Trends in Surgical Aortic Valve Replacement in More Than 3,000 Consecutive Cases in the Era of Transcatheter Aortic Valve Implantations

Abstract

Objectives Biological prostheses for surgical aortic valve replacement (sAVR) are increasingly being considered in patients < 60 years of age. Likely, preserving the option of performing a transcatheter valve-in-valve (ViV) procedure in cases of structural valve deterioration has contributed to this development. We assessed the use pattern in sAVR over an 11-year period.

Methods From 2002 through 2012, a total of 3,172 patients underwent sAVR at our center.

Results Mean age was 70.4 ± 10.6 years and mortality was 1.9%. From 2002 to 2012, mean manufacturer given valve size increased from 22.8 ± 1.7 to 23.9 ± 2.0 mm (p < 0.001). Mean true internal diameter and effective orifice area increased from 19.6 to 20.3 mm (p = 0.027) and 1.41 to 1.56 cm² (p < 0.001), respectively. Use of mechanical valves decreased from 10.9 to 1.8% (p < 0.001), and patients were younger in 2012 than in 2002 (52.8 ± 16.5 vs. 41.0 ± 14.3 years; p = 0.028).

Conclusion Profound change of use pattern in sAVR was observed as indication for biological prostheses became more liberal. Larger prostheses were implanted during the observational period. Especially in younger patients, optimal sizing is essential to preserve the option for subsequent ViV procedures.

Keywords

aortic valve - aortic root - cardiac surgery - heart valve - transcatheter aortic valve implantation

Introduction

Biological versus Mechanical Heart Valve Prostheses. Has the Paradigm Shifted Definitively?

Editor's Commentary

Surgical aortic valve replacement (sAVR) is the gold standard for the treatment of aortic stenosis.[1] It can be performed safely and is associated with low perioperative morbidity and mortality. According to national German statistics, mortality was 2.9% in 2013 for isolated aortic valve replacement. A substantial increase in use of biological prostheses was seen during the last years with a share of 62.5% of prostheses used in 2004 and 86.9% in 2013.[2]

According to international guidelines (AHA and ESC/EACTS), use of biological prostheses in the aortic position is generally recommended in patients >60 years.[3] However, there seems to be a trend toward use in younger patients even though structural valve deterioration (SVD) and graft failure remain problematic as they are known to occur earlier in younger patients.[4] Likely, preserving the option of performing a subsequent transcatheter valve-in-valve (ViV) procedure in cases of SVD has contributed to this development. Reoperation has formerly been the only treatment option for degenerated biological prostheses and it is associated with an increased perioperative risk of mortality of 5.1% in the overall population and up to 20% in high-risk patients.[5] [6] Besides the increasing implementation of ViV procedure, improved durability of biological valves and avoidance of permanent anticoagulation favor the use of biological prostheses.

Recently, transcatheter ViV procedures have been established as a less invasive alternative for treatment of degenerated biological prostheses. These can be performed safely with acceptable outcome in recent series of high-risk patients.[7] [8] [9]

According to the global ViV registry, mortality was 7.6% from 2007 to 2013.[9] Current literature recommends that ViV procedure should only be performed at experienced centers due to the complexity of the procedure. Potential disadvantages of ViV procedure may be elevated residual pressure gradients. Other clinical concerns include coronary ostia obstruction and malpositioning of the transcatheter heart valve (THV).[10] Internal dimensions of the surgical prosthesis are of crucial relevance for successful ViV procedures as the size of the initially implanted prosthesis correlates with the postoperative gradient[9] and the gradient in turn correlates directly with midterm patient survival.[9] [11] Therefore, optimal sizing during the initial sAVR is essential to preserve the option of subsequent ViV therapy when deterioration of the implanted biological prosthesis has occurred.

The objective of the present study was to investigate trends in our sAVR program. We aimed to review age development, valve types and sizes used, and the impact on use frequency of mechanical prostheses, and to assess possible impact of the introduction of transcatheter aortic valve implantation (TAVI) in 2007 on the use pattern of sAVR.

