Towards real-time cardiovascular magnetic resonance guided transarterial CoreValve implantation: in vivo evaluation in swine

Background

Real-time cardiovascular magnetic resonance (rtCMR) is considered attractive for guiding TAVI. Owing to an unlimited scan plane orientation and an unsurpassed soft-tissue contrast with simultaneous device visualization, rtCMR is presumed to allow safe device navigation and to offer optimal orientation for precise axial positioning. We sought to evaluate the preclinical feasibility of rtCMR-guided transarterial aortic valve implatation (TAVI) using the nitinol-based Medtronic CoreValve bioprosthesis.

Methods

rtCMR-guided transfemoral (n = 2) and transsubclavian (n = 6) TAVI was performed in 8 swine using the original CoreValve prosthesis and a modified, CMR-compatible delivery catheter without ferromagnetic components.

Results

rtCMR using TrueFISP sequences provided reliable imaging guidance during TAVI, which was successful in 6 swine. One transfemoral attempt failed due to unsuccessful aortic arch passage and one pericardial tamponade with subsequent death occurred as a result of ventricular perforation by the device tip due to an operating error, this complication being detected without delay by rtCMR. rtCMR allowed for a detailed, simultaneous visualization of the delivery system with the mounted stent-valve and the surrounding anatomy, resulting in improved visualization during navigation through the vasculature, passage of the aortic valve, and during placement and deployment of the stent-valve. Post-interventional success could be confirmed using ECG-triggered time-resolved cine-TrueFISP and flow-sensitive phase-contrast sequences. Intended valve position was confirmed by ex-vivo histology.

Conclusions

Our study shows that rtCMR-guided TAVI using the commercial CoreValve prosthesis in conjunction with a modified delivery system is feasible in swine, allowing improved procedural guidance including immediate detection of complications and direct functional assessment with reduction of radiation and omission of contrast media.     

Left ventricular reverse remodeling after transcatheter aortic valve implantation: a cardiovascular magnetic resonance study

Background

In patients with severe aortic stenosis, left ventricular hypertrophy is associated with increased myocardial stiffness and dysfunction linked to cardiac morbidity and mortality. We aimed at systematically investigating the degree of left ventricular mass regression and changes in left ventricular function six months after transcatheter aortic valve implantation (TAVI) by cardiovascular magnetic resonance (CMR).

Methods

Left ventricular mass indexed to body surface area (LVMi), end diastolic volume indexed to body surface area (LVEDVi), left ventricular ejection fraction (LVEF) and stroke volume (SV) were investigated by CMR before and six months after TAVI in patients with severe aortic stenosis and contraindications for surgical aortic valve replacement.

Results

Twenty-sevent patients had paired CMR at baseline and at 6-month follow-up (N=27), with a mean age of 80.7±5.2 years. LVMi decreased from 84.5±25.2 g/m² at baseline to 69.4±18.4 g/m² at six months follow-up (P<0.001). LVEDVi (87.2±30.1 ml /m²vs 86.4±22.3 ml/m²; P=0.84), LVEF (61.5±14.5% vs 65.1±7.2%, P=0.08) and SV (89.2±22 ml vs 94.7±26.5 ml; P=0.25) did not change significantly.

Conclusions

Based on CMR, significant left ventricular reverse remodeling occurs six months after TAVI.     

Hemodynamic predictors of aortic dilatation in bicuspid aortic valve by velocity-encoded cardiovascular magnetic resonance

Background

Congenital Bicuspid Aortic Valve (BAV) is a significant risk factor for serious complications including valve dysfunction, aortic dilatation, dissection, and sudden death. Clinical tools for identification and monitoring of BAV patients at high risk for development of aortic dilatation, an early complication, are not available.

Methods

This paper reports an investigation in 18 pediatric BAV patients and 10 normal controls of links between abnormal blood flow patterns in the ascending aorta and aortic dilatation using velocity-encoded cardiovascular magnetic resonance. Blood flow patterns were quantitatively expressed in the angle between systolic left ventricular outflow and the aortic root channel axis, and also correlated with known biochemical markers of vessel wall disease.

