Activation Front Research Articles

Temporally and spatially segregated discretization for a coupled electromechanical myocardium model

Abstract In this paper, we propose a novel temporally and spatially segregated numerical scheme to discretize the coupled electromechanical model of myocardium. We perform several numerical experiments with activation of a myocardial slab with structural inhomogeneity and evaluate the dependence of numerical errors on the size of spatial and temporal discretization steps. In our study, we show that the spatial step for the mechanical equations h m ⩽2.5 mm yields reasonable results with noticeable errors only in the region of myocardial inhomogeneity. We also show that time step τ m ⩽1 ms can be used for temporal discretization of mechanical equations, and the propagation velocity of the activation and contraction fronts differs from the reference one by no more than 1.3%for such time step. Finally, we show that the increase of time discretization steps of the mechanical equations τ m and the monodomain equation τ e leads to phase errors with opposite signs, and we can compensate these errors by tuning the relationship between the time steps.

Generic Coupling between Internal States and Activity Leads to Activation Fronts and Criticality in Active Systems.

To understand the onset of collective motion, we investigate active systems where particles switch on and off their self-propulsion. We prove that even when the only possible transition is off→on, an active two-state system behaves as an effective three-state (inactive/passive) system that exhibits a sharp phase transition in 1D, and critical behavior in 2D, with scale-invariant activity avalanches. The obtained results show how criticality can naturally emerge in active systems, providing insight into the way collectives distribute, process, and respond to local environmental cues.

Theoretical limits of energy extraction in active fluids

Active materials form a class of far-from-equilibrium systems that are driven internally and exhibit self-organization, which can be harnessed to perform mechanical work. Inspired by experiments on synthetic active polymer networks, in this paper we examine limits of work extraction from an active viscoelastic medium by analyzing the transport of a particle. The active viscoelastic material possesses an equilibrium density where the active and passive forces are balanced out. In a one-dimensional system, a gliding activation front (AF), which converts a passive to an active medium, provides active energy at a constant rate, which is injected into the system at one end and propagates to the other. We demonstrate that there exists a maximum velocity of the AF, above which the activated region fails to deliver the transport power. We hypothesize and intuitively argue based on the limit cases that the feasibility and the velocity of transport of the particle can be interpreted in terms of the velocity of an equilibration domain wall of the field, which is set by two parameters: (i) a measure of activity, and (ii) the viscoelastic timescale. The phase diagram is divided into “transport” and “no-transport” sectors, namely, for any pair of the two parameters, there exists a threshold velocity of the AF above which the particle transport becomes impossible. Constructing the phase diagram we find that (1) there are regions of the phase diagram for which the threshold velocity of the AF diverges, and (2) larger viscoelastic timescale makes the transport region more accessible and also increases the transport velocity therein. Furthermore, we find that increasing the velocity of AF, results in larger extracted power but smaller transport coefficient; defined as the ratio of the transport velocity and that of the AF. Our model provides a framework for understanding the energetics of transport phenomena in biology and designing efficient mechanisms of transport in synthetic active materials. Published by the American Physical Society 2024

Spatially Conserved Spiral Wave Activity During Human Atrial Fibrillation.

Atrial fibrillation is the most common cardiac arrhythmia in the world and increases the risk for stroke and morbidity. During atrial fibrillation, the electric activation fronts are no longer coherently propagating through the tissue and, instead, show rotational activity, consistent with spiral wave activation, focal activity, collision, or partial versions of these spatial patterns. An unexplained phenomenon is that although simulations of cardiac models abundantly demonstrate spiral waves, clinical recordings often show only intermittent spiral wave activity. In silico data were generated using simulations in which spiral waves were continuously created and annihilated and in simulations in which a spiral wave was intermittently trapped at a heterogeneity. Clinically, spatio-temporal activation maps were constructed using 60 s recordings from a 64 electrode catheter within the atrium of N=34 patients (n=24 persistent atrial fibrillation). The location of clockwise and counterclockwise rotating spiral waves was quantified and all intervals during which these spiral waves were present were determined. For each interval, the angle of rotation as a function of time was computed and used to determine whether the spiral wave returned in step or changed phase at the start of each interval. In both simulations, spiral waves did not come back in phase and were out of step." In contrast, spiral waves returned in step in the majority (68%; P=0.05) of patients. Thus, the intermittently observed rotational activity in these patients is due to a temporally and spatially conserved spiral wave and not due to ones that are newly created at the onset of each interval. Intermittency of spiral wave activity represents conserved spiral wave activity of long, but interrupted duration or transient spiral activity, in the majority of patients. This finding could have important ramifications for identifying clinically important forms of atrial fibrillation and in guiding treatment.