Methods

Study Population and Data Collection

From 2002 to 2012, 3,172 consecutive patients underwent sAVR at our center. All combined or isolated procedures (e.g., additional coronary artery bypass graft [CABG] or valve procedures), as well as reoperative procedures for degenerated biological prostheses, were included. Reoperative procedures for acute prosthesis endocarditis were excluded from our analysis.

Data were collected retrospectively and entered into a dedicated database. In addition to baseline characteristics, information about valve types and manufacturer given sizes, true internal diameter (true ID), and standard effective orifice area (EOA) of the implanted prostheses as reported in the literature[12] was gathered and patient–prosthesis mismatch (PPM) calculated. True ID was defined as the ID of the inflow of the biological prosthesis as measured by Hegar dilators.[13]

PPM was graded according to the definition by Blais and colleagues,[14] where it was quantified by relating EOA to body surface area (BSA) (indexed EOA, iEOA). Based on iEOA, three categories of PPM are defined: not relevant (>0.85 cm²/m²), moderate (0.65–0.85 cm²/m²), and severe (<0.65 cm²/m²). BSA was derived using the Du Bois equation.[15]

Statistical Analysis

Data are presented as absolute numbers and percentages for categorical variables and mean values and standard deviations for continuous variables. Dichotomous variables are compared using Fisher exact test and continuous variables by t-tests. Linear regression was applied to examine the association between valve size (manufacturer size, true ID, EOA) and the year of treatment. The regression coefficient was applied to estimate the change in valve size per year. p-Values are reported without correction for multiple testing. Level of significance is set to a two-tailed p < 0.05. All statistical analysis was performed using SPSS 19.0.

Results

Development of sAVR in the TAVI Era

During the study period from 2002 to 2012, 3,172 patients underwent sAVR at our center. Additionally, 750 patients underwent TAVI from 2007 to 2012.

Combined surgical procedures were performed in 1,342 patients. Number of procedures performed in a single year increased from 139 patients in 2002 to 322 patients in 2012 (+131%). A total of 85 patients underwent reoperative sAVR for degenerated bioprostheses.

Until the introduction of TAVI at our center in 2007, annual numbers of sAVR increased by 43% (n = 226 in 2006 to n = 324 in 2007; [Fig. 1]), but slightly declined from 2007 to 2012 (n = 324 in 2007 vs. n = 322 in 2012). Mean 30-day mortality was 1.9% for sAVR during the study period and did not change significantly in between single years (p = 0.245; see [Fig. 1]). In 2012, 30-day mortality was 0% after isolated sAVR. Mean age of sAVR patients was 70.4 ± 10.6 years through the study period and did not differ significantly between the years (p = 0.235). Regarding biological prostheses, the proportion of patients aged 50 to 60 years increased significantly from 6.9% in 2002 to 12.4% in 2012 (p = 0.015). Proportion of patients <50 years was 4.6% in 2002 and 2.3% in 2012 and did not change significantly in between years (p = 0.180). The same was true for the proportion of patients >60 years with 88.5% in 2002 and 85.3% in 2012. Proportion of patients 70 to 80 years increased from 42.4% in 2002 to 49.1% in 2012 (p = 0.222).

Fig. 1 Total number of sAVR and TAVI procedures at UHC Hamburg. Total caseload of sAVR constantly increased at our center; the addition of TAVI to this calculation produces a threefold increase in surgical activity. Since the introduction of TAVI, total numbers of sAVR slightly declined. Thirty-day mortality of isolated sAVR decreased from 4.4% before the introduction of TAVI in 2006 to 0% in 2012 (p = 0.029).

Patient Characteristics

Comparison of patients undergoing biological sAVR in 2002 and 2012 yielded no significant differences regarding typical baseline variables ([Table 1]). The proportion of patients undergoing biological sAVR after any kind of previous cardiac surgery decreased significantly from 14.4% in 2002 to 5.0% in 2012 (p < 0.001). Reoperations for degenerated biological prostheses were performed in a total of 85 cases throughout the study period; here, mean proportion did not change significantly (6.5% in 2002 vs. 3.4% in 2012; p = 0.178; [Fig. 2]). Time to reoperation for SVD was 11.8 ± 5.6 years in 2002 and 10.1 ± 6.3 years in 2012 (p = 0.540; [Fig. 2]). Mode of degeneration was leaflet tear with consecutive regurgitation in the majority of patients (46/85, 54.2%). Leaflet thickening with resultant prosthesis stenosis was observed in 29.4% of patients (25/85) and mixed steno-insufficiency was seen in 15.4% of patients (13/85). In one case, mode of degeneration was not described. Combined procedures (e.g., additional valve or CABG) were performed in 49.6% (n = 64) in 2002 and 51.6% (n = 161) in 2012 (p = 0.630).

