Decision Trees for Predicting Mortality in Transcatheter Aortic Valve Implantation

Current prognostic risk scores in cardiac surgery do not benefit yet from machine learning (ML). This research aims to create a machine learning model to predict one-year mortality of a patient after transcatheter aortic valve implantation (TAVI). We adopt a modern gradient boosting on decision trees classifier (GBDTs), specifically designed for categorical features. In combination with a recent technique for model interpretations, we developed a feature analysis and selection stage, enabling the identification of the most important features for the prediction. We base our prediction model on the most relevant features, after interpreting and discussing the feature analysis results with clinical experts. We validated our model on 270 consecutive TAVI cases, reaching a C-statistic of 0.83 with CI [0.82, 0.84]. The model has achieved a positive predictive value ranging from 57% to 64%, suggesting that the patient selection made by the heart team of professionals can be further improved by taking into consideration the clinical data we identified as important and by exploiting ML approaches in the development of clinical risk scores. Our approach has shown promising predictive potential also with respect to widespread prognostic risk scores, such as logistic European system for cardiac operative risk evaluation (EuroSCORE II) and the society of thoracic surgeons (STS) risk score, which are broadly adopted by cardiologists worldwide

Decision Trees for Predicting Mortality in Transcatheter Aortic Valve Implantation

Current prognostic risk scores in cardiac surgery do not benefit yet from machine learning (ML). This research aims to create a machine learning model to predict one-year mortality of a patient after transcatheter aortic valve implantation (TAVI). We adopt a modern gradient boosting on decision trees classifier (GBDTs), specifically designed for categorical features. In combination with a recent technique for model interpretations, we developed a feature analysis and selection stage, enabling the identification of the most important features for the prediction. We base our prediction model on the most relevant features, after interpreting and discussing the feature analysis results with clinical experts. We validated our model on 270 consecutive TAVI cases, reaching a C-statistic of 0.83 with CI [0.82, 0.84]. The model has achieved a positive predictive value ranging from 57% to 64%, suggesting that the patient selection made by the heart team of professionals can be further improved by taking into consideration the clinical data we identified as important and by exploiting ML approaches in the development of clinical risk scores. Our approach has shown promising predictive potential also with respect to widespread prognostic risk scores, such as logistic European system for cardiac operative risk evaluation (EuroSCORE II) and the society of thoracic surgeons (STS) risk score, which are broadly adopted by cardiologists worldwide

Gradient boosting on decision trees for mortality prediction in transcatheter aortic valve implantation

Current prognostic risk scores in cardiac surgery are based on statistics and do not yet benefit from machine learning. Statistical predictors are not robust enough to correctly identify patients who would benefit from Transcatheter Aortic Valve Implantation (TAVI). This research aims to create a machine learning model to predict one-year mortality of a patient after TAVI. We adopt a modern gradient boosting on decision trees algorithm, specifically designed for categorical features. In combination with a recent technique for model interpretations, we developed a feature analysis and selection stage, enabling to identify the most important features for the prediction. We base our prediction model on the most relevant features, after interpreting and discussing the feature analysis results with clinical experts. We validated our model on 270 TAVI cases, reaching an AUC of 0.83. Our approach outperforms several widespread prognostic risk scores, such as logistic EuroSCORE II, the STS risk score and the TAVI2-score, which are broadly adopted by cardiologists worldwide

Multi-view 3D skin feature recognition and localization for patient tracking in spinal surgery applications

