Surg Today DOI 10.1007/s00595-014-0902-8

REVIEW ARTICLE

Transcatheter aortic valve implantation Yoshiki Sawa

Received: 13 November 2013 / Accepted: 4 March 2014 Ó Springer Japan 2014

Abstract With the improvement in the overall life expectancy, the incidence of aortic stenosis has been increasing. Although aortic valve replacement is a standard therapy, many patients do not undergo surgery for various reasons, including advanced age or the presence of multiple comorbidities. Transcatheter aortic valve implantation (TAVI) has been proposed as a less invasive and equally effective treatment for inoperable or high-risk symptomatic aortic stenosis. Numerous rigorous global clinical trials, as well as a pivotal clinical trial in Japan, have been conducted. In this review, we provide data on the development of TAVI worldwide and discuss the prospects for TAVI in Japan. Keywords Aortic valve stenosis
Transcatheter aortic valve implantation
Aortic valve replacement Background Aortic valve stenosis is an important cause of cardiac morbidity and mortality in elderly patients, with 1–2 % of patients older than 65 reported to have moderate to severe aortic stenosis (assessed by limited mobility of the valve leaflet and/or increased velocity across the aortic valve seen on echocardiography) in population-based observational studies [1, 2]. However, the natural history of aortic valve stenosis is still poorly understood [3–5]. The severity of aortic stenosis should be assessed on the basis of echocardiographic findings. According to previously published

guidelines [6], severe stenosis is defined as a peak velocity [ 4.0 m/s, a mean gradient [ 40 mmHg and an aortic valve area \ 1.0 cm2, when the left ventricular systolic function is normal. To account for patient size, the valve area is often indexed to the body surface area, with 0.6 cm2/m2 considered to represent severe aortic stenosis. In the United States, the census has predicted that the incidence of aortic stenosis among people older than 65 will increase from 800,000 patients in 2010 to 1,400,000 in 2030 [3, 4, 7]. Aortic valve replacement (AVR) is the standard treatment for aortic valve stenosis and is known to improve survival [8–12]. Currently, surgery in moderate-to-high risk patients (Society of Thoracic Surgery predicted risk of mortality of 4–8 %) can achieve acceptable results (30-day mortality: 2.8 %). Nevertheless, approximately half of patients do not undergo surgery for various reasons, including advanced age or the presence of multiple comorbidities [13–15]. Transcatheter aortic valve implantation (TAVI) has been implemented for such high-risk aortic stenosis patients since 2002 [16]. Various clinical trials have been conducted thus far, and the results from these trials suggest that TAVI is feasible and effective to improve symptoms. In Japan, a pivotal clinical trial of TAVI was initiated in 2009. In this review, we provide data on the development of TAVI worldwide and discuss the prospects for TAVI in Japan.

History of transcatheter aortic valve implantation Edwards SAPIEN

Y. Sawa (&) Department of Cardiovascular Surgery, Osaka University Graduate School of Medicine, 2-2 Yamada-Oka, Suita, Osaka 565-0871, Japan e-mail: [email protected]

The Edwards SAPIEN valve (Edwards SAPIEN THV; Edwards Lifesciences Inc., Irvine, CA, USA) is a trileaflet bovine pericardial valve mounted with a tubular slotted

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septally from the femoral vein to the aortic valve [17]. However, this antegrade approach is no longer performed because it is complicated. After Hanzel et al. implanted a percutaneous heart valve in a patient with critical aortic stenosis via the iliac artery [18], retrograde approaches, such as the trans-femoral approach, have been developed. Using this technique, Webb et al. implanted the Cribier-Edwards valve in 18 patients. The valve was implanted successfully in 14 patients, and 16 of the 18 patients were still alive at a follow-up of 73 ± 49 days. Furthermore, the authors published their 12-month experience using the Cribier-Edwards valve implanted with the retrograde technique in 50 highrisk patients. The clinical outcomes were satisfactory: the procedural success was 86 %, the overall 30-day mortality was 12 % and there was improvement of the valve area and New York Heart Association (NYHA) functional class at the 1-year follow-up [19]. Ye et al. [20] reported the first human case involving a trans-apical approach. This approach is more invasive and performed more commonly by surgeons. The pleural space over the left ventricle apex is exposed through a 5-to-8-cm fifth or sixth intercostal anterolateral thoracotomy. The delivery system and prosthetic valve are advanced through the left ventricle and are positioned at the aortic annulus [21]. Lichtenstein et al. [21, 22] reported their initial