Fig. 2 Development of reoperative sAVR for degenerated biological SHV. Both proportion of reoperative sAVR for SVD and mean time to reoperation did not change significantly during the study period.

Table 1 Baseline variables of patients undergoing sAVR and TAVI

Variable	sAVR 2002 (n = 139)	sAVR 2012 (n = 322)	p-Value	TAVI 2009 (n = 75)	TAVI 2012 (n = 281)	p-Value
Age (y)	69.7 ± 12.1	70.2 ± 9.4	0.673	79.6 ± 6.9	79.9 ± 7.3	0.725
Body surface area (m2)	1.9 ± 0.2	2.0 ± 0.2	0.233	n.a.	n.a.	–
Female gender (%)	33.3	31.5	0.823	52.0	49.5	0.850
Logistic EuroSCORE I (%)	8.8 ± 8.4	9.1 ± 9.5	0.815	26.8 ± 12.8	19.5 ± 12.2	<0.001
Arterial hypertension (%)	50.0	74.5	<0.001	76.0	78.3	0.613
Diabetes (%)	13.8	17.7	0.399	24.0	25.6	0.910
Dialysis (%)	1.5	1.9	1.000	5.3	1.1	0.038
Reoperation[a] (%)	14.4	5.0	<0.001	21.3	19.2	0.743
Combined procedures (%)	49.6	51.4	0.630	n.a.	n.a.	–

Abbreviation: TAVI, transcatheter aortic valve implantation.

^a Including all kinds of previous cardiac surgeries.

Valve Details

Of all patients, 94.9% (n = 3,010) received biological prostheses. In the majority of cases, pericardial valves were used (61.1%). Proportion of porcine valves decreased from 48.5% in 2002 to 33.4% in 2012 (p < 0.001). The three most commonly used brands were Edwards Perimount (27.5%; Edwards Lifesciences Inc., Irvine, California, United States), Medtronic Hancock (II or Ultra) (32.2%; Medtronic Inc., Minneapolis, Minnesota, United States), and Sorin Mitroflow (28.7%; Sorin Group, Milano, Italy) ([Table 2]).

Table 2 List of SHV brands used at UHC Hamburg

Brand %	2002	2003	2004	2005	2006	2007	2008	2009	2010	2011	2012
Edwards Perimount	50.8	18.3	48,7	51.8	56.4	24.5	26.7	14	21.6	14.5	12.2
Medtronic Hancock[a]	38.9	53.6	48.6	42.6	29.4	38.6	34.8	21.1	19	25.3	32.5
Sorin Mitroflow	0	0	0	0	3.9	35.8	35.4	57.4	45.6	49.1	30.2
Sorin Freedom Solo	0	0	0	0	2.9	0	0.7	1.8	9.2	5.4	1.3
Medtronic Freestyle	0	0	0	0	0	0	2.1	3.1	0.3	0.9	0.9
Edwards Magna	0	0	0	0	0	0	0	0	0.8	3.6	3.2
St. Jude Trifecta	0	0	0	0	0	0	0	0	0.3	0	17.4
St. Jude Biocor/Epic	7.9	10.2	0.5	0	0	0	0	0	0	0	0
Edwards SAV	0	0	0	2.8	4.9	0	0	0	0	0	0
Sorin Perceval S	0	0	0	0	0	0	0	0	2	0.3	0
Shellhigh	2.4	1.4	1.1	2.3	2.5	0.9	0	0	0	0	0

^a Hancock includes Hancock, Hancock II, and Hancock II Ultra.