Background Minimally invasive spine surgery is dependent on accurate navigation. Computer-assisted navigation is increasingly used in minimally invasive surgery (MIS), but current solutions require the use of reference markers in the surgical field for both patient and instruments tracking. Purpose To improve reliability and facilitate clinical workflow, this study proposes a new marker-free tracking framework based on skin feature recognition. Methods Maximally Stable Extremal Regions (MSER) and Speeded Up Robust Feature (SURF) algorithms are applied for skin feature detection. The proposed tracking framework is based on a multi-camera setup for obtaining multi-view acquisitions of the surgical area. Features can then be accurately detected using MSER and SURF and afterward localized by triangulation. The triangulation error is used for assessing the localization quality in 3D. Results The framework was tested on a cadaver dataset and in eight clinical cases. The detected features for the entire patient datasets were found to have an overall triangulation error of 0.207 mm for MSER and 0.204 mm for SURF. The localization accuracy was compared to a system with conventional markers, serving as a ground truth. An average accuracy of 0.627 and 0.622 mm was achieved for MSER and SURF, respectively. Conclusions This study demonstrates that skin feature localization for patient tracking in a surgical setting is feasible. The technology shows promising results in terms of detected features and localization accuracy. In the future, the framework may be further improved by exploiting extended feature processing using modern optical imaging techniques for clinical applications where patient tracking is crucial

Machine learning for predicting mortality in transcatheter aortic valve implantation: An inter-center cross validation study

Current prognostic risk scores for transcatheter aortic valve implantation (TAVI) do not benefit yet from modern machine learning techniques, which can improve risk stratification of oneyear mortality of patients before TAVI. Despite the advancement of machine learning in healthcare, data sharing regulations are very strict and typically prevent exchanging patient data, without the involvement of ethical committees. A very robust validation approach, including 1300 and 631 patients per center, was performed to validate a machine learning model of one center at the other external center with their data, in a mutual fashion. This was achieved without any data exchange but solely by exchanging the models and the data processing pipelines. A dedicated exchange protocol was designed to evaluate and quantify the model’s robustness on the data of the external center. Models developed with the larger dataset offered similar or higher prediction accuracy on the external validation. Logistic regression, random forest and CatBoost lead to areas under curve of the ROC of 0.65, 0.67 and 0.65 for the internal validation and of 0.62, 0.66, 0.68 for the external validation, respectively. We propose a scalable exchange protocol which can be further extended on other TAVI centers, but more generally to any other clinical scenario, that could benefit from this validation approach

Machine learning for predicting mortality in transcatheter aortic valve implantation: An inter-center cross validation study

Current prognostic risk scores for transcatheter aortic valve implantation (TAVI) do not benefit yet from modern machine learning techniques, which can improve risk stratification of oneyear mortality of patients before TAVI. Despite the advancement of machine learning in healthcare, data sharing regulations are very strict and typically prevent exchanging patient data, without the involvement of ethical committees. A very robust validation approach, including 1300 and 631 patients per center, was performed to validate a machine learning model of one center at the other external center with their data, in a mutual fashion. This was achieved without any data exchange but solely by exchanging the models and the data processing pipelines. A dedicated exchange protocol was designed to evaluate and quantify the model’s robustness on the data of the external center. Models developed with the larger dataset offered similar or higher prediction accuracy on the external validation. Logistic regression, random forest and CatBoost lead to areas under curve of the ROC of 0.65, 0.67 and 0.65 for the internal validation and of 0.62, 0.66, 0.68 for the external validation, respectively. We propose a scalable exchange protocol which can be further extended on other TAVI centers, but more generally to any other clinical scenario, that could benefit from this validation approach

Inter-center cross-validation and finetuning without patient data sharing for predicting transcatheter aortic valve implantation outcome

Transcatheter aortic valve implantation (TAVI) is the routine treatment worldwide for aortic valve stenosis in low-to high-risk patients. Assessing patient risk is essential to identify the most suitable candidates that could benefit from the procedure. Despite the broad use of statistical predictors in patient selection, current machine learning predictors have only been validated on retrospective data collected in single centers. Further, external validation is needed to assess the improvement in accuracy, which is offered by machine learning and deep learning techniques. In this study, we propose a finetuning approach for deep learning models by performing an inter-center cross-validation and finetuning technique, in order to improve the cross-validation accuracy results. We aimed to overcome data exchange and policy-related issues of two medical centers with a dedicated protocol, exploiting the exchange of deep learning models, data processing and validation steps which does not require any patient data sharing. The finetuning is based on the other center's data for further training of the initial model. After finetuning the model, we obtain an average AUC improvement of 13% and 7% with respect to the initial models. This research demonstrates that the predicting capabilities of deep learning models can be extended to and cross-validated with other centers, independent of limitations in data-sharing policies. Moreover, the study shows that finetuning can be exploited to considerably improve the accuracy of the prediction models.</p

