Extrapolation of Ventricular Activation Times From Sparse Electroanatomical Data Using Graph Convolutional Neural Networks

Electroanatomic mapping is the gold standard for the assessment of ventricular tachycardia. Acquiring high resolution electroanatomic maps is technically challenging and may require interpolation methods to obtain dense measurements. These methods, however, cannot recover activation times in the entire biventricular domain. This work investigates the use of graph convolutional neural networks to estimate biventricular activation times from sparse measurements. Our method is trained on more than 15,000 synthetic examples of realistic ventricular depolarization patterns generated by a computational electrophysiology model. Using geometries sampled from a statistical shape model of biventricular anatomy, diverse wave dynamics are induced by randomly sampling scar and border zone distributions, locations of initial activation, and tissue conduction velocities. Once trained, the method accurately reconstructs biventricular activation times in left-out synthetic simulations with a mean absolute error of 3.9 ms ± 4.2 ms at a sampling density of one measurement sample per cm2. The total activation time is matched with a mean error of 1.4 ms ± 1.4 ms. A significant decrease in errors is observed in all heart zones with an increased number of samples. Without re-training, the network is further evaluated on two datasets: (1) an in-house dataset comprising four ischemic porcine hearts with dense endocardial activation maps; (2) the CRT-EPIGGY19 challenge data comprising endo- and epicardial measurements of 5 infarcted and 6 non-infarcted swines. In both setups the neural network recovers biventricular activation times with a mean absolute error of less than 10 ms even when providing only a subset of endocardial measurements as input. Furthermore, we present a simple approach to suggest new measurement locations in real-time based on the estimated uncertainty of the graph network predictions. The model-guided selection of measurement locations allows to reduce by 40% the number of measurements required in a random sampling strategy, while achieving the same prediction error. In all the tested scenarios, the proposed approach estimates biventricular activation times with comparable or better performance than a personalized computational model and significant runtime advantages.

Non-invasive assessment of patient-specific aortic haemodynamics from four-dimensional flow MRI data

We introduce a parameter estimation framework for automatically and robustly personalizing aortic haemodynamic computations from four-dimensional magnetic resonance imaging data. The framework is based on a reduced-order multiscale fluid-structure interaction blood flow model, and on two calibration procedures. First, Windkessel parameters of the outlet boundary conditions are personalized by solving a system of nonlinear equations. Second, the regional mechanical wall properties of the aorta are personalized by employing a nonlinear least-squares minimization method. The two calibration procedures are run sequentially and iteratively until both procedures have converged. The parameter estimation framework was successfully evaluated on 15 datasets from patients with aortic valve disease. On average, only 1.27 ± 0.96 and 7.07 ± 1.44 iterations were required to personalize the outlet boundary conditions and the regional mechanical wall properties, respectively. Overall, the computational model was in close agreement with the clinical measurements used as objectives (pressures, flow rates, cross-sectional areas), with a maximum error of less than 1%. Given its level of automation, robustness and the short execution time (6.2 ± 1.2 min on a standard hardware configuration), the framework is potentially well suited for a clinical setting.

N-Methylmorpholine-N-oxide ring cleavage registration by ESR under heating conditions of the Lyocell process

Thermal cleavage processes of N-methylmorpholine-N-oxide monohydrate (NMMO) were observed in pure NMMO as well as in cellulose/NMMO solutions by ESR at temperatures of the industrial Lyocell process ( approximately 370K). Generated radicals were attributed to the alkylnitroxyl type radicals -CH(2)-NO-CH(3) in NMMO and additional (and dominated) -CH(2)-NO-CH(2)- in cellulose/NMMO solutions. Formation of both radical types formed due to NMMO ring scission is suggested.

Electron spin resonance study of radicals generated in cellulose/N-methylmorpholine solutions after flash photolysis at 77 K

The processes of radical formation in N-methylmorpholine-N-oxide monohydrate (NMMO) and cellulose/NMMO solutions were studied by ESR at 77 K under high-power UV (lambda = 248 nm) excimer laser flash photolysis. Radicals mainly generated were attributed to the nitroxide type radicals -CH2-NO*-CH2- and -CH2-NO*-CH3 at the first step and methyl *CH3 and formyl *CHO radicals at the second step of the photoreaction. Kinetic studies of these radicals revealed that formation and recombination rates of the radicals depend on the cellulose concentration in cellulose/NMMO solutions and the concentration of additional ingredients, e.g. Fe(II) and propyl gallate. Even at frozen state temperature, acceleration or quenching of radical reaction processes was found. The proposed scheme of UV light-induced NMMO degradation during irradiation based on ESR data correlates well with independently obtained results based on high-performance liquid chromatography (HPLC). The analysis of degradation products by HPLC, e.g. aminoethanol and acetaldehyde, supports the assumption concerning a radical-initiated ring opening of NMMO.

