By Danny Dvir
Danny Dvir provides a short summary of practical recommendations that can improve procedural success during valve-in-valve procedures
The implantation of a transcatheter valve inside failed surgical valve (valve-in-valve) has recently emerged as a less invasive approach and an alternative to redo surgical valve replacement. Even though the procedure is similar to transcatheter aortic valve implantation (TAVI) in the setting of native aortic valve stenosis, there are several differences that deserve consideration. Safety and efficacy concerns include high rate of device malposition, coronary obstruction and elevated post procedural gradients.
Before the procedure
The treating group must gather the most information possible about the failed bioprosthetic valve: the exact model, its size, structure, position in relation to the native annulus, and the mode of failure. Obtaining a surgical report is very helpful. Several mechanisms of failure must be excluded, optimally by transesophageal echocardiography evaluation: valve thrombosis, endocarditis and paravalvular regurgitation. These pathologies are usually better treated by a different approach.
Identification of the fluoroscopic target for implantation is a key issue and could be facilitated by reviewing images of a similar valve-in valve procedure. Incomplete understanding of the implantation target is clearly a major aetiology for device malposition (15% of cases). Since most recognised events of coronary obstruction post valve-in-valve were associated with fatality, risk factors for that complication (3.5% of cases) must be identified. The risk of obstruction is determined primarily by the characteristics of the specific surgical valve and its position in relation to the coronary ostia. The distance from the annulus to the coronary ostia is less relevant in valve-in-valve setting. Factors that may predispose to coronary obstruction include: supra-annular surgical valve position, bulky bioprosthetic leaflets, narrow aortic root and re-implanted coronaries. Bioprosthetic valves that are stentless or are internally stented (eg. Mitroflow, Sorin) are associated with higher risk. Aortography and CT angiography can show the proximity of the bioprosthetic leaflets to the coronary ostia. Aortography during balloon valvuloplasty may be especially helpful to evaluate the risk of coronary obstruction.
During the procedure
Sizing of the device is often not an easy decision. Generally, the operator should select a device that is slightly larger than the internal diameter of the surgical bioprosthesis (could be found in charts). Because of better haemodynamic results, the operator may consider using a device with supra-annular leaflets (eg. CoreValve, Medtronic) when the surgical bioprosthesis is small (internal diameter < 20mm). During the procedure, the use of transesophageal echocardiography is recommended and could be particularly useful in treating stentless valves where the bioprosthetic basal ring is radiolucent. Balloon predilation is typically not necessary in the setting of valve-in-valve implantation, particularly in the presence of regurgitation. Degenerated surgical valves are often friable and following balloon inflation, they are at high risk of embolisation and subsequent stroke or acute valve regurgitation. Nevertheless, difficulty in crossing a severely calcified, bulky, stenotic bioprostheses can sometimes be encountered when predilatation is not used. High rate of device malposition results in relatively high rates of additional manoeuvres during valve-in-valve procedures; using a second transcatheter device in 8.4%, attempted device retrieval, and post-implantation balloon dilatation. Operators should be skilled in handling device malposition, retrieval techniques, and implantation of second transcatheter devices, if needed. Identification of a fluoroscopic view that is perpendicular to the valve ring which allows assessment of coaxial deployment is crucial during implantation phase.
Since reoperation is associated with high morbidity and mortality we can speculate that the volume of valve-in-valve procedures will continue to grow. Improved communication between centres and analysis of data obtained by the global registry may improve the efficacy and safety of this less-invasive approach.
Danny Dvir, Medstar Washington Hospital Center, Washington DC, USA