balloon-expandable stent composed of a cobalt chromium alloy (Fig. 1). Since Cribier et al. [16] first performed TAVI in 2002, many rigorous global clinical trials of the SAPIEN valve have been conducted (Fig. 2). When it was initially developed, an anterograde approach was utilized in TAVI. In this approach, the bioprosthetic valve was delivered trans-

Fig. 1 The Edwards SAPIEN transcatheter heart valve (Edwards Lifesciences Inc., Irvine, CA, USA). The bioprosthetic valve is a trileaflet bovine pericardial valve mounted with a balloon-expandable stent composed of a cobalt–chromium alloy

Start of the US CoreValve pivotal trial PARTNER cohort A published United States

Start of Edwards feasibility trial

Start of the PARTNER trial

Edwards Lifesciences Acquisition of percutaneous valve technologies

2002

2003

1st Edwards-Cribier implantation

2004

2005

1st CoreValve implantation

PARTNER cohort B published

FDA approval for the EdwardsSAPIEN device

Medtronic Ltd acquisition of CoreValve

2006

2007

CoreValve EU approval

2008

2009

Edwards-SAPIEN EU approval

2010

2011

CE approval for Edwards-XT 18Fr Novaflex sheath and Ascendra II

1st EdwardsSAPIEN implantation in JAPAN

Europe

Japan

Start of the PREVAIL JAPAN

Fig. 2 The history of transcatheter aortic valve replacement worldwide and in Japan

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Start of the PARTNER II trial

2012

2013

SAPIEN XT Reimbursement approval

1st CoreValve implantation in JAPAN Start of the MDT-2111 JAPAN

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experience and clinical outcomes at the 6-month follow-up using the Cribier-Edwards valve with the trans-apical technique in seven patients. Of the four patients who remained alive, the aortic valve area, aortic mean gradient and quality of life, as assessed by the NYHA class, were well maintained at the 6-month follow-up [23]. The PARTNER (Placement of Aortic Transcatheter Valves) trial The Edwards SAPIEN is currently being studied in the Placement of Aortic Transcatheter Valve (PARTNER) trial. This trial is a multicenter, randomized clinical trial comparing transcatheter aortic valve replacement (TAVR; which indicates TAVI) with standard therapy in high-risk patients with severe aortic stenosis, including a pre-specified cohort of patients who were not considered to be suitable candidates for surgery [24, 25]. TAVR reduced the rates of death (43.3 % in the TAVR group and 68.0 % in the standard-therapy group; P \ 0.001) and hospitalization (35.0 % in the TAVR group and 72.5 % in the standardtherapy group; P \ 0.001), with a decrease in symptoms and improvements in the valve hemodynamics that were sustained at the 2-year follow-up (cohort B). The rate of stroke was higher after TAVR than after standard therapy (13.8 % in the TAVR group and 5.5 % in the standardtherapy group; P = 0.01); and this was considered to be because the TAVR group had higher occurrence rates of ischemic events in the first 30 days (6.7 %, compared to 1.7 % in the standard-therapy group; P = 0.02) and of hemorrhagic strokes beyond 30 days (2.2 %, compared to 0.6 % in the standard-therapy group; P = 0.16). Moreover, transcatheter and surgical procedures for AVR were associated with similar rates of survival at the 2-year follow-up (33.9 % in the TAVR group and 35.0 % in the surgery group; P = 0.78), although important differences in periprocedural risks were observed in high-risk patients with severe aortic stenosis (cohort A) [26, 27]. The frequency of all strokes at 2 years did not differ significantly between the two groups, while strokes were more frequent with TAVR than with surgical replacement at 30 days (4.6 % in the TAVR group and 2.4 % in the surgical group; P = 0.12). Regarding the prosthetic valve function, the improvement in the valve area was similar between TAVR and surgical replacement, and was maintained for 2 years. However, paravalvular regurgitation was more frequently detected after TAVR (P \ 0.001), and even mild paravalvular regurgitation was associated with increased late mortality (P \ 0.001). The investigators indicated that clinicians should be attentive to reducing paravalvular aortic regurgitation and stressed the need for the improvement of devices, techniques for more precise valve sizing and positioning, and accurate post-dilation.

