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Absent any clinical red flags, the slow deterioration of valve hemodynamics after transcatheter aortic valve replacement (TAVR) may be a sign of valve thrombosis, a registry study suggested.

After up to 4 years of follow-up, 4.5% of TAVR patients displayed signs of valve hemodynamic deterioration -- defined as a 10 mm Hg or more increase in transprosthetic mean gradient during follow-up – with more than half of these individuals reaching such a state within 1 year, according to , of Quebec Heart and Lung Institute in Canada, and colleagues.

they reported in the Feb. 16 issue of the Journal of the American College of Cardiology were:

• Lack of anticoagulation therapy at hospital discharge (hazard ratio 3.35, 95% confidence interval 1.57-7.13)
• Use of valve-in-valve procedures (HR 2.32, 95% CI 1.07-5.04)
• Use of a 23-mm valve or smaller (HR 2.07, 95% CI 1.14-3.76)
• Higher BMI (HR 1.08, 95% CI 1.03-1.13)

"These findings suggest the need for closer clinical and echocardiographic follow-up in patients with such characteristics," the authors concluded.

Lack of anticoagulant therapy remained strongly linked to hemodynamic deterioration (HR 4.58, 95% CI 1.07-19.57) even after a subanalysis excluded patients with small valves, previous valve-in-valve procedures, and moderate-to-severe aortic regurgitation.

This finding supported "valve thrombosis as one of the main mechanisms underlying valve hemodynamic deterioration and suggested that the incidence of subclinical valve thrombosis post-TAVR may be higher than previously reported," the authors wrote.

Despite arriving relatively late to the TAVR world, interest in hemodynamic deterioration will grow in importance "considering the recent rapid expansion of transcatheter heart valve technologies, the inevitable push to treat lower-risk and young patients with transcatheter heart valve technologies, and the current lack of evidence-based post-TAVR antithrombotic therapeutic strategies," they emphasized.

Even though modern TAVR valves "have shown no significant clinical signal of early structural valve deterioration or valve thrombosis," there is growing evidence that "presumptive bioprosthetic valve leaflet thrombosis may be a more important issue than previously realized," according to an accompanying editorial by , of Baylor Scott & White Health in Plano, Texas, and colleagues.

Mack's group wrote that it is a condition that was, until recently, likely underdiagnosed.

When the initial report in October raised concern about reduced leaflet mobility of both surgical and transcatheter aortic valves, believed to be due to subclinical leaflet thrombosis, the FDA and researchers cautioned that the clinical significance is unknown.

In the registry study of 1,521 patients who underwent TAVR between 2007 and 2014 and received echocardiographic evaluations thereafter, those with hemodynamic dysfunction did not suffer more deaths (33.5% versus 30.0%, log-rank P=0.915), cardiovascular deaths (18.2% versus 13.5%, log-rank P=0.782), or strokes (7.1% versus 3.2%, log-rank P=0.969).

For now, "the relationships among the abnormalities seen with imaging, the hemodynamic changes seen with transthoracic echocardiography, and clinical events remain unclear," Mack's group wrote.

Nonetheless, "if an interval increase in transvalvular mean gradient is detected, there should be consideration of anticoagulation, on the basis of a clinical evaluation of risk versus benefit in that individual patient," they wrote, adding that, in fact, "anticoagulation should be considered in the first 3 months in those patients at highest risk for valve thrombosis."

"TAVR has undeniably benefit thousands of patients with severe aortic stenosis. However, as with any new therapy, adverse events and limitations – many unanticipated – may gradually become known as usage and experience expand. Over the past 2 years, light has been shed on the issue of subclinical valve thrombosis and valve hemodynamic deterioration," Mack and colleagues concluded.

They found it clear that now "the harder one looks, the more one finds."