Computed tomography for planning and postoperative imaging of transvenous mitral annuloplasty: first experience in an animal model

Canine mitral valve size as measured by computed tomography

OBJECTIVE

To measure the mitral annulus in dogs. Our hypothesis was that mitral measurement would be possible and consistent among observers using CT.

SAMPLE

Thoracic CT scans of dogs without known heart disease.

PROCEDURES

Five trained investigators measured 4 aspects of the mitral valve and the fourth thoracic vertebrae (T4) length using multiplanar reformatting tools. Ten randomly chosen animals were measured by all investigators to determine interobserver reliability.

RESULTS

There were 233 CT scans eligible for inclusion. Dogs weighed 2 to 96 kg (mean, 28.1 kg), with a variety of breeds represented. Golden Retrievers (n = 28) and Labrador Retrievers (n = 37) were overrepresented. The intraclass correlations were all greater than 0.9, showing excellent agreement between observers. The means and SDs of each measurement were as follows: trigone-to-trigone distance, 17.2 ± 4.7 mm; the remaining circumference, 79.0 ± 17.5 mm; commissure-to-commissure distance, 30.8 ± 6.5 mm; septal leaflet-to-lateral leaflet distance, 26.3 ± 6.0 mm; T4 length, 16.9 ± 3.1 mm; and the total circumference normalized by T4, 5.7 ± 0.7 mm.

CLINICAL RELEVANCE

This study provides information that may help in the development of future treatment for mitral valve dysfunction and subsequent annular enlargement.

Association of transcatheter direct mitral annuloplasty with acute anatomic, haemodynamic, and clinical outcomes in severe mitral valve regurgitation

AIMS

Several approaches for transcatheter mitral valve repair for functional mitral valve regurgitation are established. Interventional direct annuloplasty is a novel trans-venous, trans-septal approach. While feasibility was proven recently, knowledge on its influence on cardiac dimensions, pressures, biomarkers, and clinical outcomes is sparse.

METHODS AND RESULTS

Patients consecutively treated with direct annuloplasty-only procedures between December 2015 and April 2018 were included in this monocentric analysis. Echocardiographic measurements, biomarker levels, clinical status [New York Heart Association (NYHA) class and 6 min walk test] were assessed at baseline, at discharge, and at a 30 day follow-up. Overall, 18 patients (in mean 77.0 ± 7.4 years, 44.4% women) with initially all high-grade mitral valve regurgitation (MR) were included in this study. Procedural success rate was high (94.4%) without severe complications. Direct annuloplasty resulted in MR-reduction (post-procedural-MR mild or no/trace: 72.2%) and the proportion of patients with severe dyspnoea (NYHA III/IV) was reduced (88.9% vs. 50%, P = 0.008). Clinical results were associated with a relevant diminution of left atrial volumes (-16.5%, P < 0.001) and cardiac pressures [left atrial pressure (-32.3%, P = 0.019) and systolic pulmonary arterial pressure (PAP, -15.8%, P = 0.025)]. Patients with lower baseline levels of PAP (P = 0.022) as well as elevated highly sensitive troponin (P = 0.034) were more likely to archive clinical benefit (improvement in NYHA class ≥1 grade) after 1 month, which could not be correlated with the grade of MR-reduction.

CONCLUSIONS

Transcatheter mitral valve repair by direct annuloplasty results in a relevant reduction of intracardiac pressures, left atrial volumes, dyspnoea, and MR. Lower PAP and higher troponin values at baseline could be associated to dyspnoea reduction.

Computed Tomography-based evaluation of porcine cardiac dimensions to assist in pre-study planning and optimized model selection for pre-clinical research

The pig (Sus Scrofa Domestica) is an accepted model for preclinical evaluation of prosthetic heart valves and trans-catheter implantation techniques. Understanding porcine cardiac dimensions through three-dimensional computed tomography (CT), increases preclinical study success, leading to higher cost efficiency and to the observance of the obligation to the 3 R principles. Cardiac CT images of twenty-four Swiss large white pigs were segmented; aortic root, mitral valve, pulmonary trunk, tricuspid valve, as well as the aorto-mitral angle and left atrial height were analyzed. Correlation coefficient (r) was calculated in relation to body weight. In Swiss large white pigs, valvular dimensions, length of the pulmonary artery and ascending aorta as well as left atrial height correlate with body weight. Coronary ostia heights and aorto-mitral angle size can be neglected in animal size selection; no changes were found for either of the two parameters with increasing body weight.

Cardiac Computed Tomography and Magnetic Resonance Imaging in the Evaluation of Mitral and Tricuspid Valve Disease

Transcatheter interventions to treat mitral and tricuspid valve disease are becoming increasingly available because of the growing number of elderly patients with significant comorbidities or high operative risk. Thorough clinical and imaging evaluation in these patients is essential. The latter involves both characterization of the mechanism and severity of valvular disease as well as determining the hemodynamic consequences and extent of ventricular remodeling, which is an important predictor of future outcomes. Moreover, an assessment of the suitability and risk of complications associated with device-specific therapies is also an important component of the preprocedural evaluation in this cohort. Although echocardiography including 2-dimensional and 3-dimensional methods has an important role in the initial assessment and procedural guidance, cross-sectional imaging, including both computed tomographic imagning and cardiac magnetic resonance imaging, is increasingly being integrated into the evaluation of mitral and tricuspid valve disease. In this review, we discuss the role of cross-sectional imaging in mitral and tricuspid valve disease, primarily valvular regurgitation assessment, with an emphasis on the preprocedural evaluation and implications for transcatheter interventions.

Current challenges in interventional mitral valve treatment

Transcatheter mitral valve therapies have emerged as an alternative option in high surgical risk or inoperable patients with severe and symptomatic mitral regurgitation (MR). As multiple technologies and different approaches will become available in the field of mitral valve interventions, different challenges are emerging, both patient- (clinical challenges) and procedure-related (technical challenges). This review will briefly explore the current open challenges in the evolving fields of interventional mitral valve treatment.

[Mitral valve interventions: Where do we stand?]

Mitral valve regurgitation (MR) with resulting heart failure is one of the most prevalent types of valvular heart disease. Currently, various approaches to catheter-based therapy of MR are already available for patients deemed to be at high-risk for surgery. Most experience has been gained with the MitraClip® system. Technological developments in the field of catheter-based treatment of MR is advancing at a rapid pace, with treatment modalities suited for patients with both primary and secondary MR. Annuloplasty is the surgical gold standard, particularly for patients with secondary MR. For catheter-based therapy of secondary MR a distinction is made between indirect and direct annuloplasty, with the latter most closely corresponding to surgical ring implantation. Catheter-based mitral valve replacement is technically feasible at present; however, experience is still limited and only few reports have been published. Technological development is markedly slower than in the field of transcatheter aortic valve replacement, predominantly owing to the far more complex structure of the mitral valve. Positive experience has already been gained with catheter-based implantation of prostheses designed for the aortic valve into degenerated mitral valve bioprostheses and failed surgical mitral annuloplasty rings (valve-in-valve and valve-in-ring implantation). Further approaches to catheter-based treatment of MR in high-risk surgical patients are expected in the future.