This study shows that stented bioprosthetic aortic valve replacement, using the continuous suture technique, is safe and feasible. Continuous suture technique is associated with reduced transvalvular gradients, especially in smaller annular sizes, compared to the interrupted pledget-reinforced technique, for both the Magna Ease and the Trifecta prosthesis. Moreover, cardiopulmonary bypass and cross-clamp times are shorter in the continuous suture technique, and there is no difference in other valve-related outcomes.
Paravalvular leak after aortic valve replacement is an important issue, which, if untreated, could results in impaired hemodynamics (10). The continuous suture technique has earlier been suggested to increase the risk of paravalvular leak after AVR compared to the pledget-reinforced sutures (8, 9), leading to more reoperations. However, these studies are performed in patients with mainly a mechanical prosthesis and a mixed cohort of mitral and aortic valve replacements. In our study, the continuous suture technique was not associated with increased rates of PVL. Nevertheless, we believe that application of the CST in mechanical valves, which have a flat shaped “annular” sewing ring, is not appropriate, as the shape of the ring forces placement of the sutures below the commissures into the muscular part anteriorly and fibrous part posteriorly, and at the level of the “basal ring”. This may potentially lead to a tear or rupture of the annulus there, especially at the commissure between left coronary and right coronary cusp, at the muscular part. Accordingly, this can lead to higher rates of PVL, or possibly pseudoaneurysms of mitro-aortic continuity. For this reason, we use the CST only for stented bioprostheses and not for mechanical valves.
Another issue is the need for pacemaker implants after aortic valve replacement, which is associated with higher hospital stay and mortality. This is true for both in SAVR and TAVI, which was elucidated from the PARTNER trial data by Nazif et al. (11). In our study the CST was not associated with more pacemaker implants compared to the IPT. Nevertheless, there are several factors that may increase the risk of a new-onset conduction disorder, such as e.g. age, valve anatomy, endocarditis. Most patients eligible for SAVR are relatively young and active with a low risk profile and a long life expectancy. These patients can be particularly affected by the need for a pacemaker in term of quality of life and clinical outcomes. Hence surgeons should be cautious to prevent damage to the conduction system. The continuous suture technique does not initiate any additional risk with this regard and could be applied safely.
Furthermore, there is no consensus in the literature regarding hemodynamic performance of bioprosthetic valves in different suture techniques. Tabata et al. have suggested that using a pledgeted technique to implant a biological stented valve in aortic position is associated with higher prosthesis-patient mismatch, in small annular sizes (10). However, Ugur and colleagues reported that in smaller annular sizes (implanted prosthesis of 19- and 21mm), comparing pledgeted technique to non-pledgeted, there is no difference in outcomes with regard to prosthesis-patient mismatch, and they suggest that the differences between the findings may be due to the use of the Trifecta valve prosthesis, which may have better hemodynamic performance (12). We have found lower transvalvular gradients in similar valve sizes in the CST compared to IPT. As one may suspect these gradients are higher in smaller sizes, and both the Magna Ease and the Trifecta showed the same differences, except for the bigger sizes (25 and bigger), where we did not find any difference only in the Trifecta valve. Especially in smaller annuli, where a prothesis size 19 or 21 are used, this may be of clinical importance, although other characteristics may also be important for these differences in gradient such as left ventricular outflow tract (septum) obstruction. Since the prosthesis size labeling is rather arbitrary and does not represent the actual annular size, we could not compare the size of the specific type of prosthesis to one another.
Due to lack of postoperative echocardiographic effective orifice area (EOA) data, we were not able to identify the PPM that is suggested by Pibarot et al. and widely accepted (13), with the transvalvular pressure gradient as a major factor. However, we have identified the BSA which is used in a calculation to determine indexed EOA and subsequently PPM, and the BSA was comparable between the CST and IPT cohort. Nevertheless, for comparable mean BSA and same valve size and valve brand representation, we found more patients with higher mean and peak gradient in the IPT compared to the CST, which suggests that the higher gradients are presumably due to the pledgets used in the IPT cohort, leading to some obstruction of the LVOT. Moreover, suture technique may affect the hemodynamic outcome of AVR with bioprosthetic stented prosthesis. In patients with a small aortic annulus, the IPT may reduce annular diameter by 1 mm or more (14). Additionally, in an experimental study Capelli and colleagues evaluated the overall hydrodynamic performance under identical conditions in pledgeted and non-pledgeted sutured biological stented prosthetic valves, and computational fluid dynamics analyses were performed, which showed flow disturbances in pledget-armed sutures, which in turn increased the mean pressure gradient and decreased the effective orifice area (15).
One can argue to use a stentless valve in small annular size, but this is usually extending the operation to an aortic root replacement, which may not be necessary in the majority of patients. Besides, the hemodynamic performance of the third-generation supra-annular stented bioprosthesis is generally similar to that of stentless valves (16). Nevertheless, long-term follow-up of hemodynamic performance and analysis of degeneration of the bioprostheses over time is warranted to evaluate the effects of suture technique on the hemodynamics.
Furthermore, the in-hospital mortality and risk of a stroke were low and comparable between the CST and the IPT, as one may expect. There were no major differences in preoperative characteristics between the two techniques used for AVR. We can assume that the suture technique is not associated with higher hazard of major valve-related hospital events.
Finally, a potential issue may be a presumed higher risk of infectious endocarditis due to the pledget (Teflon) material that is used in the IPT. Although there are no comprehensive data available in the literature, the incidence of a prosthetic valve endocarditis is suggested to be 6 per 1000 cases with a cumulative risk of around 6% after 10 years in high-risk patients (17). A recently published study by Velders et al. clinical outcomes were comparable between patients undergoing AVR with pledgeted and non-pledgeted sutures, up to 5 years of follow-up with comparable endocarditis rates. Nevertheless, pledget use was associated with a slightly smaller EOA eventually. Notably, only 15% of patients in the non-pledget cohort were treated with the continuous suture technique.
In the current study, the follow-up is too short to evaluate the risk of endocarditis. However, we do hypothesize that there may be a slightly higher risk when using pledgets, especially in immune incompetent patients. Long-term follow-up may provide further insights in the future. We are more cautious in using the CST in patients with extended annular calcification and endocarditis, especially when not accustomed in using this technique.
Limitations
A limitation is that this study contains only in-hospital outcomes. Although we do not expect the valve-related events to be different at long-term follow-up, the echocardiographic parameters (i.e. transvalvular gradients and paravalvular leakage) may change during follow-up and affect patient outcome. Another issue is the use of two type of prosthesis, Edwards’ Perimount Magna and Abbott’s Trifecta. The valves have distinct characteristics. However, the difference in transvalvular gradients was observed also in subgroups of the different valves, over different annular sizes in both suture techniques. Furthermore, the number of events are low for the examined outcome, which makes analyzing the data challenging in term of statistical testing, however, the main goal of this study was to show the safety and efficacy of the CST, which could be addressed adequately.
In conclusion, the continuous suture technique is safe to implement for bioprosthetic aortic valve replacement and is associated with lower transvalvular gradients. Moreover, there is no additional risk of paravalvular leak or newly onset conduction disorders. Hence, the continuous suture technique should be considered a valuable technique for aortic valve replacement with stented biological prosthesis, especially in smaller annular sizes. Long-term follow-up of hemodynamic performance and analysis of degeneration of the bioprostheses over time is warranted to evaluate the effect of suture technique on the long-term hemodynamics.