The proportion of mechanical valves decreased from 10.9% in 2002 to 1.8% in 2012 at our center (p < 0.001). Mean age of patients receiving a mechanical valve decreased significantly from 2002 to 2012 (52.8 ± 16.5 vs. 41.0 ± 14.3 years; p = 0.028).

Valve Size

From 2002 to 2012, mean valve size as specified by the manufacturer increased from 22.8 ± 1.7 to 23.9 ± 2.0 mm (p < 0.001); the regression coefficient indicated a mean increase of 0.11 ± 0.01 mm per year. The most commonly used valve size was 23 mm throughout the study period, although its overall proportion decreased from 54.6% in 2002 to 33.6% in 2012 (p < 0.001). The proportion of small valve sizes (≤21 mm) decreased significantly from 27.7% to 19.0%, while use of larger sizes (≥25 mm) increased significantly from 17.7% to 47.4% (both p < 0.001).

Correspondingly, true ID and EOA of biological prostheses increased from 19.6 ± 1.7 to 20.3 ± 2.1 mm (p < 0.001) and 1.4 ± 0.2 to 1.6 ± 0.2 cm² (p < 0.001), respectively. Mean increase by each year in regression analysis was 0.10 ± 0.01 mm and 0.02 ± 0.01 cm² for true ID and EOA, respectively. Results are summarized in [Fig. 3].

Fig. 3 Development of mean valve size and mean true ID from 2002 to 2012. Mean valve size as specified by the manufacturer increased by 1.1 mm from 2002 to 2012 (p < 0.001). Correspondingly, mean true ID increased by 0.7 mm during the study period (p = 0.027) and EOA increased by 0.14 cm² (p < 0.001).

Severe PPM, defined as an iEOA ≤0.65 cm²/m², tended to be less frequent, although this did not reach statistical significance (24.4% in 2002 vs. 10.7% in 2012; p = 0.092; [Fig. 4]). Mean iEOA increased significantly from 2002 to 2012 (0.75 ± 0.1 vs. 0.80 ± 0.1 cm²/m²; p = 0.020).

Fig. 4 Proportion (%) of iEOA ≤ 0.65 cm²/m² among sAVR patients. Severe PPM (iEOA ≤ 0.65 cm²/m²) decreased constantly from 24.4% in 2002 to 10.7% in 2012, although this was not significant (p = 0.092).

Age and Valve Size

Throughout the study period, younger patients (≤60 years) received significantly larger prostheses compared with patients ≥60 years (23.8 ± 1.7 vs. 22.6 ± 1.6 mm in 2002 and 24.7 ± 2.3 vs. 23.7 ± 2.0 mm in 2012; both p < 0.001). Mean difference in valve size between patients ≤ 60 years and patients ≥60 years was 1.0 ± 0.1 mm. Although in both patient groups an increase in valve sizes was seen regarding manufacturer given size, differences between age groups remained unchanged. iEOA was significantly larger in patients ≤60 in 2002 (0.83 ± 0.12 vs. 0.73 ± 0.10 cm²/m²; p = 0.045) and tended to be larger in 2012, although this was not statistically significant (0.81 ± 0.20 vs. 0.79 ± 0.11 cm²/m²; p = 0.360).

Discussion

Development of sAVR in the TAVI Era

Total number of sAVR increased significantly from 2002 to 2012. The addition of TAVI procedures to this calculation resulted in a threefold increase in surgical activity at our center ([Fig. 1]). However, in the most recent 5 years a slight decline of sAVR was observed. This is in contrast to the national background where total numbers of sAVR remained stable after the introduction of TAVI.[2] The decline in sAVR numbers after introduction of TAVI at our center may be explained by a substantial amount of patients eligible for both types of procedures and the consequence that in a center with a large interventional program this leads to a reduction of those patients treated surgically. As 30-day mortality of isolated sAVR decreased to 0% in 2012, we assume that the introduction of TAVI may have had an influence on mortality rate of sAVR by decreasing the amount of unsuitable surgical candidates, leading to a more individual decision-making process. There has been a tendency toward a slightly more liberal indication for TAVI at our center; however, it is still restricted to high-risk patients. Moreover, as we report data obtained in a surgical center, the real number of TAVI performed may be underestimated as there are nonsurgical centers performing TAVI as well. The introduction of TAVI did lead to an increased overall caseload of procedures performed on the aortic valve, suggesting an on-top recruitment phenomenon.