Abstract 14991: Local Prolongation of Repolarization Prevents Post Myocardial Infarction Ventricular Tachycardia

Introduction: Reentry is the predominant mechanism underlying ventricular arrhythmias in chronic myocardial infarction patients. Reentry can be prevented by prolonging effective refractory period, thereby blocking reexcitation of recently activated tissue. This is currently achieved with systemically administered class III antiarrhythmic drugs. These therapies are limited by their risk of provoking ventricular arrhythmias by off-target effects. Hypothesis: Local prolongation of repolarization in healthy myocardium adjacent to the exit site attenuates reentry and postinfarction arrhythmias. Method and results: We used a pig model and generated myocardial infarction by balloon occlusion of the left anterior descending coronary artery and performed epicardial mapping 6 weeks later during Langendorff-perfusion. Programmed stimulation induced reentry leading to ventricular premature beats and sustained ventricular tachycardia (VT). Local injection of Sotalol adjacent to the infarcted myocardium prolonged repolarization and prevented VT after programmed stimulation. To translate these experimental findings to the patient situation we used a virtual heart based on data from a patient suffering from postmyocardial infarction VTs. The patient underwent pre-ablation cardiac late gadolinium enhanced- magnetic resonance imaging followed by geometrical reconstruction of the left ventricle and computational electrophysiological modelling of VT induction. We used a rapid pacing protocol to induce VT and determined the site where the activation front exited the infarct zone and reactivated the adjacent normal myocardium. Next, we prolonged repolarization of the normal myocardium adjacent to the exit site with 50 ms and performed rapid pacing to induce VT. This only resulted in a single premature ventricular beat after which sinus rhythm restored. Conclusion: Our experimental and in silico findings show the potential of local prolongation of repolarization a novel potentially genetic anti-arrhythmic therapy in post-infarction patients.

Influence of atrial cycle length and site of origin on the peak frequency of bipolar electrograms to discriminate isthmus conduction in atrial scar

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Abbott Background Peak frequency (PF) of conventional bipolar electrograms is a novel parameter which may distinguish between near-field (NF) and far-field (FF) signals. However, the influence of activation rate and the direction of the activation front on it is unknown. Purpose 1. To study the influence of atrial cycle length and wavefront origin on PF to detect residual conduction in a well-defined model of narrow isthmus of conduction such as subacute pulmonary vein (PV) reconnection following atrial fibrillation ablation. 2. To compare this influence with that found for Bipolar voltage (BiV). Methods Baseline maps were acquired in redo PV isolation (PVI) procedures with a 16-pole grid catheter (HD-Grid) during low rate sinus rhythm (SR), low rate coronary sinus pacing at 500 ms cycle length (CSLR) and high rate coronary sinus pacing at 300 ms cycle length (CSHR). PFs were retrospectively computed. PVI sites requiring ≤3 radiofrequency applications were included, with EGMʼs ≤1cm from the PVI site classified as GAP (vs >1cm, No-GAP). Results 28 GAPs were found in 12 of 14 consecutive patients in the study. 3976 EGMʼs (1547 GAP vs 2429 No-GAP) were analyzed. In both GAP and No-GAP, PF was similar in SR vs CSLR (GAP: 363±132 Hz -SR vs 345±135 Hz -CSLR, P=NS ; No-GAP: 196±110 Hz -SR vs 181±116 Hz -CSLR, P=NS). PF was slightly higher for CSLR vs CSHR. (GAP: 345±135 Hz -CSLR vs 317±154 Hz -CSHR, P<0.001; No-GAP 181±116 mV -CSLR vs 162±129 mV -CSHR, P<0.01). (Panel A). BiV was significantly higher in SR vs CS pacing but similar between CSLR and CSHR (GAP: 1.86±2.11 mV -SR vs 0.87±1.19 mV -CSLR vs 0.74±0.92 mV -CSHR, P= NS, No-GAP: 0.62±1.22 mV -SR vs 0.33±0.68 mV - CSLR vs 0.27±0.48 mV - CSHR, P=NS. (Panel B). ROC GAP discrimination for PF was similar between SR and CSLR (AUCʼs: 0.86-SR, 0.84-CSLR) and slightly lower for CSHR (AUC: 0.81) with optimal cutoffs of 260, 240 and 220 Hz, respectively. ROC GAP discrimination for BiV was lower vs PF in all rhythm modes (AUCʼs: 0.77-SR, 0.74-CSLR, 0.75-CSHR), with optimal cutoffs of 0.3, 0.2 and 0.15 mV, respectively. Conclusion ROC gap discrimination was significantly higher for all rhythm modes with PF vs BiV. PF showed slightly decreasing cutoff values for SR, CSLR and CSHR respectively, whereas BiV showed a greater relative decrease in cutoffs for SR, CSLR and CSHR.

