Background-Defining the presence, extent, and nature of the dysfunctional myocardial tissue remains a cornerstone in diagnostic cardiology. A nonfluoroscopic, catheter-based mapping technique that can spatially associate endocardial mechanical and electrical data was used to quantify electromechanical changes in the canine chronic infarction model. Methods and Results-We mapped the left ventricular (LV) electromechanical regional properties in 11 dogs with chronic infarction (4 weeks after LAD ligation) and 6 controls. By sampling the location of a special catheter throughout the cardiac cycle at multiple endocardial sites and simultaneously recording local electrograms from the catheter tip, the dynamic 3-dimensional electromechanical map of the LV was reconstructed. Average endocardial local shortening (LS, measured at end systole and normalized to end diastole) and intracardiac bipolar electrogram amplitude were quantified at 13 LV regions. Endocardial LS was significantly lower at the infarcted area (1.2Ϯ0.9% [meanϮSEM], PϽ0.01) compared with the noninfarcted regions (7.2Ϯ1.1% to 13.5Ϯ1.5%) and with the same area in controls (15.5Ϯ1.2%, PϽ0.01). Average bipolar amplitude was also significantly lower at the infarcted zone (2.3Ϯ0.2 mV, PϽ0.01) compared with the same region in controls (10.3Ϯ1.3 mV) and with the noninfarcted regions (4.0Ϯ0.7 to 10.2Ϯ1.5 mV, PϽ0.01) in the infarcted group. In addition, the electrical maps could accurately delineate both the location and extent of the infarct, as demonstrated by the high correlation with pathology (Pearson's correlation coefficientϭ0.90) and by the precise identification of the infarct border. Conclusions-Chronic myocardial infarcted tissue can be characterized and quantified by abnormal regional mechanical and electrical functions. The unique ability to assess the regional ventricular electromechanical properties in various myocardial disease states may become a powerful tool in both clinical and research cardiology. (Circulation. 1998;98:2055-2064.)
Message filtering is important for distributed multiagent systems, where a large number of dynamic agents participate in the system activity, but a typical agent is interested in only a very small dynamic subset of the other agents. The agent must be constantly informed on the status of this subset, and this is achieved by message passing between relevant agents. Message filtering is required to reduce the communications load on the system, which could be prohibitive if each agent must communicate with all others in order to obtain the information it needs. This paper deals with the case of a multiagent virtual environment, where each agent has a location in 2D space, and is interested in a small subset of the other agents, either those within a fixed range-as treated by previous authors, or the k other agents nearest to it-treated here for the first time. Furthermore, we treat the case of a fully distributed system, where no central server(s) are available to coordinate between the agents. The main challenge is then to design protocols that perform significant message filtering, yet enable each agent to maintain a consistent image of the other agents it is interested in. These protocols are useful in multiagent games, simulations, and other virtual environments in which the geometric relationships between agents are important. They could also be useful for mobilecommerce and cellphone-based gaming applications.
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