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Ann Thorac Surg 2009;88:1468-1474. doi:10.1016/j.athoracsur.2009.07.033
© 2009 The Society of Thoracic Surgeons
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Original Articles: Adult Cardiac

Transcatheter Aortic Valve Implantation in Patients With Very High Risk for Conventional Aortic Valve Replacement

Matthias Thielmann, MDa,*, Daniel Wendt, MDa, Holger Eggebrecht, MDb, Philipp Kahlert, MDb, Parwis Massoudy, MDa, Markus Kamler, MDa, Raimund Erbel, MDb, Heinz Jakob, MDa, Stefan Sack, MDb

a Department of Thoracic and Cardiovascular Surgery, West German Heart Center Essen, University Hospital Essen, Essen, Germany
b Department of Cardiology, West German Heart Center Essen, University Hospital Essen, Essen, Germany

Accepted for publication July 21, 2009.

* Address correspondence to Dr Thielmann, Department of Thoracic and Cardiovascular Surgery, West German Heart Center Essen, University Hospital Essen, Hufelandstrasse 55, Essen, 45122, Germany (Email: matthias.thielmann{at}uni-due.de).

Presented at the Poster Session of the Forty-fifth Annual Meeting of The Society of Thoracic Surgeons, San Francisco, CA, Jan 26–28, 2009.


   Abstract
Top
 Abstract
Introduction
 Patients and Methods
 Results
 Comment
 References
 
Background: We sought to determine whether transcatheter aortic valve implantation is a reasonable treatment option in patients with a very or extremely high risk for conventional aortic valve replacement, presenting with a logistic EuroSCORE greater than 30% or a Society of Thoracic Surgeons score greater than 15%.

Methods: Between May 2005 and November 2008, 39 of 85 transcatheter aortic valve implantation patients with a very high risk for aortic valve replacement underwent either transfemoral (n = 15) or transapical (n = 24) transcatheter aortic valve implantation with a mean estimated logistic EuroSCORE of 44.2% ± 12.6% (mean ± standard deviation) and a Society of Thoracic Surgeons score of 17.9% ± 6.1%. Transcatheter aortic valve implantation was performed in a hybrid operative theater using the Cribier-Edwards or Edwards SAPIEN prosthesis.

Results: Valve implantation was successful in 97% of the patients. Operative mortality was 2.6%, and mortality at 30 days was 17.9%. After valve implantation, hemodynamic improvement was assessed by decreased mean pressure gradient (p < 0.001) and increased aortic valve area (p < 0.001), accompanied by improved New York Heart Association functional status (p < 0.01). Actuarial survival was 74.4% at 3 months, 74.4% at 6 months, and 64.1% at 12 months of follow-up. Echocardiography revealed aortic regurgitation in 58% of the patients during hospital stay, 43% at 6 months of follow-up, and 40% at 12 months of follow-up, but no structural valve deterioration could be observed during the complete follow-up period.

Conclusions: Transcatheter aortic valve implantation in patients with severe aortic stenosis and a very high risk for aortic valve replacement is feasible and may be a reasonable treatment option in these patients.


   Introduction
Top
 Abstract
 Introduction
Patients and Methods
 Results
 Comment
 References
 
Aortic valve replacement (AVR) is currently the treatment of choice in patients with symptomatic aortic stenosis, and numerous reports have demonstrated excellent and highly convincing results in most patients [1, 2]. However, the risk of conventional AVR with the use of sternotomy, cardiopulmonary bypass, and cardioplegic arrest is obviously higher in elderly patients, in whom significant comorbidities additionally exist. Moreover, there is recent evidence that 30% to 40% of patients with symptomatic aortic stenosis in Europe and the United States remain untreated, and nearly half of them are considered too sick for surgery [3–5]. Therefore, there seems to be a role for less invasive treatment options addressing an unmet patient and medical need.

Transcatheter aortic valve implantation (TAVI) has been suggested as an endovascular alternative to conventional AVR in high-risk patients [6, 7]. We sought to determine whether TAVI is a feasible and reasonable treatment option for patients with a very or extremely high risk for conventional AVR, presenting with a logistic EuroSCORE greater than 30% or Society of Thoracic Surgeons (STS) score greater than 15%.