Characterization of conduction gaps at the pulmonary vein antra by omnipolar voltage mapping

Abstract Funding Acknowledgements Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Abbott provided some software to perform special maps Introduction Voltage mapping of atrial tissue may be influenced by the direction of the activation front. Omnipolar electrograms may result in better characterization of the atrial tissue. However, little is known about characterization of the pulmonary vein (PV) antra with omnipolar mapping in patients with recurrent atrial fibrillation (AF) following PV isolation (PVI). Purpose To study differences in voltage between regions with (Gap) and without (No-Gap) conduction recurrence at the PV antra by both omnipolar and conventional bipolar mapping in redo PVI procedures. Methods Single centre prospective study of consecutive patients who underwent a redo PVI procedure for AF ablation. Activation and voltage bipolar maps were developed on a electroanatomical system (Ensite Precision) by a steerable catheter with a 16 grid-patterned electrode configuration (HD-Grid) during coronary sinus pacing at both 500 and 300 ms. Precise location of conduction gaps in the PV antra was attempted by atrial and PV pacing. Only conduction gaps that were ablated by ≤3 focal radiofrequency applications were included in the analysis. Electrograms recorded within 1 cm at both sides of the RF application site were considered related to the gap region. Off-line omnipolar voltage maps were developed with a dedicated experimental software after the procedure . Results 11 patients were included in the study and 18 gaps were found in 9 patients. 6762 (2688 Gap and 4074 No-Gap) electrograms were analyzed. Compared with No-Gap PV regions, Gap regions showed significantly (P < 0.0001) higher voltages by omnipolar mapping (0.3 ± 0.6 mV vs 1.1 ± 1.4 mV) and by absolute (0.2 ± 0.5 mV vs 0.8 ± 1.2 mV), grid-along (0.3 ± 0.5 mV vs 0.8 ± 1.2 mV) and grid-across (0.3 ± 0.5 mV vs 0.8 ± 1.1 mV) bipolar mapping. Omnipolar mapping resulted in higher voltage electrograms when compared with absolute bipole, longitudinal and horizontal bipolar electrograms (P < 0.0001). ROC curves (figure) to differentiate between Gap and No-Gap regions were slightly better for omnipolar electrograms (AUC 0.79) than for conventional grid -along or grid-across bipolar mapping (AUC 0.76 and 0.77) with the best discrimination value of 0.3 and 0.2 mV respectively. Conclusion: There are significant differences in voltage between conduction Gap and No-Gap regions at the PV antra which are more apparent with omnipolar than with conventional bipolar mapping. 0.3 mV and 0.2 mV values are the best to differentiate between PV conduction Gap and No-Gap regions with ominpolar and conventional mapping respectively