Fig. 3 The third-generation Medtronic CoreValve (Medtronic Inc., MN, USA). The bioprosthetic valve is a trileaflet porcine pericardial tissue valve with a self-expanding stent composed of nitinol

The PARTNER II trial is currently underway. The purpose of this trial is to determine the safety and effectiveness of the Edwards SAPIEN XT and the Edwards SAPIEN 3 transcatheter heart valve and different delivery systems (trans-femoral, trans-apical and transaortic) which are intended for use in patients with symptomatic, calcific, severe aortic stenosis. This trial includes patients with not only high risk, but also intermediate risk, for surgical AVR (cohort A—operable). Medtronic CoreValve The Medtronic CoreValve (Medtronic Inc., MN, USA) is a trileaflet porcine pericardial tissue valve with a selfexpanding stent composed of nitinol (Fig. 3). In 2006, Grube et al. [28] reported the feasibility and safety of the CoreValve in a prospective multicenter trial. The device was successfully implanted using the retrograde technique in 22 of 25 patients. The aortic mean pressure gradient was markedly improved, from a mean preprocedural gradient of 44.24 ± 10.79 to 12.38 ± 3.03 mmHg post-procedure, and was the same at the 30-day follow-up (11.82 ± 3.42 mmHg). The NYHA class improved by 1–2 grades in all patients. Major adverse cardiac events (MACEs) occurred in eight of the 25 patients during hospitalization. Furthermore, Grube et al. [29] reported their singlecenter experience with the second and third generations of the CoreValve. Overall, the procedural success rate was

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74 %, and all MACEs were evident in the first 48 h. The mortality at 30 days was 12 %, including five procedural deaths. The NYHA class improved from 2.85 ± 0.73 to 1.85 ± 0.60 after valve implantation (P \ 0.001). During the development of the device, new approaches, including subclavian and direct aortic approaches, have been reported. After Ruge et al. [30] reported the first use of a transsubclavian approach; several descriptions of this approach have been published [31–34]. Petronio et al. [31] conducted a multicenter study of 13 centers in Italy comparing 460 patients who underwent TAVI via the femoral approach and 54 patients treated via the subclavian approach, and observed similar rates of all-cause mortality, cardiac death, MACEs and major advanced valve-related events (including valve-related mortality, valve-related morbidity and the need for new permanent pacemaker or defibrillator placement within 14 days) during the 12-month follow-up. The authors added that this approach does not require a relevant learning curve, as the procedural and short-term clinical results were highly satisfactory even in the initial cases. Moreover, the direct aorta technique, first reported by Bauernschmitt et al. [35], is a feasible approach in patients in whom other access roots are not available [36–39]. The Safety and Efficacy Study of the Medtronic CoreValveÒ System in the Treatment of Severe, Symptomatic Aortic Stenosis in Intermediate Risk Subjects Who Need Aortic Valve Replacement (SURTAVI) study is currently underway. This study aims to evaluate the safety and efficacy of TAVI with the CoreValve in aortic stenosis patients with intermediate risk (STS mortality score C4 and B8 %).

