Extinction dynamics of spiral defect chaos

Spatially extended excitable systems can exhibit spiral defect chaos (SDC) during which spiral waves continuously form and disappear. To address how this dynamical state terminates using simulations can be computationally challenging, especially for large systems. To circumvent this limitation, we treat the number of spiral waves as a stochastic population with a corresponding birth-death equation and use techniques from statistical physics to determine the mean episode duration of SDC. Motivated by cardiac fibrillation, during which the heart's electrical activity becomes disorganized and shows fragmenting spiral waves, we use generic models of cardiac electrophysiology. We show that the duration can be computed in minimal computational time and that it depends exponentially on domain size. Therefore, the approach can result in efficient and accurate predictions of mean episode duration which may be extended to more complex geometries and models.

Characterizing Electrogram Signal Fidelity and the Effects of Signal Contamination on Mapping Human Persistent Atrial Fibrillation

Objective: Determining accurate intracardiac maps of atrial fibrillation (AF) in humans can be difficult, owing primarily to various sources of contamination in electrogram signals. The goal of this study is to develop a measure for signal fidelity and to develop methods to quantify robustness of observed rotational activity in phase maps subject to signal contamination.

Methods: We identified rotational activity in phase maps of human persistent AF using the Hilbert transform of sinusoidally recomposed signals, where localized ablation at rotational sites terminated fibrillation. A novel measure of signal fidelity was developed to quantify signal quality. Contamination is then introduced to the underlying electrograms by removing signals at random, adding noise to computations of cycle length, and adding realistic far-field signals. Mean tip number N and tip density δ, defined as the proportion of time a region contains a tip, at the termination site are computed to compare the effects of contamination.

Results: Domains of low signal fidelity correspond to the location of rotational cores. Removing signals and altering cycle length accounted for minor changes in tip density, while targeted removal of low fidelity electrograms can result in a significant increase in tip density and stability. Far-field contamination was found to obscure rotation at the termination site.

Conclusion: Rotational activity in clinical AF can produce domains of low fidelity electrogram recordings at rotational cores. Observed rotational patterns in phase maps appear most sensitive to far-field activation. These results may inform novel methods to map AF in humans which can be tested directly in patients at electrophysiological study and ablation.

Two Independent Mapping Techniques Identify Rotational Activity Patterns at Sites of Local Termination During Persistent Atrial Fibrillation

Introduction

The mechanisms for atrial fibrillation (AF) are unclear in part because diverse mapping techniques yield diverse maps, ranging from stable organized sources to highly disordered waves. We hypothesized that AF mechanisms may be clarified if mapping techniques were compared in the same patients, and referenced to a clinical endpoint. We compared two independent AF mapping techniques in patients in whom ablation terminated persistent AF before pulmonary vein isolation (PVI).

Methods and Results

We identified 12 patients with persistent AF (61.2 ± 10.8 years, four female) in whom mapping with 64 pole baskets and technique 1 (activation/phase mapping, FIRM) identified rotational activation patterns during at least 50% of the 4‐second mapping interval and targeted ablation at these rotational sites terminated AF to sinus rhythm (n = 10) or atrial tachycardia. We analyzed the unipolar electrograms of these patients to determine phase maps of activation by an independent technique 2 (Kuklik, Schotten et al., IEEE Trans Biomed Eng 2015). Compared to technique 1, technique 2 revealed a source in 12 of 12 (100%) cases with spatial concordance in all cases (P <0.05) and similar rotational characteristics.

Conclusion

At sites where ablation terminated persistent AF, two independent mapping techniques identified stable rotational activation for multiple cycles that drove peripheral disorder. Future comparative studies referenced to a clinical endpoint may help reconcile if discrepancies between AF mapping studies reports represent techniques, patient populations or models of AF, and improve mapping to better guide ablation.

Determining conduction patterns on a sparse electrode grid: Implications for the analysis of clinical arrhythmias

We present a general method of utilizing bioelectric recordings from a spatially sparse electrode grid to compute a dynamic vector field describing the underlying propagation of electrical activity. This vector field, termed the wave-front flow field, permits quantitative analysis of the magnitude of rotational activity (vorticity) and focal activity (divergence) at each spatial point. We apply this method to signals recorded during arrhythmias in human atria and ventricles using a multipolar contact catheter and show that the flow fields correlate with corresponding activation maps. Further, regions of elevated vorticity and divergence correspond to sites identified as clinically significant rotors and focal sources where therapeutic intervention can be effective. These flow fields can provide quantitative insights into the dynamics of normal and abnormal conduction in humans and could potentially be used to enhance therapies for cardiac arrhythmias.