Age Development

During the study period, an increasing trend toward implantation of biological prostheses in patients ≤60 years was observed. Several factors may have contributed to this liberal indication. For one, improved durability of biological prostheses has been suggested, but not proven.[16] In our experience, mean time to reoperation from 2002 to 2012 did not increase ([Fig. 2]); therefore, this hypothesis remains subject of further investigation. On the other hand, avoidance of permanent anticoagulation is among the most important reasons for patients' choice of a biological prosthesis. Our observation regarding lower age limits for biological sAVR corresponds to data reported in the literature.[16] [17] The factor age for the choice of a valve is still important in considerably young patients but not a major selection criterion in patients ≥60 years.[18] It is well known with extensive documentation in the literature that probability of SVD dramatically increases in a younger patient population.[18] This has to be taken into consideration when choosing the type of prosthetic heart valve: the common treatment of SVD used to be reoperative sAVR with either a biological or mechanical prosthesis.

More recently, the option of subsequent ViV avoiding complex reoperation may influence decision making. ViV has proven to be technically safe and feasible in most biological prostheses with a clearly defined landing zone easily identifiable by the radio-opaque valve sewing ring. This may be more challenging in certain types of stented biological prostheses or in stentless prostheses. It is possible to perform it via transapical or transarterial access, and major complications seen after conventional TAVI, such as conduction disturbances and paravalvular leakage, are expected to occur less frequently in ViV. The recently reported rate of paravalvular leakage is ∼5% in ViV compared with 17.2% in conventional TAVI.[19] Pacemaker implantation rate is significantly lower after ViV compared with TAVI in native aortic stenosis (17% in TAVI vs. 8.3% in ViV).[9] [20]

As a consequence, it seems possible to reach advantages of a biological prosthesis in a younger person (< 60 years) without the dilemma of a future reoperation. As performing a ViV will not complicate possible subsequent open reoperative AVR, it may be justified even in younger patients aged between 50 and 60 years who are more likely to experience structural deterioration of the THV used for ViV. Thus, surgical options are preserved. However, to date no clinical evidence exists that the implantation of a biological prosthesis into a young patient (< 60 years) with subsequent ViV therapy ensures more quality of life and less complications in comparison to other treatment strategies using mechanical devices. Until scientific evidence proves superiority of the above-described concept, international guidelines should be followed and biological prostheses should only be implanted in patients ≤60 years if indicated either by patients' choice or by contraindication to life-long anticoagulation.

Mean age of patients undergoing sAVR did not change significantly at our center. This observation may be explained when considering that there has also been a substantial increase in elderly patients as well. Especially the introduction of TAVI led to a broadened referral pattern, since elderly and high-risk patients were historically often denied surgical treatment and are now increasingly referred to our center as a consequence of supplementary treatment options. Likely, this caused a crossover of patients in between interventional and surgical treatment options.

Patient Characteristics

Typical baseline patient characteristics did not change significantly throughout the study period (see [Table 1]), although sAVR was less frequently a reoperative procedure after any kind of previous cardiac surgery (14.1 vs. 5.0%; p < 0.001). It seems possible that patients with severe aortic stenosis and a history of previous cardiac surgery are more likely to receive TAVI in 2012 than to undergo sAVR.

On the other hand, rate of reoperative sAVR for degenerated surgical heart valve (SHV) at our center remained stable, being 2.6% before the implementation of ViV in 2008 and 3.4% in 2012. Evidently, the introduction of ViV did not lead to a reduction of reoperative sAVR for degenerated SHV. We state that some patients still have to undergo reoperative sAVR in times of ViV despite elevated operative risk when considering that there are different types of biological prostheses, some of them not suitable for a ViV procedure as they might lead to elevated postinterventional pressure gradients. ViV is an effective treatment option for degenerated biological prostheses but indication in some cases is limited due to an adverse aortic root anatomy with low-coronary takeoff and shallow aortic sinuses, or the presence of paraprosthetic leakage and endocarditis. Furthermore, conventional reoperative SAVR is a proven therapeutic option with predictable long-term performance which is—and still should be—recommended to patients at low surgical risk. Therefore, we state that both procedures serve as complementary approaches toward an increasing population of patients with degenerated SHV.