Table 1 European Society for Cardiology (ESC) guideline for TAVI Class

Level

TAVI should only be undertaken with a multidisciplinary ‘‘heart team’’ including cardiologists, cardiac surgeons and other specialists if necessary

I

C

TAVI should only be performed in hospitals with cardiac surgery on-site

I

C

TAVI is indicated in patients with severe symptomatic AS who are not suitable for AVR as assessed by a ‘‘heart team’’ and who are likely to gain improvement in their quality of life and to have a life expectancy of more than 1 year after consideration of their comorbidities

I

B

TAVI should be considered in high surgical risk patients with severe symptomatic AS who may still be suitable for surgery, but in whom TAVI is favored by a ‘‘heart team’’ based on the individual risk profile and anatomic suitability

IIa

B

Table 2 Contraindications for TAVI Absolute contraindiactions Absence of a ‘‘heart team’’ and no cardiac surgery on the site Appropriateness of TAVI, as an alternative to AVR, not confirmed by a ‘‘heart team’’ Clinical Estimated life expectancy \1 year Improvement of quality of life by TAVI unlikely because of comorbidities Severe primary associated disease of other valves with major contribution to the patient’s symptoms that can be treated only by surgery Anatomical

Indications/contraindications for TAVI

Inadequate annulus size (\18 mm, [29 mm) Thrombus in the left ventricle

In terms of the indications for TAVI, the European Society for Cardiology (ESC) emphasizes the clinical judgment of a ‘heart team,’ including cardiologists, cardiovascular surgeons and other specialists, in addition to the combination of the EuroSCORE and STS score. A multidisciplinary team should evaluate the surgical risk for conventional AVR based on patients’ comorbidities, activities of daily living (ADL) and the efficacy of the TAVI procedure. In terms of the contraindications for TAVI, this multidisciplinary discussion is necessary for evaluating both clinical and anatomical contraindications (Tables 1, 2) [40].

Procedures Edwards SAPIEN The TAVI procedure should be performed in a catheterization laboratory or hybrid operating room (Fig. 4) with

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Active endocarditis Elevated risk of coronary ostium obstruction (asymmetric valve calcification, short distance between annulus and coronary ostia, small aortic sinuses) Plaques with mobile thrombi in the ascending aorta, or arch For trans-femoral/subclavian approach: inadequate vascular access (vessel size, calcification, tortuosity) Relative contraindications Bicuspid or non-calcified valves Untreated coronary artery disease requiring revascularization Hemodynamic instability LVEF \ 20 % For trans-apical approach: severe pulmonary disease, LV apex not accessible

the patient under general anesthesia and the use of transesophageal echocardiography (TEE). A standard balloon aortic valvuloplasty is performed after either trans-iliofemoral insertion of an 18-French (Fr) sheath when using

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the trans-iliofemoral (retrograde) approach, or after transapex insertion of a 24-Fr sheath when using a trans-apical (anterograde) approach, depending on the selected size of the valve. The bioprosthetic valve is advanced across the native aortic valve. During rapid right ventricular pacing, balloon inflation of the crimped heart valve and support frame simultaneously deploys the prosthetic valve and expands the frame, which is secured to the underlying aortic valve annulus and leaflets. Pharmacological therapy including heparin, during the procedure, and dual antiplatelet therapy (aspirin and clopidogrel) for 6 months after the procedure is recommended. Medtronic CoreValve The CoreValve procedure is also performed in a catheterization laboratory or hybrid operating room using TEE with the patient under general anesthesia. Currently, only retrograde approaches are available, including the trans-iliofemoral approach, trans-subclavian approach and direct aorta technique. A standard balloon aortic valvuloplasty is performed after trans-iliofemoral insertion of an 18-Fr sheath. The bioprosthetic valve is advanced across the native aortic valve and deployed slowly (using the step-wise technique). The self-expanding nitinol frame enables controlled, accurate deployment and partial repositionability. Pharmacological therapy including heparin, during the procedure, and dual antiplatelet therapy (aspirin and clopidogrel) for 3 months after the procedure is recommended. Useful modalities for the TAVI procedure During the TAVI procedure, precise intraoperative information is required to detect the ideal landing zone with the lowest risk. Several modalities are useful to achieve this aim.