Results

The data confirm larger ascending aortas in BAV patients than in controls, and show more angled LV outflow in BAV (17.54 ± 0.87 degrees) than controls (10.01 ± 1.29) (p = 0.01). Significant correlation of systolic LV outflow jet angles with dilatation was found at different levels of the aorta in BAV patients STJ: r = 0.386 (N = 18, p = 0.048), AAO: r = 0.536 (N = 18, p = 0.022), and stronger correlation was found with patients and controls combined into one population: SOV: r = 0.405 (N = 28, p = 0.033), STJ: r = 0.562 (N = 28, p = 0.002), and AAO r = 0.645 (N = 28, p < 0.001). Dilatation and the flow jet angle were also found to correlate with plasma levels of matrix metallo-proteinase 2.

Conclusions

The results of this study provide new insights into the pathophysiological processes underlying aortic dilatation in BAV patients. These results show a possible path towards the development of clinical risk stratification protocols in order to reduce morbidity and mortality for this common congenital heart defect.     

Electrocardiographic diagnosis of left ventricular hypertrophy in aortic valve disease: evaluation of ECG criteria by cardiovascular magnetic resonance

Background

Left ventricular hypertrophy (LVH) is a hallmark of chronic pressure or volume overload of the left ventricle and is associated with risk of cardiovascular morbidity and mortality. The purpose was to evaluate different electrocardiographic criteria for LVH as determined by cardiovascular magnetic resonance (CMR). Additionally, the effects of concentric and eccentric LVH on depolarization and repolarization were assessed.

Methods

120 patients with aortic valve disease and 30 healthy volunteers were analysed. As ECG criteria for LVH, we assessed the Sokolow-Lyon voltage/product, Gubner-Ungerleider voltage, Cornell voltage/product, Perugia-score and Romhilt-Estes score.

Results

All ECG criteria demonstrated a significant correlation with LV mass and chamber size. The highest predictive values were achieved by the Romhilt-Estes score 4 points with a sensitivity of 86% and specificity of 81%. There was no difference in all ECG criteria between concentric and eccentric LVH. However, the intrinsicoid deflection (V6 37 ± 1.0 ms vs. 43 ± 1.6 ms, p < 0.05) was shorter in concentric LVH than in eccentric LVH and amplitudes of ST-segment (V5 -0.06 ± 0.01 vs. -0.02 ± 0.01) and T-wave (V5 -0.03 ± 0.04 vs. 0.18 ± 0.05) in the anterolateral leads (p < 0.05) were deeper.

Conclusion

By calibration with CMR, a wide range of predictive values was found for the various ECG criteria for LVH with the most favourable results for the Romhilt-Estes score. As electrocardiographic correlate for concentric LVH as compared with eccentric LVH, a shorter intrinsicoid deflection and a significant ST-segment and T-wave depression in the anterolateral leads was noted.     

二维、三维经食管超声心动图在经导管主动脉瓣植入术中的应用价值

目的探讨二维、三维经食管超声心动图在经导管主动脉瓣植入术（TAVI）中的应用价值。 方法对2010年5月至2015年10月在复旦大学附属中山医院行TAVI的11例重度主动脉瓣狭窄[主动脉瓣狭窄口面积<1.0 cm²,主动脉瓣口最大流速>4 m/s,平均跨瓣压差>40 mmHg（1 mmHg=0.133 kPa）]和1例人工生物主动脉瓣中重度反流患者术前均行常规经胸超声心动图检查及二维、三维经食管超声心动图检查（2DTEE、3DTEE）,术中二维、三维经食管超声心动图监测,术后常规经胸超声心动图随访。采用Pearson相关分析分析3DTEE与计算机断层扫描（MDCT）评价主动脉瓣环最大值、最小值、瓣环面积以及狭窄口面积的相关性及3DTEE、MDCT与连续性方程评价狭窄口面积的相关性。 结果所有患者均成功植入人工生物主动脉瓣,其中1例患者术中发现心脏压塞合并升主动脉夹层分离,经心包穿刺以及升主动脉夹层分离保守治疗3 d后突发心脏压塞死亡。所有患者MDCT与3DTEE评价主动脉瓣环最大径、最小径、瓣环面积及狭窄口面积的相关性均较好（r=0.98、0.97、0.97、0.99,P均<0.01）;术前连续性方程测量的主动脉狭窄口面积与MDCT及3DTEE评价结果的相关性均很好（r值均为0.99,P均<0.01）。 结论2DTEE、3DTEE能快速、准确地定量主动脉瓣环的大小及评价主动脉的解剖结构,能实时引导和监测经导管主动脉瓣植入及其并发症。     

