The study of cognitive load (CL) has been an active field of research across disciplines such as psychology, education, and computer graphics and visualization for decades. In the context of Virtual Reality (VR), understanding mental demand becomes particularly relevant, as immersive experiences increasingly integrate multisensory stimuli that require users to distribute their limited cognitive resources. In this work, we investigate the effects of cognitive load during a search task in VR, combining objective and subjective measurements, including physiological signals and validated questionnaires. We designed an experiment in which participants performed a visual search task under two cognitive load conditions (either alone or while responding to a concurrent auditory task) and across two visual search areas (90° and 360°). We collected a rich dataset comprising task performance, eye tracking, electrocardiogram (ECG), electrodermal activity (EDA), photoplethysmography (PPG), and inertial measurements, along with subjective assessments (NASA-TLX questionnaires). Our analysis shows that increased cognitive load hinders visual search performance and affects multiple physiological markers, offering a solid foundation for future research on cognitive load in multisensory virtual environments.

Objective: Atrial fibrillation (AF) rhythm gives rise to an irregular response in ventricular activity, preventing the use of standard ECG-derived risk markers based on ventricular repolarization heterogeneity under this particular condition. In this study, we proposed new indices to quantify repolarization variations in AF patients, assessing their stratification performance in a chronic heart failure population with AF. Methods: We developed a method based on a selective bin averaging technique. Consecutive beats preceded by a similar RR interval were selected, from which the average variation within the ST-T complex for each RR range was computed. We proposed two sets of indices: 1) the 2-beat index of ventricular repolarization variation, (IV2), computed from pairs of stable consecutive beats; and 2) the 3-beat indices of ventricular repolarization variation, computed in triplets of stable consecutive beats (IV3). Results: These indices showed a significant association with sudden cardiac death (SCD) outcome in the study population. In addition, risk assessment based on the combination of the proposed indices improved stratification performance compared to their individual potential. Conclusion: Patients with enhanced ventricular repolarization variation computed in terms of the proposed indices were successfully associated to a higher SCD incidence in our study population, evidencing their prognostic value. Significance: using a simple ambulatory ECG recording, it is possible to stratify AF patients at risk of SCD, which may help cardiologists in adopting most effective therapeutic strategies, with a positive impact in both the patient and healthcare systems.