Transcatheter aortic valve replacement in patients with critical aortic stenosis: rationale, device descriptions, early clinical experiences, and perspectives

New Model for the Assessment of Transcatheter Aortic Valve Replacement Devices in Sheep

BACKGROUND

Transcatheter aortic valve replacement (TAVR) is an effective therapy in treating high-risk patients suffering from aortic stenosis. Animal models used to evaluate safety and efficacy of TAVR devices prior to clinical use lack a stenotic aortic annulus, a critical impediment to long-term TAVR device evaluation. We sought to create a reproducible model of aortic stenosis using a modified aortic annuloplasty (MAA) procedure in sheep, followed by deployment and long-term evaluation of TAVR devices using this model.

METHODS

Twelve sheep underwent the MAA procedure and were recovered. Transthoracic echocardiography (TTE) was used to monitor changes in the aortic annulus in the postoperative period. At 60 days post-MAA, Test group animals were anesthetized for TAVR insertion and Control animals underwent a necropsy. Test animals were recovered following TAVR insertion and observed for a postoperative period of 140 days.

RESULTS

Twelve sheep survived the annuloplasty procedure and the 60-day recovery period. Gross examination of seven Control group animals revealed the implanted annuloplasty ring segments formed hard protrusions into the aortic annulus. Five sheep in the Test group underwent successful deployment of Abbott's experimental TAVR device without evidence of migration. Examination at 140 days post-TAVR insertion showed all devices tightly anchored within the modified aortic annulus.

CONCLUSIONS

The MAA procedure creates stenotic segments in the aortic annulus with adequate rigidity for anchorage and long-term evaluation of TAVR devices. This represents the first model that successfully mimics human aortic stenosis and provides a clinically relevant TAVR deployment platform for long-term evaluation in sheep.

Calcification Characteristics of Low-Flow Low-Gradient Severe Aortic Stenosis in Patients Undergoing Transcatheter Aortic Valve Replacement

Low-flow low-gradient severe aortic stenosis (LFLGAS) is associated with worse outcomes. Aortic valve calcification patterns of LFLGAS as compared to non-LFLGAS have not yet been thoroughly assessed. 137 patients undergoing transcatheter aortic valve replacement (TAVR) with preprocedural multidetector computed tomography (MDCT) and postprocedural transthoracic echocardiography were enrolled. Calcification characteristics were assessed by MDCT both for the total aortic valve and separately for each leaflet. 34 patients had LFLGAS and 103 non-LFLGAS. Total aortic valve calcification volume (p < 0.001), mass (p < 0.001), and density (p = 0.004) were lower in LFLGAS as compared to non-LFLGAS patients. At 30-day follow-up, mean transaortic pressure gradients and more than mild paravalvular regurgitation did not differ between groups. In conclusion, LFLGAS and non-LFLGAS express different calcification patterns which, however, did not impact on device success after TAVR.

Incidence and sequelae of prosthesis-patient mismatch in transcatheter versus surgical valve replacement in high-risk patients with severe aortic stenosis: a PARTNER trial cohort--a analysis

BACKGROUND

Little is known about the incidence of prosthesis-patient mismatch (PPM) and its impact on outcomes after transcatheter aortic valve replacement (TAVR).

OBJECTIVES

The objectives of this study were: 1) to compare the incidence of PPM in the TAVR and surgical aortic valve replacement (SAVR) randomized control trial (RCT) arms of the PARTNER (Placement of AoRTic TraNscathetER Valves) I Trial cohort A; and 2) to assess the impact of PPM on regression of left ventricular (LV) hypertrophy and mortality in these 2 arms and in the TAVR nonrandomized continued access (NRCA) registry cohort.

METHODS

The PARTNER Trial cohort A randomized patients 1:1 to TAVR or bioprosthetic SAVR. Postoperative PPM was defined as absent if the indexed effective orifice area (EOA) was >0.85 cm(2)/m(2), moderate if the indexed EOA was ≥0.65 but ≤0.85 cm(2)/m(2), or severe if the indexed EOA was <0.65 cm(2)/m(2). LV mass regression and mortality were analyzed using the SAVR-RCT (n = 270), TAVR-RCT (n = 304), and TAVR-NRCA (n = 1,637) cohorts.