A mechanical model of early somite segmentation

SummarySomitogenesis is often described using the clock-and-wavefront (CW) model, which does not explain how molecular signaling rearranges the pre-somitic mesoderm (PSM) cells into somites. Our scanning electron microscopy analysis of chicken embryos reveals a caudally-progressing epithelialization front in the dorsal PSM that precedes somite formation. Signs of apical constriction and tissue segmentation appear in this layer 3-4 somite lengths caudal to the last-formed somite. We propose a mechanical instability model in which a steady increase of apical contractility leads to periodic failure of adhesion junctions within the dorsal PSM and positions the future inter-somite boundaries. This model produces spatially periodic segments whose size depends on the speed of the activation front of contraction (F), and the buildup rate of contractility (Λ). The Λ/F ratio determines whether this mechanism produces spatially and temporally regular or irregular segments, and whether segment size increases with the front speed.

High heart rate associated early repolarization causes J-waves in both zebra finch and mouse.

High heart rates are a feature of small endothermic—or warm‐blooded—mammals and birds. In small mammals, the QT interval is short, and local ventricular recordings reveal early repolarization that coincides with the J‐wave on the ECG, a positive deflection following the QRS complex. Early repolarization contributes to short QT‐intervals thereby enabling brief cardiac cycles and high heart rates. We therefore hypothesized high hearts rates associate with early repolarization and J‐waves on the ECG of endothermic birds. We tested this hypothesis by comparing isolated hearts of zebra finches and mice and recorded pseudo‐ECGs and optical action potentials (zebra finch, n = 8; mouse, n = 8). In both species, heart rate exceeded 300 beats per min, and total ventricular activation was fast (QRS < 10 ms). Ventricular activation progressed from the left to the right ventricle in zebra finch, whereas it progressed from apex‐to‐base in mouse. In both species, the early repolarization front followed the activation front, causing a positive J‐wave in the pseudo‐ECG. Inhibition of early repolarization by 4‐aminopyridine reduced J‐wave amplitude in both species. Action potential duration was similar between ventricles in zebra finch, whereas in mouse the left ventricular action potential was longer. Accordingly, late repolarization had opposite directions in zebra finch (left‐right) and mouse (right‐left). This caused a similar direction for the zebra finch J‐wave and T‐wave, whereas in the mouse they were discordant. Our findings demonstrate that early repolarization and the associated J‐wave may have evolved by convergence in association with high heart rates.

Optimal pacing sites in cardiac resynchronization by left ventricular activation front analysis

Cardiac resynchronization therapy (CRT) can substantially improve dyssynchronous heart failure and reduce mortality. However, about one-third of patients who are implanted, derive no measurable benefit from CRT. Non-response may partly be due to suboptimal activation of the left ventricle (LV) caused by electrophysiological heterogeneities. The goal of this study is to investigate the performance of a newly developed method used to analyze electrical wavefront propagation in a heart model including myocardial scar and compare this to clinical benchmark studies. We used computational models to measure the maximum activation front (MAF) in the LV during different pacing scenarios. Different heart geometries and scars were created based on cardiac MR images of three patients. The right ventricle (RV) was paced from the apex and the LV was paced from 12 different sites, single site, dual-site and triple site. Our results showed that for single LV site pacing, the pacing site with the largest MAF corresponded with the latest activated regions of the LV demonstrated during RV pacing, which also agrees with previous markers used for predicting optimal single-site pacing location. We then demonstrated the utility of MAF in predicting optimal electrode placements in more complex scenarios including scar and multi-site LV pacing. This study demonstrates the potential value of computational simulations in understanding and planning CRT.

Validation of Intramural Wavefront Reconstruction and Estimation of 3D Conduction Velocity.

