Transcatheter aortic valve implantation: Our vision of the future

A Specific Assessment of the Normal Anatomy of the Aortic Root in Relation to Age and Gender

Background

A limitation associated with coronary computed tomography angiography (CCTA) is the lack of a normal reference value for aortic root dimensions and the uncertainty of the influence of age and gender on these dimensions. The purpose of the present study was to identify the normal values and variations of aortic root dimensions in healthy individuals and investigate how gender and age affect aortic root size.

Methods

A total of 1286 healthy yellow population (52.7 ± 11.0 years, 634 male) who underwent CCTA were retrospectively included in the present study. Male and female patients were divided into seven groups according to age (< 30 years old, 30–39, 40–49, 50–59, 60–69, 70–79, ≥ 80 years old). In these age groups, we measured and compared the parameters of the aortic root.

Results

After body surface area (BSA) correction, the aortic root parameters of females were found to be greater than those of males in the 40–49 age group (P<0.05). There were no significant differences in aortic root parameters between genders in other age groups, except for the diameter of the ascending aorta, which was greater in females (P<0.05). In males, age was positively correlated with aortic root parameters (P<0.05), except for the annulus short diameter and LVOT short diameter. In females, age was positively correlated with aortic root parameters (P<0.05), except for the left coronary ostia height and the LVOT short diameter.

Conclusion

Aortic root dimensions are affected by age and gender. After BSA correction, females show larger aortic root dimensions than males, and aortic root diameters increase with age.

Advantages of a prospective multidisciplinary approach in transcatheter aortic valve implantation: Eight years of experience

INTRODUCTION

Aortic stenosis is the most prevalent type of valvular disease in Europe. Surgical aortic valve replacement (SAVR) is the standard therapy, while transcatheter aortic valve implantation (TAVI) is an alternative in patients at unacceptably high surgical risk. Assessment by a heart team is recommended by the guidelines but there is little published evidence on this subject. The purpose of this paper is to describe the experience of a multidisciplinary TAVI program that began in 2008.

METHODS

The heart team prospectively assessed 473 patients using a standardized approach. A total of 214 patients were selected for TAVI and 80 for SAVR. Demographic, clinical and procedural characteristics and long-term success rates were compared between the groups.

RESULTS

TAVI patients were older than the SAVR group (median 83 vs. 81 years), and had higher surgical risk scores (median EuroSCORE II 5.3 vs. 3.6% and Society of Thoracic Surgeons score 5.1 vs. 3.1%), as did the patients under medical treatment only. These scores were unable to assess multiple comorbidities. Patients' outcomes were different between the three groups (mortality with SAVR 25% vs. TAVI 37.6% vs. conservative therapy 57.6%, p=0.001).

CONCLUSIONS

The heart team program was able to select candidates appropriately for TAVI, SAVR and conservative treatment, taking into account the risk of both invasive treatments. The use of a prospective standardized heart team approach is recommended, but requires continuous monitoring to ensure effectiveness in a timely manner.

Multidetector computed tomography evaluation of candidates for transcatheter aortic valve implantation

In transcatheter aortic valve implantation (TAVI), a biologic valve mounted in a stent is implanted without removing the native valve. This procedure was first done in humans by Alain Cribier in 2002 and was included in clinical guidelines after the multicenter PARTNER (Placement of AoRtic TraNscathetER) randomized clinical trial, which showed that TAVI obtained better outcomes than conservative medical treatment and is an alternative to surgery in patients with high surgical risk. Candidates for TAVI must be assessed to determine whether the procedure is feasible, because TAVI is not ideal for all patients who are considered inoperable. Multidetector computed tomography plays an important role in the anatomic evaluation of candidates and in guiding the procedure in those who are finally selected.

Advances in the management of severe aortic stenosis

BACKGROUND

Recent developments in the management of severe aortic stenosis have resulted in a paradigm shift in the way we view the condition. Patients previously denied intervention in the form of surgical aortic valve replacement (SAVR) are now candidates for transcatheter aortic valve implantation and the risk and age profiles of those undergoing SAVR are rising with the ageing population. This review article is designed to provide an overview of developments in the surgical management of severe aortic stenosis. We also discuss the expanding role of minimally invasive surgical approaches to outline the current techniques available to treat patients with severe aortic stenosis.

