PRIME score for prediction of permanent pacemaker implantation after transcatheter aortic valve replacement.

OBJECTIVES: We sought to produce a simple scoring system that can be applied at clinical visits before transcatheter aortic valve replacement (TAVR) to stratify the risk of permanent pacemaker (PPM) after the procedure. BACKGROUND: Atrioventricular block is a known complication of TAVR. Current models for predicting the risk of PPM after TAVR are not designed to be applied clinically to assist with preprocedural planning. METHODS: Patients undergoing TAVR at the University of Colorado were split into a training cohort for the development of a predictive model, and a testing cohort for model validation. Stepwise and binary logistic regressions were performed on the training cohort to produce a predictive model. Beta coefficients from the binary logistic regression were used to create a simple scoring system for predicting the need for PPM implantation. Scores were then applied to the validation cohort to assess predictive accuracy. RESULTS: Patients undergoing TAVR from 2013 to 2019 were analyzed: with 483 included in the training cohort and 123 included in the validation cohort. The need for a pacemaker was associated with five preprocedure variables in the training cohort: PR interval > 200 ms, Right bundle branch block, valve-In-valve procedure, prior Myocardial infarction, and self-Expandable valve. The PRIME score was developed using these clinical features, and was highly accurate for predicting PPM in both the training and model validation cohorts (area under the curve 0.804 and 0.830 in the model training and validation cohorts, respectively). CONCLUSIONS: The PRIME score is a simple and accurate preprocedural tool for predicting the need for PPM implantation after TAVR.

Evaluation of Quantitative Decision-Making for Rhythm Management of Atrial Fibrillation Using Tabular Q-Learning.

Background Rhythm management is a complex decision for patients with atrial fibrillation (AF). Although clinical trials have identified subsets of patients who might benefit from a given rhythm-management strategy, for individual patients it is not always clear which strategy is expected to have the greatest mortality benefit or durability. Methods and Results In this investigation 52 547 patients with a new atrial fibrillation diagnosis between 2010 and 2020 were retrospectively identified. We applied a type of artificial intelligence called tabular Q-learning to identify the optimal initial rhythm-management strategy, based on a composite outcome of mortality, change in treatment, and sustainability of the given treatment, termed the reward function. We first applied an unsupervised learning algorithm using a variational autoencoder with K-means clustering to cluster atrial fibrillation patients into 8 distinct phenotypes. We then fit a Q-learning algorithm to predict the best outcome for each cluster. Although rate-control strategy was most frequently selected by treating providers, the outcome was superior for rhythm-control strategies across all clusters. Subjects in whom provider-selected treatment matched the Q-table recommendation had fewer total deaths (4 [8.5%] versus 473 [22.4%], odds ratio=0.32, P=0.02) and a greater reward (P=4.8×10-6). We then demonstrated application of dynamic learning by updating the Q-table prospectively using batch gradient descent, in which the optimal strategy in some clusters changed from cardioversion to ablation. Conclusions Tabular Q-learning provides a dynamic and interpretable approach to apply artificial intelligence to clinical decision-making for atrial fibrillation. Further work is needed to examine application of Q-learning prospectively in clinical patients.

Evaluating temperature gradients across the posterior left atrium with radiofrequency ablation.