Valve Details

The use of porcine valves decreased significantly from 2002 to 2012 at our center. This reflects an observed national tendency toward pericardial valves, for which there may be some indication of superior durability beyond 10 years after implantation.[21]

Generally, we expect the suitability of a biological prosthesis for later ViV to be of growing importance as the awareness of ViV procedures will increase. This will lead to an influence on the surgeons' decision on which biological prostheses to implant. Biological prostheses not suitable for ViV may be avoided if future need for ViV due to SVD is probable. However, the suitability of different biological prostheses for ViV is scarcely described and should be further analyzed in future to adapt surgical strategies accordingly.

A substantial reduction in the rate of mechanical valves implanted was seen, from 10.9 to 1.8% (p < 0.001), at our center. This effect was more pronounced compared with the national background (p < 0.001) where a decrease from 44.8 to 14.1% was observed. In each year during the study period, the rate of mechanical AVR was lower as compared with corresponding years of the national background.[2] Possibly, this is due to a higher awareness for ViV in a center with a large TAVI program. Patients receiving mechanical valves at our center were significantly younger in 2012 compared with 2002.

One could argue that the use of a mechanical prosthesis is limited to considerably young patients and if the patient clearly requests it. Furthermore, according to international guidelines,[3] mechanical sAVR is still recommended in patients with increased risk of SVD, in patients already on anticoagulation as a result of having a mechanical prostheses in another valve position, or in patients with reasonable life expectancy for whom future reoperative valve surgery would be a high-risk procedure. The latter argument appears to become less relevant when considering possible future ViV procedure as a bailout strategy in high-risk cases. In addition, even in young patients, the use of anticoagulation for a mechanical prosthesis may restrict quality of life substantially and tremendous complications can occur, a circumstance that physicians and patients are increasingly becoming aware of, and consequently biological prostheses are chosen over mechanical prostheses.

To date, several studies regarding survival after biological versus mechanical sAVR exist and are contradictory; thus, no clinical evidence exists that one treatment option is superior to the other in patients <60 years.[17] [18] It has been demonstrated that the risk of major bleeding after mechanical sAVR equals the risk of reoperation after biological sAVR in patients aged 60 years at surgery.[18]

In a large historical trial, a survival advantage for mechanical prostheses was present at 12 years; however, the actuarial survival curves between the groups converged at 20 years of follow-up.[22] Further studies comparing two strategies—biological sAVR at an age of 50 to 60 years using subsequent ViV versus mechanical sAVR—are needed to determine advantages of either strategy and to evaluate long-term outcomes.

Valve Size

There are two predictors of SVD: patient age at the time of sAVR and severe PPM defined as iEOA ≤0.65 cm².[23] Growing awareness that PPM independently increases the risk of SVD and decreases survival[23] may have led to a strategy avoiding implantation of valves sized ≤21 mm. The proportion of valves ≥23 mm increased significantly, as well as mean true ID and EOA without a significant change of BSA. Therefore, during the past years, truly larger valves were implanted at our center. However, this may also in part be explained by an improved valve design of biological prostheses with a positive impact on hemodynamic performance. The changes in use of prostheses are documented in [Table 2]. However, the use of valve sizes <25 mm has decreased significantly, indicating a change in surgeon's practice. We expect that this leads to better hemodynamic performance and fewer cases of SVD in the later course.