RESULTS

The incidence of PPM was 60.0% (severe: 28.1%) in the SAVR-RCT cohort versus 46.4% (severe: 19.7%) in the TAVR-RCT cohort (p < 0.001) and 43.8% (severe: 13.6%) in the TAVR-NRCA cohort. In patients with an aortic annulus diameter <20 mm, severe PPM developed in 33.7% undergoing SAVR compared with 19.0% undergoing TAVR (p = 0.002). PPM was an independent predictor of less LV mass regression at 1 year in the SAVR-RCT (p = 0.017) and TAVR-NRCA (p = 0.012) cohorts but not in the TAVR-RCT cohort (p = 0.35). Severe PPM was an independent predictor of 2-year mortality in the SAVR-RCT cohort (hazard ratio [HR]: 1.78; p = 0.041) but not in the TAVR-RCT cohort (HR: 0.58; p = 0.11). In the TAVR-NRCA cohort, severe PPM was not a predictor of 1-year mortality in all patients (HR: 1.05; p = 0.60) but did independently predict mortality in the subset of patients with no post-procedural aortic regurgitation (HR: 1.88; p = 0.02).

CONCLUSIONS

In patients with severe aortic stenosis and high surgical risk, PPM is more frequent and more often severe after SAVR than TAVR. Patients with PPM after SAVR have worse survival and less LV mass regression than those without PPM. Severe PPM also has a significant impact on survival after TAVR in the subset of patients with no post-procedural aortic regurgitation. TAVR may be preferable to SAVR in patients with a small aortic annulus who are susceptible to PPM to avoid its adverse impact on LV mass regression and survival. (The PARTNER Trial: Placement of AoRTic TraNscathetER Valve Trial; NCT00530894).

The percutaneous coronary intervention prior to transcatheter aortic valve implantation (ACTIVATION) trial: study protocol for a randomized controlled trial

Background

Current guidelines recommend treatment of significant coronary artery disease by concomitant coronary artery bypass grafting (CABG) in patients undergoing surgical aortic valve replacement. However there is no consensus as to how best to treat coronary disease in high-risk patients requiring transcatheter aortic valve implantation (TAVI).

Methods/Design

The percutaneous coronary intervention prior to transcatheter aortic valve implantation (ACTIVATION) trial is a randomized, controlled open-label trial of 310 patients randomized to treatment of significant coronary artery disease by percutaneous coronary intervention (PCI - test arm) or no PCI (control arm). Significant coronary disease is defined as ≥1 lesion of ≥70% severity in a major epicardial vessel or 50% in a vein graft or protected left main stem lesion. The trial tests the hypothesis that the strategy of performing pre-TAVI PCI is non-inferior to not treating such coronary stenoses with PCI prior to TAVI, with a composite primary outcome of 12-month mortality and rehospitalization. Secondary outcomes include efficacy end-points such as 30-day mortality, safety endpoints including bleeding, burden of symptoms, and quality of life (assessed using the Seattle Angina Questionnaire and the Kansas City Cardiomyopathy Questionnaire).

In conclusion, we hope that using a definition of coronary artery disease severity closer to that used in everyday practice by interventional cardiologists - rather than the 50% severity used in surgical guidelines - will provide robust evidence to direct guidelines regarding TAVI therapy and improve its safety and efficacy profile of this developing technique.

Trial registration

ISRCTN75836930, http://www.controlled-trials.com/ISRCTN75836930 (registered 19 November 2011).

Impact of three-dimensional imaging and pressure recovery on echocardiographic evaluation of severe aortic stenosis: a pilot study

AIMS

In patients with aortic stenosis (AS), echocardiographic grading of stenosis severity is important, in particular for transcatheter aortic valve implantation (TAVI). Three-dimensional (3D) echocardiography and correction for pressure recovery (PR) by energy loss index (ELI) may improve aortic valve area (AVA) calculation.