Changes in conduction velocity are indicative of a wide variety of cardiac abnormalities yet measuring conduction velocity is challenging, especially within the myocardial volume. In this study we investigated a novel technique to reconstruct activation fronts and estimate three-dimensional (3D) conduction velocity (CV) from experimental intramural recordings. From the intermittently sampled electrograms we both reconstruct the activation profile and compute the reciprocal of the gradient of activation times and a series of streamlines that allows for the CV estimation. The reconstructed activation times agreed closely with simulated values, with 50% to 70% of the nodes ≤ 1ms of absolute error. We found close agreement between the CVs calculated using reconstructed versus simulated activation times. Across the reconstructed stimulation sites we saw that the reconstructed CV was on average 3.8% different than the ground truth CV. This study used simulated datasets to validate our methods for reconstructing 3D activation fronts and estimating conduction velocities. Our results indicate that our method allows accurate reconstructions from sparse measurements, thus allowing us to examine changes in activation induced by experimental interventions such as acute ischemia, ectopic pacing, or drugs.

Transmitting metal–oxide interaction by solitary chemical waves: H2 oxidation on ZrO2 supported Rh

The interaction of catalytically active metal particles with supporting oxide surfaces is still an actual topic in catalysis. Particularly, the exact role of metal-support boundary effects, caused by the active sites along the metal–oxide interface, is not entirely clear. Here we demonstrate a long-range effect of metal–oxide boundaries in a Rh/ZrO2 model system on the reactivity of Rh in H2 oxidation. The atomically narrow (<1 nm) interface between a Rh particle and ZrO2 causes a remarkable shift in the kinetic behavior of the entire µm-sized particle, i.e. affecting metal sites thousands of nanometers away from the interface. The effect was directly observed by photoemission electron microscopy (PEEM) using the kinetics by imaging approach which allows the evaluation of reaction kinetics for individual supported particles within the resolution limit of PEEM. The observed effect is attributed to the critical role of the perimeter sites for the initiation of activation and deactivation fronts (chemical waves) during H2 oxidation, which transmit the metal–oxide interface effect over the entire Rh particle.

Speed hysteresis and noise shaping of traveling fronts in neural fields: role of local circuitry and nonlocal connectivity

Neural field models are powerful tools to investigate the richness of spatiotemporal activity patterns like waves and bumps, emerging from the cerebral cortex. Understanding how spontaneous and evoked activity is related to the structure of underlying networks is of central interest to unfold how information is processed by these systems. Here we focus on the interplay between local properties like input-output gain function and recurrent synaptic self-excitation of cortical modules, and nonlocal intermodular synaptic couplings yielding to define a multiscale neural field. In this framework, we work out analytic expressions for the wave speed and the stochastic diffusion of propagating fronts uncovering the existence of an optimal balance between local and nonlocal connectivity which minimizes the fluctuations of the activation front propagation. Incorporating an activity-dependent adaptation of local excitability further highlights the independent role that local and nonlocal connectivity play in modulating the speed of propagation of the activation and silencing wavefronts, respectively. Inhomogeneities in space of local excitability give raise to a novel hysteresis phenomenon such that the speed of waves traveling in opposite directions display different velocities in the same location. Taken together these results provide insights on the multiscale organization of brain slow-waves measured during deep sleep and anesthesia.

QRS complex waveform indicators of ventricular activation slowing: Simulation studies

Diffuse or regional activation slowing in ventricular myocardium can result from different cardiac pathologies, such as left ventricular hypertrophy, ischemia or fibrosis. Altered ventricular activation sequence leads to deformations of the activation front and consequently to the changes in the QRS complex. Using a computer model we simulated the effect of slowed ventricular activation on the QRS waveform with a special interest in ECG changes which reproduce the ECG criteria of left ventricular hypertrophy (ECG-LVH). This paper describes results of a set of computer modeling experiments and discusses visual QRS patterns. Slowed ventricular activation in the whole left ventricle resulted in the prolongation of QRS duration, leftward shift of electrical axis, and increase in the QRS amplitude mainly in the precordial leads, having thus their main impact on simulated Sokolow–Lyon index and Cornell voltage. Slowed ventricular activation in the anteroseptal region resulted in a leftward shift of the electrical axis and increased values of ECG-LVH criteria seen in limb leads or in a combination with precordial leads (Gubner criterion, Cornell voltage). Transmural slowing and midwall slowing in two layers in the anteroseptal area led also to the QRS duration prolongation. Changes in QRS complex were more pronounced in the cases of transmural slowing as compared to the left ventricular midwall slowing. Using computer modeling, we showed that slowed ventricular activation is a potent determinant of QRS complex morphology and can mimic ECG patterns that are usually interpreted as the effect of left ventricular hypertrophy, i.e., increased left ventricular mass. These results contribute to understanding the variety of ECG finding documented in patients with LVH, considering not only anatomical enlargement but also the altered electrical properties of hypertrophied myocardium.