METHODS

PubMed was searched using the terms 'severe aortic stenosis', 'surgical aortic valve replacement', 'transcatheter aortic valve replacement', 'mechanical aortic valve replacement' and 'sutureless aortic valve replacement'. Selection of articles was based on peer review, journal and relevance. Where possible articles from high-impact factor peer review journals were included.

RESULTS

Minimally invasive operative approaches include mini-sternotomy and mini-thoracotomy. Sutureless aortic prostheses reduce aortic cross-clamp time and cardiopulmonary bypass time; however, long-term follow-up data are unavailable at this time. Mechanical prostheses are advised for those under 60.

CONCLUSION

Multiple advances in the surgical management of aortic stenosis have occured in the past decade. An evolving spectrum of surgical and transcatheter interventions is now available depending on patient age and operative risk.

Percutaneous heart valves; past, present and future

Percutaneous heart valves provide a promising future for patients refused surgery on the grounds of significant technical challenges or high risk for complications. Since the first human intervention more than 10 years ago, over 50 different types of valves have been developed. The CoreValve and Edwards SAPIEN valves have both experienced clinical trials and the latter has gained FDA approval for implantation in patients considered inoperable. Current complications, such as major vascular bleeding and stroke, prevent these valves from being commonly deployed in patients considered operable in conventional surgery. This review focuses on the past and present achievements of these valves and highlights the design considerations required to progress development further. It is envisaged that, with continued improvement in valve design and with increased clinical and engineering experience, percutaneous heart valve replacement may one day be a viable option for lower-risk operable patients.

Imaging in Transcatheter Aortic Valve Replacement (TAVR): role of the radiologist

BACKGROUND

Transcatheter aortic valve replacement (TAVR) is a novel technique developed in the last decade to treat severe aortic stenosis in patients who are non-surgical candidates because of multiple comorbidities.

METHODS

Since the technique is performed using a transvascular approach, pre-procedural assessment of the aortic valve apparatus, ascending aorta and vascular access is of paramount importance for both appropriate patient selection and correct device selection. This assessment is performed by a multi-disciplinary team with radiology being an integral and important part.

RESULTS

Among imaging modalities, there is growing scientific evidence supporting the crucial role of MDCT in the assessment of the aortic valve apparatus, suitability of the iliofemoral or alternative pathway, and determination of appropriate coaxial angles. MDCT also plays an important role in post-procedure imaging in the assessment of valve integrity and position.

CONCLUSION

This review outlines the principal aspects of TAVR, the multidisciplinary approach and utilisation of different imaging modalities, as well as a step-by-step approach to MDCT acquisition protocols, reconstruction techniques, pre-procedure measurements and post-procedure assessment.

TEACHING POINTS

• TAVR is a new technique to treat severe aortic stenosis in high-risk and nonsurgical candidates. • MDCT assessment of the aortic annulus is important for appropriate patient and device selection. • Multidisciplinary approach is required for patient selection, procedure planning and performance. • MDCT is required for assessment of the aortic root, iliofemoral or alternative vascular pathway.

Imaging for approach selection of TAVI: assessment of the aorto-iliac tract diameter by computed tomography-angiography versus projection angiography