   Patients and Methods
Top
 Abstract
 Introduction
 Patients and Methods
Results
 Comment
 References
 
Study Design
This study was a prospective single-center study including a subset of 41 very high risk patients of a total of 85 patients who underwent TAVI between May 2005 and November 2008 at the West German Heart Center Essen (Fig 1). Patients were enrolled with a very high risk for conventional AVR having a logistic EuroSCORE greater than 30% or STS score greater than 15%. All remaining patients did not fulfill the inclusion criteria because of a calculated risk score lower than the cutoff points of the present study. Transcatheter aortic valve implantation was performed either by means of the transfemoral or transapical access. All patients who were not suitable for a transfemoral approach were then considered as candidates for the transapical approach. In any case a thoughtful and conscientious patient selection was performed. The individual decision to offer a TAVI was based on multiple decisions. First, each case was discussed in an interdisciplinary session between our departments of cardiology and cardiovascular surgery. Either the patients were declined for conventional AVR by an experienced surgeon or the individual patient refused conventional AVR. The final decision to perform a TAVI was based on intensive discussions and interviews including the patients' relatives or family.


Figure 1
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  		Fig 1. Study summary. (AVR = aortic valve replacement; TA = transapical implantation; TAVI = transcatheter aortic valve implantation; TF = transfemoral.)

 
The study protocol was approved by the institutional review board and the university ethics committee, and all patients enrolled gave their written informed consent before screening. A total of 9 of these 41 patients were also included in the multicentric PARTNER (Placement of AoRTic transcatheter valves) EU trial.

Primary study end points were (1) in-hospital mortality, defined as all-cause death within 30 days including all enrolled patients and (2) long-term survival at 3, 6, and 12 months. Secondary end points were (1) procedure- and valve-related complications, (2) hemodynamic valve function, and (3) functional status of the patients.

Technique and Periprocedural Management
All TAVI procedures were performed using the Cribier-Edwards or Edwards SAPIEN (Edwards Lifesciences, Irvine, CA) heart valve in a hybrid operating room under fluoroscopy and simultaneous transesophageal echocardiography by means of either the transfemoral (Retroflex I & II delivery system) or the transapical access (Ascendra delivery system) as previously described [8–11].

Statistical Analysis
Descriptive statistics are summarized for categorical variables as frequencies (%) and compared between groups using Pearson's {chi}2 exact test. Continuous variables, expressed as mean ± standard deviation, were compared between groups using Student's t test. Changes of aortic regurgitation and New York Heart Association functional class during the follow-up period were analyzed with the sign test. Survival curves were generated with the Kaplan-Meier method. An analysis of variance for repeated measurements was used to compare echocardiographic data (mean pressure gradient, left ventricular ejection fraction, effective orifice area). A probability value less than 0.05 was considered to indicate statistical significance. All statistical analyses were performed using the SPSS software (SPSS Inc, Chicago, IL).

Statement of Responsibility
The authors had full access to the data and take full responsibility for its integrity. All authors have read and agreed to the manuscript as written.


   Results
Top
 Abstract
 Introduction
 Patients and Methods
 Results
Comment
 References
 
Of a total of 85 TAVI patients, a subgroup of 41 patients was enrolled in the present study with a very high risk according to the inclusion criteria mentioned above. Of these, two valve implantations were aborted. One intended transfemoral valve implantation had to be aborted after successful balloon valvuloplasty owing to a too small vascular access for the 24F sheath; the patient was then scheduled for transapical implantation but died a day before the procedure. Another transapical valve implantation was aborted because of an evolving infection before the procedure. Therefore, a total of 39 patients underwent high-risk TAVI, 15 patients by means of the transfemoral and 24 patients by means of the transapical approach. One patient was successfully converted to conventional AVR after transapical low valve malpositioning, which caused prosthetic valve dysfunction with severe aortic regurgitation (Fig 1).

Patient demographics, risk factors, and comorbidities are presented in Table 1 demonstrating a very high risk subgroup of TAVI patients. By comparing the transfemoral and transapical groups, patients were significantly different according to peripheral vascular disease, mitral valve regurgitation, and prior aortic balloon valvuloplasty. Preoperative risk assessment of the complete high-risk TAVI group revealed a mean additive and logistic EuroSCORE of 14.2% ± 3.6% and 44.2% ± 12.6%, respectively, a mean additive and logistic Parsonnet score of 32.4% ± 5.5% and 27% ± 8.5%, respectively, and a mean STS score of 17.9% ± 6.1%. Additive and logistic EuroSCORE and logistic Parsonnet score, as well as the STS score, were significantly higher in the transapical than in the transfemoral group, thus characterizing a different and much sicker patient population (Table 1). By comparing the predicted and the observed mortality rates of the TAVI groups for the EuroSCORE, the STS score, and the Parsonnet score, we could demonstrate that the STS score seems to be most accurately predicting the 30-day mortality rate after TAVI (Fig 2).