INTRODUCTION: Esophageal injury is a well-known complication associated with catheter ablation. Though novel methods to mitigate esophageal injury have been developed, few studies have evaluated temperature gradients with catheter ablation across the posterior wall of the left atrium, interstitium, and esophagus. METHODS: To investigate temperature gradients across the tissue, we developed a porcine heart-esophageal model to perform ex vivo catheter ablation on the posterior wall of the left atrium (LA), with juxtaposed interstitial tissue and esophagus. Circulating saline (5 L/min) was used to mimic blood flow along the LA and alteration of ionic content to modulate impedance. Thermistors along the region of interest were used to analyze temperature gradients. Varying time and power, radiofrequency (RF) ablation lesions were applied with an externally irrigated ablation catheter. Ablation strategies were divided into standard approaches (SAs, 10-15 g, 25-35 W, 30 s) or high-power short duration (HPSD, 10-15 g, 40-50 W, 10 s). Temperature gradients, time to the maximum measured temperature, and the relationship between measured temperature as a function of distance from the site of ablation was analyzed. RESULTS: In total, five experiments were conducted each utilizing new porcine posterior LA wall-esophageal specimens for RF ablation (n = 60 lesions each for SA and HPSD). For both SA and HPSD, maximum temperature rise from baseline was markedly higher at the anterior wall (AW) of the esophagus compared to the esophageal lumen (SA: 4.29°C vs. 0.41°C, p < .0001 and HPSD: 3.13°C vs. 0.28°C, p < .0001). Across ablation strategies, the average temperature rise at the AW of the esophagus was significantly higher with SA relative to HPSD ablation (4.29°C vs. 3.13°C, p = .01). From the start of ablation, the average time to reach a maximum temperature as measured at the AW of the esophagus with SA was 36.49 ± 12.12 s, compared to 16.57 ± 4.54 s with HPSD ablation, p < .0001. Fit to a linear scale, a 0.37°C drop in temperature was seen for every 1 cm increase in distance from the site of ablation and thermistor location at the AW of the esophagus. CONCLUSION: Both SA and HPSD ablation strategies resulted in markedly higher temperatures measured at the AW of the esophagus compared to the esophageal lumen, raising concern about the value of clinical intraluminal temperature monitoring. The temperature rise at the AW was lower with HPSD. A significant time delay was seen to reach the maximum measured temperature and a modest increase in distance between the site of ablation and thermistor location impacted the accuracy of monitored temperatures.

Longitudinal Impacts of Simulated Long-Duration Spaceflight Missions on Operationally Relevant Measures of Human Performance Using a Portable Simulation Platform.

OBJECTIVE: This project quantifies operationally relevant measures of flight performance and workload in a high-fidelity long-duration spaceflight analog, longitudinally across mission duration, using a portable simulation platform. BACKGROUND: Real-time performance measures allow for the objective assessment of task performance and the timely identification of performance degradations. METHODS: Measures of flight performance on a piloted lunar lander task were collected on 32 total crewmembers across 8 simulated space missions of 45 days each (623 total sessions). RESULTS: Mission duration demonstrated a significant effect on measures of flight performance across all campaigns. Flight measures showed a general pattern of peaking in accuracy during the middle-late quartiles of overall mission time, then degrading again towards baseline. On the workload measure, however, a general linear decrease in workload consistent with progressive task learning was observed in both campaigns. CONCLUSION: This investigation demonstrated the disruptive effect of time in mission on some, but not all, aspects of task performance. While mission interval differentially impacted measures of flight accuracy, workload, by contrast, seemed to steadily decrease with in-mission time. APPLICATION: While more work is needed, the observed discrepancy between progression of flight performance and workload assessment highlights the importance of sensitive and specific measurement tools for the tracking of distinct performance metrics.

The Variable Vector Countermeasure Suit (V2Suit) for space habitation and exploration.

The "Variable Vector Countermeasure Suit (V2Suit) for Space Habitation and Exploration" is a novel system concept that provides a platform for integrating sensors and actuators with daily astronaut intravehicular activities to improve health and performance, while reducing the mass and volume of the physiologic adaptation countermeasure systems, as well as the required exercise time during long-duration space exploration missions. The V2Suit system leverages wearable kinematic monitoring technology and uses inertial measurement units (IMUs) and control moment gyroscopes (CMGs) within miniaturized modules placed on body segments to provide a "viscous resistance" during movements against a specified direction of "down"-initially as a countermeasure to the sensorimotor adaptation performance decrements that manifest themselves while living and working in microgravity and during gravitational transitions during long-duration spaceflight, including post-flight recovery and rehabilitation. Several aspects of the V2Suit system concept were explored and simulated prior to developing a brassboard prototype for technology demonstration. This included a system architecture for identifying the key components and their interconnects, initial identification of key human-system integration challenges, development of a simulation architecture for CMG selection and parameter sizing, and the detailed mechanical design and fabrication of a module. The brassboard prototype demonstrates closed-loop control from "down" initialization through CMG actuation, and provides a research platform for human performance evaluations to mitigate sensorimotor adaptation, as well as a tool for determining the performance requirements when used as a musculoskeletal deconditioning countermeasure. This type of countermeasure system also has Earth benefits, particularly in gait or movement stabilization and rehabilitation.