Cross-sectional radiological imaging systems The TAVI procedure generally requires the use of conventional 2-D fluoroscopy images with contrast injection. However, especially in cases with extensive calcification at the annulus or the cusp, this approach often requires a large amount of contrast to identify the ideal landing zone, which may result in postoperative renal failure [41, 42]. Syngo DynaCT [Artis Zee (Siemens AG, Forchheim, Germany)] and the HeartNavigator (Philips Healthcare; Best, The Netherlands) are cross-sectional radiological imaging systems that can be applied intraoperatively in a hybrid operating room or interventional angiography suite (Fig. 4). They are considered to be useful devices in many fields, including endovascular aortic repair [43, 44], neurosurgery [45] and TAVI [46, 47]. During the TAVI procedure, 3-D reconstructions can be obtained, which may be overlaid on live fluoroscopy images for intraoperative realtime guidance. Kempfert et al. [46] reported that optimal imaging of the aortic root is critical during TAVI, and that DynaCT is a useful modality to facilitate the exact sizing of the aortic annulus and thus avoid the obstruction of the coronary arteries. Intracardiac echocardiography (ICE) The ICE probe is introduced into the femoral vein and advanced through the superior vena cava into the right atrium. ICE imaging has clear advantages in terms of the ease of the procedure and control of imaging by a single operator. The aortic valve is particularly clear in the longitudinal and horizontal axes with ICE imaging. Bartel et al. [48] reported that ICE could be considered an alternative to TEE for intraprocedural guidance during TAVI. However, the technique has several limitations. For example, the probe is not optimal for the assessment of left ventricular wall motion and the mitral valve. Although echocardiographic interrogation by ICE is not routinely required, it can be helpful in the event of a complication. Intraoperative complications with TAVI Intraoperative complications with TAVI are fairly common due to both the complexity of the procedure and the morbidity of the patients being treated. This high rate of complications has led to the development of new tools and techniques to manage them [49]. Shock and low cardiac output post-TAVI

Fig. 4 A hybrid operating room [Artis Zee (Siemens AG, Forchheim, Germany)]. The TAVI procedure should be performed in a catheterization laboratory or hybrid operating room

The hypertrophied ventricles in TAVI patients are susceptible to myocardial ischemia. The combination of anesthesia, rapid pacing, volume shifts and brief periods of

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no cardiac output makes patients susceptible to hemodynamic shock and low cardiac output during and immediately after deployment. The need for careful management of the systemic pressure, inotropic support and optimal ventilation to avoid and mitigate pulmonary hypertension is clear. In patients at extreme risk for hemodynamic instability (i.e., those with a low ejection fraction, collateral-dependent coronary circulation or pulmonary hypertension), elective cardiopulmonary bypass or intra-aortic balloon pumps have been used to facilitate the procedure [50, 51]. Coronary occlusion Occlusion of the coronary ostia by deployment is a rare complication that occurs in approximately 1 % of cases. Although this event may be addressed percutaneously at times, it may alternatively require cardiopulmonary bypass support for brief periods to allow recovery. Using a combination of these techniques, cardiac failure as a cause of death in TAVI has been rare [52, 53]. Left ventricular suicide Rarely, left ventricular ‘‘suicide’’ can occur and must be looked for. This phenomenon occurs in patients with combined aortic valve stenosis and subaortic stenosis or severe LV hypertrophy and cavity obliteration [54]. The situation is exacerbated by diuresis and inotropes, and is managed with volume expansion and beta blockade. Annular rupture Annular rupture is a rare but devastating complication of TAVI, occurring in approximately 1 % of cases [55]. Predisposing factors include bulky and dense calcification, a small sinotubular junction, a smaller annular size, aggressive balloon predilation and possibly a porcelain aorta. Once it occurs, the mortality is high. Management can include decisions for comfort care and sedation, attempts at medical management with pericardial drainage and autotransfusion of smaller leaks, and emergency conversion to open surgery, which makes it even more important to define and plan for this possibility in patients in a high-risk stratum [56]. Post-TAVI heart block TAVI is associated with a variable incidence of complete heart block and/or the need for pacemaker implantation [57]. This complication is much more common in CoreValve recipients (approximately 30 % of cases) [58, 59]. Preoperative conduction delay is also associated with

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an increased implantation.