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  		Table 1 Baseline Patient Characteristics a
 

Figure 2
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  		Fig 2. Comparison of different risk score models, with predicted and observed mortality rates for the different groups shown. (STS Society of Thoracic Surgeons; TA = transapical implantation; TAVI = transcatheter aortic valve implantation; TF = transfemoral.)

 
Comparing echocardiographic valve characteristics of the patients who received a 23-mm valve (n = 15) with those who received a 26-mm valve (n = 24), native annulus diameter was 20.5 ± 0.9 mm versus 23.1 ± 0.8 mm (p < 0.001), preprocedural mean gradient 50.6 ± 17.9 mm Hg versus 38.5 ± 16.7 mm Hg (p < 0.01), postprocedural mean gradient 9.0 ± 7.4 mm Hg versus 7.4 ± 5.5 mm Hg (p = 0.56), preprocedural effective orifice area 0.6 ± 0.2 cm2 versus 0.8 ± 0.3 cm2 (p < 0.01), and postprocedural effective orifice area 1.5 ± 0.1 cm2 versus 1.7 ± 0.2 cm2 (p < 0.01).

Intraprocedural results are illustrated in Table 2. Balloon valvuloplasty was successful in all patients and valve implantation in all except 1. Valve deployment and fluoroscopy time was 10.4 ± 5.9 minutes and 7.3 ± 1.9 minutes, which was significantly different between the transfemoral and transapical group (p < 0.001). One patient required intraaortic balloon pump support, and another patient had to be connected to the heart–lung machine to convert to conventional AVR. General anesthesia was applied in 53% of the transfemoral patients and 100% of the transapical patients, in whom on-table extubation was intended and could be performed in 27% and 58%, causing a postprocedural ventilation time of 17 ± 23 hours and an intensive care unit stay of 3 ± 5 days, which differed significantly between the groups (Table 2). According to periprocedural complications, a total of 4 transfemoral patients required a pacemaker because of atrioventricular blockade, and peripheral vascular complications could be observed in 5 transfemoral patients (2 vascular dissections, 2 occlusions, 1 perforation), necessitating further interventions (Table 2).


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  		Table 2 Periprocedural Data a
 
Operative mortality was 2.5% (1 transfemoral patient). All-cause 30-day mortality was 17.9% for the complete high-risk TAVI group, with a mortality rate of 13.3% for the transfemoral and 20.8% for the transapical group, which was acceptable in view of the high-risk profile and the predicted mortality of the patients (Table 2). Long-term survival and Kaplan-Meier curves are given in Table 2 and Figure 3. The mean pressure gradient decreased whereas the effective orifice area increased significantly in the complete high-risk TAVI group (pooled echocardiographic data) and remained unchanged throughout the 12-month follow-up period. Furthermore, left ventricular ejection fraction remained unchanged during the first 6 months and tended to increase after 1 year of follow-up as compared with baseline. Aortic regurgitation was present in nearly 50% of the patients at discharge and remained unchanged throughout the follow-up time. No structural valve deterioration could be observed during the complete follow-up period. In addition, the initial improvement of New York Heart Association functional class achieved after valve implantation was maintained during the 12-month follow-up interval (Table 3).


Figure 3
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  		Fig 3. Kaplan-Meier survival of the entire high-risk transcatheter aortic valve implantation (TAVI) group (solid line), transfemoral (TF) group (dashed line), and transapical (TA) group (dotted line). Patients at risk are shown above the x axis.

 

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  		Table 3 Follow-Up Data (Pooled Transfemoral and Transapical Data) a
 

   Comment
Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
References
 
The present study clearly demonstrates that TAVI in patients with severe aortic stenosis and a very or extremely high risk for conventional prosthetic AVR is a promising treatment option that is feasible and provides hemodynamic and clinical improvement. Surgical AVR is currently the treatment of choice in patients with symptomatic aortic stenosis, and numerous studies have demonstrated excellent and highly convincing results in most patients [1, 2]. However, the risk of conventional AVR with the use of sternotomy, cardiopulmonary bypass, and cardioplegic arrest is significantly increased in elderly patients, in whom significant comorbidities may exist. Moreover, there is recent evidence that 30% to 40% of patients in Europe and the United States with symptomatic aortic stenosis remain untreated, and nearly one half of them are considered too sick for surgery [4]. Therefore, there seems to be a role for less invasive treatment options addressing an unmet patient and medical need.