Transcatheter aortic valve implantation: technique,complications and perspectives

Transcatheter aortic valve implantation (TAVI) has become the preferred treatment option for patients with symptomatic severe aortic stenosis who are inoperable or at high risk for surgical aortic valve replacement. TAVI has shown a clear mortality benefit compared to conservative treatment in inoperable patients, and is at least non-inferior to surgical aortic valve replacement in high-risk operable patients. Through improvements in the field of imaging, refinement in valve technologies, increasing operator and team experience and continuous valuable research, TAVI has developed rapidly in the past years and is expected to further boost in the near future. In this review, we discuss the technical and procedural aspects of TAVI, the acute and late outcomes, and highlight the current expectations and potential future development of this rapidly evolving technology.     

Evaluation of aortic valve stenosis using cardiovascular magnetic resonance: comparison of an original semiautomated analysis of phase-contrast cardiovascular magnetic resonance with Doppler echocardiography

Background- Accurate quantification of aortic valve stenosis (AVS) is needed for relevant management decisions. However, transthoracic Doppler echocardiography (TTE) remains inconclusive in a significant number of patients. Previous studies demonstrated the usefulness of phase-contrast cardiovascular magnetic resonance (PC-CMR) in noninvasive AVS evaluation. We hypothesized that semiautomated analysis of aortic hemodynamics from PC-CMR might provide reproducible and accurate evaluation of aortic valve area (AVA), aortic velocities, and gradients in agreement with TTE. Methods and Results- We studied 53 AVS patients (AVA(TTE)=0.87±0.44 cm(2)) and 21 controls (AVA(TTE)=2.96±0.59 cm(2)) who had TTE and PC-CMR of aortic valve and left ventricular outflow tract on the same day. PC-CMR data analysis included left ventricular outflow tract and aortic valve segmentation, and extraction of velocities, gradients, and flow rates. Three AVA measures were performed: AVA(CMR1) based on Hakki formula, AVA(CMR2) based on continuity equation, AVA(CMR3) simplified continuity equation=left ventricular outflow tract peak flow rate/aortic peak velocity. Our analysis was reproducible, as reflected by low interoperator variability (<4.56±4.40%). Comparison of PC-CMR and TTE aortic peak velocities and mean gradients resulted in good agreement (r=0.92 with mean bias=-29±62 cm/s and r=0.86 with mean bias=-12±15 mm Hg, respectively). Although good agreement was found between TTE and continuity equation-based CMR-AVA (r>0.94 and mean bias=-0.01±0.38 cm(2) for AVA(CMR2), -0.09±0.28 cm(2) for AVA(CMR3)), AVA(CMR1) values were lower than AVA(TTE) especially for higher AVA (mean bias=-0.45±0.52 cm(2)). Besides, ability of PC-CMR to detect severe AVS, defined by TTE, provided the best results for continuity equation-based methods (accuracy >94%). Conclusions- Our PC-CMR semiautomated AVS evaluation provided reproducible measurements that accurately detected severe AVS and were in good agreement with TTE.     

Cardiovascular magnetic resonance for the assessment of patients undergoing transcatheter aortic valve implantation: a pilot study

Background

Before trans-catheter aortic valve implantation (TAVI), assessment of cardiac function and accurate measurement of the aortic root are key to determine the correct size and type of the prosthesis. The aim of this study was to compare cardiovascular magnetic resonance (CMR) and trans-thoracic echocardiography (TTE) for the assessment of aortic valve measurements and left ventricular function in high-risk elderly patients submitted to TAVI.

Methods

Consecutive patients with severe aortic stenosis and contraindications for surgical aortic valve replacement were screened from April 2009 to January 2011 and imaged with TTE and CMR.

Results

Patients who underwent both TTE and CMR (n = 49) had a mean age of 80.8 ± 4.8 years and a mean logistic EuroSCORE of 14.9 ± 9.3%. There was a good correlation between TTE and CMR in terms of annulus size (R² = 0.48, p < 0.001), left ventricular outflow tract (LVOT) diameter (R² = 0.62, p < 0.001) and left ventricular ejection fraction (LVEF) (R² = 0.47, p < 0.001) and a moderate correlation in terms of aortic valve area (AVA) (R² = 0.24, p < 0.001). CMR generally tended to report larger values than TTE for all measurements. The Bland-Altman test indicated that the 95% limits of agreement between TTE and CMR ranged from -5.6 mm to + 1.0 mm for annulus size, from -0.45 mm to + 0.25 mm for LVOT, from -0.45 mm² to + 0.25 mm² for AVA and from -29.2% to 13.2% for LVEF.