METHODS AND RESULTS

Thirty-nine patients with severe AS evaluated for TAVI were included. Left ventricular outflow tract (LVOT) and ascending aorta (AA) cross-sectional area were determined in transthoracic two-dimensional echocardiography (2DTTE), 2D transesophageal echocardiography (TEE), 3DTEE, and multislice computed tomography (MSCT). AVA was calculated by the continuity equation and corrected for PR. ELI was determined as [(AVA × AA)/(AA - AVA)]/body surface area. LVOT area was 2.41 ± 0.17 cm(2) calculated using 2DTTE, 2.82 ± 0.16 cm(2) calculated using 2DTEE, 3.96 ± 0.14 cm(2) planimetered in 3DTEE, and 4.47 ± 0.18 cm(2) planimetered in MSCT (P < 0.001). AA area was 4.62 ± 0.23 cm(2) calculated using 2DTTE, 4.64 ± 0.23 cm(2) calculated using 2DTEE, 5.35 ± 0.25 cm(2) planimetered in 3DTEE, and 6.56 ± 0.31 cm(2) planimetered in MSCT (P < 0.001). Indexed aortic valve area (AVAI) calculated by 2DTTE and 2DTEE was smaller (0.27 ± 0.02 cm(2) /m(2) and 0.32 ± 0.02 cm(2) /m(2) ) compared to 3DTEE (0.45 ± 0.02 cm(2) /m(2) ; P < 0.001). When AVAI determined by 3DTEE was corrected for PR by calculation of ELI, there was a further increase (0.52 ± 0.03 cm(2) /m(2) ; P < 0.001), and 10/36 (27.8%) patients were reclassified to moderate AS.

CONCLUSION

Three-dimensional TEE is more accurate than 2DTTE and 2DTEE for determining LVOT and AA dimensions. When AS severity is determined by 3DTEE and corrected for PR using the 3D values, it needs to be reclassified from severe to moderate in almost a third of patients.

With the back against the wall: TAVI in a patient with endocarditis

Transcatheter Aortic Valve Implantation (TAVI) is currently a well-established therapeutic option in patients with severe aortic stenosis considered at prohibitive risk for open heart aortic valve replacement (Cribier et al., Circulation 2002;106:3006-3008; Leon et al., Semin Thorac Cardiovasc Surg 2006;18:165-174). We report a case of a patient with endocarditis by severe homograft aortic stenosis for which a TAVI procedure was performed with an excellent result. The patient was undergoing a presurgery standard screening in preparation for a planned aortic valve replacement operation when he developed a Staphyloccocus aureus sepsis. Transoesophageal echocardiography demonstrated an aortic valve vegetation. A few days later, the patient developed a stroke probably due to embolization of a vegetation. Given the clinical severity of the case a standard open heart aortic valve replacement was considered too risky and the patient underwent a TAVI procedure. Postintervention the patient had a spectacular evolution with fast normalization of the septic shock parameters and clinical status. Antibiotics were continued for a total of nine weeks. By the ambulatory controls at three weeks, two months and six months postdischarge, the patient was completely asymptomatic and his echocardiography showed a normally functioning aortic valve without indications of endocarditis.

CoreValve® transcatheter self-expandable aortic bioprosthesis

Transcatheter aortic valve implantation has been designed to treat patients affected by severe symptomatic aortic stenosis considered extremely high risk for surgical aortic valve replacement. The CoreValve® (Medtronic Inc., MN, USA) is a multilevel self-expanding and fully radiopaque nitinol frame with a diamond cell configuration that holds a trileaflet porcine pericardial tissue valve and anchors the device in the native anatomy. CoreValve was the first percutaneous valve to be granted the CE mark for transfemoral implantation in May 2007 and the CoreValve US Pivotal Trial is actively underway. The CoreValve is available in four sizes (23, 26, 29 and 31 mm) to serve a broad range of patients' annulus from 18 to 29 mm. All the valves fit into an 18-Fr size catheter. Currently, more than 35,000 patients have been treated in more than 60 countries worldwide from the femoral artery, the axillary artery and, more recently, from a direct aortic approach, with excellent results up to 4-year follow-up.

Future perspectives in transcatheter aortic valve implantation

Transcatheter aortic valve replacement (TAVR) constitutes a relatively new treatment option for the patients with severe symptomatic aortic stenosis. Evidence from registries and randomized control trials has underscored the value of this treatment in inoperable and high risk populations, while new developments in valve technology and TAVR enabling devices have reduced the risk of complications, simplified the procedure, and broadened the applications of this therapy. The initial promising clinical results and the potential of an effective less invasive treatment of aortic stenosis has not only created high expectations but also the need to address the pitfalls of TAVR technology. The evolving knowledge concerning the groups of patients who would benefit from this treatment, the limited long term follow-up data, the concerns about devices' long term durability, and the severity of complications remain important caveats which restrict the widespread clinical adoption of TAVR. The aim of this review article is to present the recent advances, highlight the limitations of TAVR technology, and discuss the future perspectives in this rapidly evolving field.