Phase synchrony reveals organization in human atrial fibrillation

It remains unclear if human atrial fibrillation (AF) is spatially nonhierarchical or exhibits a hierarchy of organization sustained by sources. We utilize activation times obtained at discrete locations during AF to compute the phase synchrony between tissue regions, to examine underlying spatial dynamics throughout both atria. We construct a binary synchronization network and show that this network can accurately define regions of coherence in coarse-grained in silico data. Specifically, domains controlled by spiral waves exhibit regions of high phase synchrony. We then apply this analysis to clinical data from patients experiencing cardiac arrhythmias using multielectrode catheters to simultaneously record from a majority of both atria. We show that pharmaceutical intervention with ibutilide organizes activation by increasing the size of the synchronized domain in AF and quantify the increase in temporal organization when arrhythmia changes from fibrillation to tachycardia. Finally, in recordings from 24 patients in AF we show that the level of synchrony is spatially broad with some patients showing large spatially contiguous regions of synchronization, while in others synchrony is localized to small pockets. Using computer simulations, we show that this distribution is inconsistent with distributions obtained from simulations that mimic multiwavelet reentry but is consistent with mechanisms in which one or more spatially conserved spiral waves is surrounded by tissue in which activation is disorganized.

An unusual complication after percutaneous drainage of a pancreatic pseudocyst into the stomach

In the period between September 1995 and June 1999, we performed percutaneous drainage into the stomach in 12 patients. There were no complications or pseudocyst recurrences on insertion or after endoscopic removal of the catheter, which was left in site for 1 year on average. After endoscopic removal of the drainage catheter, one of the patients presented with a cystic formation in the stomach wall, which caused stomach emptying disorder. Therefore, the patient had to be reoperated. The cyst wall was incised and a part of the cystic wall sampled for histological examination. The cyst was then drained into the isolated Roux loop of the jejunum. Histological findings of the cystic wall specimen showed the presence of granulation tissue and smooth muscle layers with ganglia cells of myenteric nerve plexus. Despite this complication, we believe that percutaneous endoscopically and ultrasonographically guided drainage of pancreatic pseudocyst into the stomach by means of a double pigtail catheter is a good method that yields encouraging results in sonographically selected cases. The position of the drainage catheter needs to be checked endoscopically, and the catheter should be removed only after 1 year.

Percutaneous drainage of pancreatic pseudocyst into the stomach

BACKGROUND

We present our experience with percutaneous ultrasonographically guided internal cystogastric drainage of pancreatic pseudocysts using a double pigtail catheter.

METHODS

In nine patients, the pancreatic pseudocysts following acute pancreatitis were drained percutaneously into the stomach with the double pigtail catheter under ultrasonographical (US) control. The needle insertion through both gastric walls and the final position of the proximal curve of the catheter were monitored with a gastroscope. The position of the distal curve of the catheter was checked by US. There were no procedure-related complications. The patients were followed up monthly by clinical and US examination.

RESULTS

At first follow-up 1 month after the intervention, none of the patients had evidence of the pseudocyst. The patients were not aware of the catheter and functioned normally throughout the procedure and catheter removal. The catheter was removed endoscopically after 5-8 months.

CONCLUSIONS

The method is minimally invasive and also feasible in high-risk surgical patients. It requires a team consisting of an interventional radiologist, an ultrasonographer, and an endoscopist. In properly selected patients, the results are excellent.

Extensive dermal metastases from primary signet-ring carcinoma of the urinary bladder

Dermal metastasis from internal carcinoma occurs infrequently. Bladder carcinoma is a rare source of skin metastasis. This report details the case of a twenty-five-year-old man with a fatal primary signet-ring adenocarcinoma of the bladder who experienced unique, extensive, infiltrative, cutaneous metastases within a few weeks of his initial presentation with an occultly carcinomatous ruptured spleen. The literature on cutaneous metastasis from carcinoma of the bladder is reviewed.

The uncombable hair syndrome

The uncombable hair syndrome was first described by Dupre as "cheveux incoiffables." Since that time more than fifty cases have been reported. We wish to present three more cases, review the salient features of the syndrome, and describe some new observations.