Conclusions

In elderly patients candidates to TAVI, CMR represents a viable complement to transthoracic echocardiography.     

Transcatheter aortic valve implantation: role of multimodality cardiac imaging

Current evidence based on more than 8000 high-risk patients with severe aortic stenosis has demonstrated that transcatheter aortic valve implantation (TAVI) is a feasible alternative to surgical aortic valve replacement in selected patients. Despite current promising results on hemodynamic and clinical improvements, there are several unresolved safety issues, such as the frequency of vascular complications, postprocedural paravalvular leak, atrioventricular heart block and stroke. Multimodality cardiac imaging may help to minimize these complications and may play a central role before (optimizing patient selection, selection of appropriate prosthesis size and anticipating the procedural approach), during and after TAVI (evaluating the immediate and long-term procedural results). This article reviews the state-of-the-art TAVI procedures and the role that multimodality cardiac imaging plays before, during and after TAVI.     

A pilot study on magnetic navigation for transcatheter aortic valve implantation using dynamic aortic model and US image guidance

Purpose   In this paper, we propose a pilot study for transcatheter aortic valve implantation guided by an augmented magnetic tracking system (MTS) with a dynamic aortic model and intra-operative ultrasound (US) images. Methods    The dynamic 3D aortic model is constructed from the preoperative 4D computed tomography, which is animated according to the real-time electrocardiograph (ECG) input of patient. Before the procedure, the US probe calibration is performed to map the US image coordinate to the tracked device coordinate. A temporal alignment is performed to synchronize the ECG signals, the intra-operative US image and the tracking information. Thereafter, with the assistance of synchronized ECG signals, the spatial registration is performed by using a feature-based registration. Then the augmented MTS guides the surgeon to confidently position and deploy the transcatheter aortic valve prosthesis to the target. Results   The approach was validated by US probe calibration evaluation and animal study. The US calibration accuracy achieved $1.37\pm 0.43\, \text{ mm}$ , whereas in the animal study on three porcine subjects, fiducial, target, deployment distance and tilting errors reached $3.16\pm 0.55\,\text{ mm}$ , $3.80\pm 1.83\,\text{ mm}$ , $3.13\pm 1.12\,\text{ mm}$ and $5.87\pm 2.35^{\circ }$ , respectively. Conclusion   Our pilot study has revealed that the proposed approach is feasible and accurate for delivery and deployment of transcatheter aortic valve prosthesis.     

Optimization and simplification of transcatheter aortic valve implantation therapy

Introduction: Transcatheter aortic valve implantation (TAVI) is now a widely adopted therapy for the treatment of elderly patients with severe aortic stenosis. Improved pre-procedural screening, increased operators’ experience and technology advancement have made this technique highly reliable and standardized.

Areas covered: The purpose of this review article is to provide an overview of the strategies that can be adopted to optimize the TAVI procedure (pre-interventional work-up and procedural simplification and early discharge).

Expert commentary: Optimization of TAVI therapy is already a reality and has shown to be safe in most patients, but its penetration has to face with real-world practice. The adoption of a minimalistic and optimized approach requires integration of multidisciplinary competences and an extended, dynamic conception of heart team, which also includes patients’ families, referring cardiologist and general practitioners.     

MDCT imaging before transcutanous aortic valve implantation: rationale and measurements

Since its introduction in 2002, transcatheter aortic valve implantation (TAVI) has assumed growing importance in the treatment of patients with severe aortic stenosis (AS), because it offers a much less invasive alternative for those in high risk for surgery. Good early results and advances in percutaneous valve technology have led to a substantial increase in procedural success rate and number of patients undergoing this less invasive treatment. Pre-procedural screening of several anatomic factors to assess the feasibility of this technique is important. Multidetector row computed tomography (MDCT) is the technique of choice in assessing these factors.This technical note aims to describe and illustrate the key elements that need to be evaluated before the procedure.     

