Rotational Activation Pattern During Functional Substrate Mapping: Novel Target for Catheter Ablation of Scar-Related Ventricular Tachycardia

Background: Recent advancements in a 3-dimensional mapping system allow for the assessment of detailed conduction properties during sinus rhythm and thus the establishment of a strategy targeting functionally abnormal regions in scar-related ventricular tachycardia (VT). We hypothesized that a rotational activation pattern (RAP) observed in maps during baseline rhythm was associated with the critical location of VT. Methods: We retrospectively examined the pattern of wavefront propagation during sinus rhythm in patients with scar-related VT. The prevalence and features of the RAP on critical VT circuits were analyzed. RAP was defined as >90° of inward curvature directly above or at the edge of the slow conductive areas. Results: Forty-five VTs in 37 patients (66±15 years old, 89% male, 27% ischemic heart disease) were evaluated. High-density substrate mapping during sinus rhythm (median, 2524 points) was performed using the CARTO3 system before VT induction. Critical sites for reentry were identified by direct termination by radiofrequency catheter ablation in 21 VTs or by pace mapping in 12 VTs. Among them, RAP was present in 70% of the 33 VTs. Four VTs had no RAP at the critical sites during sinus rhythm, but it became visible in the mappings with different wavefront directions. Six VTs, in which intramural or epicardial isthmus was suspected, were rendered noninducible by radiofrequency catheter ablation to the endocardial surface without RAP. RAP had a sensitivity and specificity of 70% and 89%, respectively, for predicting the elements in the critical zone for VT. Conclusions: The critical zone of VT appears to correspond to an area characterized by the RAP with slow conduction during sinus rhythm, which facilitates targeting areas specific for reentry. However, this may not be applicable to intramural VT substrates and might be affected by the direction of wavefront propagation to the scar during mapping.

Alterations of tibialis anterior muscle activation pattern in subjects with type 2 diabetes and diabetic peripheral neuropathy

Diabetic peripheral neuropathy (DPN) is associated with loss of motor units (MUs), which can cause changes in the activation pattern of muscle fibres. This study investigated the pattern of muscle activation using high-density surface electromyography (HD-sEMG) signals from subjects with type 2 diabetes mellitus (T2DM) and DPN. Thirty-five adults participated in the study: 12 healthy subjects (HV), 12 patients with T2DM without DPN (No-DPN) and 11 patients with T2DM with DPN (DPN). HD-sEMG signals were recorded in the tibialis anterior muscle during an isometric contraction of ankle dorsiflexion at 50% of the maximum voluntary isometric contraction (MVIC) during 30-s. The calculated HD-sEMG signals parameters were the normalised root mean square (RMS), normalised median frequency (MDF), coefficient of variation (CoV) and modified entropy (ME). The RMS increased significantly (p = 0.001) with time only for the DPN group, while the MDF decreased significantly (p < 0.01) with time for the three groups. Moreover, the ME was significantly lower (p = 0.005), and CoV was significantly higher (p = 0.003) for the DPN group than the HV group. Using HD-sEMG, we have demonstrated a reduction in the number of MU recruited by individuals with DPN. This study provides proof of concept for the clinical utility of this technique for identifying neuromuscular impairment caused by DPN.

Coronary sinus electrogram characteristics predicts termination of AF with ablation and long-term clinical outcome.

Introduction- Markers predicting AF termination and freedom from AF/atrial tachycardia (AT) has been proposed. The role of CS electrogram characteristics has not yet been evaluated. Methods- Patients undergoing ablation for persistent AF as part of the Stochastic Trajectory Analysis of Ranked signals mapping study were included. Novel CS electrogram characteristics including CS cycle length variability (CLV) and CS activation pattern stability (APS) and proportion of low voltage zones (LVZs) were reviewed as potential predictors for AF termination on ablation and freedom from AF/AT during follow-up. The relationship between localized driver characteristics and CS electrogram characteristics were also assessed. Results- Sixty-five patients were included. AF termination was achieved in 51 patients and 80% of patients were free from AF/AT during a follow-up of 29.5±3.7 months. CS CLV of <30ms, CS APS of ≥30% and proportion of LVZ <30% showed a high diagnostic accuracy in predicting AF termination on ablation and freedom from AF/AT during follow-up (CS CLV OR 25.6, AUC 0.91; CS APS OR 15.9, AUC 0.94; proportion of LVZs OR 21.4, AUC 0.88). These markers were independent predictors of AF termination on ablation and AF/AT recurrence during follow-up. Ablation of a smaller number of drivers that demonstrate greater dominance strongly correlate with greater CS organization. Conclusions- Novel CS electrogram characteristics were independent predictors of AF termination and AF/AT recurrence during follow-up. These markers can potentially aid in predicting outcomes and guide ablation and follow-up strategies.

