An index for T-wave pointwise amplitude variability quantification

The comparison between the pointwise amplitude of different T-waves provides insight into ventricular repolarization liability. However, T-wave pointwise amplitude variability can be confounded by time-domain variability. We, first, compared two algorithms for removing (warping) time-domain variability, one using the original and another one using a transformed T-wave (SRSF). We, next, compared the robustness against noise of two markers, dy and da, of pointwise amplitude variability, after warping the underlying temporal variability with the preferred warping algorithm. dy was obtained from the transformed T-waves while da was proposed in this work and was derived from the original T-waves. We, finally, used the most robust marker to measure the T-wave pointwise amplitude variability between every T-wave recorded during a Tilt test and their mean T-wave. Results showed that the preferred warping algorithm was the SRSF because it is not affected by differences between the amplitudes of the original T-waves. In addition, the marker da presented lower relative error values than dy for every level of noise. The analysis of electrocardiogram records showed that da was significantly lower during the tilt than in supine position (5.5 % vs 6.5 %, p<0.01). In conclusion, da robustly quantifies physiological variabilities of the T-wave amplitude, showing its potential to be used as an arrhythmic risk predictor in future clinical situations

An index for T-wave pointwise amplitude variability quantification

The comparison between the pointwise amplitude of different T-waves provides insight into ventricular repolarization liability. However, T-wave pointwise amplitude variability can be confounded by time-domain variability. We, first, compared two algorithms for removing (warping) time-domain variability, one using the original and another one using a transformed T-wave (SRSF). We, next, compared the robustness against noise of two markers, dy and da, of pointwise amplitude variability, after warping the underlying temporal variability with the preferred warping algorithm. dy was obtained from the transformed T-waves while da was proposed in this work and was derived from the original T-waves. We, finally, used the most robust marker to measure the T-wave pointwise amplitude variability between every T-wave recorded during a Tilt test and their mean T-wave. Results showed that the preferred warping algorithm was the SRSF because it is not affected by differences between the amplitudes of the original T-waves. In addition, the marker da presented lower relative error values than dy for every level of noise. The analysis of electrocardiogram records showed that da was significantly lower during the tilt than in supine position (5.5 % vs 6.5 %, p<0.01). In conclusion, da robustly quantifies physiological variabilities of the T-wave amplitude, showing its potential to be used as an arrhythmic risk predictor in future clinical situations

Synergy analysis as a tool to design and assess an effective stroke rehabilitation

The poor rehabilitation success rate, including the cases of ineffective and detrimental adaptations, make stroke a leading cause of disability. Thus, it is essential to recognize the mechanisms driving healthy motor recovery to improve such rate. Stroke alters the Synergy Architecture (SA), the modular muscle control system. So SA analysis may constitute a powerful tool to design and assess rehabilitation procedures. However, current impairment scales do not consider the patient’s neuromuscular state. To gain insights into this hypothesis, we recorded multiple myoelectric signals from upper-limb muscles, in healthy subjects, while executing a set of common rehabilitation exercises. We found that SA reveals optimized motor control strategies and the positive effects of the use of visual feedback (VF) on motor control. Furthermore we demonstrate that the right and left arm’s SA share the basic structure within the same subject, so we propose using the unaffected limb’s SA as a reference motion pattern to be reached through rehabilitation.Peer ReviewedPostprint (author’s final draft