Influence of vacuum on nanosecond laser-induced surface damage morphology in fused silica at 1064 nm

The influence of vacuum on nanosecond laser-induced damage at the exit surface of fused silica components is investigated at 1064nm. In the present study, as previously observed in air, ring patterns surrounding laser-induced damage sites are systematically observed on a plane surface when initiated by multiple longitudinal modes laser pulses. Compared to air, the printed pattern is clearly more concentrated. The obtained correlation between the damage morphology and the temporal structure of the pulses suggests a laser-driven ablation mechanism resulting in a thorough imprint of energy deposit. The ablation process is assumed to be subsequent to an activation of the surface by hot electrons related to the diffusive expansion of a plasma formed from silica. This interpretation is strongly reinforced with additional experiments performed on an optical grating in vacuum on which damage sites do not show any ring pattern. Qualitatively, in vacuum, the intensity-dependent ring appearance speed V∝I1/2 is shown to be different than in air where V∝I1/3. This demonstrates that the mechanisms of formation of ring patterns are different in vacuum than in air. Moreover, the mechanism responsible of the propagation of the activation front in vacuum is shown to be outdone when experiments are performed in air.

Asymmetrical multiphase front propagation and localized oscillations in a reaction-migration iron electrodissolution model with microfluidic flow cell geometry

We study nonlinear patterns in a reaction-migration system in microfluidic flow cell geometry with potentiostatic metal electrodissolution by using one- and two-variable electrode kinetics to model bistable, excitable, and oscillatory dynamics. On long electrodes in flow channel geometry, which is often used in lab-on-chip devices, the propagation of activity front (in the bistable region) was found to be a strongly asymmetrical, complex, multiphase process, with the onset of spontaneous secondary inactivation waves. On segmented electrodes, because of strong coupling, the activation front can hop over insulating segments. A common feature of bistable and excitable dynamics is that the front initiation from the remote (high resistance) edge is easier (requires less perturbation) compared to the close (low resistance) edge. In the oscillatory region, we found spatially localized oscillations located on the close part of the electrode, with oscillation properties depending on cell geometry parameters. The flow cell geometry induces large changes in the local resistance along the electrodes in the flow channel, especially between the remote and close edges; this variation creates largely heterogeneous dynamical units, whose coupling accounts for many features of the observed complex behavior.

Patient-specific generation of the Purkinje network driven by clinical measurements of a normal propagation.

The propagation of the electrical signal in the Purkinje network is the starting point for the activation of the ventricular muscular cells leading to the contraction of the ventricle. In the computational models, describing the electrical activity of the ventricle is therefore important to account for the Purkinje fibers. Until now, the inclusion of such fibers has been obtained either by using surrogates such as space-dependent conduction properties or by generating a network based on an a priori anatomical knowledge. The aim of this work was to propose a new method for the generation of the Purkinje network using clinical measures of the activation times on the endocardium related to a normal electrical propagation, allowing to generate a patient-specific network. The measures were acquired by means of the EnSite NavX system. This system allows to measure for each point of the ventricular endocardium the time at which the activation front, that spreads through the ventricle, has reached the subjacent muscle. We compared the accuracy of the proposed method with the one of other strategies proposed so far in the literature for three subjects with a normal electrical propagation. The results showed that with our method we were able to reduce the absolute errors, intended as the difference between the measured and the computed data, by a factor in the range 9-25 %, with respect to the best of the other strategies. This highlighted the reliability of the proposed method and the importance of including a patient-specific Purkinje network in computational models.

