gradient (HR 0.98, 95% CI 0.97-0.99)
“The benefit of percutaneous mitral valve therapies after TAVR in this patient population has yet to be shown and may represent an area for further investigation,” according to the authors.
The authors pointed out that theirs was a retrospective study. They also acknowledged that they failed to collect echocardiographic data for patients with resting transvalvular gradients under 40 mm Hg.
“Furthermore, these data are not completely relevant to the larger issue of low-flow, low-gradient aortic stenosis,” James D. Thomas, MD, of Northwestern Memorial Hospital in Chicago commented in an accompanying editorial.
There are “few data from this study regarding the patient with truly low-gradient severe aortic stenosis, though the fact that larger valves and lower gradients were associated with worse survival suggests that not all of these patients may benefit from aortic valve replacement,” he wrote.
Thomas noted that the area and velocity measurements used to determine low-flow were made in different places pre- and post-TAVR. “None of this should negate the observations, as consistent methods were used, but it should challenge the echocardiography community to strive continually for more accurate methods in the future, perhaps using 3-dimensional flow calculations,” he wrote.
Herrmann’s group did not use 3-dimensional echocardiography, computed tomography, or invasive hemodynamic assessment to measure low-flow.
Indeed, “low flow before TAVR is one of the most important predictors of mortality following TAVR, but it is one of the harder qualities to measure. This presents a challenge to properly treating patients with low flow aortic stenosis, and can leave some patients at higher risk,” Herrmann acknowledged in a press release.
“Unfortunately, many centers do not routinely measure flow, but rather focus more on a patient’s pressure gradient or valve area when evaluating aortic stenosis pre-and post-TAVR,” Herrmann emphasized. “While low flow is more challenging to monitor, this measurement can better inform the patient’s risk of mortality, and in turn lead to better treatment.”
The PARTNER study was funded by Edwards Lifesciences.
Herrmann reported receiving grant support from Edwards Lifesciences, St. Jude Medical, Medtronic, Boston Scientific, Abbott Vascular, Gore, Siemens, Cardiokinetix, and Mitraspan; consulting fees and honoraria from Edwards Lifesciences and Siemens; and holding equity in Microinterventional Devices.
Thomas declared receiving honoraria from Edwards Lifesciences, Abbott Vascular, and GE Medical.
Anjan VY, et al “Evaluation of flow after transcatheter aortic valve replacement in patients with low-flow aortic stenosis: a secondary analysis of the PARTNER randomized clinical trial” JAMA Cardiol 2016; DOI: 10.1001/jamacardio.2016.0759.
Thomas JD “Low-flow aortic stenosis after transcutaneous aortic valve replacement: it’s all about the flow” JAMA Cardiol 2016; DOI:10.1001/jamacardio.2016.1206.