Topological data analysis identified prognostically-distinct phenotypes in MitraClip patients

Background

Topological data analysis (TDA) is the state-of-the-art unsupervised machine learning framework that can provide insight into the dataset and visualize condensed information via the topological network graph. This robust approach was never used to assess the heterogeneous MitraClip population.

Purpose

We aim to develop a TDA model that will identify prognostically-distinct phenogroups in MitraClip patients without a priori knowledge of the population and their outcomes.

Method

Patients who underwent MitraClip (June 2014-September 2020) at Mayo Clinic sites were identified from the institutional database for baseline and follow-up data. Thirteen variables were used for TDA. The topological network graph was created using the Python Scikit-TDA Kepler-Mapper package (v. 2.0.1), and clustering was performed at the graph level with Louvain's modularity method. Kaplan-Meier survival analysis was used to assess the all-cause mortality endpoint of each cluster identified in an unsupervised manner. The dataset with cluster labels was also used to train a Light Gradient Boosted Machine model, and SHapley Additive exPlanations (SHAP) analysis was applied to determine the feature importance.

Results

A total of 389 consecutive patients were included in the final analysis and two major clusters consisting of 384 patients were identified. The mean age was 80.3±8.7 years; 256 (65.8%) were male. The mean Society of Thoracic Surgeons Mitral Valve Replacement risk score was 9.6±6.9%. Fifty-five (14.5%) patients died during the mean follow duration (185 days). Kaplan-Meier analysis showed significant survival differences among the two clusters (HR: 2.38; 95% CI: 1.39–4.06, p=0.001; Figure 1). Clusters 1 (n=195) was associated with > mild residual mitral regurgitation and worse survival performance and was characterized with worse tricuspid regurgitation severity, a higher proportion of patients with atrial fibrillation/flutter, anterior leaflet prolapse, and mitral annular/leaflet calcification, as summarized in Table 1.

Conclusion

TDA can identify distinct phenotype clusters with prognostic significance in MitraClip patients based on mitral valve morphology and clinical risk factors. This simple model can facilitate clinical risk stratification for MitraClip patients regarding procedural success and survival performance.

Funding Acknowledgement

Type of funding sources: None.

581 Renal Arteriovenous Fistula Percutaneous Embolization Using the Amplatzer Vascular Plug II

Introduction

Renal arteriovenous fistula (AVF) is not considered a common condition; however, it can occasionally complicate with renal impairment and heart failure secondary to high cardiac output. Recently, percutaneous embolization has overcome traditional surgery as the first line of its management, because of better success rates as well as less morbidity and mortality.

Case report

A 68-year-old male who presented with a renal AVF post left partial nephrectomy associated with a large pseudoaneurysm. This was found on a computed tomography angiography (CTA) scan, a routine follows up for his endovascular aortic aneurysm repair. Due to the patient’s co-morbidities and to avoid the potentially fatal pseudoaneurysm rupture, a minimal invasive approach was agreed in the multidisciplinary meeting. He was treated by percutaneous transcatheter embolization using the Amplatzer Vascular Plug II (AVP-II) through a right femoral arterial access. The patient recovery was uneventful, following an overnight stay he was discharged home. CTA done four and ten months later showed the AVP-II device inside the left renal artery branch feeder with no artifacts seen. There was absence of recanalization of the AVF. In the literature, adopting the transarterial route for the renal AVF treatment with AVP-II device as a single embolotherapy device has not been reported before.

Conclusions

Our report display the feasibleness of AVP-II in renal AVF treatment by arterial feeder embolization, specifically in fistulas with high flow and short communication as our case in which it showed offered multiple advantages over coils and is more cost effective.

Acoustic metamaterials with circular sector cavities and programmable densities

Considerable interest has been devoted to the development of various classes of acoustic metamaterials that can control the propagation of acoustical wave energy throughout fluid domains. However, all the currently exerted efforts are focused on studying passive metamaterials with fixed material properties. In this paper, the emphasis is placed on the development of a class of composite one-dimensional acoustic metamaterials with effective densities that are programmed to adapt to any prescribed pattern along the metamaterial. The proposed acoustic metamaterial is composed of a periodic arrangement of cell structures, in which each cell consists of a circular sector cavity bounded by actively controlled flexible panels to provide the capability for manipulating the overall effective dynamic density. The theoretical analysis of this class of multilayered composite active acoustic metamaterials (CAAMM) is presented and the theoretical predictions are determined for a cascading array of fluid cavities coupled to flexible piezoelectric active boundaries forming the metamaterial domain with programmable dynamic density. The stiffness of the piezoelectric boundaries is electrically manipulated to control the overall density of the individual cells utilizing the strong coupling with the fluid domain and using direct acoustic pressure feedback. The interaction between the neighboring cells of the composite metamaterial is modeled using a lumped-parameter approach. Numerical examples are presented to demonstrate the performance characteristics of the proposed CAAMM and its potential for generating prescribed spatial and spectral patterns of density variation.