incidence

of

permanent

pacemaker

Post-TAVI device migration/malposition Rarely, TAVI devices become malpositioned or migrate. In the self-expanding models, they can be moved to some degree until fully deployed. The balloon-expandable models do not demonstrate this degree of flexibility. A malpositioned valve may be ‘‘unstable’’ or may form emboli. If the valve is unstable, rapid placement of a second overlapping valve may salvage the procedure. Valves embolizing distally may occasionally be extracted in the aorta, and a second device can then be implanted. Ventricular embolization requires urgent surgery [60]. Ventricular and vascular perforation Ventricular perforation is a rare complication of transfemoral TAVI. Its management is similar to that for ventricular perforation during percutaneous balloon aortic valvuloplasty, with pericardial drainage and autotransfusion or conversion to open closure. Large-vessel aortoiliac injury is similarly uncommon, but if present, can be managed in most cases by the introduction of a covered stent. Post-TAVI aortic regurgitation Post-TAVI aortic valve regurgitation (AR) must be characterized with respect to its location, severity and cause, and both central and paravalvular origins should be considered to estimate the overall volumetric impact. Central regurgitation is generally a result of improper valve deployment or sizing. Additionally, damage to the leaflets can occur during crimping. Significant central AR requires rapid consideration of a valve-in-valve deployment. In contrast, paravalvular regurgitation is common immediately post-TAVI, occurring with an incidence of 85 %. The predisposing factors include eccentric calcification and heavy irregular calcific deposits within the annular area and incorrectly sized prostheses. Experience has demonstrated that, after placement of self-expanding TAVI devices, aortic paravalvular regurgitation can be reduced by sufficient balloon aortic valvuloplasty prior to deployment of a percutaneous prosthesis for self-expanding valves. Occasionally in heavily calcified valves, repeat balloon dilation after valve deployment is needed to fully expand the prosthesis. Appropriate preprocedural planning utilizing both echocardiography and CT for an annular analysis is important to avoid undersizing the valve compared with the annulus, which can also cause significant paravalvular regurgitation. Acute postprocedural regurgitation requires continued surveillance, because regurgitation may change in the days

Surg Today Table 3 Results of PREVAIL JAPAN Characteristic

Total (n = 64)

TF (n = 37)

TA (n = 27)

Age (years)

84.3 ± 6.1

83.2 ± 6.5

85.9 ± 5.3

STS score (%)

8.96 ± 4.48

7.79 ± 3.43

10.55 ± 5.28

Euro SCORE (%)

15.54 ± 8.06

13.32 ± 5.99

18.59 ± 9.55

All-cause mortality—30 days/6 months (%)

5 (7.8)/7 (10.9)

2 (5.4)/2 (5.4)

3 (11.1)/5 (18.5)

Cardiac mortality—30 days/6 months (%)

4 (6.3)/6 (9.4)

2 (5.4)/2 (5.4)

2 (7.4)/4 (14.8)

Major stroke—30 days/6 months (%)

1(1.6)/2 (3.1)

1(2.7)/1 (2.7)

0 (0)/1(3.7)

Vascular complication—30 days/6 months (%)

5 (7.8)/7 (10.9)

2 (5.4)/2 (5.4)

3(11.1)/5(18.5)

Major bleeding—30 days/6 months (%)

5 (7.8)/5 (7.8)

2 (5.4)/2 (5.4)

3(11.1)/3 (11.1)

New pacemaker—30 days/6 months (%)

5 (7.8)/6 (9.4)

2 (5.4)/2 (5.4)

3(11.1)/4(14.8)

Device success (only one valve in appropriate annulus position, AVA C 1.0 cm2 and AR B 2 ?) (%)

57/62 (91.9)

33/36 (91.7)

24/26 (92.3)

NYHA improvement C 1 class and AVA C 1.0 cm2 at 6 months (%)—doctor assessment

51/58(87.9)

32/34(94.1)

19/24(79.2)

