Few techniques have been developed for deriving quantitative measures of activation patterns during ventricular fibrillation (VF). Such measures have many potential applications, for example, assessing the effects of time, drugs, or electrical interventions. We have developed a new framework for quantifying VF patterns as mapped from an array of approximately 500 unipolar electrodes. Individual activation wavefronts are isolated from one another using an algorithm that groups together adjacent active electrogram samples (dV/dt < -0.5 V/sec). Contacts between wavefronts are detected: these include fractionations, in which a single wavefront breaks into multiple wavefronts, and collisions, in which multiple wavefronts coalesce to form a new wavefront. The timing and contact relationships between wavefronts are summarized as a directed graph. From this model of the VF episode, we derive several parameters: number of wavefronts, number of fractionations, number of collisions, mean wavefront size, mean area swept out, and mean duration. As an example of this analysis, we computed these parameters in six open-chest pigs at 5, 10, 15, and 20 sec after electrical induction of VF. The number of wavefronts and the number of collisions decreased, whereas the mean wavefront size and mean area swept out increased during this period. These results are consistent with previous studies showing a recovery of organization during the first minute of VF.

Algorithms↗

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Recurrent wavefront morphologies: a method for quantifying the complexity of epicardial activation patterns.

We have developed a method for quantifying the complexity of activation patterns observed during ventricular fibrillation (VF) that is based on our previously reported methodology for decomposing epicardial mapping data into a set of isolated wavefronts. One-half second datasets are acquired from a 21 x 24 array of unipolar electrodes (1 mm spacing), and the wavefronts are isolated. A correlation technique is used to compute the similarity between all possible pairs of the isolated wavefronts. From these data, the wavefronts are sorted into clusters, each of which represents a recurring wavefront morphology. We define multiplicity (M) as the number of clusters needed to account for 90% of the total activations in the VF episode. M measures the complexity of the rhythm. In repetitive patterns (e.g., sinus rhythm), M = 1, indicating that the same morphology repeatedly activates the mapped region. Typically, in VF, M > 1, with larger numbers representing more complex, disorganized patterns. As an example, we computed M at 5, 10, 15, and 20 sec after electrical induction of VF in six pigs. M decreased significantly (p < 0.001), suggesting increasing organization during this period.

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PubMedDate not supplied

The characteristics of static visual fields in children with psychogenic visual disturbances.

PURPOSE: It is well-known that patients with psychogenic visual disturbances (PVD) exhibit characteristic kinetic visual fields. Even when the kinetic fields are normalized, the static fields of PVD children frequently remain abnormal. To verify this finding, we performed static perimetry on those children whose kinetic fields were initially normal or which normalized during the follow-up period, and compared the results with those of children with psychosomatic disorders (PSD) and normal children. METHODS: We examined 9 PVD children (17 eyes), 16 PSD children (32 eyes), and 16 normal children (16 eyes). Program 30-2 or 24-2 of the Humphrey Field Analyzer was used in the examinations on all subjects. RESULTS: The average mean deviation (MD) of the PVD group was significantly lower than that of the other groups (P <. 01). False negative errors and short-term fluctuations were significantly higher in the PVD group than in the other groups (P <. 05). CONCLUSION: Although PVD and PSD children possess a similar underlying psychological dysfunction, their performances in visual field testing proved to be quite different. In the PVD group, even when kinetic fields were normal, functional visual field loss in the static fields was common and had characteristic response properties.

Child↗

PubMedDate not supplied

Differentiation of Th1 and Th2 cells in lymph nodes and spleens of mice during experimental autoimmune uveoretinitis.

PURPOSE: Experimental autoimmune uveoretinitis (EAU) is a T-cell-mediated autoimmune disease that can be elicited in susceptible rodent strains by immunization with a retinal autoantigen, such as interphotoreceptor retinoid-binding protein (IRBP). In this study, we investigated whether there is a correlation between inflammation in the eye and T-helper (Th)1- and Th2-type responses in the lymph nodes and the spleen after immunization of B10.A mice with IRBP. METHODS: B10.A mice were immunized with IRBP emulsified with complete Freund's adjuvant (CFA), and eyes were then enucleated for histological examination of EAU at 1, 2, 4, 6, or 8 weeks after immunization. In addition, lymph node cells and spleen cells were collected, and cultured with IRBP to measure T-cell proliferation responses and Th1-type (interleukin [IL]-2, interferon [IFN]-gamma), Th2-type (IL-4, IL-10) cytokine production. RESULTS: Pathologically, severe ocular inflammation occurred 2 weeks after IRBP immunization, persisted for 2 weeks, and then gradually resolved. Interleukin-2 and IFN-gamma production were observed in draining lymph node cells at 1 and 2 weeks after IRBP immunization. Those responses then diminished, whereas IFN-gamma production by spleen cells was observed from week 1, peaked at week 4, and gradually decreased. Alternatively, significant production of IL-4 or IL-10 by draining lymph node cells was not detected at any time point. Both IL-4 and IL-10 production by spleen cells was observed at week 6. CONCLUSIONS: Th1-type responses were observed early in draining lymph nodes, then in the spleen after IRBP immunization. The levels of IFN-gamma production by spleen cells reflected the severity of EAU, confirming their pathogenic role in this disease. Th2-type responses were generated in the spleen only as the disease receded, suggesting a role for Th2 cells in the spontaneous termination of EAU.