Evaluation of Muscle Function by Means of a Muscle-Specific and a Global Index

Gait analysis applications in clinics are still uncommon, for three main reasons: (1) the considerable time needed to prepare the subject for the examination; (2) the lack of user-independent tools; (3) the large variability of muscle activation patterns observed in healthy and pathological subjects. Numerical indices quantifying the muscle coordination of a subject could enable clinicians to identify patterns that deviate from those of a reference population and to follow the progress of the subject after surgery or completing a rehabilitation program. In this work, we present two user-independent indices. First, a muscle-specific index (MFI) that quantifies the similarity of the activation pattern of a muscle of a specific subject with that of a reference population. Second, a global index (GFI) that provides a score of the overall activation of a muscle set. These two indices were tested on two groups of healthy and pathological children with encouraging results. Hence, the two indices will allow clinicians to assess the muscle activation, identifying muscles showing an abnormal activation pattern, and associate a functional score to every single muscle as well as to the entire muscle set. These opportunities could contribute to facilitating the diffusion of surface EMG analysis in clinics.

Pseudo micro-reentrant activation pattern created by coherent mapping of the right atrial free wall: A case report

Coherent mapping with CARTO3 is useful to identify the critical isthmus of scar-related AT. However, it has also a pitfall. We present atrial tachycardia (AT) with pseudo micro-reentrant activation pattern created by coherent mapping on the right atrial free wall. It is possible that a pseudo tachycardia circuit was created due to the algorithm for the reconstruction of coherent mapping. Finally, entrainment mapping led to the identification of correct tachycardia circuit and termination of tachycardia by catheter ablation. When using coherent mapping with CARTO3, it is necessary to understand the pitfall well.

Optimized Torque Assistance During Walking With an Idealized Hip Exoskeleton

The hip muscles account for a great percentage of the total human energy expenditure during walking and many wearable devices have been developed in assisting the hip joint to reduce the metabolic Cost Of Transport (COT) for walking. However, the effectiveness of assisting the hip in only one direction (either flexion or extension) or both directions has not been systematically studied and the underlying muscle mechanics and energetics affected by the assistance are not well understood. In this study, human-exoskeleton simulation based optimizations were performed to find optimized hip assistance torque profiles for (1) unidirectional flexion assistance, (2) unidirectional extension assistance, and (3) bidirectional flexion and extension assistance. Our results show that the bidirectional assistance is the most effective in reducing the COT of walking (22.7% reduction) followed by flexion (19.2%) and extension (11.7%). The flexion assistance resulted in more COT saving than the output of its net work by 35.9%, which indicates that the negative work done (42.2% of its positive counterpart) also played an important role in reducing the COT. The bidirectional assistance also reduced the activations of the hip extensors to a great extent and shifted the activation pattern of the hip flexor (ilipsoas). These results can provide valuable information for optimal hip actuation (timing and profiles) and help exoskeleton designers make informed decisions.

High density mapping guided partial antral ablation for a pulmonary vein isolation

The muscular discontinuities at the pulmonary vein (PV)–left atrial (LA) junction are known. The high-density mapping may help to find the muscular discontinuity. This study evaluated the efficacy of a partial antral ablation for a pulmonary vein (PV) isolation using high density (HD) mapping. A total of 60 drug-refractory atrial fibrillation (AF) patients undergoing catheter ablation were enrolled. The detailed activation mapping of each PV and LA junction was performed using an HD mapping system, and each PV segment’s activation pattern was classified into a “directly-activated from the LA” or “passively-activated from an adjacent PV segment” pattern. The antral ablations were performed at the directly-activated PV segments only when the PV had “passively-activated segments”. If the PV did not contain passively-activated segments, a circumferential antral ablation was performed on those PVs. A “successful partial antral ablation” was designated if the electrical isolation of targeted PV was achieved by ablation at the directly-activated segments only. If the isolation was not achieved even though all directly-activated segments were ablated, a “failed partial antral ablation” was designated, and then a circumferential ablation was performed. Among 240 PVs, passively-activated segments were observed in 140 (58.3%) PVs. Both inferior PVs had more passively-activated segments than superior PVs, and the posteroinferior segments had the highest proportion of passive activation. The overall rate of successful partial antral ablation was 85%. The atrial tachyarrhythmia recurrence was observed in 10 patients (16.7%) at 1-year. HD mapping allowed the evaluation of the detailed activation patterns of the PVs, and passively-activated segments may represent muscular discontinuity. Partial antral ablation of directly-activated antral segments only was feasible and effective for a PVI.