Transcatheter aortic valve implantation has been suggested as an endovascular alternative to surgical AVR for high-risk patients or as a reasonable treatment option even for those patients who had so far been refused for surgical AVR. Nevertheless, several previous reports on TAVI defined high-risk patients as patients with a logistic EuroSCORE between 10% and 30% [10, 12, 13]. At the same time, there is a growing debate about the definition of such high-risk patients and the validity of risk assessment using different risk-scoring systems for prediction of mortality [14–17]. The aim of the present study was therefore to evaluate whether TAVI (either by means of transfemoral or transapical access) is a feasible and reasonable treatment option for patients with a very or extremely high risk presenting with a logistic EuroSCORE above 30% or STS score higher than 15%. As a matter of fact, the mean logistic EuroSCORE was 38.1% ± 8.1% and STS score 15.1% ± 4.1% for the transfemoral group and 52.5% ± 13.4% and 19.9% ± 7.5% for the transapical group, representing a subgroup of patients at highest risk for surgical AVR. The present study also confirms recent reports and analyses that the logistic EuroSCORE clearly overestimates the risk of mortality, whereas the STS score seems to be more accurate in predicting the risk of mortality [14–17]. In the present study, mortality rates of this high-risk TAVI subgroup were indeed higher as recently reported [6, 7, 13]; however, mortality rates were actually as high as predicted by the STS score with 15% ± 4% for the transfemoral and 20% ± 8% for the transapical group (Fig 2). Although the logistic EuroSCORE and the Parsonnet score clearly overestimated the risk of mortality, the STS score as well as the additive EuroSCORE were much more accurate in predicting the risk of mortality. It should also be considered that the incidence of patient comorbidities were much higher as compared with previous reports, including more than 50% of patients with mitral valve regurgitation, 54% with renal disease, 56% concomitant coronary artery disease, 36% prior percutaneous coronary intervention, 26% prior coronary artery bypass grafting, and 51% with prior myocardial infarction, presenting a high-risk patient profile. The highest 30-day mortality rates (20.8%) were present in the transapical group. However, transapical patients appear to be a rather different patient population compared with transfemoral patients, exhibiting a higher incidence of comorbidities, which was reflected by significantly higher risk scores in the transapical group. However, there are multiple additional risk factors, which are so far not considered by the present risk scoring systems; for example nearly 25% of patients in the transapical group additionally present a porcelain aorta compared with only 2 patients in the transfemoral group. Moreover, the 21% mortality rate of the very high-risk transapical group within the first 30 days seems to be the result of a learning curve, either in technical aspects or in proper patient selection. What we have learned is to evaluate patients presenting with a very low left ventricular ejection fraction. A dobutamine stress echocardiographic test may be useful to determine preoperatively the contractile reserve of those patients. Additionally, it is important to evaluate and quantify potential concomitant mitral valve disease, which appears to be another important risk factor for TAVI. Complete coronary artery bypass graft perfusion before TAVI is essential to avoid or even reduce a prolonged temporary myocardial ischemia during TAVI, especially after a longer period of hypotension owing to the rapid pacing period. Furthermore, nearly 40% of our TAVI patients presented with a severe chronic obstructive pulmonary disease, which may raise the question of epidural anesthesia application during the postoperative course.

Despite increasing risk profiles of actual patients, most of the groups performing TAVI could improve their results [18, 19]. This may be based on critical patient selection [20]. Factors like social integration, mobility, frailty, and the individual overall health status must be taken into account to carefully evaluate preoperative TAVI patients as these factors were not reflected by the recent risk scoring systems. Furthermore, technical improvements, such as placing four apical U-stitches for a safer apical closure of the left ventricle or a stepwise balloon inflation during valve prosthesis positioning as well as an exact axial positioning of the prosthesis, have been implemented and applied [21].

Limitations
The present study summarizes a rather small number of high-risk patients and encompasses the experience of a single center; therefore, the generalizability of our findings may not extend to all clinical centers performing TAVI. Second, the present study was prospective but the choice of treatment was not randomized. In addition, there may be a learning curve not only regarding the procedure itself but also for careful patient selection considering several risk factors and contraindications that are known so far and are better understood with increasing experience. Finally, further technical improvements of the technology itself will definitely lead to evolution of smaller devices, which may result in a rapid increase in the number of transfemoral procedures performed.

Conclusions
Transcatheter aortic valve implantation by means of either the transfemoral or the transapical approach is a reasonable and promising treatment option for patients who are at high risk or had been refused for conventional AVR.


   References
Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
 References
 

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