Management of the Patient for Transcatheter Aortic Valve Implantation in the Perioperative Period

Aortic stenosis is a prevalent valvular disease among aging patients, and surgical correction is the most definitive treatment. Yet many elderly patients are deemed to be “inoperable” or at excessive risk to undergo open surgical aortic valve replacement (AVR). Transcatheter aortic valve implantation (TAVI), either through a transfemoral or transapical approach, has become a potential option for these high-risk patients. Although TAVI technology will continue to be developed and perfected, most studies at this time reveal that symptoms are improved and that 1-year morbidity and mortality are similar to those for open surgical AVR. Anesthetic management for patients undergoing TAVI involves maintaining hemodynamic stability during periods of rapidly changing conditions and providing echocardiographic guidance and assessment. Postoperative care includes a variety of challenges such as managing pain control, monitoring for potential complications, and providing hemodynamic management.

Design of a Surgical Port for Minimally Invasive Beating-Heart Intracardial Procedures

Direct-access, minimally invasive, beating-heart intracardial procedures have the potential to replace many traditional surgical procedures requiring cardio-pulmonary bypass as long as micro-emboli are prevented from entering the cardiovascular system. A new surgical port was developed to introduce surgical instruments into chambers of the beating heart during minimally invasive, intracardial surgical procedures without allowing the introduction of micro-emboli 0.1 mm or larger in size. The design consists of an outer port body that is secured to the heart wall using a purse string suture and a series of inner tubular sleeves that form the interface between the port and the transecting instrument. The design enables rapid tool changes and accommodates a wide variety of instruments. The port uses a fluid purging system to dislodge and remove emboli from a surgical instrument. Laboratory and clinical tests show that the port adequately seals around a surgical instrument and prevents the introduction of emboli with diameters greater than 0.1 mm into the heart while minimizing hemorrhage.

Anesthetic considerations of percutaneous transcatheter aortic valve implantation: first attempt in Korea -A report of 2 cases-

Conventional aortic valve replacement for severe aortic stenosis is associated with a high operative mortality in the elderly patients with significant comorbidities, including severe respiratory dysfunction, renal insufficiency, and compromised cardiac function. Human transcatheter aortic valve implantation was first reported in 2002 and has become a valid alternative in selected high-risk patients in Europe and North America. This article describes the first attempt of transfemoral transcatheter aortic valve implantation in Korea. The procedure was applied in two consecutive patients with severe aortic stenosis. Despite several intra-operative complications during procedure, the post-operative outcomes were good for both patients. At post-operative 30 days there was satisfactory prosthetic valve function and hemodynamic stability.

Transcatheter aortic valve implantation after heart transplantation

Conventional cardiac surgical procedures after orthotopic heart transplantation are generally uncommon. We report the case of a 67-year-old man who had severe symptomatic aortic stenosis develop 9 years after heart transplantation. After joint evaluation of the cardiovascular team, transcatheter aortic valve implantation was preferred due to patient medical conditions. The CoreValve prosthesis (Medtronic, Minneapolis, MN) was inserted percutaneously into the femoral artery. At 4 months postoperatively, the patient is asymptomatic in New York Heart Association functional class II. This case report provides evidence that transcatheter aortic valve implantation is safe and suitable for selected patients with severe aortic stenosis and a history of heart transplantation that must improve allograft function.

The trans-subclavian retrograde approach for transcatheter aortic valve replacement: single-center experience

OBJECTIVE

Aortic valve disease is the most common acquired valvular heart disease in adults. With the increasing elderly population, the proportion of patients with symptomatic aortic stenosis who are unsuitable for conventional surgery is increasing. Transcatheter aortic valve implantation has rapidly gained credibility as a valuable alternative to surgery to treat these patients; however, they often have severe iliac-femoral arteriopathy, which renders the transfemoral approach unusable. We report our experience with the trans-subclavian approach for transcatheter aortic valve implantation using the CoreValve (Medtronic CV Luxembourg S.a.r.l.) in 6 patients.