New Electrocardiographic Criteria to Differentiate Acute Pericarditis and Myocardial Infarction: Rossello X, Wiegerinck RF, Alguiersuari J, et al. Am J Med 2014;127:233–9.

Accurately diagnosing ST-segment elevation myocardial infarctions (STEMIs) in the emergency department can prove to be a challenging task, and misdiagnosis can lead to unnecessary coronary angiography. This article from four tertiary hospitals in Spain sought to improve the distinction between pericarditis and STEMI by examining the duration of the QRS complex and QT interval. The authors hypothesized that the QRS interval would be prolonged in acute MI due to slowed propagation of the local activation front by transmural ischemia; the QT interval was expected to be shortened in the acute period. They performed a multi-centric case-control study examining 150 patients with acute chest pain associated with ST elevation: 71 who presented with STEMIs and 79 who had acute pericarditis. Admission electrocardiograms (ECGs) were manually analyzed for deviation of the PR segment from baseline, ST-segment deviation from the J-point, QRS duration, and QT interval. Each ECG was analyzed using one of three models: Model A included the duration of the QRS complex and QT interval; Model B utilized the classic ECG criteria of PR deviation and J-point level in aVR, as well as the number of leads with ST-segment elevation, ST-segment depression, and PR depression; and Model C tested all of the above variables. Receiver operating characteristic curves (ROCs) were constructed for each model, and the ROCs were compared using the DeLong method. Overall, patients with acute pericarditis were younger with fewer cardiac risk factors. Additionally, these patients showed greater upright PR deviation and deeper J-point in aVR, as well as a higher number of ECG leads with ST elevation and PR depression and a lower number of leads with reciprocal ST depression compared to STEMI ECGs. In patients with pericarditis, the QRS and QT intervals were the same in leads with and without ST elevation, whereas patients diagnosed with STEMIs showed a longer duration of the QRS complex and shorter QT interval length in leads with ST elevation compared to isoelectric leads. Comparison of the aforementioned models showed improvement in the ROC when QRS and QT interval duration were included in the analysis, with the ROC for model A being 0.807, model B 0.863, and model C 0.914. This study demonstrates that factoring the QRS duration and QT interval in your analysis of an ECG can help the clinician identify pericarditis and acute STEMI. The authors note that the study was limited by a lack of randomization, and that the ECG findings significantly influenced the ultimate diagnosis for patients at discharge.

Does cardiac resynchronization therapy benefit patients with right bundle branch block: cardiac resynchronization therapy has a role in patients with right bundle branch block.

Does cardiac resynchronization therapy benefit patients with right bundle branch block: cardiac resynchronization therapy has a role in patients with right bundle branch block.

Revisiting heart activation-conduction physiology, part I: atria

This discussion paper re-examines the conduction-activation of the atria, based on observations, with respect to the complexity of the heart as an organ with a brain, and its evolution from a peristaltic tube. The atria do not require a specialized conduction system because they use the subendocardial layer to produce centripetal transmural activation fronts, regardless of the anatomical and histological organization of the transmural atrial wall. This has been described as "two-layer" physiology which provides robust transmission of activation from the sinus to the AV node via a centripetal transmural activation front. New productive insights can come from re-examining the physiology, not only during sinus rhythm but also during atrial tachycardias, in particular atrial flutter and atrial fibrillation (AF). During common flutter, the areas of slow conduction, in the isthmus and following trabeculations, particularly the subendocardial layer confines conduction through the trabeculations which supports re-entry. During experimental or postoperative flutter, the circular 2D activation around the obstacle follows the physiological transmural activation. Understanding this physiology offers insights into AF. During acute or protracted AF, the presence of stationary or drifting rotors is characteristic and consistent with normal physiological 2D atrial activation, suggesting that suppressing physiological transmural activation of AF will permanently restore normal sinus node atrial activation. In contrast, during permanent AF, normal 2D activation is abolished; the presence of transmural, serpentine, and chaotic atrial activation suggests that the normal physiological activation pattern has been replaced by a new, irreversible variety of atrial conduction that is a new physiology, which is consistent with evolution of complex systems.