STS The Society of Thoracic Surgeons, AVA aortic valve area, AR aortic valve regurgitation, NYHA New York Heart Association

following TAVI. The self-expanding properties of the stent in the CoreValve prosthesis may reduce the grade of paravalvular AR, and recoil from the compressive forces of the heavy calcification on either prosthesis may worsen it [29]. Clinical concern regarding the impact of paravalvular regurgitation after TAVI is prudent, given the findings that after surgical AVR, patients with moderate–severe or severe AR develop chronic volume overload that can lead to left ventricular remodeling/dysfunction and increase the risk for hemolysis. Currently, no sufficient long-term follow-up data after TAVI are available to determine the clinical significance of paravalvular regurgitation or for determining whether the severity of paravalvular regurgitation progresses with time. However, it is clear that postprocedural regurgitation is associated with adverse outcomes [61]. Cost-effectiveness of TAVI TAVI is considered likely to be a more cost-effective treatment for high-risk patients with AS compared with standard AVR [62, 63]. Using data from the United Kingdom, Fairbairn et al. reported that, despite greater procedural costs (£16,500 vs. £9,256), TAVI was more cost-effective compared with standard AVR over a 10-year model horizon (£52,593 vs. £53,943 and 2.81 vs. 2.75 quality-adjusted life years) [62]. However, further investigation is required to validate the substantive cost-effectiveness, because the long-term outcomes for TAVI patients are unknown. TAVI in Japan In the current era, the pivotal clinical trial of TAVI in Japan (PREVAIL JAPAN) was conducted in 2009. This clinical

trial aimed to evaluate the safety and efficacy of the Edwards SAPIEN XT valve (THV-9300) in high-risk patients with aortic stenosis in Japan. A total of 64 patients with aortic stenosis who were not considered to be suitable candidates for surgery were enrolled at three centers in Japan. The procedure was performed via a trans-femoral approach in 37 patients, while a trans-apical approach was adopted in 27 patients. The device success rate was 91.9 %, and at 30 days and 6 months, the rates of death from any cause (Kaplan–Meier analysis) were 7.8 and 10.9 %, respectively. Stroke or transient ischemic attack was observed in 10.9 % of patients (major stroke in 3.1 %). Among the survivors at 6 months, the NYHA functional classification based on the physicians’ assessment was improved in 94.1 % of the patients treated via the transfemoral approach and in 79.2 % of those treated with the trans-apical approach (Table 3). Consequently, the PREVAIL JAPAN trial has demonstrated comparable results, such as acceptable 30-day survival, to other major TAVI trials. Notably, Japanese are relatively smaller than those of other races, demonstrating a mean body surface area of 1.41 ± 0.14 m2 in this trial, while in the PARTNER trial, the mean body surface area in TAVI arms was 1.83 m2 in cohort A and 1.79 m2 in cohort B. Consequently, in the PREVAIL JAPAN study, the 23-mm valve was employed at a higher rate than in other studies. The 23-mm valve was implanted in 46 patients (71.9 %), while the 26-mm valve was used in 18 patients (28.1 %). This trial suggests that balloon-expandable TAVI is an effective treatment option even for small Japanese aortic stenosis patients who are at high risk or inoperable. The MDT-2111 JAPAN study, which is the first pivotal clinical trial to evaluate the safety and efficacy of the third generation of Medtronic CoreValve in high-risk patients with aortic stenosis in Japan, has been underway since

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2011. Because this delivery system is relatively fine (18 Fr), more Japanese patients with severe aortic stenosis can undergo TAVI via various approaches with a lower rate of complications, not only the trans-femoral approach, but also trans-subclavian or direct aortic approaches are possible. Furthermore, the PREVAIL 20 JAPAN, a pivotal clinical trial of the Edwards SAPIEN XT 20 mm, is now underway, and a trial of the smaller Medtronic CoreValve valve (23 mm) will be conducted in the near future. Because these smaller valves are more suitable for Japanese patients with aortic stenosis, these trials may be important for demonstrating the safety and efficacy of TAVI in patients with small annuli worldwide.

Conclusion The use of TAVI is rapidly spreading worldwide, and many satisfactory mid-term results have been reported. It is important to know the indications, appropriate patient profile, early and mid-term results, and possible complications of TAVI before beginning to use the procedure. Because early popularization of TAVI is expected in Japan, it is indispensable for cardiothoracic surgeons, as well as cardiologists and anesthesiologists, to become more familiar with this technique and to learn to avoid or minimize its risks using relevant modalities.

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