Local and Distributed Machine Learning for Inter-hospital Data Utilization: An Application for TAVI Outcome Prediction

Background: Machine learning models have been developed for numerous medical prognostic purposes. These models are commonly developed using data from single centers or regional registries. Including data from multiple centers improves robustness and accuracy of prognostic models. However, data sharing between multiple centers is complex, mainly because of regulations and patient privacy issues. Objective: We aim to overcome data sharing impediments by using distributed ML and local learning followed by model integration. We applied these techniques to develop 1-year TAVI mortality estimation models with data from two centers without sharing any data. Methods: A distributed ML technique and local learning followed by model integration was used to develop models to predict 1-year mortality after TAVI. We included two populations with 1,160 (Center A) and 631 (Center B) patients. Five traditional ML algorithms were implemented. The results were compared to models created individually on each center. Results: The combined learning techniques outperformed the mono-center models. For center A, the combined local XGBoost achieved an AUC of 0.67 (compared to a mono-center AUC of 0.65) and, for center B, a distributed neural network achieved an AUC of 0.68 (compared to a mono-center AUC of 0.64). Conclusion: This study shows that distributed ML and combined local models techniques, can overcome data sharing limitations and result in more accurate models for TAVI mortality estimation. We have shown improved prognostic accuracy for both centers and can also be used as an alternative to overcome the problem of limited amounts of data when creating prognostic models

Inter-center cross-validation and finetuning without patient data sharing for predicting transcatheter aortic valve implantation outcome

Transcatheter aortic valve implantation (TAVI) is the routine treatment worldwide for aortic valve stenosis in low-to high-risk patients. Assessing patient risk is essential to identify the most suitable candidates that could benefit from the procedure. Despite the broad use of statistical predictors in patient selection, current machine learning predictors have only been validated on retrospective data collected in single centers. Further, external validation is needed to assess the improvement in accuracy, which is offered by machine learning and deep learning techniques. In this study, we propose a finetuning approach for deep learning models by performing an inter-center cross-validation and finetuning technique, in order to improve the cross-validation accuracy results. We aimed to overcome data exchange and policy-related issues of two medical centers with a dedicated protocol, exploiting the exchange of deep learning models, data processing and validation steps which does not require any patient data sharing. The finetuning is based on the other center's data for further training of the initial model. After finetuning the model, we obtain an average AUC improvement of 13% and 7% with respect to the initial models. This research demonstrates that the predicting capabilities of deep learning models can be extended to and cross-validated with other centers, independent of limitations in data-sharing policies. Moreover, the study shows that finetuning can be exploited to considerably improve the accuracy of the prediction models

Inter-center cross-validation and finetuning without patient data sharing for predicting transcatheter aortic valve implantation outcome

Transcatheter aortic valve implantation (TAVI) is the routine treatment worldwide for aortic valve stenosis in low-to high-risk patients. Assessing patient risk is essential to identify the most suitable candidates that could benefit from the procedure. Despite the broad use of statistical predictors in patient selection, current machine learning predictors have only been validated on retrospective data collected in single centers. Further, external validation is needed to assess the improvement in accuracy, which is offered by machine learning and deep learning techniques. In this study, we propose a finetuning approach for deep learning models by performing an inter-center cross-validation and finetuning technique, in order to improve the cross-validation accuracy results. We aimed to overcome data exchange and policy-related issues of two medical centers with a dedicated protocol, exploiting the exchange of deep learning models, data processing and validation steps which does not require any patient data sharing. The finetuning is based on the other center's data for further training of the initial model. After finetuning the model, we obtain an average AUC improvement of 13% and 7% with respect to the initial models. This research demonstrates that the predicting capabilities of deep learning models can be extended to and cross-validated with other centers, independent of limitations in data-sharing policies. Moreover, the study shows that finetuning can be exploited to considerably improve the accuracy of the prediction models