Recognition and management of complications during transcatheter aortic valve implantation

In the field of interventional cardiology, transcatheter aortic valve implantation is the newest and most exciting development of recent years. With a growing evidence base for both prognostic and symptomatic benefit, more and more interventionalists are keen to learn the procedure. However, the concomitant risk associated with a technically challenging procedure in a high-risk patient population is significant, and complications can arise suddenly and often unexpectedly. It is essential that new, and even established, operators are meticulously aware of the potential for complications, are able to identify them at an early stage, and manage them quickly and effectively. We have significant experience with transcatheter aortic valve implantation, through the implantation of 260 devices, which brings first-hand experience of most major complications. This article provides insight into the potential for complications, offering advice on effective treatment, recognition, and ultimately, prevention. It also suggests a number of procedural and technical modifications, which might improve outcomes in the future.     

Current and new-generation transcatheter aortic valve devices: an update on emerging technologies

Transcatheter aortic valve implantation (TAVI) has become an accepted treatment option for patients with symptomatic severe aortic stenosis who are at high risk for traditional surgical aortic valve replacement. In particular, TAVI has been shown to reduce mortality in a randomized comparison with medical treatment and to be non-inferior to surgical aortic valve replacement in ‘high-risk operable’ patients. From its early stages it became apparent that TAVI has tremendous potential and thus considerable efforts were made to design new devices and advance valve technology in order to improve outcomes and increase TAVI applications in complex anatomies and in patients with multiple co-morbidities. In this review, we present the advances in transcatheter aortic valve technology and discuss the current evidence on the new-generation TAVI devices.     

Impact of asymmetry on measurements of the aortic root using cardiovascular magnetic resonance imaging in patients with a bicuspid aortic valve

To assess the impact of aortic root asymmetry on the relationship between aortic dimensions derived from two-dimensional transthoracic echocardiography (TTE) as compared with cross-sectional cardiovascular magnetic resonance (CMR) imaging in adults with a bicuspid aortic valve (BAV). Maximal CMR cross-sectional aortic measurements at the level of the sinuses of Valsalva, including cusp–commissure, cusp–cusp diameters and aortic root areas, from 68 consecutive patients (65 % male) were retrospectively analyzed. The degree of aortic root asymmetry on CMR was expressed using the coefficient of variance of the root diameters in each dimension for an individual (CoeffVi) as compared with the median of the entire population (CoeffVp) and asymmetry was defined as CoeffVi > CoeffVp. Values obtained from CMR were compared with standard root measurements using TTE from contemporary studies (48 patients, 71 %). Reproducibility of CMR measurements was assessed using the intra-class correlation coefficient (ICC). Echocardiography systematically underestimated aortic root dimensions in comparison with CMR, particularly in asymmetric roots with cusp–cusp measurements in systole (bias: ?4.9 mm). Best agreement between modalities existed in symmetric roots with cusp–commissure measurements in diastole (bias: ?0.01 mm). CMR measurements showed excellent intra-reader (ICC ≥ 0.98) and moderate inter-reader (ICC range 0.37–0.95) reproducibility, particularly aortic root area (inter/intra-reader ICC ≥ 0.94). In comparison to cross-sectional CMR diameters, standard TTE measurements consistently underestimates maximum aortic root diameter in adults with a BAV and aortic root asymmetry further decreases the agreement between CMR and TTE. CMR-derived aortic root measurements are reproducible and aortic root area showed the best reproducibility.     

适宜单层缝合置入的无支架猪主动脉瓣膜性能评价

背景：现有的生物瓣膜主要分为有支架和无支架两种。有支架瓣膜方便了手术操作,容易植入,植入后发生关闭不全的可能性小,但这种瓣膜并没有很好的模拟天然瓣膜。目的：为缩短瓣膜植入时间,进一步改善瓣膜性能,在参考猪主动脉根构型优化瓣膜设计的基础上,开发一种新型的适合单层缝合置入的无支架猪主动脉瓣膜,体外测试评估其性能。方法：①制备适合单层缝合的无支架猪主动脉瓣。②采用自行设计的新型单层缝合方法进行离体瓣膜植入实验。③对新型瓣膜进行体外流体力学测试及疲劳测试。结果与结论：适合单层缝合的无支架瓣膜在设计中去除了硬质的瓣架,可减轻血流冲击对瓣叶的损害,同时去除硬质瓣环后手术时可以植入口径更大的瓣膜,改善了血流动力学,较传统双层缝合瓣膜缩短了植入时间。经体外流体力学测试及疲劳测试,结果满意。但无支架生物瓣膜植入手术操作时间长、术后长期临床效果及耐久性尚需进一步临床结果验证。