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A catheter-based aortic valve capable of being repositioned or retrieved has shown solid hemodynamic and clinical results out to 2 years in a small, first-in-human study published online November 29, 2011, ahead of print in Circulation: Cardiovascular Interventions. Despite the valve’s nonmetallic frame, its position and shape remained stable over this period.

Investigators led by Joachim Schofer, MD, PhD, of the Hamburg University Cardiovascular Center (Hamburg, Germany), evaluated the midterm performance of the Direct Flow Medical valve (Direct Flow Medical, Santa, Rosa, CA) in 16 high-risk patients with severe aortic stenosis undergoing transcatheter aortic valve replacement (TAVR) at their center between September 2007 and March 2008.

The Direct Flow valve is composed of a bovine pericardial tissue trileaflet in an inflatable polyester fabric cuff. Inflatable rings at the upper and lower margins of the valve provide temporary and—once the positioning is deemed appropriate—permanent anchoring of the bioprosthesis. The valve was delivered transfemorally via a 22-Fr catheter.

Survival was 81% at 1 year (1 patient died before discharge of an MI unrelated to TAVR and 2 died within the first year, 1 of respiratory failure and 1 of an unknown cause) and 69% at 2 years (1 additional death of unknown cause). Eleven patients were available for 2-year follow-up. 

Hemodynamic Improvements Hold Up 

No conduction disturbances occurred during this period. Echocardiography showed that the mean gradient declined significantly from baseline to 30 days and remained stable over 2 years (table 1).

Table 1. Echocardiographic Outcomes in 11 Evaluable Patients

By Valve Academic Research Consortium (VARC) criteria, at 30 days, stenosis severity was ‘normal’ (mean gradient < 20 mm Hg) in 6 of 11 patients and ‘possible’ (mean gradient 20-35 mm Hg) in the other 5 patients. By 2 years, only 1 patient has slipped from ‘normal’ to ‘possible’ status. Moreover, the aortic valve area increased significantly from baseline and remained substantially unchanged over 2-year follow-up. At 30 days, the VARC criterion for a normal effective orifice area (> 1.2 cm²) was met by 3 patients, while 7 patients had ‘possible stenosis’ (1.2-0.8 cm²). By 2 years, however, 5 patients met the criterion for ‘normal’ effective orifice area while 5 had ‘possible stenosis.’

Before implantation at least mild aortic regurgitation (1+) was present in all 11 patients available for follow-up. By 2 years, the condition was absent in 73% (P < 0.001) and remained mild in the remaining patients.

The favorable hemodynamic changes were accompanied by a consistent improvement in NYHA functional class over 2 years (P < 0.05).

Importantly, based on dual-source multislice CT imaging, the positions of the valve anchoring rings remained stable over follow-up out to 28 months.

“Because valve malposition during [TAVR] is associated with severe complications, the respositionability and retrievability of the [Direct Flow] valve has the potential to increase the safety of the procedure,” the authors write. “The excellent sealing capability minimizing [aortic regurgitation] may improve the patient’s long-term outcome after [TAVR].”

Two-Year Follow-up Promising

In a telephone interview with TCTMD, Ted Feldman, MD, of Evanston Hospital (Evanston, IL), said, “It’s very exciting to see additional published experience with next-generation valve therapy. This is the kind of report we need—2-year follow-up is very meaningful.” Nonetheless, he added, the authors are appropriately cautionary in emphasizing that this is still a first-in-man experience.

He noted that with the 2 most widely used percutaneous valves, CoreValve (Medtronic, Minneapolis, MN) and especially the Edwards Sapien (Edwards Lifesciences, Irvine, CA), “there is an element of pulling the trigger and then living with what you get.”  Even if missing the target is a highly infrequent event, operators always have the possibility in the back of their mind, he indicated. Repositionability provides the option of correcting valve misplacement.

Another feature operators put at the top of the list of features they want to see in a second-generation valve is retrievability, observed Peter C. Block, MD, of Emory University Hospital (Atlanta, GA), in a telephone interview with TCTMD. This trait means that if a valve is mis-sized, it can be removed and replaced.

No Valve Distortion, Dysfunction

In addition, the nonmetallic Direct Flow device has the major advantage of being more conformable to the irregular geometry of the annulus, providing a better seal and diminished likelihood of residual paravalvular leakage, Dr. Block said. But the downside is that the valve is not suspended in a rigid circle, which makes it potentially more vulnerable to deformation. Drs. Feldman and Block agreed that an important finding of the study is that at least over 2 years there was no distortion of the valve shape or deterioration in its function. “[The valves] remained pretty much as they were after they were deployed,” Dr. Feldman observed.

Importantly, the survival rate was very good, and in line with European reports of patients with a similar risk score, Dr. Feldman added.

Since this study, Direct Flow Medical has developed a new iteration of the device that is more robust and supplies more radial strength, said Dr. Block. It is also compatible with a smaller, 18-Fr delivery catheter. This design is currently undergoing clinical testing in an effort to win CE mark approval in Europe, he reported. As good as the results are with the earlier version in the current report, they are likely to be as good or better with the new iteration, he asserted.

Moreover, the ongoing trial will be more informative about the implantability and usefulness of the Direct Flow device in terms of operator friendliness, Dr. Block said, adding that operators he has spoken with say the learning curve is brief.

The one subgroup in which the Direct Flow device may not be the best choice is patients with severely calcified valves, Dr. Block cautioned. 

Study Details

Patients’ mean age was 82.3 ± 3.6 years; the mean logistic EuroScore was 28.6 ± 7.4%.

To implant the Direct Flow Medical device, after valvuloplasty, the lower, ventricular ring is initially inflated with a mix of saline and contrast material and the valve is drawn up into the ventricular aspect of the annulus, where the upper, aortic ring is similarly inflated. The valve position is then checked with transesophageal echocardiography, fluoroscopy, and angiography. If the position, orientation, or shape of the device is unacceptable, the valve can be repositioned or retrieved. Once the position is acceptable, the saline/contrast liquid is replaced under constant pressure by a polymer that hardens, providing permanent valve placement.

Bijuklic K, Tuebler T, Reichenspurner H, et al. Midterm stability and hemodynamic performance of a transfemorally implantable nonmetallic, retrievable, and repositionable aortic valve in patients with severe aortic stenosis. Up to 2-year follow-up of the Direct-Flow Medical valve: A pilot study. Circ Cardiovasc Interv. 2011;4:595-601.

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