[Necrotizing sialometaplasia of the nasal cavity]

In the present paper we report two cases of "necrotizing sialometaplasia" in uncommon locations. The relevant literature is reviewed. Necrotizing sialometaplasia is self-limiting and is characterized by necrosis and squamous pseudohypertrophy. Typically occurring in the minor salivary glands of the oral mucosa, our cases appear to be the sixth and seventh cases of involvement of the nasal cavity reported in the literature. Owing to the similarity of histological findings, the term "sialometaplasia" is also used for this disorder. This rare disease is a benign process but may be misdiagnosed as mucoepidermoid or squamous cell carcinoma. Therefore, the possibility of this disease in the nose should again be presented. Both of our cases show that with a histological examination considering defined morphological findings, the diagnosis of necrotizing sialometaplasia can be verified and a diagnosis of a carcinoma can be excluded. Especially with regard to radical and possibly unnecessary invasive therapeutic procedures we emphasize the importance of considering "necrotizing sialometaplasia" as part of the differential diagnosis of nasal lesions.

[Herpes simplex type 2 pneumonitis in an AIDS patient]

We report the case of a patient with AIDS, Kaposi's sarcoma and persistent herpes simplex type 2 proctitis who died of herpes simplex 2 pneumonitis following an episode of nonspecific interstitial pneumonitis. This rare complication of persistent herpes simplex mucosal infection must be considered in patients with AIDS suffering from severe pneumonitis with negative bronchoalveolar lavage.

Preserved cytosolic and synthetic liver function in jaundice of severe extrahepatic infection

We investigated prospectively 9 adult patients with the syndrome of jaundice complicating severe extrahepatic infection both clinically and by quantitative liver function tests. Five patients having severe extrahepatic infection without jaundice were used for comparison. Intraperitoneal infection was found to be a major risk factor for development of jaundice. Jaundice was mainly associated with gram-negative infection, but did not influence survival. Duration of jaundice was dependent on control of the underlying infection. Liver function tests showed a severely deranged organic anion transport, whereas synthetic, cytosolic, and microsomal functions remained preserved. Our study shows that (a) the syndrome of jaundice associated with extrahepatic infection is a functional disorder that is reversible upon control of infection, and that (b) cytosolic, synthetic, and microsomal function is preserved. This may have consequences for both assessing prognosis and clinical management.

[The long-term course of 60 patients with alveolar echinococcosis in continuous therapy with mebendazole (1976-85)]

Since 1976 60 patients with inoperable alveolar echinococcosis caused by Echinococcus multilocularis were treated with high doses of mebendazole and examined at regular intervals prospectively according to our protocol regarding clinical course, liver function, morphology, immunologically and plasma mebendazole levels. The average duration of disease was 8(1-19) years, the average duration of chemotherapy was 4.25 (0.75-9) years. The long term results showed a correlation of the clinical course with the mean plasma mebendazole levels and the duration of chemotherapy, respectively. Death (n = 5) or transient progression of the disease process (n = 14) was observed primarily in patients with low plasma mebendazole levels in the early course and within the first two years of chemotherapy. Only 9 patients showed a decrease of the parasite mass. Immundiagnosis (total serum IgE and serum antibodies against Echinococcus antigen) gave some information with regard to therapy results, but only in the long-term course. The cumulative survival of the patients under study was 96% at 5 years and 84% at 10 years, respectively which is markedly higher compared to historical control series with a letality of greater than 90% within 10 years.

Prevalence of medical problems in periodontal patients obtained from three different populations

Data from three different sources of periodontal patients were collected and examined to find if there was a significant difference between these groups relative to the prevalence of medical problems. Data were evaluated to show if age and sex were significantly related to the existence of medical problems and to determine which problems were the most prevalent. A total of 581 periodontal patients' records were obtained. Results of the evaluation showed that the private office group had 27.6% medical problems, the academic dental center had 46.3%, and the hospital dental clinic had 74.1%. Cardiovascular disease was the most prevalent medical problem in all groups and orthopedic disease or injury was second. Within each group, sex was not significantly related to the presence of a medical problem. Age was a highly significant factor, with the prevalence of medical problems increasing with advancing age.

