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An early fall in kidney function after transcatheter aortic valve replacement (TAVR) predicted mortality, although seen in less than a quarter with baseline insufficiency, according to a PARTNER 1 trial substudy.

In the PARTNER 1 trial and continued access registries, 72% of the total study population had baseline renal insufficiency (N=821). Of this group, at 30 days post-TAVR, Nirat Beohar, MD, of Mount Sinai Medical Center in Miami Beach, Fla., and colleagues reported online in JAMA Cardiology.

Associated with 1-year mortality were baseline estimated glomerular filtration rate (eGFR, OR 0.98, 95% CI 0.96-0.99) and a drop in eGFR (OR 1.51, 95% CI 1.02-2.24), as well as baseline left ventricular ejection fraction (OR 0.98, 95% CI 0.97-0.99).

From 30 days to 1 year, an improved eGFR didn't translate into less mortality or repeat hospitalization. A worsening in renal function, however, numerically trended towards more deaths (25.5% versus 19.1% for patients with no change in eGFR, P=0.07)

"The present analysis underscores the high prevalence of baseline renal insufficiency among high-risk and inoperable patients with severe symptomatic aortic stenosis, the cause of which is likely to be multifactorial, including type 2 cardiorenal syndrome (decreased renal perfusion because of cardiac dysfunction) related to aortic stenosis-induced reduced cardiac output, right ventricular dysfunction, and elevated renal venous pressure, all of which contribute to decreased renal perfusion," Beohar's group suggested.

Renal worsening also showed a trend for poorer outcomes in terms of combined death or major stroke (25.3% versus 19.0%, P=0.08).

Still, 76% of patients didn't have their renal insufficiency exacerbated with TAVR. "It appears, therefore, that among these patients, the salutary hemodynamic effects of TAVR resulting in improved renal perfusion may have outweighed the adverse procedural features," the researchers wrote, "such as using iodinated contrast, drops in blood pressure during rapid pacing at the time of valve deployment, and embolic debris.

"In the present analysis, those with improved eGFR after TAVR were more likely to have a lower baseline cardiac index and eGFR, suggesting that among these patients relief of aortic stenosis with TAVR had a beneficial impact on type 2 cardiorenal syndrome."

Independent predictors of improved eGFR were female sex (OR 1.38, 95% CI 1.03-1.85) and nonsmoking status (OR 1.49, 95% CI 1.11-2.04). Those for reduced eGFR were baseline left ventricle mass (OR 1.00, 95% CI 1.00-1.01), smoking (OR 1.51, 95% CI 1.06-2.14), and age (OR 1.03, 95% CI 1.00-1.05).

"While procedural characteristics are expected to affect post procedural eGFR, we found no significant difference between the groups in terms of procedural characteristics such as the volume of contrast used, procedural success, needing aortic valve reintervention, major bleeding, vascular complications, or needing transfusions," according to the investigators.

Even so, Beohar and colleagues suggested several measures to prevent a worsening of renal function after TAVR: careful pre-procedural hydration, limited rapid pacing during valve deployment, bringing the blood pressure up if patient is hypotensive before placing the transcatheter valve across the aortic valve, and the use of renal embolic protection devices and the RenalGuard system.

The PARTNER substudy enrolled participants from U.S. and Canada (48.8% women). Average ages across the improved, worsened, and no-change eGFR groups were 84.9, 85.4, and 84.4 years, respectively. These cohorts had median Society of Thoracic Surgeons scores of 10.9%, 11.1%, and 10.6%.

Important limitations to Beohar's study include its retrospective design and, because the exclusion of patients without 30-day eGFR and those who died during that early window, a potential for survival bias. It is also unclear what the impact of TAVR is on patients with severe renal insufficiency and those on dialysis, because they were excluded from the PARTNER trial.

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