Persistent low flow warns of mortality risk after TAVR

By Eleanor McDermid

Patients with persistent low flow at discharge after transcatheter aortic valve replacement (TAVR) have an increased risk of dying during the subsequent year, report researchers.

"The identification of remedial causes of persistent [low flow] after TAVR may represent an opportunity to improve the outcome of these patients", suggest Howard Herrmann (Hospital of the University of Pennsylvania, Philadelphia, USA) and study co-authors.

Their analysis involved 984 patients, aged an average of 84 years, who were assigned to undergo TAVR in the PARTNER randomised trial. All patients had low flow (left ventricular stroke volume index [LVSVI] ≤35 mL/m²) prior to intervention.

The team divided the patients into tertiles of postprocedural LVSVI. Those with severe low flow, in the bottom tertile with an average LVSVI of 23.1 mL/m², had the highest all-cause mortality rate over the subsequent year, at 26.5%, and the highest cardiovascular mortality rate, at 11.4%.

Conversely, patients in the top tertile, whose flow normalised (average LVSVI=43.1 mL/m²), had the lowest all-cause and cardiovascular mortality rates, at 19.6% and 6.0%, respectively. And patients whose flow was partly normalised at discharge (LVSVI=31.7 mL/m²) had intermediate rates, at a corresponding 20.1% and 7.9%. Their LVSVI continued to improve after discharge, normalising by 6 months, whereas it remained low for the whole year in patients with severe low flow at discharge.

The effect of persistent low flow on mortality was evident both in patients with classical and with paradoxical low-flow aortic stenosis, the team notes in JAMA Cardiology.

After accounting for confounders, being in the postprocedural severe low flow group increased the risk of all-cause mortality by a significant 61%, compared with having at least partly normalised flow. Moderate or severe aortic regurgitation was most common in patients with persistent low flow, at 16%, compared with around 9% in the other two groups, and this also had a significant impact on outcomes, raising patients' mortality risk by 65%.

Writing in an accompanying commentary, James Thomas (Northwestern University, Chicago, Illinois, USA) says that, while the findings are "clearly significant", they are also no surprise.

"Ideally, we would like evidence of what measures can be taken to improve outcome in these patients, and the observational nature of this study limits insight into this aspect", he says.

Thomas also points out that the trial's enrolment criteria excluded many patients 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."

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