[Quantitative liver function tests in porphyria cutanea tarda: improvement under therapeutic phlebotomy]

Quantitative liver function was assessed before and after therapy in 4 patients with porphyria cutanea tarda. Three patients underwent phlebotomy, which produced clinical and biochemical remission. Concomitantly, functional liver cell mass, as measured by galactose elimination capacity, normalized. In the last patient, treated with chloroquine, liver function did not improve during therapy. The aminopyrine breath test, a measure of microsomal function, was inconclusive. These results show that decreased hepatic function in porphyria cutanea tarda is reversible and emphasize the potential role of iron accumulation in the pathogenesis of hepatic dysfunction in porphyria cutanea tarda.

Treatment of hydatid disease with high oral doses of mebendazole. Long-term follow-up of plasma mebendazole levels and drug interactions

Plasma mebendazole levels were analysed retrospectively in patients treated for inoperable infections with Echinococcus multilocularis or granulosus. In 10 patients receiving mebendazole at 4 dose levels there was no relation between dose and plasma concentration. In 17 patients followed on the same dose for more than 18 months, the plasma levels varied with individual coefficients of variation ranging from 27 to 72%. The data reveal the limitations of single measurements of plasma mebendazole and emphasize the need for repeated monitoring. Coadministration of phenytoin and carbamazepine seemed to lower plasma levels, presumably as a result of enzyme induction. It was not possible appreciably to raise the mebendazole concentrations by inhibition of drug metabolizing enzymes with cimetidine.

[Budd-Chiari syndrome in liver echinococcosis]

In two female patients a diagnosis of Budd-Chiari syndrome secondary to hepatic echinococcosis was established by CT. One patient developed acute Budd-Chiari syndrome secondary to E. granulosus lesions of the liver. The second patient presented with a picture of chronic Budd-Chiari syndrome secondary to alveolar echinococcosis. CT findings of Budd-Chiari syndrome included ascites, low density areas in the liver parenchyma, hypertrophy of the caudate lobe, non visualisation of the hepatic veins, occlusion of the retrohepatic inferior vena cava and enlarged retroperitoneal veins.

Management of the nonerupted maxillary anterior tooth

The noneruption of maxillary anterior teeth, particularly the canine, is a common problem. The cause of the noneruption is multifactorial but almost always involves a lack of space. The literature presents an active and a passive form of orthodontic treatment and has recently stressed the periodontal management of these teeth. Two cases are presented. In both cases the orthodontic techniques of regaining space and providing traction on the unerupted tooth are described. A free gingival graft is used in one case and an apically repositioned flap in the other to achieve a healthy periodontium. The advantages and disadvantages of the techniques used as well as their rationale are discussed.

Early diagnosis and successful management of periodontosis

A brief review of the literature regarding the recognition, causes, and different therapeutic approaches of periodontosis was presented. Two cases of periodontosis in the early stages were reported, and a successful treatment plan using modalities similar to those used for other forms of periodontitis was described. Early diagnosis of the condition was critical to the success of both cases. Both patients were taught good oral hygiene, which, along with scaling, root planning, and conservative periodontal surgery, not only resulted in arresting the disease process, but also encouraged osseous regeneration. These examples emphasize the necessity of routine periodontal examinations for all children, especially at the circumpubertal period because periodontosis is often passed unnoticed until there has been massive periodontal destruction. The management of the advanced conditions is more challenging and seldom successful.

Endodontic involvement resulting from dental abrasion or erosion

A case is presented of extreme loss of tooth substance, most probably as a result of dentifrice abrasion. The lesions resulted in many instances of pulpal death and periapical pathosis. In most instances, an opening into the pulp chamber could not be demonstrated using an explorer. In two instances, an opening into the pulp chamber was present and probable. This communication with the oral cavity resulted in pulpal pathosis and an accompanying periapical lesion. In most cases of dental abrasion and erosion, or both, pulpal pathosis and periapical pathosis do not occur because of the ability of the pulp to lay down dentin as the pulp recedes. The findings in this case are not typical.

Diagnosis and possible causes of vertical root fractures

Thirty-two cases of vertical fractures were studied in an attempt to identify the causes and diagnostic signs normally present. In all of the patients except two, osseous defects were present and could be probed. The majortiy (65.63 percent) had only mild pain or a dull discomfort. Seventy-five percent showed diffuse widening of the periodontal ligament space. This study suggests that excessive force during lateral condensation of the gutta-percha caused 84.38 percent of the fractures. A secondary cause was the forcing or tapping of inlays or dowels into place. The majority (78.13 percent) of the patients were over the age of 40. In all but nine of the cases, treatment consisted of the extraction of the involved teeth.