METHODS

In May 2008 to September 2009, 6 patients (mean age of 82 ± 5 years), with symptomatic aortic stenosis and no reasonable surgical option because of excessive risk, were excluded from percutaneous femoral CoreValve implantation because of iliac-femoral arteriopathy. These patients underwent transcatheter aortic valve implantation via the axillary artery. Procedures were performed by a combined team of cardiologists, cardiac surgeons, and anesthetists in the catheterization laboratory. The CoreValve 18F delivery system was introduced via the left subclavian artery in 6 patients, 1 with a patent left internal thoracic to left anterior descending artery graft.

RESULTS

Procedural success was obtained in all patients, and the mean aortic gradient decreased 5 mm Hg or less immediately after valve deployment. One patient required implantation of a permanent pacemaker. One patient required a subclavian covered stent implantation to treat a postimplant artery dissection associated with difficult surgical hemostasis. One patient was discharged in good condition but died of pneumonia 40 days after the procedure. All patients were asymptomatic on discharge, with good mid-term prosthesis performance.

CONCLUSIONS

Transcatheter aortic valve implantation via a surgical subclavian approach seems safe and feasible, offering a new option to treat select, inoperable, and high-risk patients with severe aortic stenosis and peripheral vasculopathy.

Beta glycosphingolipids suppress rank expression and inhibit natural killer T cell and CD8+ accumulation in alleviating aortic valve calcification

CD8 lymphocytes play a role in aortic valve inflammation leading to aortic valve calcification (AVC). RANK is a transmembrane protein that is important in osteoclast differentiation and calcification. Beta-glucosylceramide (beta-GC) together with beta-lactosylceramide (beta-LC), the 1:1 combination of beta- glucosylceramide and beta-lactosylceramide, designated IGL, exerts an immune modulatory effect in various inflammatory disorders in a CD8- and NKT (natural killer T cell)-dependent manner. We hypothesized that IGL may affect the inflammatory condition associated with AVC. AVC was induced in rats by oral administration of a high-adenine, high-phosphorus diet and was assessed by multislice computer tomography. Administration of this diet was associated with a marked increase in CD8 and NKT lymphocyte accumulation in the aortic valve. Administration of IGL led to marked suppression of RANK expression, associated with inhibition of both NKT and CD8 lymphocyte accumulation in the aortic valve. These effects were associated with a significant improvement in the degree of AVC in IGL-treated animals (25 and 53 by Agatston Score, in IGL-treated and controls, respectively). CD8 and NKT lymphocytes play a role in the pathogenesis of AVC, and RANK-mediated NKT inhibition by beta-glycosphingolipids can alleviate AVC.

Transcatheter cardiac valve interventions

Currently aortic valve replacement is performed for patients with severe aortic stenosis and symptoms or objective pathophysiologic consequences such as left ventricular dysfunction. For transcatheter mitral valve interventions, the complex pathophysiology of mitral regurgitation with varying causes along with challenging imaging and delivery issues has led to slower than anticipated clinical introduction. Transcatheter pulmonary valve intervention was primarily designed to treat the difficult problem of right ventricular to pulmonary artery conduit stenosis in the congenital population. These techniques are reviewed in this article.

Transcatheter and transapical aortic valve replacement

Minimally invasive valve replacement is limited to bioprosthetic aortic and pulmonary valves for use in very specific populations of patients. Replacement via trans-catheter and transapical techniques should be used only in patients in whom traditional surgical replacement is deemed an unacceptable risk. Nursing management will focus heavily on care for comorbid conditions because of the high-risk nature of the patients in whom these valves will initially be implanted.

Calcific aortic valve disease: imaging studies and therapeutic interventions

Echocardiography is the predominant imaging method used for patients with aortic valve disease because of its excellent diagnostic accuracy, high reproducibility and noninvasive nature. Cardiac catheterization is typically reserved for patients in whom the diagnosis remains unclear, those requiring coronary angiography prior to valve replacement, and in the setting of complex valve disease. Cardiac computed tomography (CT) has recently been applied as a research tool to quantify the amount of aortic valve calcium (AVC), which has served as a clinical end point in several medical therapy trials. Medical therapy for aortic valve disease remains an active area of clinical research. Multiple retrospective studies have shown a benefit for 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (HMG-CoA reductase inhibitors or statins) in reducing disease progression. However, two recently completed prospective, randomized trials yielded conflicting results. The data for using angiotensin converting enzyme (ACE) inhibitors are in the preliminary stages. This review will focus on imaging methods that are available for patients with aortic valve disease and summarize the recent trials that have evaluated medical therapy aimed to reduce progression of aortic valve disease.