Age and Valve Size

Throughout the study period, patients <60 years received significantly larger valves, while there was a significant increase in mean valve size both in patients aged <60 and >60 years. In 2013, Price and colleagues reported that PPM adversely affects survival only in patients <70 years.[24] As mean valve size was larger in patients <60 years, it appears likely that at our center we tended to avoid surgical maneuvers to increase EOA in elderly patients to limit both procedural times and surgical risk. Similarly, Price and colleagues recommend that root enlargement techniques should be reserved for patients <70 years.[24] In their cohort, the incidence of severe PPM in patients 70 years old or older was 16.5% (46/279), compared with 4.5% (20/428) in patients less than 70 years old (p < 0.001). This corresponds to our observation that iEOA is larger in patients ≤60 years (0.83 ± 0.12 vs. 0.73 ± 0.10 cm²/m², p = 0.045 in 2002, and 0.81 ± 0.20 vs. 0.79 ± 0.11 cm²/m², p = 0.360 in 2012). As ViV performed inside smaller biological prostheses (≤23 mm) can lead to elevated postoperative pressure gradients, the strategy to implant larger valves into younger patients seems reasonable. Small-sized stented valves in small aortic roots may by nature not provide sufficient EOA. To avoid PPM and preserve later ViV options, in these cases root enlargement may help to increase the achievable iEOA. Additionally, valves suitable for later ViV should be implanted.[25]

Conclusion

Profound change of use pattern in sAVR was observed at our center as indication for biological prostheses became more liberal. Furthermore, significantly larger prostheses were implanted considering manufacturer size, true ID, and orifice area leading to increased iEOA. Less reoperative sAVR and implantations of mechanical prostheses were performed after the introduction of TAVI at our center. In younger patients with high risk of later SVD, it is essential to implant biological prostheses of suitable size and type for ViV. Optimal sizing is of crucial relevance to preserve the option for subsequent ViV procedures.

Limitations

This is an observational, retrospective single-center study and as in any retrospective analysis may contain hidden bias. Therefore, conclusions drawn from results of our analyses have to be interpreted with caution. In particular, a causal relationship between trends in sAVR and availability of TAVI is unproven and purely hypothetical at present.

Authorship Statement

M. S. and L. C. contributed equally to this work. Designation of a single first author is impossible and permission to assign a shared first authorship to the first two authors is requested for the following reasons: the initial conception of the objectives and methodology of this work was equally achieved by the first two authors. While one of the first two authors primarily drafted, revised, and edited the introduction and methods section, the second primarily performed these tasks for the discussion section. Both contributed equally to drafting, revising, and editing of the results section. Communication with all other co-authors was also equally handled by both first authors.

^* Both the authors contributed equally to this work.

