Freedom SOLO: avoiding pitfalls to avoid premature failures?

We read with interest the manuscript by Stanger et al . [ 1 ] reporting the experience and the premature failures with the Freedom SOLO (FS) pericardial stentless valve at University of Bern.

The occurrence of valve failure and explantation is quite relevant in this single-centre experience (9.3%; 14/149) and may have been influenced by the initial learning curve.

Following our extensive 12-year experience with the FS valve [ 2 ], we acknowledge that several pitfalls must be taken into account with the use of this prosthesis, such as correct implantation which is of utmost importance for valve durability.

In 9 of the 14 explanted cases, a clear relationship between improper implantation and need for reoperation could be identified. Oversizing is one of the most frequent mistakes. The FS valve has been designed for a supra-annular implantation: once the annulus has been sized (e.g. 21 mm), the valve prosthesis of the same label size (21) should be selected, without any oversizing. In fact, when a larger prosthesis is chosen, the valve leaflets are redundant and wrinkled at the level of the suture line, causing reduced mobility, higher gradients and regurgitation for irregular coaptation. Thrombosis and early degeneration may be expected, as in Cases 1 and 2. In Case 10, a very small annulus (requiring a root enlargement at reoperation) was maybe even too small for the 19 FS valve, thereby resulting oversized.

Similarly, implanting a smaller valve than indicated may lead to structural failure: leaflets do not coapt properly, they are restricted in their movements, with an excess of tension on the suture line, aortic tissue and commissures, especially the non-right coronary one [ 3 ]. This condition leads to suture dehiscence, early deterioration and commissural tears as in Case 3, 4, 6 and 7: in particular, a 33 mm annulus (as in Case 3) clearly does not match a 27 FS valve and is very likely to undergo further dilatation.

Finally, it has also been recommended not to use the FS valve in patients with a bicuspid valve (due to improper alignment and asymmetry); however, this was the case for Patient 8 of this series.

The only true structural valve deteriorations seem to have occurred in Case 11, 12, 13 and 14, at an average of 7.5 years after implantation: of note, all patients were young (56–66 years), with a small annulus. These may have been difficult cases for an initial experience, with a high risk of intra-annular implant, explaining also the finding of ‘annulus shrinkage’.

It should also be stressed that 42.8% (6/14) of explanted and 23.5% of implanted valves were of size 27: such data are quite in contrast with two recent multicentric studies in which such a valve size has been used in 10.0% [ 4 ] and 4.7% [ 5 ] of patients, respectively; again, avoidance of oversizing and incorrect indications, such as dilated annuli, seem to be of paramount importance to improve valve durability.

In conclusion, we believe that the results by Stanger et al . should be carefully interpreted since avoiding common ‘pitfalls’ in implantation might contribute to limiting premature failure and to positively influencing the rate of freedom from structural valve deterioration. More studies and a longer follow-up are warranted to conclusively assess the durability of the FS valve.

Conflict of interest: Alberto Repossini is a consultant for SORIN Group.

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