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A modified approach to transapical aortic valve replacement that facilitates precise prosthesis positioning results in fewer and milder instances of paravalvular regurgitation, similar to surgery, according to a study published in the January 17, 2012, issue of the Journal of the American College of Cardiology. This is important, the authors say, because moderate or severe residual regurgitation has been associated with a worse prognosis.

Investigators led by Miralem Pasic, MD, PhD, of the Deutsches Herzzentrum Berlin (Berlin, Germany), characterized the incidence and predictors of paraprosthetic regurgitation in 358 high-risk patients with severe aortic stenosis who underwent modified transcatheter aortic valve replacement (TAVR) via the transapical route at their institution between April 2008 and March 2011. All patients received the balloon-expandable Edwards Sapien THV bioprosthesis (Edwards Lifesciences, Irvine, CA).

‘Surgical Way of Thinking’

In adopting a “surgical way of thinking,” the operators decided to accept only trivial or mild paraprosthetic regurgitation after TAVR, and so modified the standard technique to minimize the chances of paravalvular leakage. The balloon was inflated slowly and gradually under angiographic monitoring, allowing the valve to be placed precisely (and adjusted if necessary) in a higher position than usual.

Technical success was achieved in all but 2 patients. After initial implantation, moderate or severe regurgitation was seen in 23 patients (6%). Redilation was performed in 18 patients, while additional valves of the same size were implanted in 13. (Two patients with moderate regurgitation had intraprocedural bleeding, and the apex was safely closed without moderate regurgitation.)

The researchers note that their reintervention rate decreased from 8% in the first 100 patients to 3% in the last 58 patients. Significant paraprosthetic regurgitation was more common than transvalvular. Redilation without additional implantation was performed in 8 patients, reducing the problem to mild or trace status in 6 patients and eliminating it in the others. Redilation followed by implantation of a second prosthesis was required in 10 patients, reducing regurgitation to mild or trace in 6 and eliminating it in 4.

Among the group who underwent redilation and/or reimplantation, none experienced annular rupture, aortic dissection, or coronary ostia occlusion. However, 3 patients died in-hospital.

No Regurgitation in Over Half of Patients

After TAVR, overall 52% of patients were free of regurgitation. Among the 172 patients with residual regurgitation, it was graded moderate in 1%, mild in 48%, and trace in 51%. In the latter group, regurgitation was paravalvular in 66%, transvalvular in 27%, and combined paravalvular and transvalvular in 7%.

Transesophageal echocardiography showed that the mean transvalvular gradient had decreased from 48.3 ± 14.7 mm Hg to 4.8 ± 2.4 mm Hg, while aortic valve area increased from 0.7 ± 0.2 cm² to 2.1 ± 0.5 cm² (both P = 0.001). 

Importantly, the presence of trace or mild regurgitation had no impact on survival. One-year survival rates in patients with no, trace, and mild regurgitation, were: 83 ± 3%, 85 ± 4%, and 83 ± 5%, respectively (P = 0.771). During follow-up, only 3 patients underwent conventional valve replacement.

Clinical, Morphological Predictors

In multivariate analysis, male sex (OR 1.96; 95% CI 1.23-3.12; P = 0.005) and NYHA functional class IV (OR 1.71; 95% CI 1.08-2.73; P = 0.023) increased the likelihood of postprocedural regurgitation, while the absence of previous aortic valve replacement (OR 0.08; 95% CI 0.02-0.38; P = 0.001) sharply decreased the odds.

Using data from a group of 78 patients who underwent preoperative multislice CT imaging, the investigators examined the morphological characteristics of the 39 patients who experienced intraprocedural regurgitation. Multivariate analysis identified the following predictors of intra- or post-procedural regurgitation:

• Oval-shaped annulus (OR 9.16; 95% CI 0.68-3.75; P = 0.005)
• Asymmetric cusp calcification (OR 5.65; 95% CI 0.44-3.03; P = 0.009)
• Calcification in the valve landing zone (OR 4.90; 95% CI 0.79-2.39; P = 0.001)

The authors claim that the modified TAVR strategy they use “reaches the results of conventional aortic valve replacement” in terms of minimizing regurgitation.

Thumbs-up for Slow Inflation

According to Josep Rodés-Cabau, MD, of Laval University (Quebec City, Canada), the regurgitation results seen here are unprecedented for any transcatheter valve or approach, especially for moderate leakage. “That is very important because data show that while trivial or mild regurgitation probably doesn’t matter—patients tolerate it very well—moderate regurgitation has prognostic value in determining worse acute and midterm outcomes,” he observed.

Dr. Rodés-Cabau endorsed the investigators’ ‘slow-inflation’ technique, which allows operators to pause and correct valve position before full expansion, noting that his center has been using it successfully over the past year. It is useful in both transapical and transfemoral approaches, he added, although it is unclear whether the more direct transapical approach to the annulus may give it an edge.

One potential limitation of the technique, he pointed out, is the need for longer rapid pacing to accommodate the slow inflation, which could be a problem in certain patients. But in his experience most tolerate the extra pacing well. Nor has he encountered valve embolization, another theoretical risk.

Optimal Valve Positioning Not a Panacea

However, he was skeptical of the authors’ assertion that valve positioning alone is responsible for their remarkable success.

One reason for skepticism, he suggested, is that their echocardiographic evaluation of regurgitation severity may have been inadequate and so the results may not be reproducible. In addition, he noted, the investigators were at once aggressive in terms of valve oversizing and conservative in terms of treating few patients with larger annuli—both of which may have improved regurgitation results.

Moreover, Dr. Rodés-Cabau argued that valve-in-valve patients should have been excluded from the analysis, since unlike calcified native valves, dysfunctional prostheses pose little risk of regurgitation.

While noting that the results come from a single center and are outliers in terms of all other data reported thus far, Dr. Rodés-Cabau said they remain “provocative and very important in terms of being hypothesis generating.

“But to pretend that valve positioning is the only problem related to important paravalvular leaks is too simple,” he insisted. “We know that calcium is an important player. Even if your positioning is perfect, the paravalvular space will still be occupied by heavily calcified leaflets. And probably annulus sizing is an important factor.”

Dr. Rodés-Cabau agreed with the authors that as TAVR is extended to lower-risk patients, a predisposition toward regurgitation may be a reason to steer patients toward surgery. For that reason, he said, in the future it will be important to develop and apply a regurgitation risk score.

Study Details: 

The study cohort consisted of 120 men and 238 women with a mean age of 80 ± 8 years; the mean logistic EuroScore was 38 ± 21, and the mean STS score was 19 ± 16. 

A valve size of 23 mm was chosen for aortic annuli smaller than 21 mm and a 26-mm prosthesis for annular diameters of 21 mm or larger.
 

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