• References

• 1 Ross Jr J, Braunwald E. Aortic stenosis. Circulation 1968; 38 (1, Suppl): 61-67
• 2 Funkat A, Beckmann A, Lewandowski J , et al. Cardiac surgery in Germany during 2013: a report on behalf of the German Society for Thoracic and Cardiovascular Surgery. Thorac Cardiovasc Surg 2014; 62 (5) 380-392
• 3 Vahanian A, Alfieri O, Andreotti F , et al; Joint Task Force on the Management of Valvular Heart Disease of the European Society of Cardiology (ESC) and the European Association for Cardio-Thoracic Surgery (EACTS). Guidelines on the management of valvular heart disease (version 2012) [in Italian]. Eur J Cardiothorac Surg 2012; 42 (4) S1-S44
• 4 Niclauss L, von Segesser LK, Ferrari E. Aortic biological valve prosthesis in patients younger than 65 years of age: transition to a flexible age limit?. Interact Cardiovasc Thorac Surg 2013; 16 (4) 501-507
• 5 Leontyev S, Borger MA, Davierwala P , et al. Redo aortic valve surgery: early and late outcomes. Ann Thorac Surg 2011; 91 (4) 1120-1126
• 6 Onorati F, Biancari F, De Feo M , et al. Mid-term results of aortic valve surgery in redo scenarios in the current practice: results from the multicentre European RECORD (REdo Cardiac Operation Research Database) initiative. Eur J Cardiothorac Surg 2015; 47 (2) 269-280 , discussion 280
• 7 Diemert P, Seiffert M, Frerker C , et al. Valve-in-valve implantation of a novel and small self-expandable transcatheter heart valve in degenerated small surgical bioprostheses: the Hamburg experience. Catheter Cardiovasc Interv 2014; 84 (3) 486-493
• 8 Gurvitch R, Cheung A, Ye J , et al. Transcatheter valve-in-valve implantation for failed surgical bioprosthetic valves. J Am Coll Cardiol 2011; 58 (21) 2196-2209
• 9 Dvir D, Webb JG, Bleiziffer S , et al; Valve-in-Valve International Data Registry Investigators. Transcatheter aortic valve implantation in failed bioprosthetic surgical valves. JAMA 2014; 312 (2) 162-170
• 10 Dvir D, Barbanti M, Tan J, Webb JG. Transcatheter aortic valve-in-valve implantation for patients with degenerative surgical bioprosthetic valves. Curr Probl Cardiol 2014; 39 (1) 7-27
• 11 Faerber G, Schleger S, Diab M , et al. Valve-in-valve transcatheter aortic valve implantation: the new playground for prosthesis-patient mismatch. J Interv Cardiol 2014; 27 (3) 287-292
• 12 Pibarot P, Dumesnil JG. Prosthetic heart valves: selection of the optimal prosthesis and long-term management. Circulation 2009; 119 (7) 1034-1048
• 13 Bapat VN, Attia R, Thomas M. Effect of valve design on the stent internal diameter of a bioprosthetic valve: a concept of true internal diameter and its implications for the valve-in-valve procedure. JACC Cardiovasc Interv 2014; 7 (2) 115-127
• 14 Blais C, Dumesnil JG, Baillot R, Simard S, Doyle D, Pibarot P. Impact of valve prosthesis-patient mismatch on short-term mortality after aortic valve replacement. Circulation 2003; 108 (8) 983-988
• 15 Du Bois D, Du Bois EF. A formula to estimate the approximate surface area if height and weight be known. Arch Intern Med 1916; 17: 863-871
• 16 Brown JM, O'Brien SM, Wu C, Sikora JA, Griffith BP, Gammie JS. Isolated aortic valve replacement in North America comprising 108,687 patients in 10 years: changes in risks, valve types, and outcomes in the Society of Thoracic Surgeons National Database. J Thorac Cardiovasc Surg 2009; 137 (1) 82-90
• 17 Brown ML, Schaff HV, Lahr BD , et al. Aortic valve replacement in patients aged 50 to 70 years: improved outcome with mechanical versus biologic prostheses. J Thorac Cardiovasc Surg 2008; 135 (4) 878-884 , discussion 884
• 18 Weber A, Noureddine H, Englberger L , et al. Ten-year comparison of pericardial tissue valves versus mechanical prostheses for aortic valve replacement in patients younger than 60 years of age. J Thorac Cardiovasc Surg 2012; 144 (5) 1075-1083
• 19 Abdel-Wahab M, Zahn R, Horack M , et al; German transcatheter aortic valve interventions registry investigators. Aortic regurgitation after transcatheter aortic valve implantation: incidence and early outcome. Results from the German transcatheter aortic valve interventions registry. Heart 2011; 97 (11) 899-906
• 20 Siontis GC, Jüni P, Pilgrim T , et al. Predictors of permanent pacemaker implantation in patients with severe aortic stenosis undergoing TAVR: a meta-analysis. J Am Coll Cardiol 2014; 64 (2) 129-140
• 21 Grunkemeier GL, Furnary AP, Wu Y, Wang L, Starr A. Durability of pericardial versus porcine bioprosthetic heart valves. J Thorac Cardiovasc Surg 2012; 144 (6) 1381-1386
• 22 Oxenham H, Bloomfield P, Wheatley DJ , et al. Twenty year comparison of a Bjork-Shiley mechanical heart valve with porcine bioprostheses. Heart 2003; 89 (7) 715-721
• 23 Urso S, Calderón P, Sadaba R , et al. Patient-prosthesis mismatch in patients undergoing bioprosthetic aortic valve implantation increases risk of reoperation for structural valve deterioration. J Card Surg 2014; 29 (4) 439-444
• 24 Price J, Toeg H, Lam BK, Lapierre H, Mesana TG, Ruel M. The impact of prosthesis-patient mismatch after aortic valve replacement varies according to age at operation. Heart 2014; 100 (14) 1099-1106
• 25 Silaschi M, Conradi L, Seiffert M , et al. Trends in surgical aortic valve replacement in more than 3000 consecutive cases in the era of transcatheter aortic valve implantation. Interact Cardiovasc Thorac Surg 2014; 19 (Suppl. 01) S16 10.1093/icvts/ivu276.53