The choice of preferred access route for transcatheter aortic valve implantation (TAVI) is mainly guided by the minimal aorto-femoral tract diameter. Currently, projection angiography (XA) and CT-angiography (CTA) are used interchangeably to assess this diameter in the TAVI work-up. We aimed to assess the agreement of XA and CTA diameter measurements in TAVI candidates. Diameters of 700 aorta-iliac segments of 102 TAVI candidates were analyzed on both XA and CTA. The diameters on XA were measured manually, for the CTA-based analysis semi-automated segmentation software was used. Paired sample T test was used to evaluate differences in diameter measurements between the modalities. Disagreement on the suitability for a transfemoral (TF)-TAVI approach was identified. The interobserver agreement for both measurements was assessed by calculating the intraclass correlation coefficient (ICC). The average diameters were 10.1 ± 1.8 mm and 8.4 ± 1.7 for XA and CTA respectively. The mean paired difference was 1.73 mm (p < 0.001). For 18 patients (17.6 %) diameters measured on CTA images, were bilaterally less than 6 mm, whilst XA indicated a minimum diameter exceeding 6 mm. For both modalities, the interobserver agreement was excellent (ICC 0.95). Diameters measured semi-automatically on CTA were statistically significantly smaller compared to XA. This should be acknowledged in the work-up for selecting the most appropriate approach for TAVI. In our population 17.6 % of patients would have been denied a transfemoral TAVI based on CTA measurements, whilst XA suggested diameters sufficient for a TF approach.

Transapical aortic valve replacement for severe aortic stenosis: results from the nonrandomized continued access cohort of the PARTNER trial

BACKGROUND

Transapical (TA) aortic valve replacement was an integral part of the Placement of Transcatheter Aortic Valves (PARTNER) trial. Enrollment during the randomized trial included 104 transapical (premarket approval TA [PMA-TA]) and 92 surgical aortic valve replacements (SAVR) within the TA cohort. On completion of the trial, enrollment continued in a nonrandomized continued access (NRCA) program. We compared the outcomes of NRCA-TA procedures with those of PMA-TA and SAVR.

METHODS

In 22 centers, 975 patients underwent TA aortic valve replacement as part of the NRCA registry. Inclusion and exclusion criteria were unchanged from the previously reported PARTNER trial. All patients were followed up for at least 1 year.

RESULTS

Thirty-day or in-hospital mortality was 8.8% for the NRCA-TA cohort, compared with 10.6% and 12.0% for the PMA-TA and SAVR patients, respectively (p = 0.54). One-year mortality in the NRCA-TA cohort was 22.1%, not significantly lower than the mortality in PMA-TA and SAVR patients at 29.0% and 25.3%, respectively (p = 0.27). Thirty-day or in-hospital stroke was 2.2% among NRCA-TA patients in contrast to the 6.7% stroke rate observed in the PMA-TA group and 5.4% in SAVR patients (p = 0.008). Lower rates of neurologic adverse events in the NRCA-TA group persisted at 1 year compared with the PMA-TA and SAVR patients.

CONCLUSIONS

Among the 975 patients in the NRCA-TA cohort, rates of major outcomes including death and stroke compared favorably with outcomes of PMA-TA and SAVR patients enrolled in the PARTNER trial. This trend toward improved outcomes may be attributed to improved patient selection, individual centers surmounting the procedural learning curve, and refinements in surgical technique.

Transcatheter aortic valve replacement: current application and future directions

During the last decade, the rapid evolution of transcatheter aortic valve replacement (TAVR) has revolutionized the treatment of severe aortic stenosis. Since the PARTNER A and B trials, this technique has become the treatment of reference for inoperable patients, and an attractive alternative to surgical aortic valve replacement in those at high risk for surgery. Large multicenter registries conducted since 2007, mainly in Europe, confirmed the excellent hemodynamic performances of the 2 percutaneous valves currently available on the market, the Edwards SAPIEN, and the Medtronic CoreValve, as well as their benefits in terms of symptom relief and survival. The whole process of TAVR, from patient selection to post-procedural care and result evaluation, should be conducted by a dedicated multidisciplinary "heart team," within centers with expertise in valve disease. Though currently limited to those deemed at high risk for surgery or inoperable, indications for TAVR will likely be extended to a broader spectrum of patients, in particular those with surgical bioprosthetic failure or at intermediate risk for surgery. Beforehand, it will be essential to obtain more extensive data on the durability of percutaneous prostheses, since the available follow-up is seldom longer than 5 years, and in order to further decrease the rate of complications, mainly stroke, paravalvular regurgitation, and access site complications. Furthermore, the use of the transfemoral route will undoubtedly increase because of the miniaturization of the devices, at the expense of other approaches. Above all, multidisciplinary approach, excellent imaging, and careful evaluation will remain key to the success of this technique.