Animals↗

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Comparison of detectability of visual field abnormality by frequency doubling technology in primary open-angle glaucoma and normal-tension glaucoma.

PURPOSE: To compare the effectiveness of frequency doubling technology (FDT) in detecting abnormalities in primary open-angle glaucoma (POAG) and in normal-tension glaucoma (NTG). METHODS: Twenty-nine POAG patients (29 eyes) and 27 NTG patients (27 eyes) were studied. All subjects underwent testing with program C-20 of FDT with appropriate corrective lenses. RESULTS: No significant differences were observed between the two groups in mean age, mean deviation (MD), and pattern standard deviation (PSD) measured by the Humphrey Field Analyzer (HFA). The correlation between MD values determined by HFA (x) and FDT (y) is represented by y = 0.60x - 2.7 (r = 0.78, P <.01) in the POAG group and y = 0.59x + 0.6 (r = 0.81, P <.001) in the NTG group. Although the average MD measured by FDT was significantly lower in the POAG group than in the NTG group (P <.05), no significant difference was found in average PSD between the two groups. In early glaucoma cases (MD > or = -5 dB by HFA), a larger proportion of cases in the POAG group than in the NTG group had lower significance level of MD determined by FDT than by HFA (P <.02). At many test points on the temporal periphery in the FDT, the mean sensitivity was lower in the POAG group than in the NTG group; whereas no significant differences among HFA test points were observed. CONCLUSIONS: Frequency doubling technology detected visual field abnormalities in POAG cases more sensitively than in NTG cases. This finding indicates that the pathogenesis of My-cell damage is rather different in POAG and NTG.

Glaucoma, Open-Angle↗

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5-S-cysteinyldopa as diagnostic tumor marker for uveal malignant melanoma.

PURPOSE: To evaluate the clinical significance of 5-S-cysteinyldopa (5-S-CD), a major intermediate in melanin synthesis, as a potential diagnostic tumor marker for uveal malignant melanoma. METHODS: The levels of 5-S-CD in the serum were measured by high-performance liquid chromatography in 16 patients with primary uveal melanoma. The levels of 5-S-CD were also measured in both aqueous and vitreous humor in 10 patients with uveal melanoma. The serum of healthy volunteers and patients with skin diseases other than melanoma, and the intraocular fluids of patients with cataract and vitreoretinal diseases were used as controls. RESULTS: Serum concentrations of 5-S-CD in patients with uveal melanoma in the absence of extraocular metastases were close to those of controls; however, serum concentrations of 5-S-CD were significantly elevated in patients with extraocular metastases of melanoma. Concentrations of 5-S-CD in the intraocular fluids, especially vitreous humor, were higher in patients with uveal melanoma than in controls. CONCLUSIONS: 5-S-CD in intraocular fluids may serve as a useful biochemical marker for the diagnosis of uveal melanoma. Serum 5-S-CD may contribute to the assessment of the presence and progression of extraocular metastases in patients with uveal melanoma.

Adult↗

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Histological study of intraocular changes in rabbits after intravitreal gas injection.

To study the effects of different intravitreal gases on intraocular tissues, adult pigmented rabbits were given 0.4 mL intravitreal injections of air, 50% sulfur hexafluoride (SF6) and air, 100% SF6, 50% perfluoropropane (C3F8), or 100% C3F8. On postinjection days 1, 4, 7, and 14, the eyes were removed and the iris, ciliary body and retina processed for light and electron microscopy. Histopathological examination found no abnormalities in eyes that received air and none in the irises of gas-injected eyes. Eyes that received 50% or 100% SF6, or 50% C3F8 had vacuolar changes in the ciliary body and retina after maximum gas expansion; these changes were transient, returning to normal as the gas was absorbed. Eyes that received 100% C3F8 suffered irreversible damage to the ciliary body and retina, in both the superior and inferior portions. These observations indicate that expansion of some intravitreal gases can cause both reversible and irreversible changes in intraocular tissues. The degree of damage is affected by the duration of exposure and the gas concentration. Highly concentrated, long-lasting gases can cause irreversible changes resulting in breakdown of the blood-ocular barrier and impaired retinal function.

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